KR20160033117A - Heat-sealable stretched multilayer polypropylene film - Google Patents

Abstract

A heat-sealable polypropylene laminated film having a low shrinkage factor comparable to PET at 150 DEG C and having a high strength. (A) comprising a polypropylene resin as a main component and a heat seal layer (B) comprising a propylene random copolymer and / or a polypropylene block copolymer laminated on one side or both sides of the base layer, Wherein the heat shrinkage ratio in the MD direction and the TD direction at 150 占 폚 is 10% or less and the impact strength is 0.6 J or more.

Description

HEAT-SEALABLE STRETCHED MULTILAYER POLYPROPYLENE FILM < RTI ID = 0.0 >

The present invention relates to a heat sealable polypropylene laminated stretched film. More specifically, the present invention relates to a resin composition which can be suitably used in various fields that have sufficient heat seal strength for use in packaging, good transparency, dimensional stability at high temperatures, and high rigidity, Axis stretched heat sealable polypropylene laminated stretched film.

Background Art [0002] Conventionally, a stretched film using polypropylene has been widely used for a wide range of applications such as packaging for foods and various commodities, electric insulation, surface protection film, and the like, but there is a demand for heat sealability. Conventionally, as a heat sealable film, a coextruded laminated polypropylene type resin film in which a polyolefin resin having a low melting point is laminated on a polypropylene type resin has been widely used. Such a heat sealable film has a shrinkage rate at a temperature of 150 占 폚 of several tens% and has a limited use because it has a low heat resistance and a low rigidity as compared with PET and the like. For example, if the heat seal temperature can be set high, the line speed in the bag making process can be increased. In the stretched polypropylene film, however, the heat sealability and the heat resistance at high temperature are still insufficient .

In order to solve such a problem, the polypropylene resin constituting the base layer (A) is a stretched film using polypropylene having a high stereoregularity and a narrow molecular weight distribution to produce a high temperature stiffness and heat resistant film (See, for example, Patent Document 1, etc.).

Further, there has been known a technique that can be appropriately used as a capacitor film having excellent electrical insulation, mechanical characteristics and the like by forming a stretched film using polypropylene having a high stereoregularity and a wide molecular weight distribution (see, for example, 2).

Further, there is known a technology of making a separator film using polypropylene having a low molecular weight and having a specific content of the soluble fraction at 0 DEG C by the temperature increasing fractionation method, and this film has excellent dimensional stability in the drying step and the printing step (See, for example, Patent Document 3, etc.).

However, Patent Documents 1 to 3 have difficulty in stretching, and mechanical properties such as impact resistance are also deteriorated.

Long chain branching or crosslinked polypropylene is added in a small amount to a medium molecular weight to promote the formation of subsidiary lamella to improve stretchability and excellent mechanical properties, heat resistance and withstand voltage characteristics, excellent uniformity of various physical properties (See, for example, Patent Document 4, etc.).

Further, there has been known a technique of balancing rigidity-processability by using a polypropylene containing almost the same amount of a high molecular weight and a low molecular weight (lower molecular weight), a broad molecular weight distribution and a low decalin soluble content See, for example, Patent Document 5).

These Patent Documents 4 to 5 can not say that the heat resistance at a high temperature is sufficient, and a polypropylene film having high heat resistance and excellent impact resistance and transparency has not been known.

That is, they do not exceed the area of the conventional polypropylene film, and their use is limited. For example, no attention has been paid to the heat resistance at a high temperature exceeding 150 캜.

Japanese Patent Laid-Open No. 8-325327 Japanese Patent Application Laid-Open No. 2004-175932 Japanese Patent Application Laid-Open No. 2001-146536 Japanese Patent Laid-Open No. 2007-84813 Japanese Patent Publication No. 2008-540815

The present invention has been made in the background of the problems of the prior art. That is, an object of the present invention is to provide a stretched polypropylene laminated film which has a low shrinkage ratio comparable to PET at 150 ° C and can be heat-sealed at a high temperature.

Means for Solving the Problems The present inventors have intensively studied in order to achieve these objects, and have completed the present invention. That is, the present invention is a film composed mainly of a polypropylene resin, and has a heat shrinkage ratio in the MD direction and a TD direction at 150 占 폚 of 10% or less, an impact strength of 0.6 J or more, and a haze of 6% Based on the total weight of the film.

The stretched film is industrially a film having a stretched orientation by a method such as one-axis, two-axis, two-axis and the like, and the degree of the orientation can be represented by, for example, a plane orientation coefficient obtained from the refractive index have.

In this case, the Young's modulus in the MD direction is preferably 2.1 GPa or more, and the Young's modulus in the TD direction is preferably 3.7 GPa or more.

Further, in this case, it is preferable that the heat-sealable layer of the polyolefin-based heat-seal resin (B) is laminated with a propylene random copolymer and / or a propylene block copolymer.

According to the present invention, in the heat-sealable stretched polypropylene laminated film, a low shrinkage ratio and a high rigidity comparable to PET at 150 캜 can be achieved, and further, the film can be made thinner.

In addition, the stretched polypropylene laminated film of the present invention can maintain various physical properties even when exposed to an environment of 150 DEG C or higher, and can be used even under a high temperature environment which can not be expected in the base layer (A) of a conventional stretched polypropylene laminated film .

For example, by setting the heat seal temperature high, it becomes possible to increase the line speed in the steel cord machining, and the productivity is improved. In addition, by increasing the heat seal temperature, the heat seal strength can also be improved. Furthermore, even when a high-temperature treatment such as retort is performed, the amount of deformation of the bag can be suppressed.

The present invention relates to a heat-sealable stretched polypropylene laminated film. More specifically, the present invention relates to a heat-resistant resin composition which has a sufficient heat-sealing strength for use in packaging, has good transparency, can be suitably used in various fields requiring dimensional stability at a high temperature and high rigidity, To a sealable stretched polypropylene laminated film. The characteristic of the stretched polypropylene laminated film of the present invention lies in the molecular weight distribution of the polypropylene resin used for the base layer (A).

