JP7732266B2 - Propylene polymer composition and molded article - Google Patents

Description

The present invention relates to a propylene-based polymer composition having a biomass content of 8.4 to 49% and a molded article thereof. More specifically, the present invention relates to a propylene-based polymer composition that gives a molded article that is excellent in rigidity and impact resistance and does not crack even when it contains biomass polyethylene. In the present invention, "crackable" means that the composition is broken into several parts when a force is applied. Furthermore, "not crackable" means any of the following:
(1) It does not split into several parts without creating fissures (cracks).
(2) A fissure (crack) forms, but it does not separate into several parts.

Propylene-based resins are characterized by their excellent rigidity, impact resistance, heat resistance, moldability, transparency, and chemical resistance, and are therefore widely used in a variety of applications, including various industrial materials, automobile-related parts, various medical and cosmetic containers, daily necessities, films, and fibers.
Meanwhile, environmental pollution caused by plastics has become a problem in recent years, and how to address this issue is a challenge. One solution is to use carbon-neutral plant-derived plastics (biomass plastics). Plant-derived polypropylene has also been considered, but is not currently on the market. Therefore, the addition of biomass polyethylene to polypropylene has been investigated (see, for example, Patent Documents 1 and 2).

However, the mixture obtained by mixing polypropylene and biomass polyethylene and then melt-kneading it has poor miscibility, and molded articles obtained from this mixture tend to crack. For this reason, there is a demand for polypropylene compositions that have excellent miscibility even when containing biomass polyethylene.

Japanese Patent Application Laid-Open No. 2019-34519 JP 2016-27171 A

In light of the current state of the art, the object of the present invention is to provide a propylene-based polymer composition with a biomass content of 8.4 to 49%, which produces molded articles that are superior in rigidity and impact resistance and do not crack even when containing biomass polyethylene, and a molded article made from the same.

The present inventors have conducted extensive research and have found a propylene-based polymer composition having a biomass content of 8.4 to 49%, which, when made using a specific propylene-based polymer mixture, gives molded articles that are excellent in rigidity and impact resistance and do not crack even when containing biomass polyethylene, and a molded article made from the same, thereby completing the present invention.
That is, the present invention provides a propylene-based polymer composition having a biomass content of 8.4 to 49% as follows, and a molded article thereof.

[1] A propylene-based polymer composition containing 51 to 90 parts by weight of a propylene-based copolymer (a) and 10 to 49 parts by weight of a biomass polyethylene (b) that satisfy the following conditions (A-i) to (A-iv), totaling 100 parts by weight, and having a biomass degree of 8.4 to 49%:
(Ai) Propylene-α-olefin random copolymer.
(A-ii) The α-olefin content is in the range of 1 to 5% by weight.
(A-iii) The melt flow rate (hereinafter sometimes abbreviated as MFR) according to JIS K7210 (230°C, 2.16 kg load) is in the range of 0.5 to 100 g/10 min.
(A-iv) The melting peak temperature (Tm) is in the range of 126 to 152°C.
[2] A propylene-based polymer composition containing 0.01 to 0.6 parts by weight of a nucleating agent per 100 parts by weight of the propylene-based polymer composition according to [1].
[3] A molded article obtained using the propylene polymer composition according to [1] or [2].

Molded articles produced using the propylene-based polymer composition of the present invention, which has a biomass content of 8.4 to 49%, contribute to reducing the environmental impact and are useful because they provide molded articles that are excellent in rigidity and impact resistance and do not crack, even though they contain biomass polyethylene. Injection-molded articles are particularly useful.

FIG. 1 shows a diagram of a crack test in the MD and TD directions, which is carried out by making cuts in an injection test piece of 120 mm×120 mm×2 mm. FIG. 2 is a flow sheet used to explain the production of a propylene-ethylene random copolymer in the examples.

The propylene-based polymer composition of the present invention contains 51 to 90 parts by weight of a propylene-based copolymer (a) and 10 to 49 parts by weight of a biomass polyethylene (b) that satisfy the following conditions (A-i) to (A-iv), totaling 100 parts by weight, and has a biomass degree of 8.4 to 49%, and is characterized by contributing to a reduction in environmental load and not causing a decrease in performance:
(Ai) Propylene-α-olefin random copolymer.
(A-ii) The α-olefin content is in the range of 1 to 5% by weight.
(A-iii) The melt flow rate (MFR) according to JIS K7210 (230°C, 2.16 kg load) is in the range of 0.5 to 100 g/10 min.
(A-iv) The melting peak temperature (Tm) is in the range of 126 to 152°C.
The propylene polymer composition and molded article of the present invention will be described in detail below.

