JP7345257B2 - Microporous film made of propylene polymer composition - Google Patents

Description

The present invention relates to microporous films comprising propylene polymer compositions. More specifically, the present invention relates to a microporous film with excellent air permeability and strength. Microporous films formed from polymeric materials are used in a variety of applications, such as medical and industrial filtration membranes, separation membranes, and separators such as battery separators and capacitor separators.

In recent years, the demand for secondary batteries as a power source for mobile phones, mobile personal computers, and automobiles has been increasing, and the demand for battery separators has also increased. In this context, with the spread of batteries for automobiles, higher energy density is being considered, and it is becoming increasingly necessary to ensure the safety of batteries. It is essential for the separator to have a shutdown function to ensure safety, but if the temperature rises even after the shutdown and the entire separator melts and ruptures, it will no longer be able to maintain electrical insulation. For this reason, there is a need to improve the heat resistance of separators. However, ultra-high molecular weight polyethylene, which is the main material for separators, has a low melting point of about 135 to 140°C and has limited heat resistance.Therefore, polypropylene resin with a high melting point is used as a microporous film with high heat resistance. There is. Furthermore, microporous films are generally required to have low strength and puncture strength to prevent damage when external forces are applied.

There are wet methods and dry methods for producing microporous polypropylene resin films. The wet method is a method in which a film is formed from a resin composition containing a filler and a plasticizer mixed with polypropylene resin, and a microporous film is produced by extracting the filler and plasticizer from the film. This method not only poses environmental problems such as working environment problems during the extraction process and processing of the extract liquid, but also has the possibility of leaving trace amounts of fillers, plasticizers, and extract liquid on the microporous film, which may affect battery performance and safety. I have concerns about sexuality. On the other hand, the dry method is a method in which a raw film of polypropylene resin is produced and then micropores are formed in the film by cold stretching and warm stretching. Since this method does not use any fillers, plasticizers, or extractants, there are no environmental problems such as the above-mentioned working environment problems or the processing of extracts. It is a low-cost manufacturing method, there is no possibility of trace amounts of fillers remaining in the separator, and there is no risk of impairing battery performance or safety.

However, in the dry method, since the raw film is formed by melt extrusion without blending fillers or plasticizers, it is necessary to ensure the fluidity of the polypropylene resin to some extent. For this purpose, it is necessary to lower the molecular weight of the polypropylene resin, and as a result, there is a problem in the balance between strength and air permeability of the microporous film obtained by the dry method compared to the wet method. Furthermore, if the microporous film is made thinner, air permeability is improved, but the balance cannot be improved because the strength of the film is reduced.

Patent Document 1 and Patent Document 2 disclose a microorganism made of polypropylene resin that has excellent lithium ion permeability, can constitute a high-performance lithium ion battery, and can prevent short circuits between the positive and negative electrodes due to dendrites. A perforated film is disclosed.

Patent Document 3 discloses a polypropylene resin composition for forming a microporous membrane that has excellent heat resistance and strength.
Patent Document 4 discloses a polypropylene resin for a microporous film and a microporous film that have excellent heat resistance and strength.

Japanese Patent Application Publication No. 2011-246658 Japanese Patent Application Publication No. 2011-246659 WO2010/079799 publication WO2014/065331 publication

However, Patent Document 1 and Patent Document 2 state that when the air permeability of a microporous film is low (i.e., when the air permeability is high), the strength decreases; However, there is no proposal for a technique for improving the physical property balance between air permeability and strength of a microporous film.

In Patent Document 3, regarding a polypropylene composition for a microporous film containing an ultra-high molecular weight propylene homopolymer, the air permeability of the micro-porous film is determined based on the molecular weight of the ultra-high molecular weight propylene homopolymer and the half-value width determined by temperature rising elution fractionation (TREF). and strength improvement methods have been proposed. However, the invention does not specify the structure of the entire polypropylene composition suitable for microporous films, and as a result, sufficient proposals have been made regarding techniques for improving the physical property balance between air permeability and strength of microporous films. It can not be said.

Patent Document 4 describes polypropylene for microporous films with excellent heat resistance and strength, and the value obtained by dividing the weight average molecular weight by the number average molecular weight (Mw/Mn) is adjusted to a predetermined range to improve film strength and air permeability. It is proposed to improve air permeability by increasing the value obtained by dividing the Z average molecular weight by the weight average molecular weight (Mz/Mw) (an index of ultra-high molecular weight components) while maintaining the physical property balance. However, there was a limit to the improvement in the balance between air permeability and strength of the microporous film according to the invention.

The present inventors have made extensive studies to solve the above problems. As a result, it was discovered that the above-mentioned problems could be solved by a microporous film that met the following requirements, and the present invention was completed. Aspects of the present invention are shown below.
[1] A microporous film (A-1) consisting of a propylene polymer composition (A) that satisfies the following requirements (A-1) to (A-4) has a mesopentad fraction (mmmm) of 94.0% or more (A-2) The melt flow rate (ASTM D1238, 230°C, 2.16 kg load) is 0.5 to 5.0 g/10 minutes. (A-3) Measured by gel permeation chromatography (GPC). The value obtained by dividing the weight average molecular weight by the number average molecular weight (Mw/Mn) is from 7.0 to 17.0 (A-4) The content ratio of propylene homopolymer with a molecular weight of 10 million or more is from 0.20 to 0.50% by mass [2] The propylene polymer composition (A) is propylene alone having an intrinsic viscosity [η] of 10.0 to 12.0 dL/g as measured in tetralin at 135°C. Polymer (b1) 0.4 to 10% by mass and propylene homopolymer (D) 99.6 having an intrinsic viscosity [η] of 1.5 to 3.0 dL/g measured in tetralin at 135°C. The microporous film described in [1] above, containing 90% by mass.
[3] A propylene homopolymer (B) 2 to 20% by mass that satisfies the following requirements (B-1) to (B-2) and a propylene homopolymer (C) 98 to 98% that satisfies the following requirements (C-1) The microporous film (B-1) melt flow rate described in any one of [1] to [2] above, consisting of the propylene polymer composition (A) obtained by blending the propylene polymer composition (A) with 80% by mass. (ASTM D1238, 230°C, 2.16 kg load) is 0.01 to 5.0 g/10 minutes (B-2) Intrinsic viscosity [η] measured in tetralin at 135°C is 10.0 to The content ratio of the propylene homopolymer (b1) which is 12.0 dL/g is 20 to 50% by mass, and the intrinsic viscosity [η] measured in tetralin at 135 ° C. is 0.5 to 3.0 dL/g. The content ratio of propylene homopolymer (b2) is 50 to 80% by mass (however, the total amount of propylene homopolymer (b1) and propylene homopolymer (b2) is 100% by mass).
(C-1) The melt flow rate (ASTM D1238, 230°C, 2.16 kg load) is 0.5 to 10.0 g/10 minutes. [4] The propylene polymer composition (A) meets the following requirements. The microporous film described in any one of [1] to [3] above, which satisfies (A-5).
(A-5) The number of fish eyes per 3000 cm ² of a 50 μm thick film obtained from the propylene polymer composition (A) using a T-die film forming machine is 50 or less [5] A battery separator comprising at least one layer of the microporous film described in any one of [1] to [4] above.
[6] A separation membrane having at least one layer of the microporous film described in any one of [1] to [4] above.
[7] A filtration film having at least one layer of the microporous film described in any one of [1] to [4] above.

The propylene polymer composition (A) contains a small amount of an ultra-high molecular weight propylene homopolymer with a molecular weight of 10 million or more, so it has fewer fish eyes and bumps, so it does not reduce the strength of the microporous film and has a small amount of ultra-high molecular weight propylene homopolymer. Since the formation of pores is effective, a microporous film with an excellent balance of physical properties such as air permeability and strength can be obtained.

Hereinafter, the microporous film made of the propylene polymer composition (A) according to the present invention will be specifically explained. Note that details of the measurement conditions for each physical property described below are described in the Examples column.

[Propylene polymer composition (A)]
The propylene polymer composition (A) satisfies the following requirements (A-1) to (A-4). The propylene polymer composition (A) preferably also satisfies requirements (A-5) and/or (A-6).

<Requirement (A-1)>
The mesopentad fraction of the propylene polymer composition (A) is 94.0% or more, preferably 95.5% or more and 99.5% or less, more preferably 95.5% or more and 99.0% or less. be. When the mesopentad fraction is within the above range, the crystallinity of the original film will be high, and in the stretching process, only the amorphous material will be deformed without deforming the lamellae, so that micropores will be efficiently formed, resulting in excellent This is preferable because it provides good air permeability. On the other hand, if the mesopentad fraction is less than the lower limit of the above range, the lamellae are likely to deform during the stretching process due to a decrease in crystallinity and crystal size, which is not preferable because the air permeability of the microporous film may decrease.