A stretched polypropylene laminated film comprising a polypropylene resin as a main component and having a heat shrinkage of 10% or less in the MD direction and a TD direction at 150 占 폚, an impact strength of 0.6 J or more, and a haze of 6% It is necessary.

Here, the MD direction is the flow direction of the film, and the TD direction is the direction perpendicular to the film flow direction.

(Film characteristics)

The lower limit of the heat shrinkage percentage at 150 占 폚 in the MD and TD directions of the stretched film of the present invention is preferably 0.5%, more preferably 1%, still more preferably 1.5%, particularly preferably 2% Most preferably 2.5%. If the thickness is within the above range, it may be possible to facilitate realistic manufacturing at a cost or the like and to reduce thickness irregularity.

The upper limit of the heat shrinkage percentage at 150 占 폚 in the MD and TD directions is preferably 10%, more preferably 9%, even more preferably 8%, particularly preferably 7%, and most preferably 6% to be. Within this range, it is easier to use in applications that are likely to be exposed to high temperatures such as about 150 ° C. When the heat shrinkage at 150 캜 is up to about 2.5%, for example, it is possible to adjust the stretching condition and the fixing condition to increase the low molecular weight component, but it is preferable to carry out the annealing at an off-line rate.

In the conventional stretched polypropylene laminated film, the heat shrinkage at 150 占 폚 in the MD and TD directions is 15% or more and the heat shrinkage at 120 占 폚 is 3% or so. By setting the heat shrinkage ratio within the above range, a stretched polypropylene laminated film excellent in heat resistance can be obtained.

The lower limit of the impact resistance (23 캜) of the drawn polypropylene film of the present invention is preferably 0.6 J, and more preferably 0.7 J. If the thickness is in the above range, the film has sufficient toughness and is not broken at the time of handling.

The upper limit of the impact resistance is preferably 3J, more preferably 2.5J, still more preferably 2.2J, particularly preferably 2J in view of practicality. Since the impact resistance tends to decrease when the molecular weight of the whole is low, when the high molecular weight component is small, or when the molecular weight of the high molecular weight component is low, for example, when the low molecular weight component is large, The composition can be adjusted to within the range.

The haze of the stretched polypropylene laminated film of the present invention is an actual value and the lower limit is preferably 0.1%, more preferably 0.2%, still more preferably 0.3%, particularly preferably 0.4% Is 0.5%.

The upper limit of the haze is preferably 6%, more preferably 5%, still more preferably 4.5%, particularly preferably 4%, and most preferably 3.5%. If it is in the above range, it may be easy to use in applications requiring transparency. The haze tends to deteriorate when the drawing temperature and the heat fixing temperature are too high, when the cooling roll (CR) temperature is high and when the cooling rate is slow, and when the low molecular weight is too large. .

(Polypropylene resin)

The polypropylene resin constituting the base layer (A) of the stretched polypropylene laminated film of the present invention may be a homopolypropylene obtained only from a propylene monomer or a copolymer with a copolymerizable monomer in a very small amount. Examples of the copolymerizable monomer species include ethylene, butene, hexene, octene, and the like.

Additives and other resins may be added to the base material layer (A) of the present invention, if necessary, but it is preferably 30 wt% or less.

Examples of the additive include antioxidants, ultraviolet absorbers, antistatic agents, lubricants, nucleating agents, pressure-sensitive adhesives, antifogging agents, flame retardants, anti-blocking agents, inorganic or organic fillers, and the like. Examples of the other resin include polypropylene resins other than the polypropylene resin used in the present invention, random copolymers of propylene and a copolymer of? -Olefins having 4 or more carbon atoms such as ethylene, butene, hexene and octene, and various elastomers .

(Molecular weight distribution of polypropylene resin)

The polypropylene resin constituting the cavity-containing polypropylene film of the present invention mainly contains a low molecular weight component having a mass average molecular weight (Mw) of about 100,000, for example, and has a Mw of about 1,500,000 or so And a high molecular weight component having a high molecular weight. It is considered that the crystallinity can be largely increased by mainly using a low molecular weight component and a stretched polypropylene film of high rigidity and high heat resistance which is not available in the past can be obtained. On the other hand, a low-molecular-weight polypropylene resin has a low melt tension in the case of heat softening, and generally can not be a stretched film. The presence of a high molecular weight component in an amount of several percent to several tens of percent enables the stretching, and the high molecular weight component serves as a crystal nucleus, further enhancing the crystallinity of the film, and the effect of the stretched polypropylene laminated film of the present invention Is achieved.

As an index showing such a molecular weight distribution, it is preferable that (Mz + 1) / Mn, which is the ratio of Z + 1 average molecular weight (Mz + 1) and number average molecular weight (Mn), which is an average molecular weight with emphasis on high molecular weight components, is preferable.

The lower limit of Mz + 1 / Mn is preferably 50, more preferably 60, still more preferably 70, particularly preferably 80, and most preferably 90. If it is less than the above range, the effect of the present invention, such as a low heat shrinkage at a high temperature, may not be obtained.

The upper limit of Mz + 1 / Mn is preferably 300, more preferably 200. If it exceeds the above range, it may become difficult to produce a realistic resin.

When the polypropylene resin having the molecular weight distribution is represented by a mass average molecular weight (Mw) / number average molecular weight (Mn), which is an index of the width of the molecular weight distribution, the value naturally becomes large. The lower limit of Mw / Is 5.5, more preferably 6, more preferably 6.5, particularly preferably 7, and most preferably 7.2.

The upper limit of the Mw / Mn is preferably 30, more preferably 25, still more preferably 20, particularly preferably 15, and most preferably 13. These average molecular weights can be obtained by measuring using gel permeation chromatography (GPC).

