WO2022091548A1 - Propylene-based polymer composition, biaxially stretched film, method for manufacturing biaxially stretched film, and packaging bag - Google Patents

Abstract

The present invention addresses the problem of providing a propylene-based polymer composition with which it is possible to manufacture a biaxially stretched film that has a higher Young's modulus than in the prior art and that has a lower heating shrinkage rate than in the prior art.　A propylene-based polymer composition containing a propylene-based polymer and a β crystal nucleating agent, wherein the melt flow rate measured at a temperature of 230°C and under a load of 21.18 N is 1 to 5 g/10 min, the amount of cold xylene soluble matter is 0.1-1.0 mass%, and the concentration of the β crystal nucleating agent is100 mass ppm or more and less than 500 mass ppm.

Description

Propylene-based polymer composition, biaxially stretched film, method for producing biaxially stretched film, and packaging bag.

The present invention used a propylene-based polymer composition containing a propylene-based polymer, a biaxially stretched film using the propylene-based polymer composition, a method for producing the biaxially stretched film, and the biaxially stretched film. Regarding packaging bags.

Conventionally, for example, as a film used as various packaging materials, a polyethylene terephthalate-based biaxially stretched film is used as a base film, and a polypropylene-based non-stretched film or a polyethylene-based non-stretched film is laminated as a sealant film on the base film. Is known. The film having such a structure can exhibit excellent functions as various packaging bags because the base film has high rigidity and high heat resistance and the sealant film has heat sealing property at low temperature. It has become.

In recent years, there has been an increasing demand for recycling of this type of film, and there is a demand for monomaterialization. Specifically, it is preferable to use a polypropylene-based biaxially stretched film, which is an olefin-based resin of the same type as a sealant film composed of an olefin-based resin such as polypropylene or polyethylene, as a base film.

However, the polypropylene-based biaxially stretched film has a lower tensile elastic modulus (Young's modulus) than the polyethylene terephthalate-based biaxially stretched film and the like. Therefore, a film using a polypropylene-based biaxially stretched film as a base film has a problem that its use is limited.

As a polypropylene-based biaxially stretched film having an improved tensile elastic modulus (Young's modulus), the film described in Patent Document 1 below is conventionally known. Specifically, Patent Document 1 describes a tensile elastic modulus (Young's modulus) by forming a biaxially stretched film using a propylene-based polymer composition containing a propylene-based polymer and a β-crystal nucleating agent. Methods for improvement are disclosed.

However, the polypropylene-based biaxially stretched film described in Patent Document 1 has a direction intersecting the flow direction at the time of manufacture (hereinafter, also referred to as "MD direction") (hereinafter, also referred to as "TD direction"). It cannot be said that the heat shrinkage rate of the above is sufficiently low.

Japanese Unexamined Patent Publication No. 2016-199686

The present invention is a propylene-based polymer composition capable of producing a biaxially stretched film having a relatively high tensile elastic modulus (Young's modulus) and a relatively low heat shrinkage in the TD direction, the propylene-based polymer composition. It is an object of the present invention to provide a biaxially stretched film using an article and a packaging bag using the biaxially stretched film.

The propylene-based polymer composition according to the present invention is
A propylene-based polymer composition containing a propylene-based polymer and a β-crystal nucleating agent.
The melt flow rate measured at a temperature of 230 ° C. and a load of 21.18 N is 1 g / 10 minutes to 5 g / 10 minutes.
The amount of the soluble part of cold xylene is 0.1% by mass to 1.0% by mass,
The concentration of the β crystal nucleating agent is 100 mass ppm or more and less than 500 mass ppm.

The biaxially stretched film according to the present invention contains the above-mentioned propylene-based polymer composition.

The biaxially stretched film according to the present invention is
A propylene-based polymer composition containing a propylene-based polymer and a β-crystal nucleating agent and satisfying the following requirements (1) and (2) is contained.
A biaxially stretched film that satisfies the following requirements (3) and (4).

(1) The melt flow rate measured at a temperature of 230 ° C. and a load of 21.18 N is 1 g / 10 minutes to 30 g / 10 minutes.
(2) The amount of the soluble part of cold xylene is 0.1% by mass to 1.0% by mass.
(3) The degree of orientation in the ND direction calculated from the birefringence is −0.30 or less.
(4) The difference between the degree of orientation in the MD direction and the degree of orientation in the TD direction calculated from the birefringence is 0.10 to 1.00.

The method for producing a biaxially stretched film according to the present invention is as follows.
An unstretched sheet is obtained by heating and melting a propylene-based polymer composition containing a propylene-based polymer and a β-crystal nucleating agent and satisfying the above requirements (1) and (2) and extruding it onto a cooling roll. Process and
A step of obtaining a uniaxially stretched film by multiplying the obtained unstretched sheet 3 to 12 times in the MD direction.
A step of obtaining a biaxially stretched film by stretching the obtained uniaxially stretched film 4 to 20 times in the TD direction and then relaxing by 1% to 30% in the TD direction.
It is a method for producing a biaxially stretched film including.

The packaging bag according to the present invention includes the above-mentioned biaxially stretched film.

According to the present invention, a propylene-based polymer composition capable of producing a biaxially stretched film having a relatively high tensile elastic modulus (Young's modulus) and a relatively low heat shrinkage in the TD direction, the propylene-based weight. A biaxially stretched film using the combined composition and a packaging bag using the biaxially stretched film can be provided.

The propylene-based polymer composition according to the present invention contains a propylene-based polymer and a β-crystal nucleating agent, and is a raw material for a biaxially stretched film.

<Propene polymer>
As the propylene-based polymer used in the present invention, for example, a propylene homopolymer or a propylene-based random copolymer can be used. The propylene-based polymer is preferably a propylene homopolymer from the viewpoint of relatively low heat shrinkage and relatively high rigidity of the obtained biaxially stretched film. When the propylene-based polymer used in the present invention is a propylene-based random copolymer, the propylene-based random copolymer is selected from, for example, propylene, ethylene, and an α-olefin having 4 to 20 carbon atoms. Examples thereof include those obtained by copolymerizing with at least one kind of copolymer.

Examples of α-olefins having 4 to 20 carbon atoms include 1-butene, 2-methyl-1-propene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, and 1-hexene. , 2-Ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1 -Buten, 1-hexene, methyl-1-hexene, dimethyl-1-pentene, ethyl-1-pentene, trimethyl-1-butene, methylethyl-1-butene, 1-octene, methyl-1-pentene, ethyl- 1-hexene, dimethyl-1-hexene, propyl-1-heptene, methylethyl-1-heptene, trimethyl-1-pentene, propyl-1-pentene, diethyl-1-butene, 1-nonen, 1-decene, 1 -Undesen, 1-Dodesen, etc. can be mentioned. The α-olefin is preferably 1-butene, 1-pentene, 1-hexene, or 1-octene, and more preferably 1-butene.

Examples of the propylene-based random copolymer used as the propylene-based polymer in the present invention include a propylene-ethylene random copolymer and a propylene-α-olefin random copolymer. Examples of the propylene-α-olefin random copolymer include a propylene-1-butene random copolymer, a propylene-1-hexene random copolymer, a propylene-1-octene random copolymer, and a propylene-ethylene-1-. Examples thereof include a butene random copolymer, a propylene-ethylene-1-hexene random copolymer, a propylene-ethylene-1-octene random copolymer and the like, preferably a propylene-ethylene random copolymer and a propylene-1-butene random. The copolymer is a propylene-ethylene-1-butene random copolymer.

