Method for producing propylene-based block copolymer

Abstract

To produce a propylene-based block copolymer with high catalytic efficiency while reducing gel without excessively increasing the number of reactors in a multi-stage continuous polymerization method.SOLUTION: There is provided a method for producing a propylene-based block copolymer by multi-stage continuous polymerization including a first step and a second step in the presence of a catalyst for olefin polymerization using a gas phase fluidized bed polymerization reactor, wherein an insert nozzle having one or more discharge ports is connected to the straight body of the gas phase fluidized bed polymerization reactor in at least one of the first step and the second step, the distance from the discharge port on the most tip side of the nozzle to the inner wall of the cross-section of the gas phase fluidized bed polymerization reactor at the position where the discharge port exists, even for the distance from the discharge port to the inner wall of the cross-section at any location on the inner periphery of the cross-section, is within the range of 12% to 88% of the inner diameter of the cross-section and a gel formation inhibitor is fed from the insert nozzle into a powder held inside the reactor.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for producing a propylene-based block copolymer.

Background Art

[0002] Crystalline polypropylene obtained by polymerizing propylene under a stereoregular catalyst is widely and commonly used because it is lightweight, excellent in rigidity and heat resistance among thermoplastic resins, and is also easy to recycle. On the other hand, in order to improve the impact resistance, which is a drawback of crystalline polypropylene, crystalline polypropylene is produced in the first-stage polymerization, and then copolymerization of propylene and another α-olefin such as ethylene is carried out in the subsequent second-stage polymerization to produce an amorphous propylene·α-olefin copolymer to obtain a propylene-based block copolymer. A method is widely known. For the production of such propylene-based block copolymers, a multi-stage continuous polymerization method is most commonly adopted from the viewpoint of economy. However, in the multi-stage continuous polymerization method, since the residence time distribution of the catalyst occurs in the polymerization tank of each stage, the polymerization amount per catalyst particle has a distribution, and this non-uniformity causes a problem of generating an appearance defect called gel in the product. In addition, as a characteristic of the propylene-based block copolymer, the intrinsic viscosity η of the propylene·α-olefin copolymer may be increased to improve the melt tension, improve the flow mark, and reduce the surface gloss (matting). However, it is known that the problem of this gel particularly easily occurs in such polymers. As one of the countermeasures, a method of narrowing the residence time distribution by increasing the number of reactors for crystalline propylene polymerization, which is the first step, is known (for example, Patent Document 1).

[0003] Patent Document 2 states that in the multi-stage continuous polymerization method of propylene-based block copolymers, in the multi-stage continuous polymerization method, small particles such as catalyst particles that have passed through the first step in a short residence time and catalyst particles containing only a small amount of the first step product polymerize in the second step, resulting in the generation of particles containing more propylene-ethylene copolymers that are difficult to disperse on average, which is predicted to be the main cause of gel generation. And Patent Document 2 proposes, as a countermeasure based on this prediction, a method of continuously producing a propylene-based block copolymer containing a propylene-α-olefin copolymer by gas-phase polymerization, in which a mixed reaction inhibitor containing a specific polyoxyalkylene-based compound and a specific alcohol compound in a specific ratio is supplied as a mixed stream with liquefied propylene to the reactor for propylene-ethylene copolymerization, which is the second step. According to this method, small particles can suppress polymerization throughout the particle, and large particles can suppress polymerization only on the surface portion. By the remaining catalytic activity of the large particles that account for most of the catalytic activity, while suppressing a decrease in catalytic activity, an excellent gel generation suppressing effect is exhibited.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described above, since a propylene-based block copolymer containing a propylene-α-olefin copolymer having a high intrinsic viscosity has excellent properties, it is used as an industrial sheet, an automotive member, etc., while there has been a concern about poor product appearance due to gel generation. The countermeasure of increasing the number of reactors for the crystalline propylene polymerization which is the first step disclosed in Patent Document 1 causes an increase in the construction cost of the plant and the complexity of operation due to an increase in the plant operation management items, and thus further technological improvements have been demanded. The production method of supplying a mixed reaction inhibitor containing a specific polyoxyalkylene compound and a specific alcohol compound in a specific ratio as a mixed stream with liquefied propylene to the reactor for propylene-ethylene copolymerization which is the second step disclosed in Patent Document 2 cannot be applied in an operation without using liquefied propylene in terms of reactor temperature control and the like, and thus the development of a different supply method of the reaction inhibitor has been desired.

[0006] An object of the present invention is to provide a method for producing a propylene-based block copolymer with a high catalyst efficiency while reducing gels without excessively increasing the number of reactors in a multi-stage continuous polymerization method in view of the problems of the above prior art.

Means for Solving the Problems

[0007] The present inventors predicted that the main factor for the generation of gels is that small particles such as catalyst particles that have escaped with a short residence time in the first step and catalyst particles containing a small amount of the first step product copolymerize α-olefins in the second step, generating particles containing more than the average amount of a propylene-α-olefin copolymer that is difficult to disperse. Based on this prediction, the present inventors conducted intensive studies on the basis of the idea that by using a gel formation inhibitor unevenly distributed at a relatively shallow depth of the particles, the catalytic activity of the catalyst particles present in the small particles can be selectively deactivated, thereby suppressing the formation of gels in the intermediate product. As a result, in a method for continuously producing a propylene-based block copolymer containing a propylene-α-olefin copolymer, by supplying a gel formation inhibitor into the retained powder inside the reactor by a specific method, the dispersibility of the gel formation inhibitor is improved, and the gel formation inhibitor is uniformly dispersed in the retained powder without dripping onto the inner surface of the reactor, and while suppressing a decrease in catalytic activity, it has been found that an excellent gel generation suppressing effect is exhibited. Based on these findings, the present inventors have completed the present invention.

[0008] That is, the present invention provides a method for producing a propylene-based block copolymer described in the following [1] to [7]. [1] A method for producing a propylene-based block copolymer in which multistage continuous polymerization including a first step and a second step is carried out in the presence of a catalyst for olefin polymerization using a gas-phase fluidized bed polymerization reactor, An insert nozzle having at least one discharge port is connected to the straight body portion of the gas-phase fluidized bed polymerization reactor in at least one of the first step and the second step, and the distance from the discharge port existing at the most distal end side of the insert nozzle to the inner wall of the cross section of the gas-phase fluidized bed polymerization reactor at the position where the discharge port exists is such that, for the distance from the discharge port to the inner wall existing at any position on the inner circumference of the cross section, it is within the range of 12% to 88% with respect to the inner diameter of the cross section, A method for producing a propylene-based block copolymer in which a gel formation inhibitor is supplied from the insert nozzle into the retained powder inside the reactor.

[0009] [2] The production method according to [1], wherein the gel formation inhibitor is a compound represented by the following general formula (1). [General formula (1)] HO-[CH2-CH2-O] p -[CH2-CH(CH3)-O] q -[CH2-CH2-O] r -R 1 (In general formula (1), p, q, and r are integers, and all satisfy the relational expressions of 0 ≦ p ≦ 30, 0 ≦ q ≦ 70, 0 ≦ r ≦ 30, 1 ≦ p + r ≦ 60, and 2 ≦ p + q + r. R1 represents a hydrogen atom or a hydrocarbon group having 1 to 25 carbon atoms) [3] The production method according to [1] or [2], wherein the gel formation inhibitor is supplied in a proportion of 10 mass ppm to 1000 mass ppm with respect to the production amount of the propylene-based block copolymer. This is preferable.

[0010] [4] Further, the production method according to any one of [1] to [3], wherein a reaction inhibitor represented by the following general formula (2) is supplied into the retained powder inside the reactor. [General formula (2)] HO-R 2 (In general formula (2), R 2 represents a saturated hydrocarbon group having 1 to 10 carbon atoms) [5] The production method according to [4], wherein the supply amount of the gel formation inhibitor is 10 parts by mass to 150 parts by mass with respect to 100 parts by mass of the supply amount of the reaction inhibitor.

[0011] [6] The production method according to any one of [1] to [5], wherein polymerization is carried out in the presence of a solid catalyst component containing magnesium, titanium, a halogen, and an electron-donating compound as an internal donor, and an organoaluminum compound for olefin polymerization. [7] The production method according to any one of [1] to [6], wherein in the first step, a crystalline propylene-based polymer is produced using one or more gas-phase fluidized bed polymerization reactors, and in the subsequent second step, an amorphous propylene / α-olefin copolymer is produced using one or more gas-phase polymerization reactors in the presence of the crystalline propylene-based polymer. [Advantages of the Invention]

[0012] According to the present invention, it is possible to provide a method for producing a propylene-based block copolymer with high catalyst efficiency while reducing gels without excessively increasing the number of reactors in a multi-stage continuous gas-phase fluidized bed polymerization method. [Brief Description of the Drawings]

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0014] The production method of the present invention is a method for producing a propylene-based block copolymer in which multi-stage continuous polymerization including a first step and a second step is carried out in the presence of a catalyst for olefin polymerization using a gas-phase fluidized bed polymerization reactor, an insert nozzle having at least one discharge port is connected to the straight body portion of the gas-phase fluidized bed polymerization reactor in at least one of the first step and the second step, and the distance from the discharge port at the most distal end side of the insert nozzle to the inner wall of the cross section of the gas-phase fluidized bed polymerization reactor at the position where the discharge port exists is within the range of 12% to 88% with respect to the inner diameter of the cross section for any position on the inner circumference of the cross section from the discharge port to the inner wall existing at that position, A gel formation inhibitor is supplied from the insert nozzle into the retained powder inside the reactor.

[0015] The production method of the present invention can be carried out, for example, using the continuous vertical gas-phase fluidized bed polymerization reactor shown in FIG. 1. The continuous vertical gas-phase fluidized bed polymerization reactor shown in FIG. 1 includes a gas-phase fluidized bed polymerization reactor (first reactor 100) for carrying out the first step and a gas-phase fluidized bed polymerization reactor (second reactor 200) for carrying out the second step. An insert nozzle 114 is connected to the straight body part of the first reactor 100, and an insert nozzle 213 is connected to the straight body part of the second reactor 200. Details of the distance between the discharge port of the insert nozzle and the inner wall of the gas-phase fluidized bed polymerization reactor will be described later.

[0016] The production method of the propylene-based block copolymer of the present invention includes a first step and a second step as basic steps. In the first step, homopolymerization of propylene or copolymerization of propylene and at least one comonomer selected from the group consisting of ethylene and α-olefins having 4 to 8 carbon atoms is carried out using at least one gas-phase fluidized bed polymerization reactor to produce a crystalline propylene-based resin. Subsequently, in the second step, copolymerization of propylene and at least one comonomer selected from the group consisting of ethylene and α-olefins having 4 to 8 carbon atoms is carried out using at least one gas-phase polymerization reactor to continuously produce an amorphous propylene / α-olefin copolymer. In the present invention, an insert nozzle having at least one discharge port is connected to the straight body part of the gas-phase fluidized bed polymerization reactor in at least one of the first step and the second step, and the discharge port existing at the most distal end side of the insert nozzle is such that the distance from the discharge port to the inner wall of the cross section of the gas-phase fluidized bed polymerization reactor at the position where the discharge port is located is within the range of 12% to 88% with respect to the inner diameter of the cross section for the distance from the discharge port to the inner wall existing at any position on the inner circumference of the cross section. When the gel formation inhibitor is supplied into the retained powder inside the reactor through the above-described insert nozzle, the adhesion of the gel formation inhibitor to the wall surface is reduced, and the gel formation inhibitor is uniformly dispersed in the retained powder, thereby suppressing a decrease in catalytic activity and exhibiting an excellent gel generation suppressing effect. Therefore, in the method for producing a propylene-based block copolymer of the present invention, a propylene-based block copolymer containing a propylene / α-olefin copolymer can be produced with high catalytic efficiency while reducing gels without excessively increasing the number of reactors in the first step in a multi-stage continuous polymerization method, and without supplying it as a mixed stream with liquefied propylene when supplying the gel formation inhibitor.

[0017] Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example of the embodiments of the present invention, and the present invention is not limited to the following description as long as it does not exceed the gist thereof. In this specification, "~" indicating a numerical range is used to mean including the numerical values described before and after it as the lower limit value and the upper limit value.

[0018] I. Catalyst for Olefin Polymerization The catalyst for olefin polymerization used in the present invention is not particularly limited. For example, a catalyst capable of producing a polypropylene-based polymer excellent in stereoregularity can be appropriately selected from Ziegler catalysts and metallocene catalysts, and preferably, a so-called Ziegler catalyst composed of component (A): a solid catalyst component containing magnesium, titanium, and a halogen, and component (B): an organoaluminum compound is used.