The lower limit of Mz + 1 of the entire polypropylene resin constituting the substrate layer (A) of the present invention by GPC is preferably 2,500,000, more preferably 3,000,000, further preferably 3,300,000, particularly preferably 3,500,000 And most preferably 3700000. Within this range, high molecular weight components are sufficient, and the effect of the present invention is easily obtained.

The upper limit of the total Mz + 1 is preferably 40,000,000, more preferably 35,000,000, and still more preferably 30,000,000. In the above range, it is easy to produce a realistic resin, easy drawing, or a decrease in the number of fish eyes in the film.

The lower limit of the Mn obtained by GPC of the entire polypropylene resin constituting the base layer (A) of the present invention is preferably 20,000, more preferably 22,000, even more preferably 24,000, even more preferably 26,000, Most preferably 27,000. In the above range, there is an advantage that the stretching becomes easy, the thickness unevenness becomes small, the stretching temperature and the heat fixing temperature are easily increased, and the heat shrinkage rate is lowered.

The upper limit of the total Mn is preferably 65,000, more preferably 60,000, still more preferably 55,000, particularly preferably 53,000, and most preferably 52,000. Within this range, the effect of the present invention such as a low heat shrinkage rate at a high temperature, which is an effect of a low molecular weight water, is likely to be obtained, or stretching may be facilitated.

The lower limit of the mass average molecular weight (Mw) obtained by GPC of the entire polypropylene resin constituting the substrate layer (A) of the present invention is preferably 250000, more preferably 260000, still more preferably 270000, and particularly preferably , And most preferably 290000. In the above range, there is an advantage that the stretching becomes easy, the thickness unevenness becomes small, the stretching temperature and the heat fixing temperature are easily increased, and the heat shrinkage rate is lowered.

The upper limit of the total Mw is preferably 500000, more preferably 450000, further preferably 400000, particularly preferably 380000, and most preferably 370000. When the amount is in the above range, the mechanical load is small and the drawing may be facilitated.

The lower limit of the melt flow rate (MFR) (230 DEG C, 2.16 kgf) of the entire polypropylene resin constituting the substrate layer (A) of the present invention is preferably 1 g / 10 min, more preferably 1.2 g / 10 min Preferably 1.4 g / 10 min, particularly preferably 1.5 g / 10 min, and most preferably 1.6 g / 10 min. If it is in the above range, the mechanical load is small and the drawing may be facilitated.

The upper limit of the total MFR is preferably 20 g / 10 min, more preferably 17 g / 10 min, still more preferably 15 g / 10 min, particularly preferably 14 g / 10 min, and most preferably 13 g / 10 min. In the above range, stretching is facilitated, thickness irregularity is reduced, stretching temperature and heat fixing temperature are likely to rise, and the heat shrinkage ratio may be lowered.

When the GPC integrated curves of the entire polypropylene resin constituting the film are measured, the lower limit of the amount of the component having a molecular weight of 100,000 or less is preferably 35% by mass, more preferably 38% by mass, still more preferably 40% %, Particularly preferably 41 mass%, and most preferably 42 mass%. Within this range, the effect of the present invention such as a low heat shrinkage rate at a high temperature, which is an effect of a low molecular weight water, is likely to be obtained, or stretching may be facilitated.

The upper limit of the amount of the component having a molecular weight of 100,000 or less is preferably 65% by mass, more preferably 60% by mass, still more preferably 58% by mass, particularly preferably 56% by mass, and most preferably 55% Mass%.

A molecule having a molecular weight of about 10,000 or less has an effect of solving entanglement between molecules without contributing to the entanglement of molecular chains, and therefore it is preferable that the amount of the component having a molecular weight of 10,000 or less is included in a specific amount. As a result, stretching at a low stretching stress becomes possible, and as a result, the residual stress is low, and it is considered that the shrinkage ratio at a high temperature can be lowered.

The lower limit of the amount of the component having a molecular weight of 10,000 or less is preferably 2% by mass, more preferably 2.5% by mass, still more preferably 3% by mass, particularly preferably 3.3% by mass, and most preferably 3.5% Mass%.

The upper limit of the amount of the component having a molecular weight of 10,000 or less in the GPC integrated curve is preferably 20% by mass, more preferably 17% by mass, still more preferably 15% by mass, still more preferably 14% Most preferably 13% by mass.

The high molecular weight component and the low molecular weight component suitable for forming the polypropylene resin having such a molecular weight distribution characteristic are described, but the means for expanding the molecular weight distribution is not limited thereto.

(High molecular weight component)

The lower limit of the MFR (230 DEG C, 2.16 kgf) of the high molecular weight component is preferably 0.0001 g / 10 min, more preferably 0.0005 g / 10 min, still more preferably 0.001 g / 10 min, particularly preferably 0.005 g / 10 min. In the above range, it is possible to easily manufacture the resin in reality or to reduce the fish eyes of the film.

In addition, the MFR of the high molecular weight component at 230 DEG C and 2.16 kgf is too small, which may make realistic measurement difficult. The lower limit is preferably 0.1 g / 10 min, more preferably 0.5 g / 10 min, still more preferably 1 g / 10 min, and particularly preferably 5 g / 10 min, in MFR at 10 times the weight (21.6 kgf) .

The upper limit of the MFR of the high molecular weight component is preferably 0.5 g / 10 min, more preferably 0.35 g / 10 min, still more preferably 0.3 g / 10 min, particularly preferably 0.2 g / 10 min, Is 0.1 g / 10 min. In the above range, the amount of a large amount of polymer components is not required to maintain the MFR of the whole, and the effect of the present invention such as a low heat shrinkage at a high temperature, which is an effect of a low molecular weight water, may be more easily obtained.