When the propylene-based random copolymer used as the propylene-based polymer in the present invention is a propylene-ethylene random copolymer, the ethylene content relatively lowers the heat shrinkage rate of the obtained biaxially stretched film and at the same time, it makes the heat shrinkage rate of the obtained biaxially stretched film relatively low. From the viewpoint of relatively increasing the rigidity, it is preferably 2.0% by mass or less, more preferably 1.0% by mass or less, and further preferably 0.4% by mass or less.

When the propylene-based random copolymer used as the propylene-based polymer in the present invention is a propylene-α-olefin random copolymer, the α-olefin content is relatively high in the heat shrinkage rate of the obtained biaxially stretched film. From the viewpoint of lowering and relatively increasing the rigidity, it is preferably 8.0% by mass or less, more preferably 3.0% by mass or less, and further preferably 1.0% by mass or less.

When the propylene-based random copolymer used as the propylene-based polymer in the present invention is a propylene-ethylene-α-olefin random copolymer, the total content of ethylene and α-olefin is the obtained biaxially stretched film. From the viewpoint of relatively low heat shrinkage and relatively high rigidity, the amount is preferably 8.0% by mass or less, more preferably 3.0% by mass or less, still more preferably 1.0% by mass. % Or less.

The content of the propylene-based polymer in the propylene-based polymer composition is preferably 99.0% by mass to 99.9% by mass, more preferably 99.5% by mass to 99.9% by mass. , More preferably 99.7% by mass to 99.9% by mass.

The propylene-based polymer used in the present invention has a cold xylene-soluble portion (hereinafter abbreviated as CXS) in an amount of preferably 0.1% by mass to 1.0% by mass, more preferably 0.3% by mass. % To 1.0% by mass, more preferably 0.3% by mass to 0.8% by mass. By setting CXS in the above range, there is an effect that good stretchability can be exhibited and that the obtained biaxially stretched film can exhibit relatively high rigidity and relatively low shrinkage rate at a relatively high temperature. The CXS of the propylene-based polymer can be adjusted to the above range, for example, by selecting the type of external donor used in the polymerization of propylene. Specific examples of the external donor include cyclohexylethyldimethoxysilane, dicyclopentyldimethoxysilane, di-tert-butyldimethoxysilane, and the like.
In the present invention, CXS can be obtained by the method described in the following [Example].

The propylene-based polymer used in the present invention has a melt flow rate (hereinafter abbreviated as MFR) of preferably 1 g / 10 minutes to 5 g / 10 minutes, and more preferably 1.8 g / 10 minutes to 2. It is 8 g / 10 minutes, more preferably 2.2 g / 10 minutes to 2.8 g / 10 minutes. By using a propylene-based polymer having an MFR in the above range, polypropylene (hereinafter, also referred to as “PP”) has an appropriate viscosity when in a molten state, exhibits good stretchability, and is obtained. The biaxially stretched film has the effect of being able to exhibit relatively high rigidity and a relatively low shrinkage rate at a relatively high temperature. The MFR of the propylene-based polymer can be adjusted to the above range by, for example, adjusting the hydrogen concentration used during the polymerization of propylene to 0.04 mol% to 0.29 mol%.
In the present invention, MFR can be obtained by the method described in the following [Example].

The propylene-based polymer used in the present invention may contain a plurality of types of propylene-based polymers having different MFRs. As a preferred example, the propylene-based polymer is a propylene-based polymer (a) having an MFR of 0.1 g / 10 min to 3.0 g / 10 min and a propylene having an MFR of 10 g / 10 min to 200 g / 10 min. It can contain the system polymer (b).

The content of the propylene-based polymer (a) and the propylene-based polymer (b) in the propylene-based polymer composition is relative to the total content of the propylene-based polymer (a) and the propylene-based polymer (b). The propylene-based polymer (a) is preferably 50% by mass to 90% by mass, the propylene-based polymer (b) is preferably 10% by mass to 50% by mass, and the propylene-based polymer (a) is. It is more preferably 50% by mass to 85% by mass, and more preferably 15% by mass to 50% by mass of the propylene-based polymer (b). Since the propylene-based polymer composition according to the present invention contains a plurality of types of propylene-based polymers having different MFRs, thickness unevenness during stretching is reduced, good stretching processability is exhibited, and the obtained biaxial structure is exhibited. The stretched film has the effect of being able to exhibit relatively high rigidity and a relatively low shrinkage rate at a relatively high temperature.

The propylene-based polymer used in the present invention has an isotactic pentad fraction of preferably 97% to 99%, more preferably 98% to 99%. The isotactic pentad fraction of the propylene-based polymer can be adjusted to the above range, for example, by selecting the type of external donor used during the polymerization of propylene. Specific examples of the external donor include cyclohexylethyldimethoxysilane, dicyclopentyldimethoxysilane, di-tert-butyldimethoxysilane, and the like.

<Manufacturing of propylene polymer>
Examples of the method for producing the propylene-based polymer include known polymerization methods. For example, a solvent polymerization method performed in the presence of an inert solvent, a massive polymerization method performed in the presence of a liquid monomer, a gas phase polymerization method performed in the absence of a substantially liquid medium, and the like can be mentioned. A gas phase polymerization method is preferable. Further, a polymerization method in which two or more of the above polymerization methods are combined, a method of multi-stage polymerization of two or more stages, and the like can be mentioned.

As the catalyst used for the polymerization of the propylene-based polymer, a catalyst for stereoregular polymerization of propylene can be used in any of the above polymerization methods.

As the catalyst for stereoregular polymerization of propylene, for example, an organic aluminum compound or an organic aluminum compound is required as a solid catalyst component such as a titanium trichloride catalyst, a Ti-Mg-based catalyst containing titanium, magnesium, halogen, and an electron donor as essential components. Examples thereof include a catalyst in which a third component such as an electron donating compound is combined, a metallocene-based catalyst, and the like. It is preferably a catalyst in which a solid catalyst component containing magnesium, titanium, halogen and an electron donor as essential components, an organoaluminum compound and an electron donating compound are combined, and specific examples thereof include JP-A-61-218606. Examples thereof include catalysts described in JP-A-61-287904, JP-A-7-216017, JP-A-2004-182876 and the like.

<Β crystal nucleating agent>
The β-crystal nucleating agent refers to a compound capable of forming β-crystals having a hexagonal structure in a propylene-based polymer. The β-crystal nucleating agent is not particularly limited, and various conventionally known β-crystal nucleating agents can be used. For example, amide compounds typified by N, N'-dicyclohexyl-2,6-naphthalenedicarboxyamide, N, N'-dicyclohexylterephthalamide, N, N'-diphenylhexanediamide, tetraoxaspiryl compounds, quinacridone, etc. Kinacridone Kinacridones typified by quinone, iron oxide having a nanoscale size, calcium pimelliate, potassium 1,2-hydroxystearate, magnesium benzoate or magnesium succinate, carboxylic acid typified by magnesium phthalate, etc. Alkaline or alkaline earth metal salts, aromatic sulfonic acid compounds typified by sodium benzenesulfonate or sodium naphthalene sulfonate, diesters or triesters of di- or tribasic carboxylic acids, phthalocyanine blue, etc. A composition consisting of a phthalocyanine pigment, a two-component compound consisting of a component A which is an organic dibasic acid and a component B which is an oxide, a hydroxide or a salt of a Group IIA metal of the periodic table, a cyclic phosphorus compound and a magnesium compound. Items and the like may be mentioned, and one type or a mixture of two or more of these may be used. Among the above β crystal nucleating agents, the amide compounds N, N'-dicyclohexyl-2,6-naphthalene carboxamide, N, N'-dicyclohexylterephthalamide, N, N'-diphenylhexanediamide are preferable, and N, N'-Dicyclohexyl-2,6-naphthalenedicarboxamide is more preferred.