[0019] 1. Component (A): Solid Catalyst Component The solid catalyst component used in the production of the polypropylene-based block copolymer of the present invention is not particularly limited as long as it contains magnesium, titanium, and a halogen, and known catalysts can be used. Examples of the solid catalyst component include magnesium chloride-supported Ziegler-Natta catalysts obtained by supporting titanium tetrachloride on a carrier such as magnesium chloride and reacting an electron donor such as ethers or esters as an internal donor (see, for example, JP-A-58-157808, JP-A-58-83006, JP-A-58-5310, and JP-A-61-218606). Examples of commercially available catalysts that can be used in the production method of the present invention include THC catalyst JC type manufactured by Toho Titanium Co., Ltd. (described in "Structure Control and Compositeization of Polypropylene, Molding Processing Technology", p23, Technical Information Society, 2016).

[0020] The solid catalyst component preferably contains an electron donor as an internal donor. In the polymerization technique using a Ziegler catalyst, generally, the functions of the internal donor and the external donor are considered to be different. The internal donor is a donor that is used simultaneously when a titanium compound is supported on a magnesium compound to form an active site, and controls the location where titanium atoms coordinate or changes the electronic state of the coordinating titanium atoms. On the other hand, the external donor changes the properties of the existing active sites. For example, by further using an external donor for the prepared solid catalyst component, it is possible to change to highly stereospecific active sites or poison the active sites that generate amorphous components, so that it is possible to produce a propylene-based polymer with higher stereoregularity and less amorphous components.

[0021] Examples of the electron-donating compound (internal donor) include oxygen-containing electron-donating compounds such as alcohols, phenols, ketones, aldehydes, carboxylic acids, esters of organic or inorganic acids, ethers, acid amides, and acid anhydrides, nitrogen-containing electron-donating compounds such as ammonia, amines, nitriles, and isocyanates, and sulfur-containing electron-donating compounds such as sulfonic acid esters. Specific examples include the compounds described in paragraph 0037 of JP-A-2010-70584. These electron-donating compounds can be used alone or in combination with a plurality of compounds.

[0022] The solid catalyst component can be prepared by contacting a magnesium compound, a titanium compound, a halogen compound, and optionally an electron-donating compound as an internal donor. As one means of improving stereoregularity, free titanium species present in the catalyst may be sufficiently removed. For example, as described in JP-A-2013-28705 (Example 8), JP-A-2014-37521, JP-A-2014-162905, etc., in the production process of a magnesium chloride-supported catalyst, by repeating the washing operation with a solvent, free titanium species that cause low stereoregularity polypropylene components can be removed, and high stereoregularity can be exhibited. The solid catalyst component of the present invention may be further contacted with an organoaluminum compound, an alkoxysilane compound, a vinylsilane compound, etc. after the above contact treatment. The organoaluminum compound used in this contact treatment may be the same as or different from the organoaluminum compound (B) described later that is used as a cocatalyst.

[0023] The solid catalyst component is preferably used after prepolymerization treatment. The prepolymerization treatment refers to a treatment in which a small amount of polymer is previously formed on the catalyst component. The prepolymerization treatment is preferably carried out in the presence of an organoaluminum compound. As the organoaluminum compound, the same organoaluminum compound as the organoaluminum compound of component (B) used as a cocatalyst can be used. The organoaluminum compound may be not only a single one but also a mixture of two or more. The amount of the organoaluminum compound used is usually in the range of 0.1 mol to 40 mol, preferably 0.3 mol to 20 mol, of the organoaluminum compound per 1 mol of titanium atoms.

[0024] In the prepolymerization treatment, it is preferable to use an organosilicon compound. Examples of the organosilicon compound include n-propylmethyldimethoxysilane, t-butylmethyldimethoxysilane, t-butylethyldimethoxysilane, t-butylethyldiethoxysilane, t-butyl-n-propyldimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexylethyldimethoxysilane, dicyclopentyldimethoxysilane, di-i-propyldimethoxysilane, di-i-butyldimethoxysilane, i-propyl i-butyldimethoxysilane, t-butyltriethoxysilane, bisdiethylaminodimethoxysilane, diethylaminotriethoxysilane, bis(perhydroisoquinolino)dimethoxysilane, etc. These may be used alone or as a mixture of two or more. The organosilicon compound may be used in the range of 0.01 mol to 10 mol per 1 mol of the organoaluminum compound.

[0025] Examples of the monomer used in the prepolymerization treatment include ethylene, propylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 4-methyl-1-pentene, 3-methyl-1-pentene, styrene, α-methylstyrene, allylbenzene, chlorostyrene, 1,3-butadiene, isoprene, 1,3-pentadiene, 1,5-hexadiene, 2,6-octadiene, dicyclopentadiene, 1,3-cyclohexadiene, 1,9-decadiene, divinylbenzene, etc. These may be used alone or as a mixture of two or more.

[0026] As the conditions for the prepolymerization treatment, the polymerization temperature is 0°C to 80°C, the polymerization time is 10 minutes to 48 hours, and the prepolymerization amount per 1 g of the solid catalyst component is 0.1 g to 100 g, preferably 0.5 g to 50 g. The prepolymerization treatment is generally preferably carried out under stirring, and an inert solvent can also be present at that time. The inert solvents used for the prepolymerization treatment are hexane, heptane, octane, decane, dodecane, liquid paraffin, silicone oil, etc. A molecular weight regulator such as hydrogen can be used to adjust the molecular weight of the polymer produced during the prepolymerization treatment.

[0027] 2. Component (B): Organoaluminum compound An organoaluminum compound is used as a cocatalyst for activating the solid catalyst component. Examples of the organoaluminum compound include trialkylaluminums such as trimethylaluminum, triethylaluminum, and triisobutylaluminum; alkylaluminum halides such as diethylaluminum chloride and diisobutylaluminum chloride; alkylaluminum hydrides such as diethylaluminum hydride; alkylaluminum alkoxides such as diethylaluminum ethoxide; aluminoxanes such as methylaluminoxane and tetrabutylaluminoxane; and composite organoaluminum compounds such as lithium aluminum tetraethyl. It is also possible to use a mixture of two or more of these.

[0028] The usage amount of the organoaluminum compound (B) is in terms of the molar ratio to the titanium component constituting the solid catalyst component (number of moles of the organoaluminum compound / number of moles of titanium atoms in the solid catalyst component), preferably in the range of 1 to 5,000, and particularly preferably in the range of 10 to 500. When using a magnesium chloride-supported Ziegler-Natta catalyst as the catalyst, the organoaluminum compound is preferably used in the range of 1 to 200 in terms of the molar ratio to the magnesium component constituting the catalyst (number of moles of the organoaluminum compound / number of moles of magnesium atoms) for polymerization.

[0029] 3. Electron-donating compound as external donor In the present invention, the catalyst for olefin polymerization may contain an electron-donating compound as an external donor in its components. In the polymerization technology using Ziegler catalysts, as described above, the external donor changes the properties of the already formed active sites. For example, by further using an external donor for the prepared solid catalyst component, it is possible to change to highly stereospecific active sites or poison the active sites that generate amorphous components, so that it is possible to produce a propylene-based polymer with higher stereoregularity and less amorphous components.

[0030] Examples of the electron-donating compound (external donor) include organosilicon compounds such as n-propylmethyldimethoxysilane, t-butylmethyldimethoxysilane, and t-butylmethyldiethoxysilane; compounds having at least two ether bonds such as 2,2-diisopropyl-1,3-dimethoxypropane and 2,2-diisobutyl-1,3-dimethoxypropane; compounds having a C(=O)N bond in the molecule such as tetramethylurea, 1,3-dimethyl-2-imidazolidinone, and 1-ethyl-2-pyrrolidinone; sulfite ester compounds such as dimethyl sulfite and diethyl sulfite; esters such as ethyl acetate, butyl benzoate, methyl p-toluate, and dibutyl phthalate; ketones such as acetone and methyl isobutyl ketone; ethers such as diethyl ether; organic acids such as benzoic acid and propionic acid; and alcohols such as ethanol and butanol. The electron-donating compound can be used alone or in combination of two or more.

[0031] The usage amount of the electron-donating compound (external donor) is in the molar ratio to titanium constituting the solid catalyst component (number of moles of electron-donating compound / number of moles of titanium atoms in the solid catalyst component), preferably in the range of 0.01 to 10,000, and particularly preferably in the range of 0.5 to 500.

[0032] II. Method for producing propylene-based block copolymer 1. Polymerization step The production method of the present invention is a method for producing a propylene-based block copolymer in which multi-stage continuous polymerization including a first step and a second step is carried out in the presence of a catalyst for olefin polymerization using a gas-phase fluidized bed polymerization reactor. In the production method of the present invention, in the first step, using one or more gas-phase fluidized bed polymerization reactors, propylene is polymerized alone or copolymerized with a relatively small amount of comonomer in the presence of a catalyst for olefin polymerization containing a solid catalyst component (A) and an organoaluminum compound (B) to produce a crystalline propylene-based polymer. Subsequently, in the second step, using one or more gas-phase polymerization reactors, in the presence of the crystalline propylene-based polymer containing the catalyst for olefin polymerization obtained in the first step, a relatively large amount of comonomer is copolymerized with propylene to produce an amorphous propylene / α-olefin copolymer, whereby a propylene-based block copolymer may be produced.

[0033] In the present invention, the crystalline propylene-based polymer means a polymer having stereoregularity and capable of forming lamellae, and means a propylene homopolymer or a copolymer having a propylene backbone with a relatively low comonomer content. As the comonomer, at least one selected from the group consisting of ethylene and linear or branched α-olefins having 4 to 8 carbon atoms can be used, and generally ethylene or 1-butene is preferable, and ethylene is particularly preferable. The crystalline propylene-based polymer is preferably a propylene homopolymer or a propylene / α-olefin copolymer having a comonomer content of 0% by mass to 10% by mass, more preferably 0% by mass to 3% by mass, and still more preferably 0% by mass to 0.3% by mass.

[0034] On the one hand, in the present invention, the amorphous propylene / α-olefin copolymer means a component that is dissolved and extracted at a temperature lower than the temperature range in which the crystalline propylene copolymer dissolves in various methods of separating into each temperature range based on the temperature dependence of the solubility of the olefin copolymer in a solvent, such as CFC-IR described later. That is, a propylene copolymer having a relatively high comonomer content is applicable, and as the comonomer, at least one selected from the group consisting of ethylene and linear or branched α-olefins having 4 to 8 carbon atoms can be used. Generally, ethylene or 1-butene is selected, and more preferably ethylene is selected. The comonomer content of the amorphous propylene / α-olefin copolymer is preferably in the range of 10% by mass to 90% by mass, and more preferably in the range of 20% by mass to 80% by mass.

[0035] In the polymerization mode of the production method of the present invention, a gas-phase fluidized bed polymerization method is adopted in which substantially no liquid solvent is used and each monomer is kept in a gaseous state so that the olefin polymerization catalyst and the monomer are efficiently contacted and the production efficiency per catalyst is improved. As the polymerization method, a continuous method or a batch method is applicable. The number of polymerization reactors may be one or two or more in both the first step and the second step. The first step is carried out in one or two or more gas-phase fluidized bed polymerization reactors, and the second step is carried out in one or two or more gas-phase fluidized bed polymerization reactors. When there are a plurality of polymerization reactors, they may be connected in series or in parallel.

[0036] The polymerization temperature is preferably 0°C to 90°C, more preferably 30°C to 85°C, and even more preferably 45°C to 80°C. The polymerization pressure is preferably 0.1 MPaG to 5 MPaG, more preferably 0.5 MPaG to 4 MPaG. Generally, by selecting a higher temperature and a higher pressure, it is possible to increase the productivity per gram of the catalyst. However, on the other hand, local heat generation cannot be removed, resulting in the generation of fine powder due to the collapse of growing particles and the formation of aggregates or lumps due to fusion. Therefore, considering the balance between the productivity per gram of the catalyst and the removal of local heat generation, the above temperature range and pressure range are set. The residence time can be arbitrarily adjusted according to the configuration of the polymerization tank, and is generally set within the range of 30 minutes to 10 hours. A preferable residence time is within 4 hours, and more preferably within 3 hours. Generally, by selecting a longer residence time, it is possible to increase the productivity per 1 g of the catalyst. However, when the residence time is excessive, the rate of increase in productivity per 1 g of the catalyst with respect to the increase in the residence time decreases. Therefore, considering the productivity per 1 g of the catalyst, the residence time is set within the above range.