[1] Components constituting the propylene-based polymer composition (1) propylene-based copolymer (a)

(i) α-olefin of propylene copolymer (a) The α-olefin content of the propylene copolymer (b) used in the present invention is in the range of 1 to 5 wt%, preferably 1.9 to 4.9 wt%, and more preferably 3.4 to 4.9 wt%. At 1 wt% or more, sufficient crack resistance is achieved. Furthermore, an α-olefin content of 5 wt% or less is preferred from the viewpoint of rigidity. Examples of the α-olefin used in copolymerization include α-olefins having 2 to 20 carbon atoms excluding propylene, such as ethylene, 1-butene, 1-hexene, and 1-octene. One or more α-olefins may be copolymerized with propylene. Among these, ethylene and 1-butene are preferred. Ethylene is more preferred. Furthermore, these propylene copolymers may be used in combination with two or more types.
Specific examples of propylene copolymers include binary or ternary random copolymers in which any amount of comonomer is combined, such as propylene-ethylene random copolymer, propylene-1-butene random copolymer, propylene-1-hexene random copolymer, propylene-1-octene random copolymer, propylene-ethylene-1-butene random copolymer, propylene-ethylene-1-hexene random copolymer, propylene-1-butene-1-octene random copolymer, etc. Here, the respective contents of propylene and α-olefin are values measured by ^13C -NMR under the following conditions.
Apparatus: JEOL-GSX270 manufactured by JEOL Ltd.
Concentration: 300mg/2mL
Solvent: orthodichlorobenzene

(ii) Melt flow rate (MFR) of propylene copolymer (a)
The propylene copolymer (a) used in the present invention has a melt flow rate (MFR) in the range of 0.5 to 100 g/10 min, preferably 5 to 60 g/10 min, and more preferably 10 to 40 g/10 min, according to JIS K7210 (230°C, 2.16 kg load). A melt flow rate (MFR) of 0.5 g/10 min or more improves moldability and produces a satisfactory product. An MFR of 100 g/10 min or less improves mechanical strength.
The melt flow rate (MFR) can be easily adjusted by adjusting the temperature and pressure, which are polymerization conditions for the propylene copolymer (a), or by controlling the amount of hydrogen added in a method in which a chain transfer agent such as hydrogen is added during polymerization.

(iii) Catalyst for Propylene-Based Copolymer (a) The catalyst used for the propylene-based copolymer (a) used in the present invention is not particularly limited, but it is preferable to use a stereoregular catalyst. Examples of the stereoregular catalyst include a Ziegler catalyst and a metallocene catalyst.

Examples of Ziegler catalysts include two-component catalysts consisting of transition metal components such as titanium halide compounds (e.g., titanium trichloride, titanium tetrachloride, trichloroethoxytitanium) and contact products of the titanium halide compounds with magnesium compounds (e.g., magnesium halides) and organometallic components such as alkylaluminum compounds or their halides, hydrides, and alkoxides; and three-component catalysts in which electron-donating compounds containing nitrogen, carbon, phosphorus, sulfur, oxygen, silicon, etc. are added to these components.

The metallocene catalyst is preferably a supported type.
A particularly preferred example of the supported metallocene catalyst is an ion-exchanged layered silicate in which the support also functions as a co-catalyst, which is obtained by combining the following components [A], [B], and, if necessary, the following component [C].

Component [A] Metallocene Complex: A transition metal compound of Groups 4 to 6 of the periodic table having at least one conjugated five-membered ring ligand
Component [B] Promoter: Ion-exchange layered silicate
Component [C] organoaluminum compound

Component [A] Metallocene Complex Specifically, the compound represented by the following formula [I] can be used as the component [A].
Q(C ₅ H _4-a R ¹ _a ) (C ₅ H _4-b R ² _b ) MXY...[I]
In formula [I], Q represents a linking group that bridges two conjugated five-membered ring ligands.
M represents a transition metal of Groups 4 to 6 of the periodic table, and among these, titanium, zirconium, and hafnium are preferred.
X and Y each independently represent hydrogen, halogen, a hydrocarbon group having 1 to 20 carbon atoms, an oxygen-containing hydrocarbon group having 1 to 20 carbon atoms, a nitrogen-containing hydrocarbon group having 1 to 20 carbon atoms, a phosphorus-containing hydrocarbon group having 1 to 20 carbon atoms, or a silicon-containing hydrocarbon group having 1 to 20 carbon atoms.