The mmmm fraction of the propylene polymer composition (A) means the mmmm fraction when a sample of the composition is measured by ¹³ C-NMR. The mesopentad fraction (mmmm fraction) indicates the proportion of pentad isotactic structures in the molecular chain, and is the propylene structural unit at the center of a chain of five consecutive propylene monomer units that has a meso structure. This is the fraction of

The propylene polymer composition (A) having a mmmm fraction within the above range can be produced, for example, by appropriately selecting a known catalyst described below. Specifically, the propylene polymer composition (A) usually contains a propylene homopolymer having a mmmm fraction within the above range. A propylene homopolymer that satisfies these requirements can be produced by polymerizing propylene using, for example, a known olefin polymerization catalyst that includes a solid titanium catalyst component, an organometallic compound catalyst component, and an electron donor used as necessary, as described below. It can be obtained by letting

<Requirement (A-2)>
The melt flow rate (MFR, ASTM D1238, 230°C, 2.16 kg load) of the propylene polymer composition (A) is 0.5 to 5.0 g/10 minutes, preferably 1.0 to 4. 0 g/10 minutes, more preferably 1.0 to 3.0 g/10 minutes. If the MFR is less than the lower limit, the extrusion load will increase, such as the resin pressure and motor load during molding, and the flowability of the resin will decrease, resulting in uneven melting, streaks, etc. This is not preferable because the decrease in thickness accuracy makes it difficult to produce a raw film suitable for stretching in the next step. If the MFR exceeds the upper limit, the film strength will decrease, which is not preferable.

The propylene polymer composition (A) having an MFR within the above range can be produced, for example, by changing the MFR and blending ratio of the propylene homopolymer (B) and propylene homopolymer (C) described below.

<Requirement (A-3)>
Mw/Mn of the propylene polymer composition (A) measured by gel permeation chromatography (GPC) is 7.0 or more and 17.0 or less, preferably 10.0 or more and 17.0 or less, more preferably 12 It is more than .0 and less than 17.0. If the Mw/Mn is less than the lower limit, the low molecular weight components will decrease and the resin pressure during molding will increase, which tends to cause uneven flow of the molten resin when producing the original film. Furthermore, when the Mw/Mn exceeds the upper limit, the amount of low molecular weight components increases too much, causing slippage between the molten resin and the screw wall surface, which tends to cause a decrease in the discharge rate and extrusion surging. When extrusion surging occurs, the thickness of the original film tends to become uneven.

The propylene polymer composition (A) having Mw/Mn in the above range can be produced, for example, by changing the MFR and blending ratio of the propylene homopolymer (B) and the propylene homopolymer (C) described below. It can also be produced by changing the intrinsic viscosity and blending ratio of the propylene homopolymer (b1) and the propylene homopolymer (b2) contained in the propylene homopolymer (B).

<Requirement (A-4)>
The propylene polymer composition (A) contains 0.20 to 0.50% by mass, preferably 0.20 to 0.40% by mass of a propylene homopolymer having a molecular weight of 10 million or more. It has been found that by adjusting it within this range, the air permeability can be improved without reducing the strength of the microporous film. If it is less than the lower limit, the amount of the ultra-high molecular weight component decreases, so that the molecular orientation of the raw film decreases and the efficiency of generating micropores on the film during the stretching process decreases, resulting in a decrease in air permeability. Moreover, if the upper limit is exceeded, the ultra-high molecular weight component will not be mixed uniformly, fish eyes will occur on the film, micropores will become non-uniform during the stretching process, and the film strength will decrease.

Propylene homopolymer with a molecular weight of 10 million or more has an extremely high effect on the orientation of the raw film even in a small amount, and significantly improves air permeability. It is characterized by the fact that there are no problems such as increases in resin pressure during molding, non-uniformity of micropores in the film, and occurrence of fish eyes.

Patent Document 4 proposes a polypropylene for microporous films containing 0.3 to 1.5% of polypropylene with a molecular weight of 7 million or more, but adjusting this content ratio changes the range of film forming conditions. However, the improvement effect on air permeability as described above was not observed.

The propylene polymer composition (A) in which the content ratio of the propylene homopolymer having a molecular weight of 10 million or more is within the above range is, for example, the maximum content of the propylene homopolymer (b1) contained in the propylene homopolymer (B) described below. It can be manufactured by changing the viscosity and blending amount.

<Requirements (A-5)>
When a film with a thickness of 50 μm is produced from the propylene polymer composition (A) using a T-die film forming machine, the number of fish eyes (size of 100 μm or more) in the film is 50 pieces/3000 cm ² or less. 20 pieces/3000cm ² or less, more preferably 10 pieces/3000cm ² or less. If the upper limit is exceeded, large-diameter pores caused by fish eyes will occur in the microporous film, improving air permeability, but film strength tends to decrease significantly.

The propylene polymer composition (A) capable of forming a film having the number of fish eyes in the above range is, for example, a propylene homopolymer (b1) and a propylene homopolymer (b2) contained in the propylene homopolymer (B). ) or by selecting a batch method as the polymerization method for the propylene homopolymer (B).

<Requirement (A-6)>
The propylene polymer composition (A) preferably contains a propylene homopolymer having a molecular weight of 50,000 or less from 10% by mass to less than 25% by mass, more preferably from 15% by mass to less than 25% by mass, even more preferably Contains 20% by mass or more and less than 25% by mass. If it is less than the lower limit, the melt viscosity will increase and the thickness of the film will be uneven, and if it is more than the upper limit, the strength of the microporous film will tend to decrease.

A propylene polymer composition (A) in which the content ratio of a propylene homopolymer with a molecular weight of 50,000 or less is within the above range can be prepared, for example, by adjusting the MFR and blending of the propylene homopolymer (B) and propylene homopolymer (C) described below. It can be produced by changing the ratio, and it can also be produced by changing the intrinsic viscosity and blending ratio of propylene homopolymer (b1) and propylene homopolymer (b2) contained in propylene homopolymer (B). be able to.

[Preferred composition]
In one embodiment, the propylene polymer composition (A) is propylene alone that satisfies the following requirement (B-1), preferably the following requirement (B-2), and more preferably the following requirement (B-3). It is preferable to contain a polymer (B) and a propylene homopolymer (C) that satisfies the following requirement (C-1), preferably the following requirement (C-2).

In the propylene polymer composition (A), the content of the propylene homopolymer (B) is usually 2 to 20% by mass, and the content of the propylene homopolymer (C) is usually 98 to 80% by mass. It is.

In one embodiment, the propylene polymer composition (A) comprises a propylene homopolymer (b1) having an intrinsic viscosity [η] of 10.0 to 12.0 dL/g as measured in tetralin at 135°C. , a propylene homopolymer (D) having an intrinsic viscosity [η] of 1.5 to 3.0 dL/g as measured in tetralin at 135°C.
Each component will be explained below.

[Propylene homopolymer (B)]
<Requirements (B-1)>
The melt flow rate (MFR, ASTM D1238, 230°C, 2.16 kg load) of the propylene homopolymer (B) is 0.01 to 5.0 g/10 minutes, preferably 0.05 to 4.0 g/10 minutes. 10 minutes, more preferably 0.1 to 3.0 g/10 minutes.

When the MFR of the propylene homopolymer (B) is within the above range, a microporous film with excellent extrusion moldability and uniform micropores can be obtained.
The propylene homopolymer (B) having an MFR within the above range can be produced, for example, by changing the intrinsic viscosity and blending ratio of the propylene homopolymer (b1) and the propylene homopolymer (b2).

<Requirement (B-2)>
In the propylene homopolymer (B), the content ratio of the propylene homopolymer (b1) having an intrinsic viscosity [η] of 10.0 to 12.0 dL/g measured in tetralin at 135°C is 20 to 50% by mass. %, and the content of propylene homopolymer (b2) having an intrinsic viscosity [η] of 0.5 to 3.0 dL/g measured in tetralin at 135 ° C. is 50 to 80% by mass (provided that , the total amount of propylene homopolymer (b1) and propylene homopolymer (b2) is 100% by mass).

<<Propylene homopolymer (b1)>>
The intrinsic viscosity [η] of the propylene homopolymer (b1) is 10.0 to 12.0 dL/g, preferably 10.5 to 11.5 dL/g. Further, the content ratio of the propylene homopolymer (b1) is 20 to 50% by mass, preferably 20 to 45% by mass, more preferably 20 to 40% by mass (However, the content of the propylene homopolymer (b1) and propylene homopolymer (b2) is 100% by mass).