[0037] In the method for producing a propylene-based block copolymer of the present invention, in the first step, it is preferable from the viewpoint of productivity to produce 10,000 g or more of a crystalline propylene-based polymer per 1 g of the olefin polymerization catalyst, and more preferably to produce 15,000 g or more of a crystalline propylene-based polymer per 1 g of the olefin polymerization catalyst.

[0038] 2. Gel formation inhibitor In the present invention, the gel formation inhibitor has a catalyst deactivating action, has a molecular weight of 300 or more, and has at least one functional group that functions as a hydrophilic group or a hydrophobic group with respect to a propylene homopolymer or a propylene-α-olefin copolymer, and means at least one compound selected from the group consisting of compounds that are liquid at normal temperature and normal pressure. By adding the above gel formation inhibitor in the first step or the second step of the multi-stage continuous gas-phase fluidized bed polymerization method, the generation of gel is prevented. The gel formation inhibitor may be added in both the first step and the second step. Here, normal temperature refers to the range of 0°C to 40°C, more precisely 25°C, and normal pressure refers to the range of 0.09 MPa to 0.11 MPa, more precisely 0.10 MPa.

[0039] In the multi-stage continuous gas-phase fluidized bed polymerization process of a propylene-based block copolymer containing a propylene / α-olefin copolymer, in the intermediate product of the first stage, there are small particles such as catalyst particles themselves that do not contain the product of the first stage, polymer particles in the state of primary particles with a small amount of the product of the first stage deposited on a single catalyst particle, and small-sized powder particles in which secondary particle formation has not progressed, and large particles in which secondary particle formation of the polymer particles has progressed and grown large are mixed. Since the above gel formation inhibitor easily penetrates the entire small particles, when the small particles are brought into contact with the gel formation inhibitor, it is presumed that the catalytic activity of all or most of the catalyst particles contained in the small particles is deactivated, and the polymerization ability of the small particles is almost lost. On the other hand, since the above gel formation inhibitor is ubiquitous in the relatively shallow depth position of the large particles, when the large particles are brought into contact with the gel formation inhibitor, only the catalyst particles present near the surface of the large particles are deactivated, and the deactivation of the catalyst particles present in the deep part is avoided, and it is presumed that the polymerization ability of the large particles is retained even after contact with the gel formation inhibitor. It is presumed that the above gel formation inhibitor can adjust the penetrability into the interior of the powder particles, which are intermediate products of the polymerization reaction, by the balance between hydrophilicity and hydrophobicity and the interaction of molecular sizes. Therefore, when the gel formation inhibitor is added to the intermediate product of the polymerization reaction at a stage before starting the production of the propylene / α-olefin copolymer in the second stage or at an early stage after starting, the catalytic activity of the catalyst particles present in the small particles is selectively deactivated, so that the generation of powder particles containing more than the average amount of the propylene / α-olefin copolymer that is difficult to disperse is reduced, and gel formation is suppressed.

[0040] In addition, since the proportion of the number of small particles present in the intermediate product of the first stage is small compared to the proportion of the number of large particles coexisting there, the amount of catalytic activity possessed by the small particles present in the intermediate product is small compared to the total amount of catalytic activity possessed by the intermediate product. By allowing the gel formation inhibitor to act on the intermediate product, a part of the catalytic activity possessed by the intermediate product is lost, but the loss of catalytic activity caused by selectively deactivating the catalytic activity of the small particles is small. Therefore, the above gel formation inhibitor can produce a propylene-based block copolymer with high catalytic efficiency while reducing gels in the multi-stage continuous gas-phase fluidized bed polymerization method of a propylene-based block copolymer containing a propylene-α-olefin copolymer.

[0041] As described above, in the multi-stage continuous gas-phase fluidized bed polymerization method of a propylene-based block copolymer, among the large particles and small particles mixed in the intermediate product of the polymerization reaction, the gel formation inhibitor is ubiquitous at a relatively shallow depth position of the large particles, while for the small particles, it penetrates the whole of the particles and selectively deactivates the catalytic activity of the catalyst particles present in the small particles, thereby suppressing gel formation in the intermediate product. However, the present invention is not subject to any restrictions depending on the validity of the action mechanism presumed as described above.

[0042] More specifically, as the gel formation inhibitor, polyoxyalkylene-based compounds such as polyalkylene oxide block copolymers, polyalkylene oxides, and polyalkylene oxide alkyl ethers can be used. The gel formation inhibitor is preferably a compound having an alcoholic hydroxyl group in order to deactivate the catalytic activity of the polymerization catalyst.

[0043] As the preferred polyoxyalkylene-based compound, a compound represented by the following general formula (1) can be used. [General formula (1)] HO-[CH2-CH2-O] p -[CH2-CH(CH3)-O] q -[CH2-CH2-O] r -R 1 (In general formula (1), p, q, and r are integers, and all satisfy the relational expressions of 0 ≦ p ≦ 30, 0 ≦ q ≦ 70, 0 ≦ r ≦ 30, 1 ≦ p + r ≦ 60, and 2 ≦ p + q + r. R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 25 carbon atoms.)

[0044] The above polyoxyalkylene compound has a polyoxyethylene skeleton portion and a polyoxypropylene skeleton portion. The polyoxyethylene skeleton functions as a hydrophilic group within the molecule of the above polyoxyalkylene compound, and affects the permeability to polypropylene particles and the surface potential as a surfactant. On the other hand, the polyoxypropylene skeleton functions as a hydrophobic group within the molecule of the above polyoxyalkylene compound, affects the permeability to polypropylene particles and the surface potential as a surfactant, and improves the solubility or compatibility with a reaction inhibitor composed of an alcohol compound described later. Therefore, by appropriately changing the sizes of the polyoxyethylene skeleton and the polyoxypropylene skeleton contained in the molecule of the polyoxyalkylene compound, and balancing the positions, occupancy ratios, hydrophilic or hydrophobic strengths of the hydrophilic and hydrophobic sites within the molecule, it is possible to create a low permeability to polypropylene particles of the polyoxyalkylene compound and a reducing effect on the surface potential resistance as a surfactant. Furthermore, the solubility or compatibility with a reaction inhibitor composed of an alcohol compound can be improved.

[0045] Regarding the number of oxyethylene units constituting the polyoxyethylene skeleton, that is, the symbols p and r in the general formula (1), from the viewpoint of imparting an appropriate balance between hydrophilicity and hydrophobicity to produce a low permeability to polypropylene particles and a reducing effect on the surface potential resistance as a surfactant, the range of p + r is 1 ≦ p + r, preferably 2 ≦ p + r, more preferably 3 ≦ p + r. On the other hand, when the symbol p or r in the general formula (1) is increased, there is a risk that the hydrophilicity becomes too high, resulting in a decrease in solubility in an organic solvent or solidification at room temperature, etc., which may cause limitations in handling during production. Therefore, 0 ≦ p ≦ 30 and 0 ≦ r ≦ 30. Also, as the range of p + r, p + r ≦ 60, preferably p + r ≦ 30, more preferably p + r ≦ 20, still more preferably p + r ≦ 10.

[0046] Regarding the number of oxypropylene units that constitute the polyoxypropylene skeleton, that is, the symbol q in the general formula (1), in order to create low permeability to polypropylene particles or a reduction effect on the surface potential resistance as a surfactant, or to improve the solubility and compatibility with a reaction inhibitor composed of an alcohol compound, an appropriate balance of hydrophilicity and hydrophobicity is imparted. From this point, q may be 0, and 0 ≦ q ≦ 70. However, from the point that there may be limitations in handling during production such as an increase in viscosity, preferably q ≦ 69, more preferably q ≦ 50, and even more preferably q ≦ 40. Also, from the point of having characteristics such as low permeability to polypropylene particles and a reduction in surface potential resistance as a surfactant, and not causing inconvenience in handling during production, the range of p + q + r is 2 ≦ p + q + r, and preferably 3 ≦ p + q + r. On the other hand, if p + q + r is too large, there is a risk of causing inconveniences in handling during production such as becoming solid at room temperature or having a high viscosity. Therefore, the range of p + q + r is preferably p + q + r ≦ 120, more preferably p + q + r ≦ 100, and even more preferably p + q + r ≦ 80.

[0047] R in the general formula (1) 1 represents a hydrogen atom or a hydrocarbon group having 1 to 25 carbon atoms. R 1 is preferably a hydrocarbon group having 5 to 20 carbon atoms, more preferably a saturated hydrocarbon group having 5 to 20 carbon atoms, even more preferably a hydrocarbon group having 10 to 20 carbon atoms, and still more preferably a saturated hydrocarbon group having 10 to 20 carbon atoms. When R 1 is within this range, it is easy to create characteristics such as low permeability to polypropylene particles and a reduction in surface potential resistance as a surfactant in order to function as a hydrophobic group.

[0048] Specific examples of the polyoxyalkylene compound that can be used in the present invention include polyoxyethylene(3) lauryl ether, polyoxyethylene(4) lauryl ether, polyoxyethylene(5) lauryl ether, polyoxyethylene(3) stearyl ether, polyoxyethylene(4) stearyl ether, polyoxyethylene(5) stearyl ether, polyoxyethylene(4) oleyl ether, polyoxyethylene(6) oleyl ether, polyoxyethylene(1) propylene glycol(16) polyoxyethylene(1), polyoxyethylene(2) propylene glycol(16) polyoxyethylene(2), polyoxyethylene(2) propylene glycol(30) polyoxyethylene(2), polyoxyethylene(6) propylene glycol(35) polyoxyethylene(6), polyoxyethylene(5) propylene glycol(69) polyoxyethylene(5), polyoxyethylene(3) propylene glycol(2) polyoxyethylene(3) lauryl ether, polyoxyethylene(3) polypropylene glycol(3) lauryl ether, and the like. The numerical values in parentheses represent the degree of polymerization of polyoxyalkylene. The polyoxyalkylene compound used in the gel formation inhibitor of the present invention may be a single component or a mixture of a plurality of components.

[0049] The gel formation inhibitor is usually supplied at a ratio of 10 mass ppm to 1000 mass ppm, preferably 15 mass ppm to 700 mass ppm, more preferably 20 mass ppm to 500 mass ppm, based on the production amount of the propylene-based block copolymer obtained through the first and second steps. By satisfying the above ratio, it is easy to suppress the generation of gel without reducing the catalytic activity. The gel formation inhibitor is preferably supplied in the range of 0.001 molar ratio to 0.300 molar ratio, more preferably 0.003 molar ratio to 0.200 molar ratio, and even more preferably 0.005 molar ratio to 0.100 molar ratio, based on the organoaluminum compound (B) supplied to the first step. By satisfying the above ratio, it is easy to suppress the generation of gel without reducing the catalytic activity.

[0050] 3. Reaction inhibitor In the present invention, in addition to the gel formation inhibitor, a reaction inhibitor represented by the following general formula (2) may be further supplied into the retained powder inside the gas-phase fluidized bed polymerization reactor.

[0051] [General formula (2)] HO-R 2 (In general formula (2), R 2 represents a saturated hydrocarbon group having 1 to 10 carbon atoms) In the reaction inhibitor represented by the general formula (2), R 2 is a saturated hydrocarbon group having 1 to 10 carbon atoms. R 2 is more preferably a saturated hydrocarbon group having 2 to 8 carbon atoms, and even more preferably a saturated hydrocarbon group having 2 to 3 carbon atoms. R 2 When the number of carbon atoms of R exceeds 10, it becomes difficult to remove by drying, and problems such as odor may occur in the final product. The most suitable alcohol compound is ethanol having 2 carbon atoms. In the case of methanol having 1 carbon atom, attention must be paid to its harmfulness to the human body.

[0052] In the present invention, the above reaction inhibitor is not essential, but when it is difficult to sufficiently suppress the reaction of the particles in the reactor only with the gel formation inhibitor, by supplying the reaction inhibitor into the reactor in combination with the gel formation inhibitor, the reaction on small particles can be more strongly suppressed without excessively suppressing the reaction on large particles, so that waste of the gel formation inhibitor can be avoided.

[0053] The reaction inhibitor may be used such that the supply amount of the gel formation inhibitor is 10 parts by mass to 150 parts by mass with respect to 100 parts by mass of the supply amount of the reaction inhibitor. With respect to 100 parts by mass of the supply amount of the reaction inhibitor, the supply amount of the gel formation inhibitor may be 140 parts by mass or less, and may further be 130 parts by mass or less. By coexisting the gel formation inhibitor and the reaction inhibitor in an appropriate ratio as described above, the reaction inhibitor can prevent / inhibit self-aggregation such as micelles due to the hydrophobic interaction of the gel formation inhibitor, and the supplied gel formation inhibitor can exist more efficiently on the surface of the polypropylene particles. Therefore, it is presumed that an excellent gel inhibition effect can be obtained. However, the present invention is not subject to any restrictions depending on the validity of the presumed mechanism of action as described above. Further, the reaction inhibitor may be in a molar ratio of 0.3 to 5.0, preferably 0.6 to 4.0, more preferably 0.9 to 3.0, relative to the organoaluminum compound (B) supplied to the first step.