<Manufacturing method of propylene-based polymer composition>
Examples of the method for producing the propylene-based polymer composition include a method of melt-kneading the above-mentioned propylene-based polymer and a β-crystal nucleating agent. For example, a method of mixing a propylene-based polymer and a β-crystal nucleating agent with a ribbon blender, a Henschel mixer, a tumbler mixer or the like, and melting and kneading the mixture with an extruder or the like can be mentioned. Further, a masterbatch containing 1 to 10 parts by mass of the β crystal nucleating agent is prepared in advance with respect to 100 parts by mass of the propylene-based polymer, and the concentration of the β crystal nucleating agent in the propylene-based polymer composition becomes a predetermined value. As described above, a method of appropriately mixing the propylene-based polymer and the masterbatch of the β-crystal nucleating agent can also be mentioned. Further, when the propylene-based polymer containing the above-mentioned propylene-based polymer (a) and the propylene-based polymer (b) is used, the propylene-based polymer (a) and the propylene-based polymer (b) are individually melted. The propylene-based polymer (a) pelleted by kneading and pelletizing, the pelletized propylene-based polymer (b), and the masterbatch containing the β-crystal nucleating agent are mixed in the same manner as described above, and further, the above. A method of melt-kneading in the same manner as in the above can be mentioned. Further, after blending the pelletized propylene-based polymer (a) and the pelletized propylene-based polymer (b) with a dry blend or the like as described above, a masterbatch containing a β-crystal nucleating agent is directly used in a film processing machine. Examples thereof include a method of mixing and melting and kneading. Further, the pelletized propylene-based polymer (a), the pelletized propylene-based polymer (b), and the masterbatch containing the β-crystal nucleating agent are individually fed to the extruder of the film processing machine as described above. Examples thereof include a method of mixing and melt-kneading.

Further, when mixing the propylene-based polymer and the β-crystal nucleating agent, a stabilizer, a lubricant, an antistatic agent, an anti-blocking agent, various inorganic or organic fillers and the like may be added, if necessary.

The propylene-based polymer composition according to the present invention has an MFR of 1 g / 10 min to 5 g / 10 min, preferably 1.8 g / 10 min to 2.8 g / 10 min, and more preferably 2.2 g. It is / 10 minutes to 2.8 g / 10 minutes.
Further, the propylene-based polymer composition according to the present invention has a CXS of 0.1% by mass to 1.0% by mass, preferably 0.3% by mass to 1.0% by mass, and more preferably 0. .3% by mass to 0.8% by mass.
Further, in the propylene-based polymer composition according to the present invention, the concentration of the β crystal nucleating agent in the propylene-based polymer composition is 100 mass ppm or more and less than 500 mass ppm, preferably 250 mass ppm to 450 mass ppm. Yes, more preferably 250 mass ppm to 400 mass ppm.
The MFR of the propylene-based polymer composition can be adjusted to the above range by adjusting the MFR of the propylene-based polymer as described above. Further, the CXS of the propylene-based polymer composition can be adjusted to the above range by adjusting the CXS of the propylene-based polymer as described above.
The propylene-based polymer composition according to the present invention has an isotactic-pentad fraction of preferably 97% to 99%, more preferably 98% to 99%. The isotactic-pentad fraction of the propylene-based polymer composition can be adjusted to the above range by adjusting the isotactic-pentad fraction of the propylene-based polymer as described above.
Further, in the propylene-based polymer composition according to the present invention, the maximum meso-chain length of the propylene-based polymer is preferably 80 or more, more preferably 82 or more. The maximum meso-chain length of the propylene-based polymer was measured with the composition obtained by removing the β-crystal nucleating agent from the propylene-based polymer composition. Since most of the composition being measured is a propylene-based polymer, the measured value of the composition containing no β-crystal nucleating agent can be regarded as the measured value of the propylene-based polymer. The maximum meso-chain length of the propylene-based polymer can be determined, for example, by selecting the type of external donor used during the polymerization of propylene and / or by adjusting the hydrogen concentration to 0.04 mol% to 0.29 mol%. , Can be adjusted to the above range. Specific examples of the external donor include cyclohexylethyldimethoxysilane, dicyclopentyldimethoxysilane, di-tert-butyldimethoxysilane, and the like.
In the present invention, the maximum meso-chain length can be determined by the method described in the following [Example].

The propylene-based polymer composition according to the present invention has a Young's modulus in the TD direction (hereinafter, "" (Also referred to as “TD Young's modulus”) is relatively high, and the heat shrinkage rate in the TD direction (hereinafter, also referred to as “TD heat shrinkage rate”) is relatively low.

Specifically, the TD Young's modulus is increased by orienting the PP constituting the propylene-based polymer composition in the TD direction by stretching in the TD direction in the production of the biaxially stretched film.
On the other hand, since the heat shrinkage of the biaxially stretched film is considered to be caused by the orientation of the tie molecules (amorphous chains connecting the crystals) of PP, the TD heat shrinkage rate is that of the tie molecules (amorphous part) of PP. It becomes lower by reducing the ratio.

Here, the MFR of the propylene-based polymer composition is an index of the molecular weight of PP, and it is shown that the lower the MFR, the larger the molecular weight of PP, and the easier it is for PP to be oriented by stretching.
Since the propylene-based polymer composition according to the present invention has an MFR of 1 g / 10 minutes to 5 g / 10 minutes, PP is likely to be oriented in the TD direction due to stretching in the TD direction in the production of the biaxially stretched film. Therefore, a relatively high TD Young's modulus can be obtained for the obtained biaxially stretched film.
On the other hand, when the MFR is less than 1 g / 10 minutes, the molecular weight of PP is very large and the molecular chain of PP is too long, so that there is a high possibility that the molecular chain of one PP is contained in a plurality of crystals, and PP. It is considered that the proportion of tie molecules (amorphous part) in the above increases. Therefore, it is not possible to obtain a relatively low TD heat shrinkage rate for the obtained biaxially stretched film.
Further, when the MFR exceeds 5 g / 10 minutes, it is difficult for PP to be oriented in the TD direction, so that a relatively high TD Young's modulus cannot be obtained for the obtained biaxially stretched film.

Further, the CXS of the propylene-based polymer composition is an index of the crystallinity of PP, and the lower the CXS, the higher the crystallinity of the PP and the smaller the proportion of the tie molecule (amorphous portion) of the PP.
The propylene-based polymer composition according to the present invention has a CXS of 0.1% by mass to 1.0% by mass, a relatively small proportion of tie molecules (amorphous parts) in PP, and by stretching. PP tends to be oriented in the TD direction. Therefore, a relatively high TD Young's modulus and a relatively low TD heat shrinkage can be obtained for the obtained biaxially stretched film.
When CXS is less than 0.1% by mass, the crystallinity of PP is too high, the stretchability of PP is lowered, and it may not be possible to obtain a biaxially stretched film. Further, when CXS exceeds 1.0% by mass, the proportion of tie molecules (amorphous portions) of PP is too high, and a relatively low TD heat shrinkage rate cannot be obtained.