The lower limit of the Mw of the high molecular weight component is preferably 500000, more preferably 600000, still more preferably 700000, particularly preferably 800000, and most preferably 1000000. In the above range, the amount of a large amount of polymer components is not required to maintain the MFR of the whole, and the effect of the present invention such as a low heat shrinkage at a high temperature, which is an effect of a low molecular weight water, may be more easily obtained.

The upper limit of the Mw of the high molecular weight component is preferably 10,000,000, more preferably 800,000, still more preferably 6,000,000, and particularly preferably 5,000,000. In the above range, it is possible to easily manufacture the resin in reality or to reduce the fish eyes of the film.

The lower limit of the amount of the high molecular weight component is preferably 2% by mass, more preferably 3% by mass, still more preferably 4% by mass, and particularly preferably 5% by mass. In the above range, it is not necessary to increase the molecular weight of the low molecular weight material in order to maintain the total MFR, and the effect of the present invention such as a low heat shrinkage rate at high temperature may be more easily obtained.

The upper limit of the amount of the high molecular weight component is preferably 30% by mass, more preferably 25% by mass, still more preferably 22% by mass, and particularly preferably 20% by mass. Within the above range, the effect of the present invention such as a low heat shrinkage at a high temperature, which is an effect of a low molecular weight water, may be more easily obtained.

Here, instead of a straight-chain polypropylene resin, a polypropylene resin having a long-chain branching or crosslinking structure may be used as the high-molecular-weight component. The polypropylene resin may be a polypropylene resin such as polypropylene manufactured by Borealis (Daploy) WB130HMS, and WB135HMS.

(Low molecular weight component)

The lower limit of the MFR (230 占 폚, 2.16 kgf) of the low molecular weight component is preferably 70 g / 10 min, more preferably 80 g / 10 min, still more preferably 100 g / 10 min and particularly preferably 150 g / Most preferably 200 g / 10 min. In the above range, the crystallinity is improved and the effect of the present invention such as a low heat shrinkage rate at high temperature is more likely to be obtained.

The upper limit of the MFR of the low molecular weight component is preferably 2000 g / 10 min, more preferably 1800 g / 10 min, still more preferably 1600 g / 10 min, particularly preferably 1500 g / 10 min, to be. When the content is in the above range, the MFR of the whole can be easily maintained, and the film-forming property is sometimes excellent.

The lower limit of the Mw of the low molecular weight component is preferably 50,000, more preferably 53,000, still more preferably 55,000, particularly preferably 60000, and most preferably 70000. When the content is in the above range, the MFR of the whole can be easily maintained, and the film-forming property is sometimes excellent.

The upper limit of the Mw of the low molecular weight component is preferably 150000, more preferably 1400000, still more preferably 1300000, particularly preferably 120000, and most preferably 1100000. In the above range, the crystallinity is improved and the effect of the present invention such as a low heat shrinkage rate at high temperature is more likely to be obtained.

The lower limit of the amount of the low molecular weight component is preferably 40% by mass, more preferably 50% by mass, still more preferably 55% by mass, and particularly preferably 60% by mass. Within the above range, the effect of the present invention such as a low heat shrinkage at a high temperature, which is an effect of a low molecular weight water, may be more easily obtained.

The upper limit of the amount of the low molecular weight component is preferably 98% by mass, more preferably 97% by mass, still more preferably 96% by mass, and particularly preferably 95% by mass. In the above range, it is not necessary to increase the molecular weight of the low molecular weight material in order to maintain the total MFR, and the effect of the present invention such as a low heat shrinkage rate at high temperature may be more easily obtained.

The lower limit of the MFR ratio of the low molecular weight component to the MFR ratio of the high molecular weight component is preferably 500, more preferably 1000, still more preferably 2000, still more preferably 4000. Within this range, the effect of the present invention such as a low heat shrinkage rate at a high temperature may be more easily obtained.

The upper limit of the MFR ratio of the low molecular weight component to the MFR / high molecular weight component is preferably 1,000,000.

The high molecular weight component and the low molecular weight component may be a mixture of two or more resins corresponding to the respective components, and the blending amount in that case is the total amount.

In addition to the high molecular weight component and the low molecular weight component in the above range, a component having a molecular weight other than the low molecular weight component or high molecular weight component of the present invention may be added to adjust the MFR as the whole polypropylene resin, A polypropylene resin having a molecular weight of not more than 30,000, particularly not more than 10,000, and a molecular weight of not more than 10,000, may be added to adjust the stretchability and the like.

In order to obtain a desired molecular weight distribution of the polypropylene resin by using a high molecular weight component and a low molecular weight component, for example, when the molecular weight of the low molecular weight component used is a little low, the molecular weight of the high molecular weight component may be increased, It is possible to adjust the distribution state by increasing the amount and adjust the MFR to be easy to manufacture as a stretched film.

(Regularity of polypropylene resin)

The lower limit of the mesopentad fraction ([mmmm]%) of the polypropylene resin constituting the substrate layer (A) of the present invention is preferably 96%, more preferably 96.5% 97%. When the amount is in the above range, the crystallinity is improved and the heat shrinkage rate at high temperature may be lowered.

The upper limit of the meso pentad fraction ([mmmm]%) is preferably 99.5%, more preferably 99.3%, still more preferably 99%. If it is within the above range, it may be easy to realize realistic production.

In the polypropylene resin constituting the substrate layer (A) of the present invention, it is preferable that heterogeneous bonds such as head-to-head bonding are not seen. Also, invisible here means that no peak is observed in < ¹³ > C-NMR.

The lower limit of the meso average chain length of the polypropylene resin constituting the substrate layer (A) of the present invention is preferably 100, more preferably 120, still more preferably 130. [ When the amount is in the above range, the crystallinity is improved and the heat shrinkage rate at high temperature is sometimes reduced.

The upper limit of the meso average chain length is preferably 5000 in practical terms.