[0054] 4. Supply of Gel Formation Inhibitor The gel formation inhibitor is diluted with an organic solvent such as hexane or alone from the viscosity and supply ability, and is supplied from an insert nozzle connected to the gas-phase fluidized bed polymerization reactor in at least one of the first step and the second step into the retained powder inside the reactor. By supplying the gel formation inhibitor into the retained powder inside the reactor through an insert nozzle that protrudes from the inner wall of the reactor into the internal space, the gel formation inhibitor is uniformly dispersed in the retained powder, so that an excellent gel generation suppression effect can be obtained. In the present invention, since the gel formation inhibitor is supplied from the insert nozzle into the reactor, it is not necessary to supply the gel formation inhibitor into the reactor as a mixed stream with liquefied propylene. Therefore, the production method of the present invention can be applied to a gas-phase fluidized bed polymerization reactor, which is a polymerization reactor that does not use liquefied propylene.

[0055] In order to uniformly disperse the gel formation inhibitor in the retained powder inside the reactor, it is desirable that most, ideally all, of the gel formation inhibitor discharged from the tip of the insert nozzle into the inside of the gas-phase fluidized bed polymerization reactor is scattered in the internal space of the reactor without adhering to the inner wall of the reactor and directly reaches the retained powder on the fluidized bed. For the above reasons, regarding the arrangement of the insert nozzle inside the reactor, it is required to provide a sufficient distance from the inner wall of the reactor to the discharge port at the tip of the nozzle, so as to avoid the adhesion of the gel formation inhibitor to the inner wall of the reactor due to dripping of the liquid at the tip of the nozzle.

[0056] In order to meet the above requirements, in the present invention, an insert nozzle having at least one discharge port is connected to the straight body portion of the gas-phase fluidized bed polymerization reactor, and the discharge port existing at the most distal end side of the insert nozzle is such that the distance from the discharge port to the inner wall of the cross section of the gas-phase fluidized bed polymerization reactor at the position where the discharge port is located is within the range of 12% to 88%, preferably within the range of 15% to 85%, more preferably within the range of 18% to 82% with respect to the inner diameter of the cross section, for the distance from the discharge port to the inner wall existing at any position on the inner circumference of the cross section. When the insert nozzle has two or more discharge ports, it is preferable to arrange all the discharge ports at positions where the distance from the discharge port to the inner wall of the cross section of the reactor at the position where the discharge port is located is within the above range throughout the entire inner circumference of the cross section. By satisfying the above conditions, the dispersibility of the gel formation inhibitor in the reactor is improved, the gel formation inhibitor is uniformly dispersed in the held powder without dripping onto the wall surface, and while suppressing the decrease in catalytic activity, an excellent gel generation suppressing effect is achieved.

[0057] Here, the "cross section of the gas-phase fluidized bed polymerization reactor at the position where the discharge port is located" means a cross section obtained by cutting the straight body portion of the gas-phase fluidized bed polymerization reactor through the position where the discharge port of the insert nozzle is located and in a direction perpendicular to the longitudinal central axis of the internal space of the gas-phase fluidized bed polymerization reactor. When the insert nozzle has two or more discharge ports, the cross section corresponding to each discharge port is specified. Also, the "inner diameter of the cross section of the gas-phase fluidized bed polymerization reactor" means the diameter of the inner circumference depicted by the boundary line between the inner wall appearing in the cross section of the gas-phase fluidized bed polymerization reactor and the internal space of the reactor. In addition, the "straight cylindrical part of the reactor" refers to the part of the reactor's cylindrical part that consists of a straight side surface. More precisely, it means the part of the reactor's cylindrical part that continuously maintains a certain shape and inner diameter along the longitudinal axis. The internal shape of this part takes the form of a cylindrical shape with a constant diameter. Generally, the internal space of the straight cylindrical part of a gas-phase fluidized bed polymerization reactor has a cylindrical shape, and the shape of its cross-section is a perfect circle.

[0058] Figure 2 is a cross-sectional view showing the state where an insert nozzle 114 is connected to the straight cylindrical part of the first reactor 100 of the continuous vertical gas-phase fluidized bed polymerization apparatus shown in Figure 1. Figure 3 is a perspective view corresponding to the cross-sectional view of Figure 2. In Figures 2 and 3, the straight cylindrical part of the first reactor 100 is cylindrical, and the insert nozzle 114 is inserted into the cylindrical straight cylindrical part at an angle such that the tip side of the nozzle faces upward with respect to the gravitational direction. In Figure 3, the part of the insert nozzle 114 drawn with a solid line indicates that this part is outside the first reactor 100, and the part of the first reactor drawn with a dotted line indicates that this part protrudes into the internal space of the reactor. The insert nozzle 114 has one discharge port at its tip. In this case, by cutting the straight cylindrical part of the first reactor 100 in a direction perpendicular to the longitudinal central axis X of the internal space of the first reactor 100 and at a height passing through the point P0 where the discharge port of the insert nozzle 114 is located, the cross-section A of the first reactor 100 at the position where the discharge port exists is obtained.

[0059] Figure 4 is a plan view looking down on the cross-section A shown in Figures 2 and 3 from directly above, and is a diagram for explaining an example when adjusting the position of the discharge port of the insert nozzle. Since the straight cylindrical part of the first reactor 100 has a cylindrical shape, the shape of the cross-section A is a perfect circle. In the cross-section A, the inner wall of the first reactor 100 is represented by a line that delineates the inner circumference of the cross-section A, the inner diameter of the cross-section A is represented by R, the intersection point of the longitudinal central axis X of the internal space of the first reactor 100 and the cross-section A is represented by Y, and this intersection point Y is also the center point of the cross-section A. Point P0 represents a position where the discharge port provided at the tip of the insert nozzle 114 is likely to be located. Point P1 represents a position that is the shortest distance from point P0, which is the position of the discharge port, to the inner circumference of the cross-section A. Point P2 represents a position that is the longest distance from point P0, which is the position of the discharge port, to the inner circumference of the cross-section A. Points P1 and P2 exist on the same straight line passing through the center point Y of the cross-section A. Points P3 and P4 are arbitrary points existing on the inner circumference of the cross-section A other than points P1 and P2. As virtual example 1 based on FIG. 4, when setting the shortest distance from the position of the discharge port to the inner circumference of the cross-section A, that is, the distance from point P0 to point P1, to be 15% of the length of the inner diameter R of the cross-section A, the longest distance from the position of the discharge port, point P0, to the inner circumference of the cross-section A, that is, the distance from point P0 to point P2, is 85% of the length of the inner diameter R of the cross-section A. Also, the distance from point P0 to point P3 and the distance from point P0 to point P4 are both more than 15% and less than 85% of the inner diameter R of the cross-section A. In this virtual example 1, the distance from the discharge port of the insert nozzle to any inner wall position existing on the inner circumference of the cross-section A of the reactor is adjusted within the range of 12% to 88% of the length of the inner diameter R. As virtual example 2 based on FIG. 4, when setting the shortest distance from the position of the discharge port to the inner circumference of the cross-section A, that is, the distance from point P0 to point P1, to be 10% of the length of the inner diameter R of the cross-section A, the longest distance from the position of the discharge port, point P0, to the inner circumference of the cross-section A, that is, the distance from point P0 to point P2, is 90% of the length of the inner diameter R of the cross-section A. In this virtual example 2, the discharge port of the insert nozzle is not arranged within the allowable range in the present invention.

[0060] FIG. 5 is a plan view looking down on the cross-section A shown in FIGS. 2 and 3 from directly above, but it is a figure for explaining from a different perspective from FIG. 4, and it is a figure for explaining an example when adjusting the position of the discharge port of the insert nozzle. In FIG. 5, "The distance from point P0, which is the position of the discharge port provided at the tip of the insert nozzle 114, to the inner circumference of the cross-sectional plane A representing the inner wall of the first reactor 100 is adjusted so that it falls within the range of 12% to 88% of the inner diameter of the cross-sectional plane A for any distance to any position on the inner circumference." can be rephrased as "The position of point P0 where the discharge port provided at the tip of the insert nozzle 114 is located has a center that coincides with the center of the cross-sectional plane A, and is adjusted to be inside or on the circumference of a concentric circle C that has a circumference that retreats by a width w corresponding to 12% of the inner diameter R of the cross-sectional plane A from the inner circumference of the cross-sectional plane A towards the center point Y." Or, it can also be rephrased as "The position of point P0 where the discharge port provided at the tip of the insert nozzle 114 is located has a center that coincides with the center of the cross-sectional plane A, and is adjusted to be inside or on the circumference of a concentric circle C that has a radius r with a length corresponding to 38% of the inner diameter R of the cross-sectional plane A." Here, the length of the radius r of the concentric circle C (the length corresponding to 38% of the inner diameter R of the cross-sectional plane A) is the length obtained by subtracting the retreat width w of the concentric circle from the inner circumference of the cross-sectional plane A (the length corresponding to 12% of the inner diameter R of the cross-sectional plane A) from the radius of the cross-sectional plane A (the length corresponding to 50% of the inner diameter R of the cross-sectional plane A). When the shape of "the cross-section of the gas-phase fluidized bed polymerization reactor at the position where the discharge port exists" is a perfect circle like the cross-sectional plane A shown in FIGS. 2 and 3, the position of the discharge port provided at the tip of the insert nozzle 114 can be specified by rephrasing it as described above.

[0061] In the present invention, the shape of "the cross-section of the gas-phase fluidized bed polymerization reactor at the position where the discharge port exists" is not particularly limited, and may be, for example, a shape having rotational symmetry such as a perfect circle or an ellipse, or an irregular shape. When the cross-section of the straight cylindrical part defining the inner diameter is not a perfect circle, the shortest diameter of the cross-sectional shape is taken as the inner diameter. From the viewpoint of ensuring a degree of freedom in design that can secure a wide range for setting the region where the discharge port at the tip of the insert nozzle can be arranged, the shape of the cross-section of the reactor is preferably a shape approximated to a perfect circle, and particularly preferably a perfect circle. FIG. 6 is a plan view for explaining an example in the case where the position of the discharge port of the insert nozzle is adjusted by regarding the shortest diameter of the cross-sectional shape as the inner diameter because the "cross section of the gas-phase fluidized bed polymerization reactor at the position where the discharge port exists" is not a perfect circle. In FIG. 6, the cross section A of the reactor has an elliptical shape with a minor axis of R1 and a major axis of R2, and the inner wall of the reactor is represented by a line that defines the inner circumference of the cross section A. In the example of FIG. 6, the ratio (R1:R2) of the length of the minor axis R1 to the length of the major axis R2 is set to 1:1.5. The intersection of the longitudinal central axis X of the internal space of the reactor and the cross section A is represented by Y, and this intersection Y is also the center point of the cross section A (the intersection of the minor axis R1 and the major axis R2). Points P1a and P1b are the intersections of the minor axis of the ellipse (the axis specifying the minor axis R1) and the inner circumference of the ellipse, and the distances from the center point Y of the cross section A to points P1a and P1b are the minor radii, so they correspond to 50% of the length of the minor axis R1. On the other hand, points P2a and P2b are the intersections of the major axis of the ellipse (the axis specifying the major axis R2) and the inner circumference of the ellipse, and the distances from the center point Y of the cross section A to points P2a and P2b are the major radii, so they correspond to 50% of the length of the major axis R2. Points P0a, P0b, and P0c indicate the positions where the discharge ports existing at the tip of the insert nozzle are to be arranged. Point P0a is at the same position as the center point Y of the cross section A, point P0b is a position shifted by a distance corresponding to 13% of the length of the minor axis R1 along the major axis in the direction of point P2b from the center point Y of the cross section A, and point P0c is a position shifted by a distance corresponding to 50% of the length of the minor axis R1 along the major axis in the direction of point P2b from the center point Y of the cross section A.