Further, when the propylene-based polymer composition according to the present invention contains a β-crystal nucleating agent, the melting point of the PP sheet before stretching formed from the propylene-based polymer composition can be lowered. When the crystal nucleating agent is not contained, α crystals (melting point of about 165 ° C.) are formed on the PP sheet. Since the oriented crystals responsible for the rigidity of the biaxially stretched film are α crystals, when the PP sheet is heated and stretched in the MD direction and the TD direction, the stretching temperature is limited to the melting temperature of the α crystals. .. Therefore, the α crystals in the PP sheet are stretched in a solid state, and the orientation of the amorphous portion is likely to occur. Therefore, the obtained biaxially stretched film tends to undergo heat shrinkage.
On the other hand, by containing the β crystal nucleating agent, β crystals (melting point of about 152 ° C.) are generated on the PP sheet before stretching. Since the β crystal has a lower melting point than the α crystal, the β crystal melts at a higher rate by stretching at a temperature equal to or higher than the melting point of the β crystal during stretching in the production of the biaxially stretched film. As a result, when the PP sheet is stretched while the β crystals are melted and the structure is changed to the oriented α crystals that bear the rigidity of the biaxially stretched film, the PP sheet is in a solid state as described above. The orientation of the amorphous part is less likely to occur as compared with the case of stretching. As a result, a relatively low TD heat shrinkage rate can be obtained for the obtained biaxially stretched film.
The propylene-based polymer composition according to the present invention has a β-crystal nucleating agent having a concentration of 100% by mass or more and less than 500% by mass, so that when a PP sheet before stretching is formed, β-crystals in the PP sheet are formed. The amount of production is appropriate. Therefore, a relatively low TD heat shrinkage rate can be obtained for the obtained biaxially stretched film.

As described above, the propylene-based polymer composition according to the present invention has an MFR of 1 g / 10 min to 5 g / 10 min, a CXS of 0.1 mass% to 1.0 mass%, and β crystal nuclei. When the concentration of the agent is 100 mass ppm or more and less than 500 mass ppm, it is possible to achieve both a relatively high TD Young's modulus and a relatively low TD heat shrinkage rate for the obtained biaxially stretched film.

Further, the propylene-based polymer composition according to the present invention has a higher TD Young's modulus and a lower TD heat shrinkage rate for the obtained biaxially stretched film because the isotactic pentad fraction is in the above range. Can be obtained.

Further, when the maximum meso-chain length of the propylene-based polymer is in the above range, a higher TD Young's modulus and a lower TD heat shrinkage can be obtained for the obtained biaxially stretched film.

<Biaxial stretched film>
Next, the biaxially stretched film according to the present invention will be described. The first form of the biaxially stretched film according to the present invention is the biaxially stretched film containing the above-mentioned propylene-based polymer composition according to the present invention.

The second form of the biaxially stretched film according to the present invention contains a propylene-based polymer and a β-crystal nucleating agent, and contains a propylene-based polymer composition satisfying the following requirements (1) and (2). , A biaxially stretched film satisfying the following requirements (3) and (4).

(1) The melt flow rate measured at a temperature of 230 ° C. and a load of 21.18 N is 1 g / 10 minutes to 30 g / 10 minutes.
(2) The amount of the soluble part of cold xylene is 0.1% by mass to 1.0% by mass.
(3) The degree of orientation in the ND direction calculated from the birefringence is −0.30 or less.
(4) The difference between the degree of orientation in the MD direction and the degree of orientation in the TD direction calculated from the birefringence is 0.10 to 1.00.

The MFR specified in the above requirement (1) is preferably 1 g / 10 minutes to 5 g / 10 minutes, more preferably 1.8 g / 10 minutes to 2.8 g / 10 minutes, and further preferably 2.2 g. / 10 minutes to 2.8 g / 10 minutes.
In the present invention, MFR can be obtained by the method described in the following [Example].

The CXS specified in the above requirement (2) is preferably 0.3% by mass to 1.0% by mass, and more preferably 0.3% by mass to 0.8% by mass.
In the present invention, CXS can be obtained by the method described in the following [Example].

The degree of orientation in the ND direction calculated from the birefringence specified in the above requirement (3) is preferably −0.5 to −0.3, and more preferably −0.4 to −0.3. ..
The degree of orientation in the ND direction calculated from the birefringence in the present invention can be determined by the method described in the following [Example].

The difference between the degree of orientation in the MD direction and the degree of orientation in the TD direction calculated from the birefringence specified in the above requirement (4) is preferably 0.10 to 0.70, and more preferably 0.40 to 0.40. It is 0.70.
In the present invention, the difference between the degree of orientation in the MD direction and the degree of orientation in the TD direction calculated from the birefringence can be obtained by the method described in the following [Example].

The concentration of the β crystal nucleating agent contained in the second form of the biaxially stretched film according to the present invention is preferably 100% by mass to 5000% by mass, more preferably 100% by mass or more and less than 500% by mass. It is more preferably 250 mass ppm to 450 mass ppm, and particularly preferably 250 mass ppm to 400 mass ppm.

The density of the biaxially stretched film according to the present invention is preferably 0.900 g / cm ³ to 0.912 g / cm ³ .
In the present invention, the density of the biaxially stretched film can be determined by the method described in the following [Example].

<Manufacturing of biaxially stretched film>
Next, a method for producing a biaxially stretched film using the propylene-based polymer composition according to the present invention will be described. As a method for producing such a biaxially stretched film, for example, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used.

In the method for producing a biaxially stretched film according to the present invention, a propylene-based polymer composition containing a propylene-based polymer and a β-crystal nucleating agent and satisfying the above requirements (1) and (2) is heated and melted. A step of obtaining an unstretched sheet by extruding it onto a cooling roll, a step of obtaining a uniaxially stretched film by multiplying the obtained unstretched sheet 3 to 12 times in the MD direction, and a step of obtaining the obtained uniaxially stretched film. A method for producing a biaxially stretched film, which comprises a step of obtaining a biaxially stretched film by stretching 4 to 20 times in the TD direction and then relaxing by 1% to 30% in the TD direction.

In the sequential biaxial stretching method, the propylene-based polymer composition is heated and melted using an extruder, extruded from a T-die onto a cooling roll, and cooled and fixed in the form of a sheet to cool and fix the unstretched sheet (the above PP sheet). ), And a step of obtaining a uniaxially stretched film by stretching the obtained unstretched sheet 3 to 12 times in the MD direction using a series of stretching rolls, and both sides of the obtained uniaxially stretched film. The end is grasped by two rows of chucks arranged along the MD direction, and the uniaxially stretched film is stretched 4 to 20 times in the TD direction in a heating furnace equipped with a preheating part, a stretching part, and a heat treatment part. A step of obtaining a biaxially stretched film by relaxing (relaxing) 1% to 30% in the TD direction, preferably 5% to 30% by narrowing the distance between the chucks in the two rows can be included. In addition, a step of performing corona treatment or the like may be included as needed.

In the sequential biaxial stretching method, the temperature at which the propylene-based polymer composition is heated and melted is preferably, for example, 230 ° C to 290 ° C. The temperature of the cooling roll is preferably, for example, 10 ° C to 60 ° C. The temperature of the stretched roll when the unstretched sheet is stretched in the MD direction is preferably 110 ° C. to 165 ° C., more preferably 110 ° C. to 150 ° C. The heating temperature for stretching the uniaxially stretched film in the TD direction is preferably 150 ° C. to 200 ° C., and the heating temperature for relaxing in the TD direction is preferably 150 ° C. to 200 ° C.

On the other hand, in the simultaneous biaxial stretching method, the polypropylene-based polymer composition is heated and melted using an extruder, extruded from a T-die onto a cooling roll, and cooled and fixed in the form of a sheet to cool and fix the unstretched sheet (the above-mentioned). The above-mentioned step of obtaining a PP sheet) and grasping both ends of the obtained unstretched sheet with two rows of chucks arranged along the MD direction in a heating furnace provided with a preheating part, a stretching part, and a heat treatment part. By widening the distance between the two rows of chucks in the TD direction and the distance between the individual chucks in each row in the MD direction, the unstretched sheet can be increased 3 to 12 times in the MD direction and 4 to 20 times in the TD direction. Can also include a step of simultaneously stretching and then relaxing by 1% to 30%, preferably 5% to 30% in the TD direction to obtain a biaxially stretched film. In addition, a step of performing corona treatment or the like may be included as needed.
The temperature of heating and melting in the simultaneous biaxial stretching method, the temperature of the cooling roll, and the heating temperature at the time of stretching can be the same as each condition in the above-mentioned sequential biaxial stretching method.