Further, when the total amount of propylene homopolymer (b1) and propylene homopolymer (D) is 100% by mass, the content of propylene homopolymer (b1) is preferably 0.4 to 10% by mass. is in the range of 0.5 to 6% by mass.

When the intrinsic viscosity [η] of the propylene homopolymer (b1) is less than 10.0 dL/g, the air permeability of the resulting microporous film may decrease, and the intrinsic viscosity [η] becomes 12.0 dL/g. If it exceeds , the strength of the resulting microporous film may decrease. Furthermore, if the content of the propylene homopolymer (b1) is less than 20% by mass, the air permeability of the microporous film may decrease, and if it exceeds 50% by mass, the resin pressure during molding of the raw film will increase. , which may cause defects during extrusion molding.
The propylene homopolymer (b1) can be produced by appropriately selecting a known catalyst and adjusting polymerization conditions such as hydrogen concentration, polymerization temperature, and polymerization time, as described below.

《Propylene homopolymer (b2)》
The intrinsic viscosity [η] of the propylene homopolymer (b2) is 0.5 to 3.0 dL/g, preferably 0.6 to 2.5 dL/g, more preferably 0.8 to 1.5 dL/g. It is g. Further, the content ratio of the propylene homopolymer (b2) is 50 to 80% by mass, preferably 55 to 80% by mass, more preferably 60 to 80% by mass (However, the content of the propylene homopolymer (b1) and propylene homopolymer (b2) is 100% by mass).

When the intrinsic viscosity [η] of the propylene homopolymer (b2) is less than 0.5 dL/g, fish eyes may occur and the strength of the microporous film may be reduced. Furthermore, if the content of the propylene homopolymer (b2) is less than 50% by mass, extrusion may become defective, and if it exceeds 80% by mass, the air permeability of the microporous film may decrease.
The propylene homopolymer (b2) can be produced by appropriately selecting a known catalyst and adjusting polymerization conditions such as hydrogen concentration, polymerization temperature, and polymerization time, as described below.

<Requirement (B-3)>
The mesopentad fraction (mmmm fraction) of the propylene homopolymer (B) is preferably 94.0% or more, more preferably 95.5% or more and 99.5% or less, and still more preferably 95.5% or more and 99. .0% or less. When the mesopentad fraction is within the above range, the crystallinity of the original film will be high, and in the stretching process, only the amorphous material will be deformed without deforming the lamellae, so that micropores will be efficiently formed, resulting in excellent This is preferable because it provides good air permeability. On the other hand, if the mesopentad fraction is less than the lower limit of the above range, the lamellae are likely to deform during the stretching process due to a decrease in crystallinity and crystal size, which is not preferable because the air permeability of the microporous film may decrease.
The propylene homopolymer (B) having a mmmm fraction within the above range can be produced, for example, by appropriately selecting a known catalyst described below.

<Method for producing propylene homopolymer (B)>
Propylene homopolymer (B) can be produced by various known production methods, for example, by polymerizing propylene homopolymer (b1) and propylene homopolymer (b2) that satisfy the above-mentioned physical properties, respectively, and then producing propylene homopolymer (B) within the above range. A method for obtaining a propylene homopolymer (B) by mixing or melt-kneading the polymer (b1) and a propylene homopolymer (b2), or a propylene homopolymer (b1) and a propylene homopolymer that satisfy the above-mentioned physical properties. Examples include a method of polymerizing (b2) in one polymerization system or in two or more polymerization systems.

Among these, it is preferable to produce the polymer by multi-stage polymerization of two or more stages so that a propylene homopolymer having a relatively high molecular weight contains a propylene homopolymer having a relatively low molecular weight.
A preferred method for producing the propylene homopolymer (B) is, for example, a method in which propylene is polymerized in two or more stages of multistage polymerization in the presence of a catalyst for producing highly stereoregular polypropylene.

Specifically, in the first stage polymerization, propylene is polymerized in the substantial absence of hydrogen, and the intrinsic viscosity [η] measured in tetralin at 135° C. is 10.0 to 12.0 dL/g. , preferably a relatively high molecular weight propylene homopolymer (b1) of 10.5 to 11.5 dL/g, from 20 to 50% by mass, preferably from 20 to 45% by mass, more preferably from 20 to 45% by mass of the total polymer. 20 to 40% by mass, and in the second stage polymerization, a relatively low molecular weight propylene homopolymer (b2) is produced. The intrinsic viscosity [η] of the propylene homopolymer (b2) produced in the second and subsequent polymerizations is 0.5 to 3.0 dL/g, preferably 0.6 to 2.5 dL/g, more preferably 0 .8 to 1.5 dL/g (This intrinsic viscosity [η] is the intrinsic viscosity [η] of the propylene homopolymer (b2) produced in that stage alone, and the propylene homopolymer produced up to the previous stage of that stage (b1) is not the intrinsic viscosity [η] of the propylene homopolymer (B) containing It is adjusted to 5.0 g/10 minutes, preferably 0.05 to 4.0 g/10 minutes, and more preferably 0.1 to 3.0 g/10 minutes. The method for adjusting the intrinsic viscosity [η] of the propylene homopolymer produced in the second and subsequent stages is not particularly limited, but a method using hydrogen as a molecular weight regulator is preferred.

As for the production sequence of propylene homopolymer (b1) and propylene homopolymer (b2), in the first stage, in the substantial absence of hydrogen, a relatively high molecular weight propylene homopolymer (b1) is produced. After this, it is preferable to produce a relatively low molecular weight propylene homopolymer (b2) in the second and subsequent stages. Although the production order can be reversed, a relatively low molecular weight propylene homopolymer is obtained in the first stage, and then a relatively high molecular weight propylene homopolymer is polymerized in the second and subsequent stages. In order to achieve this, it is necessary to remove molecular weight regulators such as hydrogen contained in the first-stage reaction product as much as possible before starting the second-stage and subsequent polymerizations, which makes the polymerization equipment complicated. In addition, the intrinsic viscosity [η] of the second and subsequent stages is difficult to increase.

Polymerization of the propylene homopolymer (B) can be carried out by known methods such as slurry polymerization and bulk polymerization. Moreover, although the polymerization at each stage can be carried out continuously or batchwise, it is particularly preferable to carry out the polymerization batchwise. This is because when the propylene homopolymer (B) is produced by a continuous polymerization method, there is a risk that fish eyes may increase due to differences in the molecular weight distribution of the propylene homopolymer between polymer particles due to the residence time distribution. By polymerizing in batch mode, a propylene homopolymer (B) with less fish eyes can be obtained.

The olefin polymerization catalyst used in producing the propylene homopolymer (B) includes a solid catalyst component containing magnesium, titanium, and halogen as essential components, an organometallic compound catalyst component such as an organoaluminum compound, and an organosilicon catalyst. Although it can be formed from an electron donor compound catalyst component such as a compound, the following catalyst components can be typically used.

A preferred support for the solid catalyst component is obtained from magnesium metal, an alcohol, and a halogen and/or a halogen-containing compound. In this case, magnesium metal may be in the form of granules, ribbons, powder, or the like. Further, it is preferable that this metallic magnesium is not coated with magnesium oxide or the like on its surface.

As the alcohol, it is preferable to use a lower alcohol having 1 to 6 carbon atoms, and in particular, when ethanol is used, the above-mentioned carrier can be obtained which significantly improves the expression of catalytic performance.
As the halogen, chlorine, bromine, or iodine is preferable, and iodine can be particularly preferably used. Further, as the halogen-containing compound, MgCl ₂ and MgI ₂ can be suitably used.

The amount of alcohol is preferably 2 to 100 mol, particularly preferably 5 to 50 mol, per 1 mol of magnesium metal.
The amount of halogen or halogen-containing compound to be used is usually 0.0001 gram atom or more, preferably 0.0005 gram atom or more, per 1 gram atom of metal magnesium, and Preferably it is 0.001 gram atom or more. One type of halogen and a halogen-containing compound may be used alone, or two or more types may be used in combination.

A method for reacting metallic magnesium, alcohol, and a halogen and/or halogen-containing compound is, for example, a reaction method in which metallic magnesium, alcohol, and a halogen and/or halogen-containing compound are heated under reflux (about 79°C) until generation of hydrogen gas is observed. In this method, the carrier is obtained by reacting until it disappears (usually for 20 to 30 hours). This is preferably carried out under an inert gas (eg nitrogen gas, argon gas) atmosphere.