[0062] As a virtual example 1 based on FIG. 6, when the discharge port at the tip of the insert nozzle is arranged at point P0a (center point Y), since the shortest distance from the position of the discharge port to the inner circumference of the cross-section A, that is, the distance from point P0a to points P1a and P1b, is equal to the minor radius, it is 50% of the length of the minor diameter R1. On the other hand, the longest distance from the position of the discharge port to the inner circumference of the cross-section A, that is, the distance from point P0a to points P2a and P2b, is equal to the major radius, and since the length ratio of the minor diameter R1 to the major diameter R2 is 1:1.5, it is 75% of the length of the minor diameter R1. In this virtual example 1, for the distance from the discharge port of the insert nozzle to any inner wall position existing on the inner circumference of the cross-section A of the reactor, it is adjusted within the range of 12% to 88% of the length of the minor diameter R1 regarded as the inner diameter. As a virtual example 2 based on FIG. 6, when the discharge port at the tip of the insert nozzle is arranged at point P0b, the shortest distance from the position of the discharge port to the inner circumference of the cross-section A is slightly shorter than the minor radius, so it is equivalent to less than 50% of the length of the minor diameter R1 and is within the range of 12% to 88%. On the other hand, the longest distance from the position of the discharge port to the inner circumference of the cross-section A is the sum of the distance from the center point Y of the cross-section A to point P0b (13% of the length of the minor diameter R1) and the distance from the center point Y of the cross-section A to point P2a, that is, the major radius (75% of the length of the minor diameter R1), so it is 88% of the length of the minor diameter R1. Also in this virtual example 2, for the distance from the discharge port of the insert nozzle to any inner wall position existing on the inner circumference of the cross-section A of the reactor, it is adjusted within the range of 12% to 88% of the length of the minor diameter R1 regarded as the inner diameter. As a virtual example 3 based on FIG. 6, when the discharge port at the tip of the insert nozzle is arranged at point P0c, the shortest distance from the position of the discharge port to the inner circumference of the cross-section A is the distance from the center point Y of the cross-section A to point P2b, that is, the major radius (75% of the length of the minor diameter R1), minus the distance from the center point Y of the cross-section A to point P0c (50% of the length of the minor diameter R1). Therefore, it is equivalent to slightly less than 25% of the length of the minor diameter R1 and falls within the range of 12% to 88%. However, in virtual example 3, the longest distance from the position of the discharge port to the inner circumference of the cross-section A is the sum of the distance from the center point Y of the cross-section A to point P0c (50% of the length of the minor diameter R1) and the distance from the center point Y of the cross-section A to point P2a (75% of the length of the minor diameter R1). Therefore, it becomes 125% of the length of the minor diameter R1 and exceeds the upper limit of 88%. Therefore, different from virtual examples 1 and 2, in virtual example 3, the discharge port of the insert nozzle is not arranged within the allowable range in the present invention.

[0063] According to virtual examples 1 to 3 of FIG. 6, when the cross-section A of the reactor has an elliptical shape and the length ratio (R1:R2) of the minor diameter R1 to the major diameter R2 is set to 1:1.5, even if the discharge port at the tip of the insert nozzle is arranged at a position slightly deviated from the center point Y (the intersection of the minor diameter R1 and the major diameter R2) of the cross-section A of the reactor, the distance from the discharge port of the insert nozzle to the inner wall existing on the inner circumference of the cross-section A of the reactor can be within the range of 12% to 88% of the length of the minor diameter R1 regarded as the inner diameter. Therefore, in this case, there is a degree of freedom in design that allows the position where the discharge port at the tip of the insert nozzle is arranged to be selected within a certain region. If the elliptical shape of the cross-section A of the reactor shown in FIG. 6 becomes more flattened and the length ratio (R1:R2) of the minor diameter R1 to the major diameter R2 becomes 1:1.76, the distance from the center point Y of the cross-section A to points P2a and P2b, that is, the major radius, becomes 88% of the length of the minor diameter R1. Only when the discharge port at the tip of the insert nozzle is arranged at the position of the center point Y (the intersection of the minor diameter R1 and the major diameter R2) of the cross-section A of the reactor, the distance from the discharge port of the insert nozzle to the inner wall existing on the inner circumference of the cross-section A of the reactor can be within the range of 12% to 88% of the length of the minor diameter R1 regarded as the inner diameter. When the elliptical shape of the cross-section A of the reactor shown in Fig. 6 becomes even flatter and the length ratio (R1:R2) of the minor axis R1 to the major axis R2 exceeds 1:1.76, it becomes impossible to keep the distance from the discharge port of the insert nozzle to the inner wall existing on the inner circumference of the cross-section A of the reactor within the range of 12% to 88% of the length of the minor axis R1 regarded as the inner diameter. As described above, when the shape of the cross-section of the straight body part of the gas-phase fluidized bed polymerization reactor is extremely far from a perfect circle, it becomes impossible to keep the distance from the discharge port of the insert nozzle to the inner wall existing on the inner circumference of the cross-section A of the reactor within the range of 12% to 88% of the length of the minor axis R1 regarded as the inner diameter. However, usually, the internal space of the straight body part of the gas-phase fluidized bed polymerization reactor has a cylindrical shape such that the shape of its cross-section is a perfect circle in consideration of the strength of the reactor and the uniformity of the polymerization reaction, etc. Also, even when the shape of the cross-section of the reactor is not a perfect circle, the internal space of the straight body part of the reactor is designed to have a cylindrical shape whose cross-sectional shape approximates a perfect circle. Therefore, if the reactor to which the insert nozzle is attached has a generally assumed shape, the distance from the discharge port at the tip of the insert nozzle to the inner wall of the cross-section of the gas-phase fluidized bed polymerization reactor at the position where the discharge port exists can be adjusted within the range of 12% to 88% with respect to the inner diameter of the cross-section or the length of the minor axis regarded as the inner diameter, and no special difficulty occurs when making such an adjustment.

[0064] In order to further meet the requirement of providing a sufficient distance between the inner wall of the reactor and the discharge port at the tip of the nozzle to avoid the adhesion of the gel formation inhibitor to the inner wall of the reactor due to the dripping of the liquid at the tip of the nozzle, it is preferable that the horizontal direction (the direction perpendicular to the weight direction) angle of the insert nozzle is as close to a right angle as possible with respect to the inner wall of the gas-phase fluidized bed polymerization reactor. Specifically, the horizontal direction angle formed by the part of the insert nozzle protruding into the internal space of the reactor and the inner wall of the gas-phase fluidized bed polymerization reactor is preferably 45 degrees to 90 degrees, more preferably 60 degrees to 90 degrees, even more preferably 75 degrees to 90 degrees, and ideally 90 degrees. In addition, the angle of the insert nozzle in the vertical direction (the direction parallel to the weight direction) may be perpendicular to the inner wall of the gas-phase fluidized bed polymerization reactor in order to adjust the diffusion state of the gel formation inhibitor discharged from the insert nozzle, or may be appropriately angled and tilted so that the nozzle tip faces upward or downward. Here, the above nozzle angle means the angle formed by the tangent plane in contact with the inner wall of the gas-phase fluidized bed polymerization reactor at the position of the connection between the gas-phase fluidized bed polymerization reactor and the insert nozzle and the longitudinal axis of the portion of the insert nozzle protruding into the gas-phase fluidized bed polymerization reactor.

[0065] The gel formation inhibitor may be supplied to one or both of the reactors in the first step and the second step. However, since it is possible to maintain a higher catalytic activity by supplying it to the reactor in the second step, it is preferable to supply the gel formation inhibitor to at least the reactor in the second step out of the first step and the second step.

[0066] When the gel formation inhibitor is supplied in a state diluted with an organic solvent in terms of viscosity and supply ability, it is preferable to appropriately select and use the organic solvent from among inactive hydrocarbon solvents. As the hydrocarbon solvent, a single or a mixture of saturated aliphatic or aromatic hydrocarbons such as hexane, heptane, pentane, cyclohexane, benzene, and toluene can be used.

[0067] In addition, when diluting with an organic solvent, the concentration of the gel formation inhibitor in the organic solvent may be appropriately selected according to the viscosity of the solution depending on the temperature and the addition amount. The concentration of the gel formation inhibitor may be 0.1 g to 100 g, or may be 1 g to 50 g, per 1 L of the organic solvent.

[0068] 5. Supply of reaction inhibitor When supplying a reaction inhibitor, a gel formation inhibitor and a reaction inhibitor may be premixed to form a mixed reaction inhibitor, and this mixed reaction inhibitor may be supplied to a gel formation inhibitor supply line and then supplied into the retained powder inside the reactor through an insert nozzle. Alternatively, the gel formation inhibitor and the reaction inhibitor may be separately supplied to the gel formation inhibitor supply line, mixed as a mixed reaction inhibitor within the gel formation inhibitor supply line, and then supplied into the retained powder inside the reactor through the insert nozzle. The reaction inhibitor may also be supplied into the reactor from a gas supply line of a gas circulation system provided separately from the gel formation inhibitor supply line, or a plurality of these supply routes may be arbitrarily combined. From the viewpoint of dispersibility, the reaction inhibitor may be supplied into the reactor from a gas supply line of a gas circulation system provided separately from the gel formation inhibitor supply line.

[0069] 6. Propylene-based block copolymer produced In the propylene homopolymerization or copolymerization of propylene and another α-olefin produced in the first step, the melt flow rate (MFR) of the crystalline propylene-based polymer can be controlled by using a molecular weight regulator such as hydrogen during the polymerization process. The MFR of the crystalline propylene-based polymer is set according to the molding method and application. The MFR value (unit: g / 10 min) measured under the measurement conditions of 230°C and a load of 2.16 kg is usually 0.1 or more, preferably 0.5 or more, more preferably 1 or more, and usually 1000 or less, preferably 600 or less, more preferably 400 or less. If the MFR is too small, the fluidity of the polymer will significantly decrease and molding will be difficult. If it is too large, a decrease in tensile properties will occur.

[0070] In the second step, by using a molecular weight regulator such as hydrogen during the polymerization step, the intrinsic viscosity [η] of the amorphous propylene / α-olefin copolymer can be controlled. From the viewpoints of improving melt tension and flow marks, and improving the product appearance by suppressing the number of gels, the intrinsic viscosity [η] of the amorphous propylene / α-olefin copolymer is preferably in the range of 3 dL / g to 12 dL / g, more preferably in the range of 4 dL / g to 11 dL / g. Also, from the viewpoints of improving impact resistance and improving the product appearance by suppressing the number of gels, the content of α-olefin in the amorphous propylene / α-olefin copolymer is preferably in the range of 10% by mass to 90% by mass, more preferably in the range of 20% by mass to 80% by mass. If the α-olefin content is less than this range, the amorphousness may be lost, which may impair the impact resistance of the product, and this is not preferable. If there is more α-olefin than this range, the compatibility with crystalline propylene decreases, resulting in an increase in the number of gels and a possible impairment of the product appearance, which is not preferable.

[0071] Also, from the viewpoint of suppressing the generation of gels, when the propylene block copolymer is 100% by mass, the propylene / α-olefin copolymer is preferably 10% by mass to 65% by mass, and the crystalline propylene resin is preferably 35% by mass to 90% by mass. More preferably, the propylene / α-olefin copolymer is 12% by mass to 62% by mass, and the crystalline propylene resin is 38% by mass to 88% by mass. Even more preferably, the propylene / α-olefin copolymer is 14% by mass to 59% by mass, and the crystalline propylene resin is 41% by mass to 86% by mass. Furthermore, from the viewpoint of improving the product appearance, when the propylene block copolymer is an injection sheet with a thickness of 2 mm, the number of gels with a major axis of 300 μm or more is preferably 2 500 pieces / cm 2 or less, and more preferably Examples of the method for forming the propylene-based block copolymer into an injection sheet with a thickness of 2 mm include, for example, the methods described in the examples below.

Examples

[0072] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The measurement methods for each physical property value in the present invention are shown below. [Measurement of Various Physical Properties] (1) MFR The propylene-based polymer obtained in the examples was evaluated under the conditions conforming to JIS K7210 (230 °C, 2.16 kg load).

[0073] (2) Analysis Method of Propylene-Based Block Copolymer The measurement of the ratio (Wc) of the propylene / ethylene-based copolymer portion, ethylene content (Gv), and intrinsic viscosity (η) in the propylene-based block copolymer was carried out according to the methods described in paragraphs 0082 to 0086 of Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2022-014443) using the following apparatus and conditions.

[0074] (2-1) Analytical Apparatus to be Used (i) Cross-Fractionation Apparatus CFC T-100 manufactured by Dyn Instruments Co., Ltd. (abbreviated as CFC) (ii) Fourier Transform Infrared Absorption Spectroscopy FT-IR, 1760X manufactured by PerkinElmer The wavelength-fixed infrared spectrophotometer attached as a detector of CFC was removed and replaced with FT-IR, and this FT-IR was used as a detector. The transfer line from the outlet of the solution eluted from CFC to FT-IR was set to a length of 1 m and maintained at a temperature of 140 °C throughout the measurement. The flow cell attached to FT-IR had an optical path length of 1 mm and an optical path width of 5 mmφ and was maintained at a temperature of 140 °C throughout the measurement. (iii) Gel Permeation Chromatography (GPC) For the GPC column in the latter part of CFC, three AD806MS columns manufactured by Showa Denko K.K. are connected in series and used.