In the sequential biaxial stretching method and the simultaneous biaxial stretching method, the relaxation rate when relaxing the film is 1% or more (preferably 5% or more, more preferably 15% or more) as described above, and thus heat shrinkage. A biaxially stretched film having a relatively low rate and excellent heat resistance can be obtained. Further, when the relaxation rate is 30% or less (preferably 25% or less) as described above, unevenness in the thickness of the film can be suppressed.

In the present invention, the relaxation rate R is obtained by the following formula (1').

R = (L1-L2) / L1 × 100 (1')
(In the formula, L1 indicates the distance between the chucks in the TD direction before the film is relaxed, and L2 indicates the distance between the chucks in the TD direction after the film is relaxed).

The thickness of the biaxially stretched film formed by using the propylene-based polymer composition according to the present invention is preferably, for example, 10 μm to 70 μm.

Further, the biaxially stretched film formed by using the propylene-based polymer composition according to the present invention can be used as a film for forming a part of a layer of a multilayer film. In the multilayer film, at least one layer is formed of the biaxially stretched film according to the present invention, and any other layer is laminated on the layer of the biaxially stretched film. Examples of the other layer laminated on the layer of the biaxially stretched film include any layer such as a sealant layer, a gas barrier layer, an adhesive layer, and a printing layer. In particular, it is preferable to laminate a sealant layer using an olefin-based film and a layer of a biaxially stretched film. Thereby, the obtained multilayer film can be easily recycled. Examples of the method for producing the multilayer film include an extrusion laminating method, a thermal laminating method, and a dry laminating method, which are usually used.

Further, the biaxially stretched film formed by using the propylene-based polymer composition according to the present invention can be used as a material for a packaging bag. Specifically, the packaging bag can be formed by using the above-mentioned multilayer film including a layer of the biaxially stretched film. The packaging bag can be used for packaging any packaging object such as food, clothing, and miscellaneous goods.

The measured values of each item in the examples and comparative examples were measured by the following method.

(1) MFR (unit: g / 10 minutes)
The MFR of the propylene-based polymer composition was measured at a temperature of 230 ° C. and a load of 21.18 N according to the method A specified in JIS K7210-1: 2014.

(2) CXS (unit: mass%)
After completely dissolving 1 g of the propylene-based polymer composition in 100 ml of boiling xylene, the temperature was lowered to 20 ° C., and the mixture was stirred for 1 hour. After the obtained mixture was filtered off into a precipitate and a solution, the amount of the component dissolved in the solution was quantified by liquid chromatography under the following conditions to determine CXS.

Column: SHODEX GPC KF-801
Eluent: Tetrahydrofuran Column oven temperature: 40 ° C
Sample injection volume: 130 μL
Flow rate: 1 mL / min Detector: Differential refractometer

(3) Isotactic pentad fraction ([mmmm], unit:%)
The [mmmm] of the propylene-based polymer composition was measured by 13C-NMR under the following conditions. The attribution of the NMR absorption peak of the propylene-based polymer contained in the propylene-based polymer composition is as follows. This was done according to the method published by Zambelli et al. (Macropolymers Vol. 8, p. 687, 1975).

Model: Bruker AVANCE 600
Probe: 10mm cryoprobe Measurement temperature: 135 ℃
Pulse repetition time: 4 seconds Pulse width: 45 °
Accumulation number: 256 times

(4) Maximum meso-chain length (unit: none)
A. J. The maximum meso-chain length (MSL) of a propylene-based polymer was measured according to the Seccessive Self-Nuculation and Annealing method (SSA method, European Polymer Journal, Vol. 65, p. 132, 2015) published by Muller et al. The measurement conditions are shown in (4-1) to (4-4).

(4-1) Measurement of T _{s, ideal} (unit: ° C.) Using a differential scanning calorimeter (TA Instrument DSC250), 5 mg of the propylene-based polymer composition was added to 3 at 200 ° C. under a nitrogen atmosphere. After holding for 1 minute, the mixture was cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min. Then, the propylene-based polymer composition was held at 50 ° C. for 3 minutes and then heated to a predetermined temperature T _s (unit: ° C.) at a heating rate of 10 ° C./min. Then, the propylene-based polymer composition was held at a temperature of T _s for 5 minutes, and then cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min. Then, the propylene-based polymer composition was held at 50 ° C. for 3 minutes, and then the melting curve when heated to 230 ° C. at a heating rate of 10 ° C./min was measured. After confirming that the melting curve obtained by the measurement at the temperature T _s of 173 ° C. shows a single melting peak, the temperature T _s was lowered by 1 ° C. to perform the same measurement, and the single melting peak was performed. The temperature T _s at which _a new melting peak is observed on the higher temperature side is defined as Ta (unit: ° C.), and T _{s and ideal} are calculated by the following equation.

T _{s, ideal} = T _a +1

(4-2) Measurement of T _m (unit: ° C) Using a differential scanning calorimeter (TA Instrument DSC250), hold 5 mg of the propylene-based polymer composition in a nitrogen atmosphere at 200 ° C for 3 minutes. After that, it was cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min. Then, the propylene-based polymer composition was held at 50 ° C. for 3 minutes and then heated to Ts _{, ideal} at a heating rate of 10 ° C./min. Then, the propylene-based polymer composition was held at Ts _{, ideal} for 10 minutes, and then cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min. Then, the propylene-based polymer composition was held at 50 ° C. for 3 minutes and then heated to a temperature 5 ° C. lower than Ts _{, ideal} at a heating rate of 10 ° C./min. Then, the propylene-based polymer composition was held at a temperature 5 ° C. lower than Ts _{, ideal} for 10 minutes, and then cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min. Then, the propylene-based polymer composition was held at 50 ° C. for 3 minutes, and then heated to a temperature 10 ° C. lower than Ts _{, ideal} at a heating rate of 10 ° C./min. Then, the propylene-based polymer composition was held at a temperature 10 ° C. lower than Ts _{, ideal} for 10 minutes, and then cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min. Then, the propylene-based polymer composition was held at 50 ° C. for 3 minutes, and then heated to a temperature 15 ° C. lower than Ts _{, ideal} at a heating rate of 10 ° C./min. Then, the propylene-based polymer composition was held at a temperature 15 ° C. lower than Ts _{, ideal} for 10 minutes, and then cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min. Then, the propylene-based polymer composition was held at 50 ° C. for 3 minutes, and then heated to a temperature 20 ° C. lower than Ts _{, ideal} at a heating rate of 10 ° C./min. Then, the propylene-based polymer composition was held at a temperature 20 ° C. lower than Ts _{, ideal} for 10 minutes, and then cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min. Then, the propylene-based polymer composition was held at 50 ° C. for 3 minutes and then heated to a temperature 25 ° C. lower than Ts _{, ideal} at a heating rate of 10 ° C./min. Further, the mixture was kept at a temperature 25 ° C. lower than Ts _{, ideal} for 10 minutes, and then cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min. Then, the propylene-based polymer composition was held at 50 ° C. for 3 minutes, and then heated to a temperature 30 ° C. lower than Ts _{, ideal} at a heating rate of 10 ° C./min. Then, the propylene-based polymer composition was held at a temperature 30 ° C. lower than Ts _{, ideal} for 10 minutes, and then cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min. After further holding at 50 ° C. for 3 minutes, the mixture was heated to a temperature 35 ° C. lower than Ts _{, ideal} at a heating rate of 10 ° C./min. Then, the propylene-based polymer composition was held at a temperature 35 ° C. lower than Ts _{, ideal} for 10 minutes, and then cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min. Then, the propylene-based polymer composition was held at 50 ° C. for 3 minutes and then heated to a temperature 40 ° C. lower than Ts _{, ideal} at a heating rate of 10 ° C./min. Then, the propylene-based polymer composition was held at a temperature 40 ° C. lower than Ts _{, ideal} for 10 minutes, and then cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min. Then, the propylene-based polymer composition was held at 50 ° C. for 3 minutes and then heated to a temperature 45 ° C. lower than Ts _{, ideal} at a heating rate of 10 ° C./min. Then, the propylene-based polymer composition was held at a temperature 45 ° C. lower than Ts _{, ideal} for 10 minutes, and then cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min. Then, the propylene-based polymer composition was held at 50 ° C. for 3 minutes, and then heated to a temperature 50 ° C. lower than Ts _{, ideal} at a heating rate of 10 ° C./min. Then, the propylene-based polymer composition was held at a temperature 50 ° C. lower than Ts _{, ideal} for 10 minutes, and then cooled to 50 ° C. at a temperature lowering rate of 10 ° C./min. Then, after holding the propylene-based polymer composition at 50 ° C. for 3 minutes, the melting curve when heated to 230 ° C. at a heating rate of 10 ° C./min was measured, and the temperature showing the maximum endothermic peak was set to _Tm . Was defined as.