When the obtained carrier is used for the next synthesis of the solid catalyst component, it may be dried or it may be filtered and washed with an inert solvent such as heptane. Furthermore, this carrier is nearly granular and has a sharp particle size distribution. Furthermore, even when looking at individual particles, the variation in particle size is extremely small. In this case, the sphericity (S) expressed by the following formula (I) is less than 1.60, particularly less than 1.40, and the particle size distribution index (P) expressed by the following formula (II) is less than 1.60, particularly less than 1.40. is preferably less than 5.0, particularly less than 4.0.
S=(E1/E2) ² ...(I)
Here, E1 indicates the projected outline length of the particle, and E2 indicates the circumferential length of a circle equal to the projected area of the particle.
P=D90/D10...(II)

Here, D90 refers to a particle diameter corresponding to a weight cumulative fraction of 90%. That is, it shows that the sum of the weights of the particle groups smaller than the particle diameter represented by D90 is 90% of the total weight of all particles. The same applies to D10.

In order to produce a solid catalyst component, at least a titanium compound is brought into contact with the support.
As this titanium compound, general formula (III)
TiX1 _n (OR1) _4-n ...(III)
(In formula (III), X1 is preferably a halogen atom, especially a chlorine atom, R1 is a hydrocarbon group having 1 to 10 carbon atoms, especially a linear or branched alkyl group, and when there is a plurality of R1s, They may be the same or different from each other. n is an integer from 0 to 4.) A titanium compound represented by the following can be used. Specifically, Ti(O-i-C ₃ H ₇ ) ₄ , Ti(O-C ₄ H ₉ ) ₄ , TiCl(O-C ₂ H ₅ ) ₃ , TiCl(O-i-C ₃ H ₇ ) ₃ , TiCl (O-C ₄ H ₉ ) ₃ , TiCl ₂ (O-C ₄ H ₉ ) ₂ , TiCl ₂ (O-i-C ₃ H ₇ ) ₂ , TiCl ₄ and the like. Particularly preferred is _TiCl4 .

The solid catalyst component is obtained by further contacting the above-mentioned carrier with an electron-donating compound. Di-n-butyl phthalate is used as the electron-donating compound.
Further, when bringing the titanium compound and the electron-donating compound into contact with the above-mentioned carrier, it is preferable to bring a halogen-containing silicon compound such as silicon tetrachloride into contact.

The above-mentioned solid catalyst component can be prepared by a known method. For example, the above-mentioned carrier, electron donating compound, and halogen-containing silicon compound are added to an inert hydrocarbon such as pentane, hexane, peptane, or octene as a solvent, and the titanium compound is added while stirring. Usually, 0.01 to 10 mol, preferably 0.05 to 5 mol, of the electron-donating compound is added to 1 mol of the carrier in terms of magnesium atoms, and titanium is added to 1 mol of the carrier in terms of magnesium atoms. The compound is added in an amount of 1 to 50 mol, preferably 2 to 20 mol, and subjected to a catalytic reaction at 0 to 200°C for 5 minutes to 10 hours, preferably at 30 to 150°C for 30 minutes to 5 hours. All you have to do is
Note that after the reaction is completed, it is preferable to wash the produced solid catalyst component with an inert hydrocarbon (eg, n-hexane, n-heptane).

Further, among the catalyst components, an organoaluminum compound can be suitably used as the organometallic compound catalyst component.
This organoaluminum compound has the general formula (IV)
AlR2 _n X2 _3-n ...(IV)
(In the formula, R2 is an alkyl group, cycloalkyl group, or aryl group having 1 to 10 carbon atoms, and X2 is a halogen atom, preferably a chlorine atom or a bromine atom. n is an integer of 1 to 3.) Compounds represented by are widely used. Examples include trialkylaluminium compounds such as trimethylaluminum, triethylaluminum, and triisobutylaluminum, diethylaluminum monochloride, diisobutylaluminum monochloride, diethylaluminum monoethoxide, and ethylaluminum sesquichloride. These may be used alone or in combination of two or more.

Furthermore, among the catalyst components, the electron donor compound catalyst component to be supplied to the polymerization system is at least selected from the group consisting of dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, diethylaminotriethoxysilane, diisopropyldimethoxysilane, and cyclohexylisobutyldimethoxysilane. One organosilicon compound is used.

The above-mentioned solid catalyst component is preferably pretreated before being used for polymerization. For example, the above-mentioned solid catalyst component, organometallic compound catalyst component, and electron donor compound catalyst component are added to an inert hydrocarbon such as pentane, hexane, peptane, or octene as a solvent, and propylene is supplied while stirring. Make it react. Further, the organometallic compound catalyst component is usually added in an amount of 0.01 to 20 mol, preferably 0.05 to 10 mol, per 1 mol of titanium atom in the solid catalyst component, and the electron donor compound catalyst component is It is advisable to add 0.01 to 20 moles, preferably 0.1 to 5 moles, per mole of titanium atoms in the catalyst component. Propylene is preferably supplied under a partial pressure of propylene higher than atmospheric pressure, and pretreated at 0 to 100° C. for 0.1 to 24 hours. Note that after the reaction is completed, it is preferable to wash the pretreated product with an inert hydrocarbon (eg, n-hexane, n-heptane).

In the method for producing the propylene homopolymer (B), the production conditions for the propylene homopolymer (b1) include, in the absence of hydrogen, the polymerization temperature is preferably 20 to 80°C, more preferably 40 to 70°C; It is preferable to carry out bulk polymerization of raw material monomers under polymerization pressure conditions, generally normal pressure to 9.8 MPa, preferably 0.2 to 4.9 MPa.

Further, the conditions for producing the propylene homopolymer (b2) are not particularly limited other than using the above-mentioned olefin polymerization catalyst, but the polymerization temperature is preferably 20 to 80°C, more preferably 40 to 70°C, The polymerization pressure is generally normal pressure to 9.8 MPa, preferably 0.2 to 4.9 MPa, and it is preferable to polymerize the raw material monomers under conditions in the presence of hydrogen as a molecular weight regulator.

The propylene homopolymer (B) may contain additives such as an antioxidant, a neutralizing agent, a flame retardant, a crystal nucleating agent, and the like, if necessary. The proportion of additives is not particularly limited and can be adjusted as appropriate.

[Propylene homopolymer (C)]
<Requirement (C-1)>
The melt flow rate (MFR, ASTM D1238, 230°C, 2.16 kg load) of the propylene homopolymer (C) is 0.5 to 10.0 g/10 minutes, preferably 1 to 8 g/10 minutes. be. When the MFR of the propylene homopolymer (C) satisfies the above range, the resulting propylene polymer composition (A) has good extrusion processability, and a microporous film with excellent air permeability and strength can be obtained.

In one embodiment, the propylene homopolymer (C) satisfies the above requirement (C-1) other than the propylene homopolymer (B) that satisfies the above requirements (B-1) to (B-2). It is a propylene homopolymer.

<Requirement (C-2)>
The mesopentad fraction (mmmm fraction) of the propylene homopolymer (C) is preferably 94.0% or more, more preferably 95.5% or more and 99.5% or less, and still more preferably 95.5% or more and 99. .0% or less. When the mesopentad fraction is within the above range, the crystallinity of the original film will be high, and in the stretching process, only the amorphous material will be deformed without deforming the lamellae, so that micropores will be efficiently formed, resulting in excellent This is preferable because it provides good air permeability. On the other hand, if the mesopentad fraction is less than the lower limit of the above range, the lamellae are likely to deform during the stretching process due to a decrease in crystallinity and crystal size, which is not preferable because the air permeability of the microporous film may decrease.
The propylene homopolymer (C) having a mmmm fraction within the above range can be produced, for example, by appropriately selecting a known catalyst described below.

<Method for producing propylene homopolymer (C)>
The method for producing the propylene homopolymer (C) is not particularly limited, and a Ziegler-Natta catalyst or a metallocene catalyst can be used as the catalyst, but it is preferable to use a Ziegler-Natta catalyst. Since the molecular weight distribution of the propylene homopolymer obtained by the Ziegler-Natta catalyst is wider than that of the metallocene catalyst, the propylene homopolymer (C) and the propylene homopolymer (B) are easier to mix, and therefore the propylene polymer composition This is because there is less possibility that fish eyes will occur in the film obtained from (A).

When using a Ziegler-Natta catalyst, the propylene homopolymer (C) is selected from the group consisting of the solid titanium catalyst component (I) and groups 1, 2 and 13 of the periodic table. It is preferably obtained by polymerizing propylene in the presence of an olefin polymerization catalyst containing an organometallic compound (II) containing a metal atom and, if necessary, an electron donor (III).