[0075] (2-2) Measurement Conditions of CFC (i) Solvent: Orthodichlorobenzene (ODCB) (ii) Sample Concentration: 4 mg / mL (iii) Injection Volume: 0.4 mL (iv) Crystallization: The temperature is decreased from 140 °C to 40 °C over about 40 minutes. (v) Fractionation Method: During temperature-rising elution fractionation, the fractionation temperatures are 40 °C, 100 °C, and 140 °C, and the sample is fractionated into three fractions in total. The elution ratios (unit: mass %) of the components eluting at 40 °C or lower (Fraction 1), 40 °C to 100 °C (Fraction 2), and 100 °C to 140 °C (Fraction 3) are defined as W 40 、W 100 、W 140 respectively. W 40 +W 100 +W 140 = 100. Also, each fractionated fraction is automatically transported to the FT-IR analyzer as it is. (vi) Solvent Flow Rate during Elution: 1 mL / min

[0076] (2-3) Measurement Conditions of FT-IR After the elution of the sample solution starts from the GPC in the latter part of CFC, FT-IR measurement is performed under the following conditions, and GPC-IR data are collected for each of the above-mentioned Fractions 1 to 3. (i) Detector: MCT (ii) Resolution: 8 cm -1 (iii) Measurement Interval: 0.2 minutes (12 seconds) (iv) Number of Integration Times per Measurement: 15 times

[0077] (2-4) Post-treatment and Analysis of Measurement Results The elution amount and molecular weight distribution of the components eluting at each temperature are 2945 cm obtained by FT-IR -1The absorbance is determined using it as a chromatogram. The elution amount is normalized so that the total elution amount of each elution component becomes 100%. The conversion from retention volume to molecular weight is performed using a calibration curve prepared in advance with standard polystyrene. All of the standard polystyrenes used are the following brands manufactured by Tosoh Corporation. F380, F288, F128, F80, F40, F20, F10, F4, F1, A5000, A2500, A1000. A solution dissolved in ODCB (containing 0.5 mg / mL of BHT) so that each becomes 0.5 mg / mL is injected in an amount of 0.4 mL to prepare a calibration curve. The calibration curve uses a cubic equation obtained by approximating with the least squares method. The conversion to molecular weight uses a universal calibration curve with reference to "Size Exclusion Chromatography" by Yuzuo Mori (Kyoritsu Shuppan). The viscosity formula ([η]=K×M α ) uses the following numerical values.

[0078] (i) When preparing a calibration curve using standard polystyrene K = 0.000138, α = 0.70 (ii) When measuring a sample of a propylene-based block copolymer K = 0.000103, α = 0.78 The ethylene content distribution of each elution component (distribution of ethylene content along the molecular weight axis) is obtained by using the ratio of the absorbance at 2956 cm -1 obtained by FT-IR and the absorbance at 2927 cm -1 and is converted to the ethylene content (mass%) using a calibration curve prepared in advance using ethylene-propylene rubber (EPR) and mixtures thereof whose ethylene content is known by C-NMR measurement or the like. 13

[0079] (2-5) Ratio (Wc) of the propylene-ethylene random copolymer portion The ratio (Wc) of the propylene-ethylene random copolymer portion in the propylene-based block copolymer in the present invention is theoretically defined by the following formula (I) and is determined by the following procedure. Wc (mass%) = W 40 × A 40 / B 40 + W 100 × A 100 / B 100 …(I) In formula (I), W 40 , W 100 is the elution ratio (unit: mass%) in each of the above-mentioned fractions, A 40 , A 100 is the average ethylene content (unit: mass%) of the actual measurement in each fraction corresponding to W 40 , W 100 , and B 40 , B 100 is the ethylene content (unit: mass%) of the propylene-ethylene random copolymer part contained in each fraction. For the meaning of formula (I), refer to paragraph 0083 of Patent Document 2 (Japanese Patent Application Laid-Open No. 2022-014443). For A 40 , A 100 , B 40 , B 100 , refer to paragraphs 0084 to 0085 of the same Patent Document 2. For the meaning of setting the above three types of separation temperatures, refer to paragraph 0086 of the same Patent Document 2.

[0080] (i) Let the average ethylene content corresponding to fractions 1 to 2 obtained by CFC measurement be A 40 , A 100 respectively (the unit is mass% in both cases). The method for obtaining the average ethylene content will be described later. (ii) Let the ethylene content corresponding to the peak position in the differential molecular weight distribution curve of fraction 1 be B 40 (the unit is mass%). For fraction 2, in the present invention, B 100 = 100. (iii) For the above reasons, the ratio (Wc) of the propylene-ethylene random copolymer part is obtained according to the following formula. Wc (mass%) = W 40 × A 40 / B 40 + W 100 × A 100 / 100 …(II) Here, B 40And the average ethylene content A of each of fractions 1 and 2 obtained by CFC measurement 40 , A 100 is determined as follows. The ethylene content corresponding to the peak position of the differential molecular weight distribution curve is B 40 And the sum of the product of the mass ratio of each data point and the ethylene content of each data point, which is taken in as a data point during measurement, is the average ethylene content A of fraction 1 40 And the average ethylene content A of fraction 2 100 is determined in the same manner.

[0081] (2-6) Ethylene content of the propylene-ethylene random copolymer portion In the propylene-based block copolymer of the present invention, the ethylene content of the propylene-ethylene random copolymer portion is determined from the following formula using the values described above. Ethylene content (mass %) of the propylene-ethylene random copolymer portion = (W 40 ×A 40 +W 100 ×A 100 ) / Wc However, Wc is the ratio (mass %) of the propylene-ethylene random copolymer portion determined previously.

[0082] (2-7) Measurement of intrinsic viscosity The intrinsic viscosities [η]p of the crystalline propylene-based polymer portion and the propylene-ethylene random copolymer portion in the propylene-based block copolymer of the present invention are measured at a temperature of 135 °C using a Ubbelohde viscometer with decalin as the solvent. First, after the polymerization of the crystalline propylene-based polymer portion is completed, a part is sampled from the polymerization tank and the intrinsic viscosity [η]p is measured. Next, after the crystalline propylene-based polymer portion is polymerized, the intrinsic viscosity [η]F of the final polymer (F) obtained by polymerizing the propylene-ethylene random copolymer is measured. [η]c is determined from the following relationship. [η]F = (100 - Wc) / 100 × [η]p + Wc / 100 × [η]c

[0083] (3) Method for Evaluating Gel To 100 parts by mass of the granulated product of the propylene-based block copolymer, 0.5 part of a blue pigment is dry-blended, and using an NN30-H4000 injection molding machine manufactured by Niigata Iron Works Co., Ltd. with a clamping pressure of 30 tons and a mold having a film gate with a width of 2 mm, at a molding temperature of 240 °C and an injection pressure of primary pressure = 55 kgf / cm 2 , secondary pressure = 45 kgf / cm 2 , an injection sheet with a size of 50 mm square × thickness of 0.05 mm is molded. For one side of the 10 molded sheets, the size of the gel is measured and the number of gels is counted. Among all the counted gels, gels with a major axis of 50 μm or more are regarded as "total gels" and converted to the number per square centimeter. Here, the major axis refers to the maximum length of the straight line connecting two points on the outer periphery of the observed gel. Gels with a major axis of 300 μm or more are regarded as "large gels" and evaluated by converting to the number per square centimeter.

[0084] (4) Qualitative Method for Polyoxyalkylene Compounds in Propylene-Based Block Copolymers To 5.0 g of a propylene-based block copolymer sample, 70 ml of acetonitrile is added, and the contained components are ultrasonically extracted at 30 °C for 1 hour. The acetonitrile solution is filtered through a filter paper (5C filter paper manufactured by ADVANTEC) to collect the filtrate, and acetonitrile is removed by an evaporator and vacuum drying (for 1 hour at 25 °C). Then, 1.0 ml of orthodichlorobenzene / deuterated benzene bromide = 2 / 1 (volume ratio) is added to the dried filtrate to prepare a solution. The solution is put into an NMR sample tube, and NMR measurement is carried out, 1 The presence or absence of a polyoxyalkylene compound is confirmed by the presence or absence of a peak of the polyoxyethylene structure detected at 3.8 ppm to 3.2 ppm in the 1H-NMR spectrum. In addition, regarding the presence or absence of dripping of the gel formation inhibitor supplied from the insert nozzle, powder adhering to the wall surface around the insert nozzle after production was collected, and the same NMR analysis was performed. As a result, based on the peak intensity derived from the polyoxyethylene structure detected from the powder impregnated with 300 ppm of Pluronic (registered trademark) L-31 and Pluronic (registered trademark) L-121, which are polyoxyalkylene-based compounds (gel formation inhibitors), per 100 g of the propylene-based block copolymer produced in Comparative Example 1, those showing a peak intensity 50 times or more at the same mass ppm impregnation amount were judged to have a large amount of dripping of the gel formation inhibitor. <Apparatus> JNM-ECS400 FT NMR manufactured by JEOL RESONANCE <probe>: 5mm FG / TH Auto-tuning Probe <Measured Temperature> Room Temperature < 1 <H-NMR Measurement>: Pre-saturation elimination of solvent, Flip angle = 45°, Spin on, Flip angle = 45°, Pulse interval = 9.8 seconds, Number of integrations = 256 times

[0085] [Catalyst Preparation Example] (1) Preparation of Solid Catalyst Component for Propylene Polymerization A 10-L autoclave equipped with a stirring device for preparing solid components was thoroughly purged with nitrogen, and 2 L of purified toluene was introduced. Here, 200 g of Mg(OEt)2 and 1 L of TiCl4 were added at room temperature. The temperature was raised to 90 °C, and 40 ml of dibutyl phthalate and 10 ml of diethyl phthalate were introduced. Then, the temperature was raised to 110 °C and the reaction was carried out for 3 hours. The reaction product was thoroughly washed with purified toluene. Next, purified toluene was introduced to adjust the total liquid volume to 2 L. 1 L of TiCl4 was added at room temperature, the temperature was raised to 110 °C, and the reaction was carried out for 2 hours. The reaction product was thoroughly washed with purified toluene. Next, purified toluene was introduced to adjust the total liquid volume to 2 L. 1 L of TiCl4 was added at room temperature, the temperature was raised to 110 °C, and the reaction was carried out for 2 hours. The reaction product was thoroughly washed with purified toluene. Further, using purified n-heptane, toluene was replaced with n-heptane to obtain a slurry of solid components. When a part of this slurry was sampled, dried, and analyzed, the Ti content of the solid components was 1.7 mass%. Next, a 20-L autoclave equipped with a stirring device was thoroughly purged with nitrogen, and 100 g (0.036 mol Ti) of the above solid component slurry was introduced as the solid component. Purified n-heptane was introduced to adjust the concentration of the solid component to 25 g / L. 50 ml of SiCl4 was added, and the reaction was carried out at 90 °C for 1 hour. After the reaction product was thoroughly washed with purified n-heptane, purified n-heptane was introduced to adjust the liquid level to 4 L. Here, 25 ml of [CH2=CH]2-SiMe2, 18 ml of (i-Pr)2Si(OMe)2, and 40 g (0.35 mol) of a n-heptane-diluted solution of triethylaluminum as triethylaluminum were added, and the reaction was carried out at 40 °C for 2 hours. The reaction product was thoroughly washed with purified n-heptane. When a part of the obtained slurry was sampled, dried, and analyzed, the solid components contained 1.2 mass% of Ti and 6.7 mass% of (i-Pr)2Si(OMe)2.

[0086] (2) Preparation of prepolymerization catalyst for propylene polymerization Using 100 g (0.019 mol Ti) of the solid component obtained above, prepolymerization was carried out according to the following procedure. Purified n-heptane was introduced into the above slurry to adjust the concentration of the solid component to 20 g / L. After cooling the slurry to 10 °C, 15 g (0.132 mol) of a n-heptane-diluted solution of triethylaluminum was added as triethylaluminum, and 280 g of propylene was supplied over 4 hours. After the supply of propylene was completed, the reaction was continued for an additional 30 minutes. Then, the gas phase was thoroughly replaced with nitrogen and the reaction product was thoroughly washed with purified n-heptane. The obtained slurry was withdrawn from the autoclave and vacuum dried to obtain a solid catalyst component. Analysis of this solid catalyst component revealed that it contained 2.0 g of polypropylene per 1 g of the solid component, and the portion of this solid catalyst component excluding polypropylene contained 1.2 mass% of Ti and 6.4 mass% of (i-Pr)2Si(OMe)2.