The lower limit of the xylene-soluble fraction of the polypropylene resin constituting the base material layer (A) of the present invention is preferably 0.1% by mass in view of practicality.

The upper limit of the xylene-soluble component is preferably 7% by mass, more preferably 6% by mass, and still more preferably 5% by mass. When the amount is in the above range, the crystallinity is improved and the heat shrinkage rate at high temperature is sometimes reduced.

The polypropylene resin constituting the base layer (A) of the present invention is most preferably homopolypropylene completely homopolypropylene obtained only from propylene monomer, but may be a copolymer with a copolymerizable monomer if it is a very small amount. As the copolymerizable monomer species, ethylene and butene are preferable.

The upper limit of the amount of the copolymerizable monomer is preferably 0.1 mol%, more preferably 0.05 mol%, and still more preferably 0.01 mol%. When the amount is in the above range, the crystallinity is improved and the heat shrinkage rate at high temperature is sometimes reduced.

Further, since the fully homopolypropylene has a high crystallinity, but the range of conditions that can be stretched is very narrow such that the melt tension rapidly decreases after melt-softening, it is industrially difficult to form the film, and usually, about 0.5% Component (mainly ethylene) was added. However, in the polypropylene resin having a molecular weight distribution as described above, the tensile strength after melt-softening is mild even when almost no or no copolymerization components are present, and industrial stretching is possible.

In the present invention, the resin used for the heat seal layer (B) is preferably a low-melting propylene random copolymer having a melting point of 150 DEG C or lower or a propylene block copolymer containing an elastomer component, Can be used. As the comonomer, it is preferable to use at least one selected from ethylene or? -Olefins having 3 to 10 carbon atoms such as butene, pentene, hexene, octene, and decene.

The melting point of the propylene random copolymer forming the heat seal layer (B) is preferably 60 to 150 캜. Thereby, a sufficient heat seal strength can be imparted to the stretched polypropylene type resin laminated film. If the melting point of the propylene random copolymer forming the heat seal layer (B) is less than 60 占 폚, heat resistance of the heat seal portion is insufficient, and if it exceeds 150 占 폚, improvement in heat seal strength can not be expected. The melting point of the elastomer component contained in the propylene block copolymer is also preferably 150 캜 or lower.

The MFR is in the range of 0.1 to 100 g / 10 min, preferably 0.5 to 20 g / 10 min, and more preferably 1.0 to 10 g / 10 min.

(Production method of polypropylene resin)

Polypropylene is obtained by polymerizing propylene as a raw material by using a known catalyst such as a Ziegler · Natta catalyst or a metallocene catalyst. Among them, it is preferable to use a Ziegler-Natta catalyst and a catalyst capable of polymerization with high regularity in order to eliminate heterogeneous bonds.

The polymerization of propylene may be carried out by any known method. Examples of the method include polymerization in an inert solvent such as hexane, heptane, toluene and xylene, polymerization in liquid propylene or ethylene, addition of a catalyst in gaseous propylene or ethylene, A method of polymerizing in the presence of a catalyst, or a method of polymerizing these in combination.

The high molecular weight component and the low molecular weight component may be separately polymerized and then mixed, or may be produced in a series of plants using a multi-stage reactor. Particularly, it is preferable to use a plant having a multistage reactor to polymerize a high molecular weight component first and then polymerize a low molecular weight component in the presence of the high molecular weight component.

(additive)

Additives and other resins may be added to the resin composition for film molding of the present invention, if necessary. Examples of the additive include antioxidants, ultraviolet absorbers, antistatic agents, lubricants, nucleating agents, pressure-sensitive adhesives, antifogging agents, flame retardants, anti-blocking agents, inorganic or organic fillers, and the like. Examples of the other resin include a polypropylene resin other than the polypropylene resin used in the present invention, a random copolymer of propylene and a copolymer of ethylene and / or an? -Olefin having 4 or more carbon atoms, and various elastomers. These may be blended with polypropylene resin and Henschel mixer, or master pellets prepared by using a melt kneader in advance may be diluted with polypropylene so as to have a predetermined concentration, or may be melt-kneaded in advance.

By using the polypropylene resin having such a characteristic molecular weight distribution in the base layer (A), it is possible to stretch a polypropylene mainly composed of a low molecular weight which has not been sufficiently stretched in the past, and employs a high heat setting temperature And it is considered that the heat shrinkage rate at high temperature can be lowered by the synergy effect of high crystallinity and strong heat setting.

(Film properties)

When the heat sealable polypropylene laminated stretched film of the present invention is a biaxially stretched film, the lower limit of the Young's modulus (23 DEG C) in the MD direction is preferably 1.8 GPa, more preferably 1.9 GPa, still more preferably 2.0 GPa, particularly preferably 2.1 GPa, and most preferably 2.2 GPa.

The upper limit of the Young's modulus in the MD direction is preferably 3.7 GPa, more preferably 3.6 GPa, still more preferably 3.5 GPa, particularly preferably 3.4 GPa, and most preferably 3.3 GPa. In the above-mentioned range, it is easy to make the actual production, or the MD-TD balance may be improved.

When the heat-sealable polypropylene laminated stretched film of the present invention is a biaxially stretched film, the lower limit of the Young's modulus (23 DEG C) in the TD direction is preferably 3.7 GPa, more preferably 3.8 GPa, still more preferably 3.9 GPa, and particularly preferably 4.0 GPa.

The upper limit of the Young's modulus in the TD direction is preferably 8 GPa, more preferably 7.5 GPa, further preferably 7 GPa, and particularly preferably 6.5 GPa. In the above-mentioned range, it is easy to make the actual production, or the MD-TD balance may be improved.

The Young's modulus can be increased by increasing the draw ratio. In the case of MD-TD draw, the Young's modulus in the TD direction can be increased by setting the MD draw magnification to a little lower and increasing the TD draw magnification.