[Propylene homopolymer (D)]
The intrinsic viscosity [η] of the propylene homopolymer (D) contained in the propylene polymer composition (A) of one embodiment measured in tetralin at 135°C is 1.5 to 3.0 dL/g. , preferably 1.5 to 2.5 dL/g, more preferably 1.5 to 2.0 dL/g. Further, the content ratio of the propylene homopolymer (D) in the propylene polymer composition (A) of this embodiment is preferably 90.0 to 99.6% by mass, more preferably 94.0 to 99.5% by mass. (However, the total amount of the propylene homopolymer (b1) and the propylene homopolymer (D) is 100% by mass.) The intrinsic viscosity [η] can be calculated using equation (2) described below.

When the intrinsic viscosity [η] of the propylene homopolymer (D) is less than 1.5 dL/g, fish eyes tend to occur and the strength of the microporous film decreases, and when it exceeds 3.0 dL/g, It tends to cause poor extrusion. Furthermore, if the content of the propylene homopolymer (D) is less than 99.6% by mass, extrusion tends to be poor, and if it exceeds 90.0% by mass, the air permeability of the microporous film tends to decrease. .
The propylene homopolymer (D) can be produced, for example, by adjusting the intrinsic viscosity and blending ratio of the propylene homopolymer (b2) and the propylene homopolymer (C).

[Method for producing propylene polymer composition (A)]
The propylene polymer composition (A) can be produced by various known production methods, such as dry blending or melting in an extruder, using desired amounts of the propylene homopolymer (B) and the propylene homopolymer (C). It is preferable to manufacture by mixing by a conventional method such as kneading. For example, the above-mentioned various components may be kneaded using a conventional kneading device such as a Henschel mixer, a ribbon blender, or a Banbury mixer. Melt-kneading and pelletizing are performed using a conventional single-screw extruder or twin-screw extruder, Brabender or roll, usually at 170 to 280°C, preferably 190 to 250°C, and then pelletized. A twin-screw extruder may decompose and reduce ultra-high molecular weight components, so a single-screw extruder is more preferable.

As the method for producing the propylene polymer composition (A), the propylene homopolymer (b1) and the propylene homopolymer (D) are mixed by a method such as dry blending or melt kneading in an extruder. The method of mixing the propylene homopolymer (B) and the propylene homopolymer (C) is preferable in that a uniform, high-strength microporous film can be obtained.

In addition, to the extent that the object of the present invention is not impaired, the propylene polymer composition (A) may contain at least one kind selected from the group consisting of additives, polyolefins other than propylene homopolymers, plasticizers, and inorganic powders. It may contain materials.

1. Additives The propylene polymer composition (A) preferably contains known antioxidants and neutralizing agents that can generally be blended into polypropylene resins. The amount of antioxidant added is usually 500 to 8000 mass ppm, preferably 750 to 7500 mass ppm, based on the propylene polymer composition (A), but on the other hand, it may cause film defects such as fish eyes and an increase in sticky components. The amount of the connecting neutralizing agent is usually 5 to 1000 ppm by mass, preferably 10 to 750 ppm by mass, and more preferably 15 to 500 ppm by mass.

In addition, as for additives other than antioxidants and neutralizing agents, any known additives that can be blended into polypropylene resin can be used as long as they do not impair the purpose of the present invention. For example, nucleating agents (phosphorus α-crystal nucleating agents such as acid ester metal salts and sorbitol-based compounds, β-crystal nucleating agents such as amide-based compounds), ultraviolet absorbers, lubricants, flame retardants, antistatic agents, and the like can be used.

2. Polyolefin other than propylene homopolymer The propylene polymer composition (A) may include propylene-ethylene copolymer and other propylene-based polyolefins for the purpose of imparting functions such as shutdown characteristics, as long as it does not contradict the purpose of the present invention. A copolymer or a polyolefin such as polyethylene may be blended.
The content of ethylene units in the propylene/ethylene copolymer varies depending on the properties imparted, but is usually 0.1 to 5% by mass, preferably 0.1 to 4% by mass.

3. Plasticizer The propylene polymer composition (A) may contain a plasticizer within a range that does not impede the object of the present invention. Plasticizers include aliphatic, cycloaliphatic, or aromatic hydrocarbons such as nonane, decane, decalin, paraxylene, and liquid paraffin, as well as mineral oil fractions with boiling points corresponding to these, as solvents that are liquid at room temperature. Examples of solvents that are solid at room temperature include stearyl alcohol and paraffin wax. Among these, solvents that are liquid at room temperature are preferred, and liquid paraffin is particularly preferred. When a plasticizer is blended, it is preferable that a part of the microporous film manufacturing process includes a cleaning process of the film using a solvent.

4. Inorganic Powder The propylene polymer composition (A) may contain an inorganic powder for the purpose of adjusting the shape and amount of pores and heat resistance. Examples of the inorganic powder include talc, clay, calcium carbonate, mica, silicates, carbonates, and oxides and nitrides of metals such as silicon, aluminum, and titanium. Among these, metal oxides and nitrides are preferred, and silica powder is particularly preferred. The average particle size of the inorganic powder is desirably within the range of 0.001 to 10 μm, preferably 0.01 to 5 μm. Inorganic powders can be used alone or in combination of two or more. The content of inorganic powder in the propylene polymer composition (A) is usually 1 to 80% by mass, preferably 10 to 60% by mass.

<Preparation method of microporous film>
Preferred embodiments for preparing the microporous film of the present invention using the propylene polymer composition (A) are as follows. That is, by using the propylene polymer composition (A) and forming it through the following process of producing a raw film and stretching process (cold stretching process followed by warm stretching process), better strength and breathability can be achieved. A microporous film with excellent balance can be produced. Further, if necessary, the microporous film can be surface-treated and made into a multilayer film as described later.

1. Production process of raw film In the production process of raw film, general film molding machines such as inflation molding machines that use cylindrical dies, cast molding machines that use rectangular die (T-die), and sheet molding machines are used. A molding machine can be used. In particular, a cast molding machine or a sheet molding machine having a T-die is preferred because uniaxial stretching is easy.

When molding is performed using a T-die, the extrusion temperature is usually set at 180 to 250°C, preferably 180 to 240°C, and more preferably 190 to 230°C. If the temperature is lower than the lower limit temperature, unmelted spots or uneven melting may occur, and if the temperature exceeds the upper limit temperature, the molecular orientation of the raw film may become insufficient, which is not preferable. Further, the value obtained by dividing the lip opening degree of the T-die by the thickness of the original film (withdrawal ratio) is usually set to 30 to 300, preferably 40 to 200, and more preferably 50 to 150. If it is less than the lower limit, the orientation of the original film becomes smaller, which may reduce the air permeability of the microporous film, and if it exceeds the upper limit, the thickness of the original film may become uneven, which is not preferable. This range is preferable because the orientation of the raw film is large and the thickness unevenness is small.

The temperature of the chill roll during production of the original film (chill roll temperature) is usually set at 60 to 160°C, preferably 80 to 150°C, and more preferably 100 to 140°C. When the chill roll temperature is set below the lower limit temperature, the raw film is rapidly cooled, resulting in a decrease in crystallinity and crystal size, and in the next stretching process, the lamellae in the raw film are deformed and micropores are formed. This is not preferable because it may not be formed. Moreover, if the chill roll temperature exceeds the upper limit temperature, the molten film cannot be sufficiently solidified, so it may be difficult to produce a raw film, which is not preferable.

In one embodiment, the obtained raw film is heated at a temperature of usually 80 to 170°C, preferably 80 to 160°C, more preferably 80 to 150°C, usually for 5 minutes or more, preferably 30 minutes. Aging is preferably carried out for one hour or more. This is because by aging the raw film in the above range, many uniform micropores are formed in the next stretching step, and the air permeability of the microporous film is improved. If the aging temperature range is set below the lower limit temperature, the crystals may not grow sufficiently during aging and the aging effect may not be observed, and if it is set above the upper limit temperature, the original film may melt. Therefore, it is undesirable.

If necessary, processes such as surface treatments such as corona treatment, flame treatment, and ozone treatment, and hydrophilic treatment may be performed on both surfaces or one of the surfaces of the original film. Furthermore, for the purpose of imparting a shutdown function, for example, a multilayer film may be prepared using a resin (for example, polyethylene) having a lower melting point than the propylene polymer composition (A). For the purpose of imparting further heat resistance, multilayering with a resin such as polyolefin or polyamide having a higher melting point than the propylene polymer composition (A) may be performed.