[0087] (Example 1) Figure 1 is a schematic explanatory diagram showing an example of the arrangement of a continuous vertical gas-phase reactor. The procedure carried out will be described with reference to Figure 1. Polymerization was carried out using a continuous reactor formed by connecting two fluidized bed reactors with an internal volume of 2000 L and a straight cylindrical cross-sectional shape that is a perfect circle. In the first reactor 100, at a polymerization temperature of 65 °C, a propylene partial pressure of 1.8 MPa (absolute pressure), and hydrogen as a molecular weight regulator at a hydrogen / propylene molar ratio of 0.097, gaseous propylene was continuously supplied from pipe 106, hydrogen was continuously supplied from pipe 108, and the catalyst from the above catalyst production example was supplied at 0.85 g / hr from pipe 101 so that the polymerization rate of the propylene-based polymer was 16.7 kg / hr. At the same time, a 7 mass% n-hexane-diluted solution of triethylaluminum was continuously supplied at 100 mmol / hr from pipe 110. The production efficiency of crystalline PP per gram of catalyst was 20,000 g / g. The polyoxyethylene(2)-polyoxypropylene(16)-polyoxyethylene(2) (trade name: Pluronic® L-31, manufactured by ADEKA), which is a gel formation inhibitor, was supplied from an insert nozzle 114 having one discharge port at the tip into the held powder in the first reactor, using an n-hexane dilution solution with a concentration of 10 g / L, such that polyoxyethylene(2)-polyoxypropylene(16)-polyoxyethylene(2) would be 52 ppm with respect to the total production amount of the propylene-based block copolymer powder. The insert nozzle 114 was inserted and fixed perpendicularly to the inner wall of the reactor, and the shortest distance from the discharge port at the tip to the inner wall of the cross-section of the reactor at the position where the discharge port exists was 20% with respect to the inner diameter of the cross-section. Also, since the cross-sectional shape was a perfect circle and the shortest distance from the discharge port at the tip to the inner wall of the cross-section of the reactor was 20%, the longest distance from the discharge port at the tip to the inner wall of the cross-section of the reactor was calculated to be 80% with respect to the inner diameter of the cross-section. From this calculation result, it was confirmed that the distance from the discharge port at the tip to the inner wall of the cross-section of the reactor was 20% - 80% with respect to the inner diameter of the cross-section throughout the entire inner circumference of the cross-section. The powder of the polypropylene polymer polymerized in the first reactor was continuously withdrawn from the powder discharge case 111 at a rate of 16.7 kg / hr so that the powder holding amount in the reactor would be maintained at 45 kg, and continuously transferred to the second reactor 200 through the resin transfer case 201.

[0088] In the second reactor 200, the polymerization temperature was 70°C and the monomer pressure was 1.57 MPa (propylene + ethylene). Propylene, ethylene, and hydrogen were continuously supplied as raw materials such that the molar ratio of ethylene / propylene was 0.57, the molar ratio of hydrogen / propylene as a molecular weight regulator was 0.0038, propylene gas was supplied from pipe 206, ethylene gas was supplied from pipe 207, and hydrogen was supplied from pipe 208. Also, ethanol, which is a reaction inhibitor, was supplied from pipe 209 using an n-hexane dilution solution with an ethanol concentration of 20 g / L such that it would be 17 parts by mass of the gel formation inhibitor supplied to the first reactor with respect to 100 parts by mass of ethanol. The powder of the propylene-based block copolymer polymerized in the second reactor was continuously withdrawn from pipe 210 at a rate of 20.8 kg / hr so that the powder inventory in the reactor was maintained at 50 kg, and nitrogen gas containing moisture was supplied to stop the reaction, thereby producing propylene-based block copolymer-C1. The production efficiency of the propylene-based block copolymer per gram of catalyst was 24,500 g / g.

[0089] As a result of analyzing the obtained propylene-based block copolymer, MFR = 37 g / 10 min, the ratio of the propylene-ethylene copolymer part (Wc) = 22% by mass, the ethylene content of the propylene-ethylene copolymer part = 41% by mass, and the 1 In the 1H-NMR spectrum, peaks derived from polyoxyethylene chains were observed at 3.8 ppm to 3.2 ppm. Also, the powder adhering to the wall surface around the insert nozzle after production was recovered and subjected to the same NMR analysis. As a result, based on the peak intensity derived from the polyoxyethylene structure detected from the powder impregnated with polyoxyethylene(2)-polyoxypropylene(16)-polyoxyethylene(2) (trade name: Pluronic (registered trademark) L-31), which is a gel formation inhibitor, per 100 g of the propylene-based block copolymer produced in Comparative Example 1, it showed a peak intensity 8.8 times that of the same mass ppm impregnation amount. Therefore, it was determined that there was no dripping of the gel formation inhibitor liquid.

[0090] (Example 2) The procedure carried out will be described with reference to FIG. 1. Polymerization was carried out using a continuous reactor formed by connecting two fluidized bed reactors with an internal volume of 2000 L. In the first reactor 100, while maintaining a polymerization temperature of 65°C, a propylene partial pressure of 1.8 MPa (absolute pressure), and a hydrogen / propylene molar ratio of 0.097 for hydrogen as a molecular weight regulator, gaseous propylene was continuously supplied from pipe 106 and hydrogen was continuously supplied from pipe 108. At the same time, the catalyst from the catalyst production example was supplied from pipe 101 at a rate of 0.75 g / hr so that the polymerization rate of the propylene-based polymer would be 16.7 kg / hr. A 7 mass% n-hexane diluted solution of triethylaluminum was continuously supplied from pipe 110 at 100 mmol / hr. The production efficiency of crystalline PP per gram of catalyst was 22,300 g / g. The powder of the polypropylene polymer polymerized in the first reactor was continuously withdrawn from the powder discharge case 111 at a rate of 16.7 kg / hr so that the powder inventory in the reactor would be 45 kg, and was continuously transferred to the second reactor 200 through the resin transfer case 201.

[0091] In the second reactor 200, with a polymerization temperature of 70°C and a monomer pressure of 1.57 MPa (propylene + ethylene), while maintaining an ethylene / propylene molar ratio of 0.57 and a hydrogen / propylene molar ratio of 0.0037 for hydrogen as a molecular weight regulator, gaseous propylene was continuously supplied from pipe 206, gaseous ethylene was continuously supplied from pipe 207, and hydrogen was continuously supplied from pipe 208. As a gel formation inhibitor, polyoxyethylene(2)-polyoxypropylene(16)-polyoxyethylene(2) (trade name: Pluronic® L-31, manufactured by ADEKA Corporation) was supplied into the powder inventory in the second reactor from an insert nozzle 213 having one discharge port at the tip using an n-hexane diluted solution with a concentration of 30 g / L so that the amount of polyoxyethylene(2)-polyoxypropylene(16)-polyoxyethylene(2) would be 299 ppm based on the total production amount of the propylene-based block copolymer powder. The insert nozzle 213 was inserted and fixed perpendicularly to the inner wall of the reactor. The shortest distance from the discharge port at the tip to the inner wall of the cross-section of the reactor at the position where the discharge port is located was 20% of the inner diameter of the cross-section. Also, since the cross-sectional shape was a perfect circle and the shortest distance from the discharge port at the tip to the inner wall of the cross-section of the reactor was 20%, the longest distance from the discharge port at the tip to the inner wall of the cross-section of the reactor was calculated to be 80% of the inner diameter of the cross-section. From this calculation result, it was confirmed that the distance from the discharge port at the tip to the inner wall of the cross-section of the reactor was 20% - 80% of the inner diameter of the cross-section throughout the entire inner circumference of the cross-section. Also, ethanol, which is a reaction inhibitor, was supplied from the 209 pipe using an n-hexane dilution solution with an ethanol concentration of 20 g / L so that the amount of the gel formation inhibitor supplied to the second reactor was 113 parts by mass with respect to 100 parts by mass of ethanol. The powder of the propylene-based block copolymer polymerized in the second reactor was continuously withdrawn from the pipe 210 at a rate of 20.6 kg / hr so that the powder holding amount in the reactor was maintained at 50 kg, and nitrogen gas containing moisture was supplied to stop the reaction, thereby producing propylene-based block copolymer - C2. The production efficiency of the propylene-based block copolymer per gram of the catalyst was 27,500 g / g.

[0092] As a result of analyzing the obtained propylene-based block copolymer, MFR = 42 g / 10 min, the ratio of the propylene / ethylene copolymer part (Wc) = 23% by mass, the ethylene content of the propylene / ethylene copolymer part = 42% by mass, and in the 1 1H-NMR spectrum, peaks derived from polyoxyethylene chains were observed at 3.8 ppm - 3.2 ppm. Also, the powder adhering to the wall surface around the insert nozzle after production was recovered, and the same NMR analysis was performed. As a result, based on the peak intensity derived from the polyoxyethylene structure detected from the powder impregnated with polyoxyethylene(2)-polyoxypropylene(16)-polyoxyethylene(2) (trade name: Pluronic (registered trademark) L-31), which is a gel formation inhibitor, per 100 g of the propylene-based block copolymer produced in Comparative Example 1, a peak intensity 11 times that value was shown at the same mass ppm impregnation amount. Therefore, it was determined that there was no dripping of the gel formation inhibitor liquid.

[0093] (Example 3) In Example 2, the shortest distance from the discharge port at the tip of the insert nozzle 213 connected to the reactor in the second step to the inner wall of the cross-section of the reactor at the position where the discharge port is located was set to 50% of the inner diameter of the cross-section. Propylene-based block copolymer-C3 was produced in the same manner as in Example 2, except that polyoxyethylene(2)-polyoxypropylene(16)-polyoxyethylene(2) was supplied from the insert nozzle 213 having one discharge port at the tip so as to be 288 ppm with respect to the total production amount of the propylene-based block copolymer powder into the powder held in the second reactor. Since the cross-sectional shape is a perfect circle and the shortest distance from the discharge port at the tip to the inner wall of the cross-section of the reactor is 50%, the longest distance from the discharge port at the tip to the inner wall of the cross-section of the reactor was calculated to be 50% of the inner diameter of the cross-section. From this calculation result, it was confirmed that the distance from the discharge port at the tip to the inner wall of the cross-section of the reactor was 50% of the inner diameter of the cross-section throughout the entire inner circumference of the cross-section. As a result of analyzing the obtained propylene-based block copolymer, peaks derived from polyoxyethylene chains were observed at 3.8 ppm to 3.2 ppm in the 1 1H-NMR spectrum. Also, the powder adhering to the wall surface around the insert nozzle after production was collected, and the same NMR analysis was performed. As a result, based on the peak intensity derived from the polyoxyethylene structure detected from the powder impregnated with polyoxyethylene(2)-polyoxypropylene(16)-polyoxyethylene(2) (trade name: Pluronic® L-31), which is a gel formation inhibitor, per 100 g of the propylene-based block copolymer produced in Comparative Example 1, a peak intensity 7.7 times that at the same mass ppm impregnation amount was shown. Therefore, it was determined that there was no dripping of the gel formation inhibitor liquid.

[0094] (Example 4) In Example 2, the gel formation inhibitor supplied to the second reactor was changed to polyoxyethylene(5)-polyoxypropylene(69)-polyoxyethylene(5) (trade name: Pluronic® L-121, manufactured by ADEKA Corporation), and it was used as a n-hexane dilution solution with a concentration of 30 g / L. Propylene-based block copolymer-C4 was produced in the same manner as in Example 2, except that it was supplied from an insert nozzle 213 having one discharge port at the tip into the retained powder in the second reactor so as to be 294 ppm with respect to the total production amount of the propylene-based block copolymer powder. As a result of analyzing the obtained propylene-based block copolymer, peaks derived from polyoxyethylene chains were observed at 3.8 ppm to 3.2 ppm in the 1H-NMR spectrum of the acetonitrile extract. 1 Peaks derived from polyoxyethylene chains were observed at 3.8 ppm to 3.2 ppm in the 1H-NMR spectrum. Also, the powder adhering to the wall surface around the insert nozzle after production was collected, and the same NMR analysis was performed. As a result, based on the peak intensity derived from the polyoxyethylene structure detected from the powder impregnated with polyoxyethylene(5)-polyoxypropylene(69)-polyoxyethylene(5) (trade name: Pluronic® L-121), which is a gel formation inhibitor, per 100 g of the propylene-based block copolymer produced in Comparative Example 1, a peak intensity 13.2 times that at the same mass ppm impregnation amount was shown. Therefore, it was determined that there was no dripping of the gel formation inhibitor liquid.