(4-3) Calculation of lamella thickness L _c (unit: m) J. According to the method published by Kang et al. (Polymer Bulletin Vol. 71, pp. 563, 2014), the lamella thickness _Lc of the propylene-based polymer composition was determined by the following formula.

L _c = 2σ / (ΔH ₀ × (1- (T _m + 273) / T _m ⁰ ))
(In the formula, the values of surface free energy σ = 0.0496 J / m ² , equilibrium melting enthalpy ΔH ₀ = 184 × 10 ⁶ J / m ³ , and equilibrium melting point T _m ⁰ = 460 K were used.)

(4-4) Calculation of maximum meso-chain length (MSL, unit: none) J. According to the method published by Kang et al. (Polymer Bulletin Vol. 71, pp. 563, 2014), the MSL of the propylene-based polymer composition was determined by the following formula.

MSL = 3L _c / L _helix
(In the formula, the value of crystal lattice length L _helix = 0.65 × ^10-9 m was used.)

(5) Film thickness (unit: μm)
The thickness of the biaxially stretched film was measured with a contact-type film thickness gauge according to the method A described in JIS K7130-1999.

(6) Transparency (Haze, unit:%)
The transparency of the biaxially stretched film was measured according to JIS K7105. The smaller the Haze, the better the transparency.

(7) Young's modulus (unit: GPa)
A 120 mm × 20 mm biaxially stretched film was collected so that the long side direction (120 mm) coincided with the measurement direction (MD direction, TD direction), and in an atmosphere of 23 ° C. and 50% humidity, A. Co., Ltd. Using the And Day UNIVERSAL TESTING MACHINE STB-1225, a tensile test is performed with a grip interval of 60 mm and a tensile speed of 5 mm / min, and Young's modulus (MD direction, TD direction) is measured from the tangent line at the zero point of the tensile-stress curve. bottom.

(8) Heat shrinkage rate (unit:%)
An A4 size (length 297 mm x width 210 mm) film is taken from a biaxially stretched film so that the long axis is parallel to the MD direction, and 200 mm marking lines are drawn in the MD and TD directions, respectively, and an oven at 150 ° C. It was hung inside and held for 30 minutes. Then, the film was taken out and cooled at room temperature for 30 minutes, and then the length of each marked line was measured. The heating shrinkage rate in each direction was calculated from the following formula.

Heat shrinkage rate (%) = {(200-marked line length after heating (mm)) / 200} x 100

The smaller the heat shrinkage rate, the better the dimensional stability at high temperature.

(9) Degree of orientation (unit: none)
The degree of orientation of the biaxially stretched film is described in Yuji Kumatani, Hiroshi Ito, "Introduction to Higher-order Structural Analysis of Plastic Molded Products", pp. 72-74, edited by the Plastic Molding and Processing Society, Nikkan Kogyo Shimbun (2006). Therefore, it was calculated from the retardation measurement using the Senalmon method. Using laser light with wavelengths of 632.8 nm, 532 nm, and 473 nm, each wavelength, under the condition that the biaxially stretched film is rotated in 10 ° increments from -40 to 40 ° with the MD direction of the biaxially stretched film as the axis of rotation. A retardation was obtained at each rotation angle. From the obtained retardation values, the refractive index in the MD direction ( ^NMD ), the refractive index in the TD direction (NTD), and the refractive index in the ^ND direction ( ^NND ) were calculated. Here, the average refractive index ( ^Nave ) represented by the following formula is 1.48.

^{Nave = (NMD + NTD + NND ) / 3}

From the obtained refractive indexes N ^MD , N ^TD , and N N D in each direction, the degree of orientation in the MD direction (f ^MD ), the degree of orientation in the TD direction (f ^TD ), and the degree of orientation in the ^ND direction (f TD) are calculated by the following formulas. f ^ND ) was calculated. Here, the intrinsic birefringence (Δn ₀ ) of polypropylene was set to 0.04.

(10) MD / TD orientation difference (unit: none)
The difference in MD / TD orientation was defined by the following formula.

MD / TD orientation difference = f ^TD -f ^MD

(11) Density (Unit: g / cm ³ )
The density of the biaxially stretched film was measured by the density gradient tube method according to the D method (water / ethanol) described in JIS K7112-1999.

The components used in the examples and comparative examples are as follows.

<Propene-based polymer intermediate composition 1>
Using a Ziegler-Natta type catalyst, triethylaluminum as a co-catalyst, and cyclohexylethyldimethoxysilane as an external donor, propylene is polymerized in an environment with a hydrogen concentration of 0.14 mol% by a vapor phase polymerization method to polymerize a propylene-based polymer. I got 1. 0.01 parts by mass of DHT-4C (neutralizing agent, manufactured by Kyowa Chemical Industry Co., Ltd.), IRGANOX1010 (antioxidant, manufactured by BASF Japan Co., Ltd.) 0 with respect to 100 parts by mass of the obtained propylene-based polymer 1. After blending .09 parts by mass and 0.05 parts by mass of Sumilyzer GP (antioxidant, manufactured by Sumitomo Chemical Co., Ltd.), melt extrusion was performed to obtain a pellet-shaped propylene-based polymer intermediate composition 1. The MFR of the obtained propylene-based polymer intermediate composition 1 was 2.3 g / 10 minutes, CXS was 0.4% by mass, [mm mm] was 98.2%, and the maximum meso-chain length was 84.

<Propene-based polymer intermediate composition 2>
Using a Ziegler-Natta type catalyst, triethylaluminum as a co-catalyst, and n-propylmethyldimethoxysilane and cyclohexylethyldimethoxysilane as external donors, propylene is polymerized in an environment with a hydrogen concentration of 0.06 mol% by a vapor phase polymerization method. Then, a propylene-based polymer 2 was obtained. 0.05 parts by mass of calcium stearate (neutralizing agent, manufactured by Sakai Chemical Industry Co., Ltd.) and DHT-4C (neutralizing agent, manufactured by Kyowa Chemical Industry Co., Ltd.) with respect to 100% by mass of the obtained propylene-based polymer 2. ) 0.005 part by mass, IRGANOX1010 (antioxidant, manufactured by BASF Japan Co., Ltd.) 0.15 part by mass, IRGAFOS168 (antioxidant, manufactured by BASF Japan Co., Ltd.) 0.10 part by mass, and then melt extrusion. This was carried out to obtain a pellet-shaped propylene-based polymer intermediate composition 2. The MFR of the propylene-based polymer intermediate composition 2 was 2.2 g / 10 minutes, the CXS was 2.9% by mass, the [mmmm] was 92.4%, and the maximum meso-chain length was 79.