2. Stretching Step For stretching the raw film, general stretching methods such as roll stretching, tenter stretching, and tubular stretching can be applied. Although the stretching method is not particularly limited, uniaxial stretching using a roll stretching method is preferred. The stretching process includes, for example, two steps: first, cold stretching is performed to create cracks between the lamellae, and then hot stretching is performed while maintaining the cold stretching draw ratio to widen the cracks and form micropores.

In the cold stretching process, the stretching temperature of the original film is usually 0 to 80°C, preferably 0 to 60°C, more preferably 0 to 40°C, and the stretching ratio is usually 1. 05 to 3.00 times, preferably 1.10 to 2.50 times, more preferably 1.15 to 2.50 times. If the stretching temperature is less than the lower limit, it is not preferable because the raw film may break without cracking between the lamellae. On the other hand, if the upper limit temperature is exceeded, the lamellae may also deform and cracks may not occur. If the stretching ratio is less than the lower limit, no cracks will occur, and if it exceeds the upper limit, the raw film may break.

In the hot stretching step, the stretching temperature is usually 100 to 160°C, preferably 100 to 150°C, more preferably 100 to 140°C, and the stretching ratio is usually 1.05 with respect to the film after cold stretching. ~3.00 times, preferably 1.10 to 2.50 times, more preferably 1.15 to 2.50 times. If the stretching temperature is less than the lower limit, micropores may not be formed and through holes may not be effectively formed. On the other hand, if the upper limit temperature is exceeded, the crystals may melt and micropores may not be formed. If the stretching ratio is less than the lower limit, micropores will not be formed, and if it exceeds the upper limit, the raw film may break. Further, it is preferable to hot stretch the film while maintaining the stretching ratio of the cold stretched film.

When adjusting the heat shrinkage rate of the microporous film, the microporous film may be aged after hot stretching, if necessary. The aging temperature is usually 30 to 160°C, preferably 40 to 160°C, more preferably 50 to 140°C, and the fixed ratio of the film during aging is usually 0.70 with respect to the film after hot stretching. ~1.0 times, preferably 0.75 to 1.00 times, more preferably 0.80 to 0.95 times. If the aging temperature is less than the lower limit, the thermal shrinkage rate of the microporous film cannot be adjusted, and if the aging temperature exceeds the upper limit, the crystals of the propylene polymer composition may melt and the air permeability may decrease. Additionally, if the fixed ratio of the film during aging is less than the lower limit, the micropores formed by stretching may close or the size of the micropores may become extremely small, leading to a decrease in air permeability. If the upper limit is exceeded, the thermal shrinkage rate cannot be adjusted, which is not preferable.

The thickness of the microporous film is usually 5 to 50 μm, preferably 10 to 40 μm, and more preferably 10 to 30 μm. If the film thickness is less than the lower limit, the strength of the microporous film will decrease, which is undesirable, and if it exceeds the upper limit, it will become difficult to form through holes, so there is a risk that air permeability will decrease.

The Gurley air permeability of the microporous film made of the propylene polymer composition (A) of the present invention is usually 400 sec/100 mL or less, preferably 350 sec/100 mL or less, and more preferably 300 sec/100 mL or less. In one embodiment, the lower limit of the air permeability is, for example, 150 or 200 sec/100 mL. Air permeability is measured according to JIS P8117.

3. Surface treatment: If necessary, surface treatments using inorganic coatings to impart heat resistance and chemical resistance to the obtained microporous film, or surfactants to change wettability are applied to both surfaces of the film. Alternatively, it can be applied to either surface. In addition, for the purpose of imparting a shutdown function, the obtained microporous film may be multilayered, for example, with a resin (including an ethylene polymer) having a lower melting point than the propylene polymer composition (A). For the purpose of imparting heat resistance, multilayering with a resin having a higher melting point than the propylene polymer composition (A) may be performed.

4. Making a microporous film into a multilayer film The propylene polymer composition (A) (hereinafter abbreviated as PP-A) may be coextruded with polyethylene or low melting point polypropylene. For example, for the purpose of imparting shutdown properties, PP-A/(polyethylene (PE) or low melting point polypropylene (PP))/PP-A, or (PE or low melting point PP)/PP-A/(PE or Examples include a method of producing a multilayer raw film having a three-layer structure such as low melting point PP). Alternatively, a method may be used in which microporous films using PP-A, polyethylene, and low melting point polypropylene are respectively prepared and laminated together.

Furthermore, for the purpose of imparting heat resistance, a microporous film using a heat-resistant resin such as an aramid resin is produced and bonded to the microporous film produced from the propylene polymer composition (A) according to the present invention. The microporous film may be multilayered by a method of multilayering.

<Application>
The microporous film according to the present invention is preferably used as one type selected from the group consisting of a separator, a filtration film, and a separation membrane. That is, a separator, a filtration film, or a separation membrane having at least the microporous film according to the present invention can be mentioned.

It is preferable that the separator is a battery separator or a capacitor separator, and it is particularly preferable that the battery separator is a lithium ion secondary battery separator. Further, it is preferable that the filtration film is a medical filtration film, and the separation membrane is a medical separation membrane.

Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to these Examples. The methods for measuring physical properties in Examples and Comparative Examples are as follows.

1. Test method (1) Mesopentad fraction (mmmm)
The mesopentad fraction (mmmm, %), which is one of the indicators of the stereoregularity of a polymer and whose microtacticity was investigated, is the A. This is a value determined by assignment based on Zambelli et al., Macromolecules 8, 687 (1975), and was measured by ¹³ C-NMR under the following conditions, mesopentad fraction = (peak area at 21.7 ppm) / (19 The peak area at ~23 ppm)×100.
Equipment: Bruker Iospin AVANCE III cryo-500 type nuclear magnetic resonance apparatus Measurement nucleus: ¹³ C (125 MHz)
Measurement mode: Single pulse proton broadband decoupling Pulse width: 45° (5.00 microseconds)
Repetition time: 5.5 seconds Number of integration: 256 times Measurement solvent: o-dichlorobenzene/heavybenzene (80/20% by volume) mixed solvent Sample concentration: 50 mg/0.6 mL
Measurement temperature: 120℃
Chemical shift standard: 21.59ppm
(2) Melt flow rate (MFR)
Melt flow rate (MFR) was measured under the conditions of 230° C. and 2.16 kg load according to ASTM D1238.
(3) Average molecular weight and molecular weight distribution Liquid chromatograph: Waters ALC/GPC150-Cplus type
(Differential refractometer detector integrated)
Column: Tosoh Corporation GMH6-HT x 2 and
Two GMH6-HTLs were connected in series.
Mobile phase medium: o-dichlorobenzene Flow rate: 1.0 mL/min Measurement temperature: 140°C
Calibration curve creation method: Using standard polystyrene sample Sample concentration: 0.10% (W/W)
Sample solution volume: 500μL

By measuring under the above conditions and analyzing the obtained chromatogram by a known method, the weight average molecular weight Mw and number average molecular weight Mn of the propylene polymer composition were calculated, and Mw/Mn was calculated. The molecular weight was calculated by the universal calibration method, and the value was calculated in terms of polystyrene. The baseline of the GPC chromatogram was set at the retention time at which the elution curve rises, and at the retention time corresponding to a molecular weight of 1000 as the end point.

(4) Content ratio of propylene homopolymer having a molecular weight of 10 million or more It was calculated from the area ratio of a molecular weight of 10 million or more from the GPC curve obtained under the above conditions.
(5) Content ratio of propylene homopolymer with molecular weight of 50,000 or less Calculated from the area ratio of molecular weight of 50,000 or less from the GPC curve obtained under the above conditions.
(6) Intrinsic viscosity [η]
The test was carried out at 135° C. in Tetralin using an Ubbelohde viscometer.
The intrinsic viscosity [η] _b2 of the propylene homopolymer (b2) was calculated from the following formula.
[η] _b2 = (100 [η] _total −W _b1 [η] _b1 )/W _b2 (1)
[η] _total : Intrinsic viscosity of propylene homopolymer (B) [η] _b1 : Intrinsic viscosity of propylene homopolymer (b1)
W _b1 : Mass fraction (mass%) of propylene homopolymer (b1)
W _b2 : Mass fraction (mass%) of propylene homopolymer (b2)
However, the total amount of the propylene homopolymer (b1) and the propylene homopolymer (b2) is 100% by mass.

On the other hand, the intrinsic viscosity [η] _D of the propylene homopolymer (D) was calculated from the following formula.
[η] _D = (W _b2 [η] _b2 + W _C [η] _C )/100 (2)
[η] _D : Intrinsic viscosity of propylene homopolymer (D) [η] _C : Intrinsic viscosity of propylene homopolymer (C)
W _b2 : Mass fraction (mass%) of propylene homopolymer (b2)
W _C : Mass fraction (mass%) of propylene homopolymer (C)
However, the total amount of the propylene homopolymer (b2) and the propylene homopolymer (C) is 100% by mass. Therefore, the value of W _b2 in equation (2) is different from the value of W _b2 in equation (1).