[0095] (Comparative Example 1) In Example 2, a propylene-based block copolymer-C5 was produced in the same manner as in Example 2, except that a gel formation inhibitor was not supplied to the second reactor. As a result of analyzing the obtained propylene-based block copolymer, in the 1 1H-NMR spectrum of the acetonitrile extract, no peak derived from the polyoxyethylene chain was observed at 3.8 ppm to 3.2 ppm. Also, the powder adhering to the wall surface around the insert nozzle after production was recovered, and as a result of performing the same NMR analysis as described above, no peak derived from the polyoxyethylene structure was observed.

[0096] (Comparative Example 2) In Example 1, a propylene-based block copolymer-C6 was produced in the same manner as in Example 1, except that the shortest distance from the discharge port at the tip of the insert nozzle 114 connected to the reactor in the first step to the inner wall of the cross section of the reactor at the position where the discharge port exists was set to 10% of the inner diameter of the cross section. As a result of analyzing the obtained propylene-based block copolymer, in the 1 1H-NMR spectrum of the acetonitrile extract, a peak derived from the polyoxyethylene chain was observed at 3.8 ppm to 3.2 ppm. Also, the powder adhering to the wall surface around the insert nozzle after production was recovered, and as a result of performing the same NMR analysis as described above, based on the peak intensity derived from the polyoxyethylene structure detected from the powder impregnated with polyoxyethylene(2)-polyoxypropylene(16)-polyoxyethylene(2) (trade name: Pluronic (registered trademark) L-31) with respect to 100 g of the propylene-based block copolymer produced in Comparative Example 1, it showed a peak intensity 52.8 times that of the same mass ppm impregnation amount, so it was determined that there was liquid dripping of the gel formation inhibitor.

[0097] (Comparative Example 3) In Example 2, a propylene-based block copolymer-C7 was produced in the same manner as in Example 2, except that the shortest distance from the discharge port at the nozzle tip of the insert nozzle 213 connected to the reactor in the second step to the inner wall of the cross-section of the reactor at the position where the discharge port is located was set to 0% with respect to the inner diameter of the cross-section. As a result of analyzing the obtained propylene-based block copolymer, 1 a peak derived from a polyoxyethylene chain was observed at 3.8 ppm to 3.2 ppm in the 1H-NMR spectrum. In addition, the powder adhering to the wall surface around the insert nozzle after production was recovered and subjected to the same NMR analysis. As a result, based on the peak intensity derived from the polyoxyethylene structure detected from the powder impregnated with polyoxyethylene(2)-polyoxypropylene(16)-polyoxyethylene(2) (trade name: Pluronic (registered trademark) L-31), which is a gel formation inhibitor, with respect to 100 g of the propylene-based block copolymer produced in Comparative Example 1, a peak intensity 132 times that amount was shown at the same mass ppm impregnation amount. Therefore, it was determined that there was liquid dripping of the gel formation inhibitor.

[0098] (Comparative Example 4) In Example 2, a propylene-based block copolymer-C8 was produced in the same manner as in Example 2, except that the shortest distance from the discharge port at the nozzle tip of the insert nozzle 213 connected to the reactor in the second step to the inner wall of the cross-section of the reactor at the position where the discharge port is located was set to 10% with respect to the inner diameter of the cross-section. As a result of analyzing the obtained propylene-based block copolymer, 1 a peak derived from a polyoxyethylene chain was observed at 3.8 ppm to 3.2 ppm in the 1H-NMR spectrum. Also, the powder adhering to the wall surface around the insert nozzle after production was recovered, and the same NMR analysis was performed. As a result, based on the peak intensity derived from the polyoxyethylene structure detected from the powder impregnated with polyoxyethylene(2)-polyoxypropylene(16)-polyoxyethylene(2) (trade name: Pluronic (registered trademark) L-31), which is a gel formation inhibitor, per 100 g of the propylene-based block copolymer produced in Comparative Example 1, a peak intensity 66 times that of the same mass ppm impregnation amount was shown. Therefore, it was determined that there was liquid dripping of the gel formation inhibitor.

[0099] (Comparative Example 5) In Example 4, a propylene-based block copolymer-C9 was produced in the same manner as in Example 4, except that the shortest distance from the discharge port at the tip of the insert nozzle 213 connected to the reactor in the second step to the inner wall of the cross-section of the reactor at the position where the discharge port is located was set to 10% of the inner diameter of the cross-section. As a result of analyzing the obtained propylene-based block copolymer, a peak derived from the polyoxyethylene chain was observed at 3.8 ppm to 3.2 ppm in the 1 1H-NMR spectrum. Also, the powder adhering to the wall surface around the insert nozzle after production was recovered, and the same NMR analysis was performed. As a result, based on the peak intensity derived from the polyoxyethylene structure detected from the powder impregnated with polyoxyethylene(5)-polyoxypropylene(69)-polyoxyethylene(5) (trade name: Pluronic (registered trademark) L-121, manufactured by ADEKA Corporation), which is a gel formation inhibitor, per 100 g of the propylene-based block copolymer produced in Comparative Example 1, a peak intensity 79.2 times that of the same mass ppm impregnation amount was shown. Therefore, it was determined that there was liquid dripping of the gel formation inhibitor.

[0100] [Pelletizing process] To 100 parts by mass of each of the propylene-based block polymers obtained in the above Examples and Comparative Examples, as antioxidants, 0.1 part by mass of 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione (manufactured by Nippon Cytec Industries Co., Ltd., trade name: Cyanox 1790), 0.09 part by mass of tris(2,4-di-t-butylphenyl) phosphite (manufactured by Ciba Geigy, trade name: Irgafos 168), 0.05 part by mass of 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane (manufactured by Adeka Corporation, trade name: Adeka Stab PEP-36), 0.09 part by mass of N,N-bis(octadecyl)hydroxylamine (manufactured by Ciba Geigy, trade name: Irgastab FS042), and 0.03 part by mass of calcium stearate as a neutralizing agent were added, and the mixture was mixed and blended for 5 minutes using a super mixer (manufactured by Kawada Manufacturing Co., Ltd.). Using the obtained blend, granules of the propylene-based block copolymer were obtained by the underwater cutting granulation method under the following apparatus and conditions. Kneading extruder: Single-screw extruder with an inner diameter of 110 mm Die: TiC, φ2.5 mm, 20 holes, heat channel type Cutter blade: TiC, 4 pieces, scooping angle 50° Granulation treatment rate: 200 kg / hr Screen pack filter: None

[0101] The polymerization results and evaluation results are shown in Tables 1 and 2. In the tables, "m.r." represents the molar ratio.

[0102]

Table 1

[0103]

Table 2

[0104] From the results of Comparative Example 1 and Comparative Examples 2 to 5, it can be seen that even when the amount of the reaction inhibitor is the same, without the gel formation inhibitor, the gel deactivation effect is low and there are a very large number of large gels. To reduce the gel without the gel formation inhibitor, a means of supplying a larger amount of the reaction inhibitor can be considered, but this will significantly reduce the production efficiency in the second reactor and make it impossible to reach the target propylene-ethylene copolymer content, so it is not feasible. Also, considering the results of Example 2 and Comparative Example 4, and the results of Example 4 and Comparative Example 5 comprehensively, it is considered that even when the molecular weight of the gel formation inhibitor is different, the gel deactivation effect can be expected by having the same polyethylene glycol structure. Furthermore, from the results of Comparative Examples 2 to 4, although a sufficient amount of the gel formation inhibitor was supplied with respect to the production rate, there are more gels compared to Examples 1 to 4, and a large amount of dripping of the gel formation inhibitor liquid has been confirmed. It is considered that the effect of the gel formation inhibitor has not been fully exerted due to poor dispersion of the powder in the reactor. In contrast, in Examples 1 to 4, the gel formation inhibitor was fed from the insert nozzle connected to the gas-phase fluidized bed polymerization reactor in the first step or the second step into the retained powder inside the reactor, and the insert nozzle had an insert length of 12% to 88% with respect to the inner diameter of the straight body part of the gas-phase fluidized bed polymerization reactor. Therefore, the gel formation inhibitor is uniformly dispersed in the retained powder without dripping onto the wall surface, so that a propylene-based block copolymer containing a propylene-ethylene copolymer can be produced with high catalyst efficiency while reducing the gel without excessively increasing the number of reactors in the multi-stage continuous polymerization method.

Explanation of symbols

[0105] 100 First reactor 101 Catalyst component supply pipe 102 Gas dispersion plate 103 Cycle gas extraction pipe 104 Cycle gas compressor 105 Cycle gas cooler 106 Gas propylene supply pipe 107 Ethylene gas supply pipe 108 Hydrogen supply pipe 109 External electron donor supply pipe 110 Organoaluminum supply pipe 111 Powder discharge case 112 Gel formation inhibitor supply pipe 113 Valve 114 Insert nozzle 200 Second reactor 201 Resin transfer case 202 Gas dispersion plate 203 Cycle gas extraction pipe 204 Cycle gas compressor 205 Cycle gas cooler 206 Propylene gas supply pipe 207 Ethylene gas supply pipe 208 Hydrogen supply pipe 209 Reaction inhibitor supply pipe 210 Polymer extraction pipe 211 Gel formation inhibitor supply pipe 212 Valve 213 Insert nozzle X Longitudinal central axis A Cross-section of the reactor at the position where the discharge port exists Y Intersection of the longitudinal central axis X and the cross-section A R Inner diameter of the cross-section A Point P0 Position where the discharge port of the insert nozzle exists Points P1, P2, P3, P4 Points existing on the inner circumference of the cross-section A C Concentric circle w Retraction width of the inner circumference of the concentric circle r Radius of the concentric circle R1 Minor diameter of the cross-section A R2 Major diameter of the cross-section A Points P0a, P0b, P0c Positions where the discharge port of the insert nozzle exists Points P1a, P1b, P2a, P2b Points existing on the inner circumference of the cross-section A< / probe>

Claims

1. A method for producing a propylene-based block copolymer, comprising carrying out multi-stage continuous polymerization including a first step and a second step in the presence of an olefin polymerization catalyst using a gas-phase fluidized bed polymerization reactor, an insert nozzle having at least one discharge port is connected to a straight body portion of the gas-phase fluidized-bed polymerization reactor in at least one of the first and second steps, and a distance from the discharge port located at the most tip side of the insert nozzle to an inner wall of a cross section of the gas-phase fluidized-bed polymerization reactor at a position where the discharge port is located is within a range of 12% to 88% of an inner diameter of the cross section for a distance from the discharge port to an inner wall located at any position on the inner circumference of the cross section; A method for producing a propylene-based block copolymer, comprising feeding a gel formation inhibitor from the insert nozzle into the powder contained inside the reactor.

2. The method for producing a propylene-based block copolymer according to claim 1, wherein the gel formation inhibitor is a compound represented by the following general formula (1): [General formula (1)] HO-[CH ２ -CH ２ -O] ｐ -[CH ２ -CH(CH ３ )-O] ｑ -[CH ２ -CH ２ -O] ｒ -R １ (In the general formula (1), p, q, and r are integers, and the following relational expressions are all satisfied: 0≦p≦30, 0≦q≦70, 0≦r≦30, 1≦p+r≦60, and 2≦p+q+r. R １ represents a hydrogen atom or a hydrocarbon group having 1 to 25 carbon atoms.

3. 3. The method for producing a propylene-based block copolymer according to claim 1, wherein the gel formation inhibitor is supplied in a ratio of 10 ppm by mass to 1000 ppm by mass based on the amount of the propylene-based block copolymer produced.

4. 3. The method for producing a propylene-based block copolymer according to claim 1, further comprising feeding a reaction inhibitor represented by the following general formula (2) into the powder contained inside the reactor: [General formula (2)] HO-R ２ (In general formula (2), R ２ represents a saturated hydrocarbon group having 1 to 10 carbon atoms.

5. The method for producing a propylene-based block copolymer according to claim 4, wherein the amount of the gel formation inhibitor supplied is 10 parts by mass to 150 parts by mass per 100 parts by mass of the reaction inhibitor supplied.

6. 3. The method for producing a propylene-based block copolymer according to claim 1 or 2, wherein the polymerization is carried out in the presence of an olefin polymerization catalyst containing a solid catalyst component containing magnesium, titanium, a halogen and an electron donor compound as an internal donor, and an organoaluminum compound.

7. 3. The method for producing a propylene-based block copolymer according to claim 1 or 2, wherein in a first step, a crystalline propylene-based polymer is produced using one or more gas-phase fluidized bed polymerization reactors, and in a subsequent second step, an amorphous propylene-α-olefin-based copolymer is produced in the presence of the crystalline propylene-based polymer using one or more gas-phase polymerization reactors.

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