<Propylene-based polymer intermediate composition 3>
The above-mentioned propylene-based polymer intermediate composition 1 (50 parts by mass) and the above-mentioned propylene-based polymer intermediate composition 2 (50 parts by mass) are mixed using a Henshell mixer, and then melt-extruded to form pellets. The propylene-based polymer intermediate composition 3 of the above was obtained. The MFR of the obtained propylene-based polymer intermediate composition 3 was 2.3 g / 10 minutes, CXS was 2.1% by mass, [mm mm] was 95.5%, and the maximum meso-chain length was 84.

<Β crystal nucleating agent masterbatch>
Using a Ziegler-Natta type catalyst, triethylaluminum as a co-catalyst, and cyclohexylethyldimethoxysilane as an external donor, propylene is polymerized in an environment with a hydrogen concentration of 0.95 mol% by a vapor phase polymerization method to polymerize the propylene-based polymer 3. Got 5 parts by mass of NU-100 (β crystal nucleating agent, manufactured by Shin Nihon Rika Co., Ltd.) and DHT-4C (neutralizing agent, manufactured by Kyowa Chemical Industry Co., Ltd.) with respect to 95 parts by mass of the obtained propylene-based polymer 3. ) 0.005 parts by mass, IRGANOX1010 (antioxidant, manufactured by BASF Japan Co., Ltd.) 0.09 parts by mass, and Smilizer GP (antioxidant, manufactured by Sumitomo Chemical Co., Ltd.) 0.05 parts by mass, and then melt-extruded. Was carried out to obtain a pellet-shaped β-crystal nucleating agent master batch.

<Example 1>
A propylene-based polymer intermediate composition 1 (99.5 parts by mass) and a β-crystal nucleating agent masterbatch (0.5 parts by mass) are mixed using a Henschel mixer, and then melt-extruded to obtain a propylene-based polymer. The composition 11 was prepared. The concentration of the β crystal nucleating agent in the propylene-based polymer composition 11 was 250 mass ppm. The MFR of the pellet obtained by melt-extruding the propylene-based polymer composition 11 was 2.2 g / 10 minutes, the CXS was 0.7% by mass, and the [mm mm] was 98.2%. This propylene-based polymer composition 11 is heated and melted at a resin temperature of 260 ° C. using a T-die film forming machine equipped with an extruder having a screw diameter of 65 mmφ, and is extruded onto a cooling roll at 30 ° C. to be unstretched. I got a sheet. The obtained unstretched sheet was stretched 5 times in the MD direction using a stretching roll heated to 142 ° C. to obtain a uniaxially stretched film. By grasping both ends of the obtained uniaxially stretched film with two rows of chucks arranged along the MD direction and widening the distance between the two rows of chucks in the TD direction in a heating furnace heated to 170 ° C. The uniaxially stretched film is stretched 8 times in the TD direction, and then in a heating furnace heated to 165 ° C., the chuck spacing between the two rows is narrowed and relaxed by 19.5% in the TD direction to stretch the uniaxially stretched film. I got a film. Tables 1 and 2 show the production conditions and the measured values of the physical properties of the obtained biaxially stretched film.

<Example 2>
The content of the propylene-based polymer intermediate composition 1 was changed from 99.5 parts by mass to 99.4 parts by mass, and the content of the β crystal nucleating agent masterbatch was changed from 0.5 parts by mass to 0.6 parts by mass. A biaxially stretched film was obtained in the same manner as in Example 1 except that the propylene-based polymer composition 12 was prepared. The concentration of the β crystal nucleating agent in the propylene-based polymer composition 12 was set to 300 mass ppm. The MFR of the pellet obtained by melt-extruding the propylene-based polymer composition 12 was 2.2 g / 10 minutes, the CXS was 0.6% by mass, and the [mmmm] was 98.2%. Tables 1 and 2 show the production conditions and the measured values of the physical properties of the obtained biaxially stretched film.

<Example 3>
The content of the propylene-based polymer intermediate composition 1 was changed from 99.5 parts by mass to 99.2 parts by mass, and the content of the β crystal nucleating agent masterbatch was changed from 0.5 parts by mass to 0.8 parts by mass. A biaxially stretched film was obtained in the same manner as in Example 1 except that the propylene-based polymer composition 13 was prepared. The concentration of the β crystal nucleating agent in the propylene-based polymer composition 13 was 400 mass ppm. The MFR of the pellet obtained by melt-extruding the propylene-based polymer composition 13 was 2.2 g / 10 minutes, the CXS was 0.6% by mass, and the [mmmm] was 98.3%. Tables 1 and 2 show the production conditions and the measured values of the physical properties of the obtained biaxially stretched film.

<Example 4>
The propylene-based polymer composition 13 is heated and melted at a resin temperature of 260 ° C. using a T-die film forming machine equipped with an extruder having a screw diameter of 65 mmφ, and extruded onto a cooling roll at 30 ° C. to form an unstretched sheet. Got The obtained unstretched sheet was stretched 5 times in the MD direction using a stretching roll heated to 152 ° C. to obtain a uniaxially stretched film. By grasping both ends of the obtained uniaxially stretched film with two rows of chucks arranged along the MD direction and widening the distance between the two rows of chucks in the TD direction in a heating furnace heated to 170 ° C. The uniaxially stretched film is stretched 8 times in the TD direction, and then in a heating furnace heated to 165 ° C., the chuck spacing between the two rows is narrowed and relaxed by 19.5% in the TD direction to stretch the uniaxially stretched film. I got a film. Tables 1 and 2 show the production conditions and the measured values of the physical properties of the obtained biaxially stretched film.

<Comparative Example 1>
The content of the propylene-based polymer intermediate composition 1 was changed from 99.5 parts by mass to 99.9 parts by mass, and the content of the β crystal nucleating agent masterbatch was changed from 0.5 parts by mass to 0.1 parts by mass. A biaxially stretched film was obtained in the same manner as in Example 1 except that the propylene-based polymer composition C11 was prepared. The concentration of the β crystal nucleating agent in the propylene-based polymer composition C11 was 50 mass ppm. The MFR of the pellet obtained by melt-extruding the propylene-based polymer composition C11 was 2.2 g / 10 minutes, the CXS was 0.6% by mass, and the [mmmm] was 98.3%. Tables 1 and 2 show the production conditions and the measured values of the physical properties of the obtained biaxially stretched film.

<Comparative Example 2>
A propylene-based polymer intermediate composition 1 (99.0 parts by mass) and a β-crystal nucleating agent masterbatch (1.0 part by mass) are mixed using a Henschel mixer, and then melt-extruded to obtain a propylene-based polymer. The composition C12 was prepared. The concentration of the β crystal nucleating agent in the propylene-based polymer composition C12 was 500 mass ppm. The MFR of the pellet obtained by melt-extruding the propylene-based polymer composition C12 was 2.2 g / 10 minutes, the CXS was 0.6% by mass, and the [mmmm] was 98.4%. This propylene-based polymer composition C12 is heated and melted at a resin temperature of 260 ° C. using a T-die film forming machine equipped with an extruder having a screw diameter of 65 mmφ, and is extruded onto a cooling roll at 30 ° C. to be unstretched. I got a sheet. The obtained unstretched sheet was stretched 5 times in the MD direction using a stretching roll heated to 152 ° C. to obtain a uniaxially stretched film. By grasping both ends of the obtained uniaxially stretched film with two rows of chucks arranged along the MD direction and widening the distance between the two rows of chucks in the TD direction in a heating furnace heated to 170 ° C. The uniaxially stretched film is stretched 8 times in the TD direction, and then in a heating furnace heated to 165 ° C., the chuck spacing between the two rows is narrowed and the biaxially stretched film is relaxed by 13% in the TD direction. Obtained. Tables 1 and 2 show the production conditions and the measured values of the physical properties of the obtained biaxially stretched film.