(7) Number of fish eyes The number of fish eyes in the propylene polymer composition (A) was evaluated according to the following method. That is, the number of fish eyes on a 50 μm thick film produced using a 25 mm Φ T-die film forming machine manufactured by Plastic Engineering Research Institute Co., Ltd. was calculated using a Fish Eye Counter (trademark) manufactured by Hutech Co., Ltd. as a gel counter. It was measured. The number of measurements was shown as the number of fish eyes (size 100 μm or more) per unit area of the film (3000 cm ² ). Note that since the fish eyes of the microporous film cannot be measured because they are white, measurements were made under these conditions.
The conditions for making the film are as follows.
T-die film forming machine: Made by Plastic Engineering Research Institute, Ltd. Model: GT-25-A
Screw diameter: 25mm, L/D=24
Screw rotation speed: 60rpm
Cylinder temperature setting: C1=230℃, C2=260℃
Head temperature setting: 260℃
T-die temperature setting: D1 to D3 = 260℃
T-die width: 230mm, lip opening = 1mm
Film winding speed: 4m/s
Roll temperature: 65℃
The measurement conditions of the gel counter (size 100 μm or more) are as follows.
Device configuration (1) Photoreceiver (4096 pixels)
(2) Floodlight (3) Signal processing device (4) Pulse generator (5) Inter-device cable

(8) Gurley air permeability Gurley air permeability (hereinafter abbreviated as "air permeability") was used as an index of air permeability. The lower the air permeability, the better the air permeability. Air permeability was measured according to JIS P8117. The measuring device used was a B-type Gurley densometer (manufactured by Toyo Seiki Seisakusho). Test temperature: 23°C, humidity: 50% RH. The sample area was 645 mm ² . With a cylinder weight of 567 g, air inside the cylinder is passed through the test hole to the outside of the cylinder. The time taken for 100 mL of air to pass through was measured and defined as the air permeability (sec/100 mL).
(9) Puncture strength (N)
The puncture strength (N) was calculated from the maximum load when puncturing at 2 mm/sec using a needle with a diameter of 1 mm and a radius of 0.5 mm. The measurement conditions are described below:
Testing machine: Toyo Seiki Seisakusho Strograph V10-D
Test speed: 120mm/min
Tip: 1.0mmΦ, 0.5mm
R receiving: 30.0mmΦ (gross test jig)

2. Propylene homopolymer (B) Propylene homopolymer (B1) Propylene homopolymer [Production Example 1]
(1) Preparation of magnesium compound A reaction tank equipped with a stirrer (inner volume 500 liters) was sufficiently replaced with nitrogen gas, 97.2 kg of ethanol, 640 g of iodine, and 6.4 kg of metallic magnesium were added, and the mixture was heated under reflux conditions while stirring. The reaction was carried out until no hydrogen gas was generated from the system, and a solid reaction product was obtained. The target magnesium compound (solid catalyst carrier) was obtained by drying the reaction solution containing this solid reaction product under reduced pressure.

(2) Preparation of solid catalyst component In a reaction tank with a stirrer (inner volume 500 liters) that was sufficiently purged with nitrogen gas, 30 kg of the above magnesium compound (not crushed), 150 liters of purified heptane (n-heptane), 4.5 liters of silicon tetrachloride and 5.4 liters of di-n-butyl phthalate were added. The inside of the system was maintained at 90°C, and 144 liters of titanium tetrachloride was added while stirring, and the reaction was carried out at 110°C for 2 hours.The solid components were separated and washed with purified heptane at 80°C. Further, 228 liters of titanium tetrachloride was added, and the mixture was reacted at 110° C. for 2 hours, and then thoroughly washed with purified heptane to obtain a solid catalyst component.

(3) Production of prepolymerization catalyst 10 mmol of triethylaluminum, 2 mmol of dicyclopentyldimethoxysilane, and 1 mmol of the solid catalyst component obtained in (2) in terms of titanium atoms were added to 200 mL of heptane. The internal temperature was maintained at 20° C., and propylene was continuously introduced while stirring. After 60 minutes, stirring was stopped, and as a result, a prepolymerized catalyst in which 4.0 g of propylene was polymerized per 1 g of solid catalyst component was obtained.

(4) Main polymerization 336 liters of propylene was charged into a 600 liter autoclave, and the temperature was raised to 60°C. Thereafter, 8.7 mL of triethylaluminum, 11.4 mL of dicyclopentyldimethoxysilane, and 2.9 g of the prepolymerization catalyst obtained in (3) were charged to start polymerization. 83 minutes after the start of polymerization, the temperature was lowered to 45° C. over 10 minutes (first stage polymerization completed).

The intrinsic viscosity [η] of the propylene homopolymer (b1) polymerized under the same conditions as in the first stage was 11 dL/g.
After the temperature was lowered in the same polymerization tank as in the first stage, hydrogen was continuously introduced to keep the pressure constant at 3.3 MPaG, and polymerization was carried out for 112 minutes. Next, the vent valve was opened, and unreacted propylene was purged through the integrating flow meter (completion of second stage polymerization).

In this way, polymerization was carried out in a batch manner, and 35.3 kg of powdered propylene homopolymer (B1) was obtained.
The MFR of the propylene homopolymer (B1) finally obtained in this way was 0.2 g/10 minutes. Further, the proportion of the propylene homopolymer (b1) produced in the first stage polymerization in the finally obtained propylene homopolymer (B1) calculated from the material balance was 38% by mass.

(B2) Propylene homopolymer [Production Example 2]
Polymerization was carried out in the same manner as in Production Example 1, except that the first stage polymerization time was 75 minutes, the second stage polymerization temperature was 50° C., and the polymerization time was 160 minutes. As a result, 54.4 kg of propylene homopolymer (B2) was obtained. The MFR is 1.9 g/10 minutes, and the proportion of the propylene homopolymer (b1) produced in the first stage polymerization in the finally obtained propylene homopolymer (B2) calculated from the material balance is 24 It was mass%.

(B3) Made by Prime Polymer Co., Ltd.: Product name “VP103W”
Propylene homopolymer (b1): Intrinsic viscosity [η] = 8 dL/g, component amount = 20% by mass
Propylene homopolymer (b2): Intrinsic viscosity [η] = 1.44 dL/g, component amount = 80% by mass
MFR=3g/10min Table 1 shows the physical properties of the propylene homopolymer VP103W obtained in Production Examples 1 and 2.

(C) Propylene homopolymer (C1) Propylene homopolymer Produced according to Example 3 of WO2014/65331.
(C2) Propylene homopolymer [Production Example 3]
<Preparation of solid titanium (a-1)>
After thoroughly purging a high-speed stirring device (manufactured by Tokushu Kika Kogyo) with an internal volume of 2 liters with nitrogen, 700 mL of refined kerosene, 10 g of magnesium chloride, 24.2 g of ethanol, and sorbitan distearate (manufactured by Kao Atlas Co., Ltd.) were added to the device. 3 g of Emazol 320'') was charged. The temperature of this system was raised under stirring, and the mixture was stirred for 30 minutes at 120° C. and 800 rpm. Under high-speed stirring, using a Teflon (registered trademark) tube with an inner diameter of 5 mm, the liquid was transferred to a 2-liter glass flask (equipped with a stirrer) filled with 1 liter of refined kerosene previously cooled to -10°C. The obtained solid was filtered and thoroughly washed with purified n-hexane to obtain a solid adduct in which 2.8 moles of ethanol were coordinated to 1 mole of magnesium chloride.

Next, the solid adduct (45 mmol in terms of magnesium atoms) was suspended in 20 mL of decane, and then the entire amount was introduced into 195 mL of titanium tetrachloride kept at -20°C under stirring. The temperature of this mixture was raised to 80° C. over 5 hours, and 1.8 mL (6.2 mmol) of diisobutyl phthalate was added. Subsequently, the temperature was raised to 110°C and stirred for 1.5 hours.

After 1.5 hours of reaction, the solid portion was collected by hot filtration and washed with decane at 100°C and hexane at room temperature until titanium was no longer detected in the filtrate. In this way, solid titanium (a-1) containing 3.8% by mass of titanium, 16% by mass of magnesium, 18.2% by mass of diisobutyl phthalate, and 1.1% by mass of ethanol residue was obtained. Obtained.