The lower limit of the thickness uniformity of the stretched polypropylene laminated film of the present invention is preferably 0%, more preferably 0.1%, still more preferably 0.5%, and particularly preferably 1%.

The upper limit of the thickness uniformity is preferably 20%, more preferably 17%, still more preferably 15%, particularly preferably 12%, and most preferably 10%. Within the above range, defects are unlikely to occur at the time of subsequent processing such as coating or printing, and therefore, it is easy to use for applications requiring precision.

(Production method of polypropylene film)

The stretched polypropylene laminated film of the present invention may be a monoaxially stretched film in the longitudinal direction (MD direction) or the transverse direction (TD direction), but is preferably a biaxially stretched film. In the case of biaxial stretching, sequential biaxial stretching or simultaneous biaxial stretching may be used.

By using the stretched film, it is possible to obtain a film having a low heat shrinkage even at 150 DEG C, which can not be expected in the conventional stretched polypropylene laminated film.

Hereinafter, a method for producing a longitudinally stretched-transversely stretched sequential biaxially stretched film, which is the most preferable example, will be described.

First, the substrate layer (A) is melt-extruded from one extruder, and the heat-seal layer (B) is melt-extruded by the other extruder to form the polypropylene-based resin layer (A) (B), and cooled and solidified by a cooling roll to obtain an unoriented sheet. As the melt extrusion conditions, the resin temperature is 200 to 280 占 폚, extruded from a T-die into a sheet, and cooled and solidified by a cooling roll at a temperature of 10 to 100 占 폚. Subsequently, the film is stretched 3 to 7 times in the lengthwise direction (MD) by a stretching roll at 120 to 165 DEG C and then stretched in the width direction (TD) at a temperature of 155 DEG C to 175 DEG C, preferably 158 DEG C to 170 DEG C And stretching is performed 6 to 12 times.

Further, heat treatment is carried out while allowing a relaxation of 1 to 15% at an ambient temperature of 165 to 175 ° C, preferably 166 to 173 ° C.

If necessary, a rolled sample can be obtained by subjecting at least one surface to a corona discharge treatment and then winding it into a winder.

The lower limit of the draw ratio of the MD is preferably 3 times, and more preferably 3.5 times. If it is less than the above range, the film thickness may be uneven.

The upper limit of the draw ratio of the MD is preferably 8 times, and more preferably 7 times. If it exceeds the above range, TD stretching which is performed continuously may become difficult.

The lower limit of the stretching temperature of the MD is preferably 120 占 폚, more preferably 125 占 폚, and further preferably 130 占 폚. If it is less than the above range, the mechanical load may increase, the thickness unevenness may increase, or the surface roughness of the film may be generated.

The upper limit of the stretching temperature of the MD is preferably 160 占 폚, more preferably 155 占 폚, and still more preferably 150 占 폚. A higher temperature is preferable for lowering the heat shrinkage, but it may be impossible to attach to a roll and stretch.

The lower limit of the draw ratio of TD is preferably 4 times, more preferably 5 times, and more preferably 6 times. If it is less than the above range, the thickness may be uneven.

The upper limit of the TD stretching ratio is preferably 20 times, more preferably 17 times, and even more preferably 15 times. If it is more than the above range, the heat shrinkage ratio may be increased, or may be broken at the time of stretching.

The preheating temperature in the TD stretching is set to be 10 to 15 DEG C higher than the stretching temperature in order to rapidly increase the film temperature to near the stretching temperature.

TD stretching is performed at a temperature higher than that of a conventional heat sealable polypropylene laminated stretched film.

The lower limit of the stretching temperature of TD is preferably 157 占 폚, and more preferably 158 占 폚. If it is less than the above range, it may not sufficiently soften and break or the heat shrinkage ratio may increase.

The upper limit of the TD stretching temperature is preferably 170 占 폚, and more preferably 168 占 폚. In order to lower the heat shrinkage ratio, it is preferable that the temperature is high, but if it is higher than the above range, the low molecular component melts and recrystallizes, resulting in surface roughness and film whitening.

The stretched film is thermally fixed. The heat fixation can be performed at a higher temperature than the conventional polypropylene film. The lower limit of the heat setting temperature is preferably 165 占 폚, and more preferably 166 占 폚. If it is less than the above range, the heat shrinkage ratio may be increased. In addition, it takes a long time to lower the heat shrinkage rate, and productivity may be lowered.

The upper limit of the heat setting temperature is preferably 175 占 폚, and more preferably 173 占 폚. If it is more than the above range, the low-molecular component may melt and recrystallize, resulting in surface roughness or film whitening.

It is preferable to relax (relax) when the heat is fixed. The lower limit of the relaxation is preferably 2%, more preferably 3%. If it is less than the above range, the heat shrinkage ratio may be increased.

The upper limit of the relax is preferably 10%, more preferably 8%. If it is more than the above range, thickness unevenness may become large.

In addition, in order to lower the heat shrinkage ratio, the film produced in the above-described process may be once wound in a rolled state and then annealed off-line.

The lower limit of the offline annealing temperature is preferably 160 占 폚, more preferably 162 占 폚, and still more preferably 163 占 폚. If it is less than the above range, the effect of annealing may not be obtained.

The upper limit of the off-line anneal temperature is preferably 175 ° C, more preferably 174 ° C, and even more preferably 173 ° C. If it exceeds the above range, the transparency may be lowered or the thickness irregularity may be increased.

The lower limit of the offline annealing time is preferably 0.1 min, more preferably 0.5 min, and still more preferably 1 min. If it is less than the above range, the effect of annealing may not be obtained.

The upper limit of the off-line annealing time is preferably 30 minutes, more preferably 25 minutes, and further preferably 20 minutes. If it exceeds the above range, the productivity may be lowered.