<Comparative Example 3>
A biaxially stretched film was obtained in the same manner as in Example 2 except that the propylene-based polymer intermediate composition 1 was changed to the propylene-based polymer intermediate composition 3 to prepare the propylene-based polymer composition C13. The concentration of the β crystal nucleating agent in the propylene-based polymer composition C13 was set to 300 mass ppm. The MFR of the pellet obtained by melt-extruding the propylene-based polymer composition C13 was 2.1 g / 10 minutes, the CXS was 1.8% by mass, and the [mm mm] was 95.7%. Tables 1 and 2 show the production conditions and the measured values of the physical properties of the obtained biaxially stretched film.

<Comparative Example 4>
The propylene-based polymer intermediate composition 1 is heated and melted at a resin temperature of 260 ° C. using a T-die film forming machine equipped with an extruder having a screw diameter of 65 mmφ, and is extruded onto a cooling roll at 30 ° C. to be unstretched. I got a sheet. The obtained unstretched sheet was stretched 5 times in the MD direction using a stretching roll heated to 152 ° C. to obtain a uniaxially stretched film. By grasping both ends of the obtained uniaxially stretched film with two rows of chucks arranged along the MD direction and widening the distance between the two rows of chucks in the TD direction in a heating furnace heated to 170 ° C. The uniaxially stretched film is multiplied by 8 in the TD direction, and then in a heating furnace heated to 165 ° C., the chuck spacing between the two rows is narrowed and relaxed by 19.5% in the TD direction to stretch the uniaxially stretched film. I got a film. Tables 1 and 2 show the production conditions and the measured values of the physical properties of the obtained biaxially stretched film.

<Comparative Example 5>
A propylene-based polymer intermediate composition 1 (98.0 parts by mass) and a β-crystal nucleating agent masterbatch (2.0 parts by mass) are mixed using a Henschel mixer, and then melt-extruded to obtain a propylene-based polymer. The composition C14 was prepared. The concentration of the β crystal nucleating agent in the propylene-based polymer composition C14 was 1000 mass ppm. The MFR of the pellet obtained by melt-extruding the propylene-based polymer composition C14 was 2.2 g / 10 minutes, the CXS was 0.6% by mass, and the [mmmm] was 98.2%. This propylene-based polymer composition C13 is heated and melted at a resin temperature of 250 ° C. using a T-die film forming machine equipped with an extruder having a screw diameter of 20 mmφ, and extruded onto a cooling roll at 90 ° C. to obtain a thickness. An unstretched sheet of 1.0 mm was obtained. The four sides of the obtained unstretched sheet were grasped with a chuck, preheated in a heating furnace heated to 140 ° C. for 3 minutes, and then stretched twice in the MD direction and the TD direction at the same time. After that, the temperature inside the heating furnace was raised to 160 ° C. and preheated for 3 minutes, and then the film was further stretched so that the total stretching ratio was 6.5 times in the MD direction and the TD direction at the same time. Got Tables 1 and 2 show the production conditions and the measured values of the physical properties of the obtained simultaneous biaxially stretched film.

From Table 2, the biaxially stretched film of the example has a high TD Young's modulus and a low TD heat shrinkage rate as compared with the biaxially stretched film of the comparative example, and is excellent in the balance between them. You can see that.

According to the present invention, a propylene-based polymer composition capable of producing a biaxially stretched film having a relatively high tensile elastic modulus (Young's modulus) and a relatively low heat shrinkage in the TD direction, the propylene-based weight. A biaxially stretched film using the combined composition and a packaging bag using the biaxially stretched film can be provided.

Claims (12)

1. A propylene-based polymer composition containing a propylene-based polymer and a β-crystal nucleating agent.
   The melt flow rate measured at a temperature of 230 ° C. and a load of 21.18 N is 1 g / 10 minutes to 5 g / 10 minutes.
   The amount of the soluble part of cold xylene is 0.1% by mass to 1.0% by mass,
   A propylene-based polymer composition having a β-crystal nucleating agent having a concentration of 100% by mass or more and less than 500% by mass.
2. The propylene-based polymer composition according to claim 1, wherein the concentration of the β-crystal nucleating agent is 250 mass ppm to 450 mass ppm.
3. The propylene-based polymer composition according to claim 1 or 2, wherein the melt flow rate is 1.8 g / 10 minutes to 2.8 g / 10 minutes.
4. The propylene-based polymer composition according to any one of claims 1 to 3, wherein the isotactic pentad fraction is 97% to 99%.
5. The propylene-based polymer composition according to any one of claims 1 to 4, wherein the maximum meso-chain length of the propylene-based polymer is 80 or more.
6. The β-crystal nucleating agent is at least one selected from the group consisting of N, N'-dicyclohexyl-2,6-naphthalenedicarboxamide, N, N'-dicyclohexylterephthalamide and N, N'-diphenylhexanediamide. The propylene-based polymer composition according to any one of claims 1 to 5.
7. A biaxially stretched film containing the propylene-based polymer composition according to any one of claims 1 to 6.
8. A propylene-based polymer composition containing a propylene-based polymer and a β-crystal nucleating agent and satisfying the following requirements (1) and (2) is contained.
   A biaxially stretched film that meets the following requirements (3) and (4).
   
   (1) The melt flow rate measured at a temperature of 230 ° C. and a load of 21.18 N is 1 g / 10 minutes to 30 g / 10 minutes.
   (2) The amount of the soluble part of cold xylene is 0.1% by mass to 1.0% by mass.
   (3) The degree of orientation in the ND direction calculated from the birefringence is −0.30 or less.
   (4) The difference between the degree of orientation in the MD direction and the degree of orientation in the TD direction calculated from the birefringence is 0.10 to 1.00.
9. The biaxially stretched film according to claim 8, which has a density of 0.900 g / cm ³ to 0.912 g / cm ³ .
10. An unstretched sheet is obtained by heating and melting a propylene-based polymer composition containing a propylene-based polymer and a β-crystal nucleating agent and satisfying the following requirements (1) and (2) and extruding it onto a cooling roll. Process and
    A step of obtaining a uniaxially stretched film by multiplying the obtained unstretched sheet 3 to 12 times in the MD direction.
    A step of obtaining a biaxially stretched film by stretching the obtained uniaxially stretched film 4 to 20 times in the TD direction and then relaxing by 1% to 30% in the TD direction.
    A method for producing a biaxially stretched film.
    
    (1) The melt flow rate measured at a temperature of 230 ° C. and a load of 21.18 N is 1 g / 10 minutes to 30 g / 10 minutes.
    (2) The amount of the soluble part of cold xylene is 0.1% by mass to 1.0% by mass.
11. The temperature of the cooling roll used in the step of obtaining the unstretched sheet is 10 ° C to 60 ° C.
    The temperature of the stretched roll used in the step of obtaining the uniaxially stretched film is 110 ° C. to 150 ° C.
    The heating temperature for stretching and relaxing in the step of obtaining the biaxially stretched film is 150 ° C. to 200 ° C.
    The method for producing a biaxially stretched film according to claim 10.
12. A packaging bag containing the biaxially stretched film according to any one of claims 7 to 9.