<Preparation of solid titanium catalyst component (i-1)>
In a 200 mL glass reactor that was sufficiently purged with nitrogen, 6.8 g of the obtained solid titanium (a-1), 113 mL of paraxylene, 11 mL of decane, 2.5 mL (23 mmol) of titanium tetrachloride, and diisobutyl phthalate were added. - 0.34 mL (1.2 mmol) was added. The temperature inside the reactor was raised to 130°C, and the mixture was stirred at that temperature for 1 hour for contact treatment, and then the solid portion was collected by hot filtration. This solid portion was resuspended in 101 mL of paraxylene, and 1.7 mL (15 mmol) of titanium tetrachloride and 0.22 mL (0.8 mmol) of diisobutyl phthalate were added.

Next, the temperature was raised to 130°C, and the mixture was stirred and reacted for 1 hour while maintaining this temperature. After the reaction was completed, solid-liquid separation was performed again by hot filtration, and the obtained solid portion was washed with decane at 100°C and hexane at room temperature until the paraxylene content in the catalyst was reduced to 1% by mass or less. In this way, a solid titanium catalyst component (i-1) containing 1.3% by mass of titanium, 20% by mass of magnesium, 13.8% by mass of diisobutyl phthalate, and 0.8% by mass of diethyl phthalate was obtained.

The present inventors believe that the diethyl phthalate detected in the solid titanium catalyst component (i-1) is probably caused by diisobutyl phthalate and the above-mentioned solid titanium (a-1) during the manufacturing process of the solid titanium catalyst component. It is speculated that this may be due to accompanying transesterification with the ethanol used to produce ).

<Preparation of prepolymerization catalyst (b-1)>
Insert 140.0 g of solid titanium catalyst component (i-1), 51.9 mL of triethylaluminum, 17.7 mL of dicyclopentyldimethoxysilane, and 140 L of heptane into a 200 L autoclave equipped with a stirrer, and maintain the internal temperature at 10 to 15 °C. 840 g of propylene was added and reacted with stirring for 60 minutes. The obtained prepolymerization catalyst (b-1) contains 6 g of polypropylene per 1 g of solid titanium catalyst component (i-1), and the concentration of solid titanium catalyst component (i-1) is 1.0 g/L. there were.

<Production of propylene homopolymer (C2)>
300 liters of liquefied propylene was charged into a polymerization tank with an internal volume of 500 liters equipped with a stirrer, and while maintaining this liquid level, liquefied propylene 100 kg/h, prepolymerization catalyst (b-1) 0.9 g/h, and triethyl aluminum 5. 0 mL/h, dicyclopentyldimethoxysilane 4.6 mL/h were continuously supplied, and polymerization was carried out at a temperature of 70°C. Further, hydrogen was continuously supplied so that the hydrogen concentration in the gas phase in the polymerization tank was 1.8 mol%. After the obtained slurry was deactivated, it was sent to a washing tank using liquid propylene to wash the propylene polymer powder. After vaporizing the obtained slurry, gas-solid separation was performed to obtain a propylene homopolymer (C2). The obtained propylene homopolymer (C2) had an MFR of 4.0 g/10 minutes.

(C3) Propylene homopolymer Produced according to Comparative Example 2 of JP-A No. 2006-143975. The obtained propylene homopolymer (C3) had an MFR of 3.0 g/10 minutes.

[Example 1]
(1) Granulation step In addition to 5 parts by mass of the obtained propylene homopolymer (B1) powder and 95 parts by mass of propylene homopolymer (C1) powder, 3,5-di-t-butyl-4-hydroxytoluene After blending 0.2 parts by mass of, 0.5 parts by mass of tetrakis[methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, and 0.005 parts by mass of calcium stearate, It was melted at 230° C. and pelletized using a GMZ50-32 (L/D=32) single-screw extruder manufactured by GM Engineering Co., Ltd. to prepare a measurement sample, and its physical properties were evaluated. Furthermore, a microporous film was manufactured using the produced pellets as a raw material in the following method, and the results of evaluating the physical properties of the microporous film are also listed in Table 3 together with the results of evaluating the physical properties of the pellets.

(2) Production of microporous film A microporous film was produced as follows. Using a sheet molding machine made by GM Engineering, the pellets obtained in (1) above were melt-extruded at 230°C using a T-die with a width of 200mm and a lip opening of 2.0mm, and then with a cooling roll at 120°C. It was pulled at a speed of 12 m/min. The thickness of the raw film obtained at this time was 25 μm. Thereafter, annealing was performed at 120° C. for 1 hour. Next, using a uniaxial stretching machine, it was cold stretched to 1.4 times between nip rolls held at 25°C, followed by hot stretching to 1.7 times using rolls heated to 120°C, and then heated to 120°C. The film was relaxed by a factor of 0.9 using a roll, and a microporous film was obtained.

[Example 2] to [Example 5], [Comparative Example 1] to [Comparative Example 5]
It was carried out in the same manner as in Example 1, except that the amount of propylene homopolymer blended was as shown in Table 1.
Note that the air permeability of the microporous film obtained in Comparative Example 1 is lower than that of Example 3 of Patent Document 4. The reason for this is that in Example 3 of Patent Document 4, the melting temperature during film forming was 210°C, whereas in Comparative Example 1 of this specification, the melting temperature was as high as 230°C, and as the degree of orientation of the original film decreased, the microporous formation rate This is because the air permeability decreases. Another reason is that the roll temperature was 130°C in Example 3 of Patent Document 4, while it was as low as 120°C in Comparative Example 1 of this specification, and as the crystallinity of the propylene homopolymer in the film decreased, microporous formation occurred. This is because the rate decreases.

Table 4 shows the formulation compositions of Examples and Comparative Examples in Table 3 as a propylene homopolymer (b1) with an intrinsic viscosity [η] of 10.0 to 12.0 dL/g measured in tetralin at 135°C. A propylene homopolymer consisting of a propylene homopolymer (C) and a propylene homopolymer (b2) and having an intrinsic viscosity [η] of 1.5 to 3.0 dL/g as measured in tetralin at 135°C. This is a table reconstructed into the formulation composition (D).

Claims (7)

It is made of a propylene polymer composition (A) that satisfies the following requirements (A-1) to (A-4), has a thickness of 5 to 50 μm , and has a Gurley air permeability of 150 sec/100 mL or more and 400 sec/100 mL or less. Microporous film.
(A-1) Mesopentad fraction (mmmm) is 94.0% or more (A-2) Melt flow rate (ASTM D1238, 230°C, 2.16 kg load) is 0.5 to 5.0 g/10 (A-3) The value obtained by dividing the weight average molecular weight by the number average molecular weight (Mw/Mn) measured by gel permeation chromatography (GPC) is 7.0 to 17.0 (A-3) 4) The content of propylene homopolymer with a molecular weight of 10 million or more is 0.20 to 0.50% by mass. The propylene polymer composition (A) is a propylene homopolymer (b1) having an intrinsic viscosity [η] of 10.0 to 12.0 dL/g measured in tetralin at 135° C. 0.4 to 10 mass % and 99.6 to 90 mass % of a propylene homopolymer (D) having an intrinsic viscosity [η] of 1.5 to 3.0 dL/g as measured in tetralin at 135°C. 1. The microporous film described in 1. Propylene homopolymer (B) 2 to 20% by mass that satisfies the following requirements (B-1) to (B-2) and propylene homopolymer (C) 98 to 80% by mass that satisfies the following requirement (C-1) The microporous film according to any one of claims 1 to 2, comprising the propylene polymer composition (A) obtained by blending the propylene polymer composition (A).
(B-1) Melt flow rate (ASTM D1238, 230°C, 2.16kg load) is 0.01 to 5.0g/10 minutes (B-2) Intrinsic viscosity measured in tetralin at 135°C The content of the propylene homopolymer (b1) having [η] of 10.0 to 12.0 dL/g is 20 to 50% by mass, and the intrinsic viscosity [η] measured in tetralin at 135°C is 0. The content of the propylene homopolymer (b2), which is . is defined as 100% by mass.)
(C-1) Melt flow rate (ASTM D1238, 230°C, 2.16 kg load) is 0.5 to 10.0 g/10 minutes. The microporous film according to any one of claims 1 to 3, wherein the propylene polymer composition (A) satisfies the following requirement (A-5).
(A-5) The number of fish eyes per 3000 cm ² of a 50 μm thick film obtained from the propylene polymer composition (A) using a T-die film forming machine is 50 or less. A battery separator comprising at least one layer of the microporous film according to claim 1. A separation membrane comprising at least one layer of the microporous film according to any one of claims 1 to 4. A filtration film comprising at least one layer of the microporous film according to any one of claims 1 to 4.