The thickness of the film is set for each application. The lower limit of the film thickness is preferably 2 탆, more preferably 3 탆, and further preferably 4 탆. The upper limit of the film thickness is preferably 300 占 퐉, more preferably 250 占 퐉, further preferably 200 占 퐉, particularly preferably 100 占 퐉, and most preferably 50 占 퐉.

The thus obtained polypropylene film is generally formed into a roll having a width of 2000 to 12000 mm and a length of 1000 to 50000 m, and is wound into a roll. It is also provided as a slit roll having a width of 300 to 2000 mm and a length of 500 to 5000 m according to each application.

The stretched polypropylene laminated film of the present invention has excellent properties as described above.

When used as a packaging film, it is highly rigid and can be made thinner, thereby reducing cost and weight.

Further, since the heat resistance is high, it becomes possible to dry at a high temperature during drying of coating or printing, and it is possible to use a coating agent, an ink, a laminate adhesive or the like which has been difficult to be used conventionally. There is no need for a laminating process using an organic solvent or the like. Therefore, it is economically advantageous in terms of the effect on the global environment.

Example

Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to these examples. The method of measuring the physical properties in the examples is as follows.

1) melt flow rate (MFR, g / 10 min)

Measurement was made at a temperature of 230 캜 according to JIS K 7210.

2) Molecular weight and molecular weight distribution

Molecular weight and molecular weight distribution were determined by mono-dispersed polystyrene standards using gel permeation chromatography (GPC).

The column and solvent used in the GPC measurement are as follows.

Solvent: 1,2,4-trichlorobenzene

Column: TSKgel GMH _HR- H (20) HT 3

Flow rate: 1.0 ml / min

Detector: RI

Measuring temperature: 140 ° C

The number average molecular weight (Mn), the weight average molecular weight (Mw) and the average molecular weight of Z + 1 (Mz + 1) were calculated from the molecular number (Ni) of the molecular weight (Mi) at each elution position of the GPC curve obtained through the molecular weight calibration curve Is defined by the following equation.

Number average molecular weight: Mn =? (Ni 占)) /? Ni

The weight average molecular weight: Mw = Σ (Ni · Mi 2) / Σ (Ni · Mi)

Z + 1-average molecular weight: Mz + 1 = Σ (Ni · Mi 4) / Σ (Ni · Mi 3)

Molecular weight distribution: Mw / Mn, Mz + 1 / Mn

The molecular weight at the peak position of the GPC curve was defined as Mp.

When the baseline is not clear, the baseline is set in a range from the elution peak on the high molecular weight side closest to the elution peak of the reference material to the lowest position of the flat region on the high molecular weight side.

From the obtained GPC curve, peak separation was performed with two or more components having different molecular weights. The molecular weight distribution of each component was assumed to be Mw / Mn = 4, assuming a Gaussian function, to be the same as the normal molecular weight distribution of polypropylene. From the curves of the respective components obtained, the respective average molecular weights were calculated.

3) Stereoregularity

The measurement of the meso pentad fraction ([mmmm]%) and the meso average chain length was carried out by using ¹³ C-NMR. The meso pentad fraction was measured according to the method described in Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973), and the meso average chain length was determined according to JC Randall, Polymer Sequence Distribution, (Academic Press, New York). &Quot;

^{The 13} C-NMR measurement was carried out by dissolving 200 mg of a sample in a mixture of o-dichlorobenzene and 8: 2 of heptane at 135 占 폚 using AVANCE 500 manufactured by BRUKER, .

4) Cold xylene soluble part (CXS, mass%)

1 g of the polypropylene sample was dissolved in 200 ml of boiling xylene, allowed to cool, and recrystallized in a constant temperature water bath at 20 ° C for 1 hour. The ratio of the mass dissolved in the filtrate to the original sample amount was CXS (mass%) .

5) Heat shrinkage (%)

And measured according to JIS Z 1712.

(The stretched film was cut in MD and TD directions with a width of 20 mm and a length of 200 mm, and each was suspended in a hot air oven at 150 ° C. for 5 minutes.) The length after heating was measured and the shrinked length The heat shrinkage ratio was calculated as a ratio.

6) Impact resistance

The film was measured at 23 占 폚 using an Impact Tester manufactured by Toyo Seiki.

7) Young's modulus (unit: GPa)

Young's modulus in the MD and TD directions was measured at 23 캜 according to JIS K 7127.

8) Haze (Unit:%)

And measured according to JIS K 7105.

9) Heat seal strength

In the heat sealing temperature of 140 ℃, pressure 1kg / cm ^2, 1 second condition heat sealing time, the laminated stretched to overlap the side heat-sealed layer (B) between the film subjected to a hot plate seal, to prepare a test piece of 10mm width. The 180 degree peel strength of the test piece was measured to obtain a heat seal strength (N / 15 mm).

10) Curling

9), the degree of curl of the laminated stretched film of the film was visually measured.

○: No curl

△: slightly curl

X: remarkable curl

11) Thickness variation

A square sample having a length of 1 m was cut out from the wound film roll and divided into 10 pieces in the MD direction and 100 pieces in the TD direction, and 100 samples for measurement were prepared. The thickness of the measurement sample was measured with a contact type film thickness meter at almost the center of the sample.

The obtained average value of the data of 100 points was obtained, and the difference between the minimum value and the maximum value was obtained, and the value obtained by dividing the absolute value of the difference between the minimum value and the maximum value by the average value was regarded as the thickness unevenness of the film.

12) Heat seal appearance

The produced film was piled up with Pyrene Film-CT1128 manufactured by Toyo Boseki Kabushiki Kaisha, and heat sealing was carried out by using a test sealer manufactured by Seibu Kagaku Kikai Co., Ltd. for 1 second at 170 캜 under a load of 2 kg. The state of change of the appearance due to shrinkage of the film after heat sealing was evaluated by visual observation. ?, The amount of deformation of the heat-sealed portion was small, and the range of not affecting the use was?, The shrinkage due to the heat seal was large and the deformation amount was large.

(Example 1)

Propylene homopolymer having a Mw / Mn ratio of 7.7, Mz + 1 / Mn of 140, MFR of 5.0, and [mmmm] of 97.3% as a polypropylene resin was used as a first extruder by using two melt extruders Ethylene-butene random copolymer (Pr-Et-Bu) having a density of 0.89 g / cm ³ and an MFR (density of 0.89 g / cm ³ ) was used as the base layer (A) Propylene-butene random copolymer (Pr-Bu) (density: 0.89 g / cm ³ , MFR: 9.0 g / 10 min, melting point: 130 ° C) in an amount of 15% by weight (A) and the heat seal layer (B) in this order to form the base layer (A) / heat seal layer (B) in the die as a heat seal layer Co-extruded from a T-die at 250 占 폚 into a sheet, cooled and solidified by a cooling roll at 30 占 폚, stretched 4.5 times in the longitudinal direction at 135 占 폚, and then both ends were inserted into a clip, Yes at 170 ℃ After eleven times, the film was stretched 8.2 times in the transverse direction at 160 DEG C, and then heat-treated at 168 DEG C with 6.7% relaxation. Thereafter, one side of the film was subjected to corona treatment and wound into a winder. The thus obtained film had a thickness of 20 占 퐉, and a layered stretched film having a base layer and a heat-seal layer of thicknesses of 18 占 퐉 and 2 占 퐉, respectively, was obtained in this order. As shown in Table 1, Table 2 and Table 3, the obtained laminated stretched film satisfied the requirements of the present invention, had a low heat shrinkage ratio, had a sufficient heat seal strength, a sense of urgency and lubrication.

(Example 2)

10 parts by weight of low molecular weight polypropylene (high wax "NP105" manufactured by Mitsui Chemicals, Inc.) having a molecular weight of 10000 and 90 parts by weight of "SA4L" were added to the base layer (A) to make 100 parts by weight, Thereafter, the mixture was melt-kneaded with a 30 mm twin-screw extruder to obtain pellets of the mixture. Using this pellet as the base layer (A), a laminated film was obtained in the same manner as in Example 1. The physical properties of the obtained film are shown in Tables 1, 2 and 3.

(Example 3)

A laminated film was obtained in the same manner as in Example 1 except that the preheating temperature in the transverse stretching was 173 deg. C, and the stretching temperature and the heat treatment temperature were 167 deg. The physical properties of the obtained film are shown in Tables 1, 2 and 3.

(Example 4)

A laminated film was obtained in the same manner as in Example 2 except that the film was stretched 5.5 times in the longitudinal direction and 12 times in the transverse direction. The physical properties of the obtained film are shown in Tables 1, 2 and 3.

(Example 5)

Using the laminated film produced in Example 1, heat treatment was performed at 170 占 폚 for 5 minutes in a tenter-type hot air oven. The physical properties of the obtained film are shown in Tables 1, 2 and 3.

(Example 6)

A polypropylene homopolymer having a Mw / Mn ratio of 8.9, Mz + 1 / Mn = 110, MFR = 3.0 g / 10 min and a meso pentad fraction [mmmm] = 97.1% Quot; HU300 " manufactured by Total Co., Ltd.) was used, and the preheating temperature for transverse stretching was 171 DEG C and the heat treatment temperature after transversely stretching was 170 DEG C, a stretched polypropylene laminated film was obtained in the same manner as in Example 1. [ The obtained film had a thickness of 20 탆, and physical properties thereof were shown in Tables 1, 2 and 3.

(Comparative Example 1)

As the polypropylene resin, Sumitomo Blaren "FS2011DG3" (Mw / Mn = 4, Mz + 1 / Mn = 21, MFR = 2.5 g / 10 min, mmmm "= 97.0%, the amount of ethylene = 0.6 mol%), and the transverse stretching temperature was 168 ° C., the stretching temperature was 155 ° C., and the heat treatment temperature was 163 ° C. To obtain a laminated film. The physical properties of the obtained film are shown in Tables 1, 2 and 3.

(Comparative Example 2)

A laminated film was produced in the same manner as in Comparative Example 1 except that the preheating temperature was 171 캜, the stretching temperature was 160 캜, and the heat treatment temperature was 165 캜. The physical properties of the obtained film are shown in Tables 1, 2 and 3.

(Comparative Example 3)

As the polypropylene resin, a film was produced in the same manner as in Comparative Example 2, using a propylene homopolymer having MFR of 0.5 g / 10 min, Mw / Mn of 4.5, and Mz + 1 / Mn of 10 . The physical properties of the obtained film are shown in Tables 1, 2 and 3.

(Comparative Example 4)

In the base layer (A), biaxial orientation was attempted in the same manner as in Example 1 by using Novatech PP "SA03" (MFR = 30 g / 10 min) manufactured by Nippon Polypropylene Corporation as a polypropylene resin, It was broken at the transverse stretching to obtain a film.

Since the stretched polypropylene film of the present invention has high heat resistance, it can be dried at a high temperature during drying of the coating or printing, thereby remarkably contributing to the efficiency of the processing step. Further, it can be widely used for packaging use and industrial use. Since it is highly rigid, it can be thinned, and it is possible to reduce weight and cost.

Claims (3)

(A) composed mainly of a polypropylene resin and a polyolefin-based heat-seal layer (B) laminated on one side or both sides of the base layer, wherein the heat shrinkage ratio in the MD direction and the TD direction Is 10% or less, and the impact strength is 0.6 J or more. The oriented polypropylene laminated film according to claim 1, wherein the Young's modulus in the MD direction is 2.1 GPa or more and the Young's modulus in the TD direction is 3.7 GPa or more. The stretched polypropylene laminated film according to claim 1 or 2, wherein the polyolefin-based heat seal resin (B) comprises a propylene random copolymer and / or a propylene block copolymer.