^R1 and ^R2 each independently represent a hydrocarbon group having 1 to 20 carbon atoms, a halogen, a halogen-containing hydrocarbon group having 1 to 20 carbon atoms, an alkoxy group, an aryloxy group, a silicon-containing hydrocarbon group, a phosphorus-containing hydrocarbon group, a nitrogen-containing hydrocarbon group, or a boron-containing hydrocarbon group. Two adjacent ^R1s or two adjacent ^R2s may be bonded to form a _C4 to _C10 ring. In particular, it is preferable that they form a 6- or 7-membered ring, which, together with the conjugated 5-membered ring, forms an indene ring or an azulene ring.
a and b are integers satisfying 0≦a≦4 and 0≦b≦4.
Examples of the bonding group Q that bridges two conjugated five-membered ring ligands include an alkylene group, an alkylidene group, a silylene group, and a germylene group. These groups may have hydrogen atoms substituted with alkyl groups, halogens, etc. A silylene group is particularly preferred.

Specific preferred examples of the metallocene complex include the following compounds:
(1) Methylenebis(cyclopentadienyl)zirconium dichloride
(2) Methylene(cyclopentadienyl)(3,4-dimethylcyclopentadienyl)zirconium dichloride
(3) Isopropylidene(cyclopentadienyl)(3,4-dimethylcyclopentadienyl)zirconium dichloride
(4) Ethylene(cyclopentadienyl)(3,5-dimethylpentadienyl)zirconium dichloride
(5) Methylenebis(indenyl)zirconium dichloride
(6) Ethylenebis(2-methylindenyl)zirconium dichloride
(7) Ethylene 1,2-bis(4-phenylindenyl)zirconium dichloride
(8) Ethylene(cyclopentadienyl)(fluorenyl)zirconium dichloride

(9) Dimethylsilylene(cyclopentadienyl)(tetramethylcyclopentadienyl)zirconium dichloride
(10) Dimethylsilylenebis(indenyl)zirconium dichloride
(11) Dimethylsilylenebis(4,5,6,7-tetrahydroindenyl)zirconium dichloride
(12) Dimethylsilylene(cyclopentadienyl)(fluorenyl)zirconium dichloride
(13) Dimethylsilylene(cyclopentadienyl)(octahydrofluorenyl)zirconium dichloride
(14) Methylphenylsilylenebis[1-(2-methyl-4,5-benzo(indenyl)]zirconium dichloride
(15) Dimethylsilylenebis[1-(2-methyl-4,5-benzoindenyl)]zirconium dichloride
(16) Dimethylsilylenebis[1-(2-methyl-4H-azulenyl)]zirconium dichloride
(17) Dimethylsilylenebis[1-(2-methyl-4-(4-chlorophenyl)-4H-azulenyl)]zirconium dichloride
(18) Dimethylsilylenebis[1-(2-ethyl-4-(4-chlorophenyl)-4H-azulenyl)]zirconium dichloride
(19) Dimethylsilylenebis[1-(2-ethyl-4-naphthyl-4H-azulenyl)]zirconium dichloride

(20) Diphenylsilylenebis[1-(2-methyl-4-(4-chlorophenyl)-4H-azulenyl)]zirconium dichloride
(21) Dimethylsilylenebis[1-(2-methyl-4-(phenylindenyl))]zirconium dichloride
(22) Dimethylsilylenebis[1-(2-ethyl-4-(phenylindenyl))]zirconium dichloride
(23) Dimethylsilylenebis[1-(2-ethyl-4-naphthyl-4H-azulenyl)]zirconium dichloride
(24) Dimethylgermylenebis(indenyl)zirconium dichloride
(25) Dimethylgermylene(cyclopentadienyl)(fluorenyl)zirconium dichloride. Other preferred examples of Group 4, 5, and 6 transition metal compounds, such as titanium compounds and hafnium compounds, are similar to those listed above. These compounds may be used in combination with the catalyst component and catalyst of the present invention.

Component [B] Promoter (ion-exchange layered silicate)
The ion-exchangeable layered silicate is not limited to a naturally occurring one, but may also be an artificially synthesized product. Clay compounds can be used as the ion-exchangeable layered silicate, and specific examples of clay compounds include the following layered silicates described in "Clay Mineralogy" by Haruo Shiramizu, Asakura Shoten (1995):
(A) Kaolin group such as dickite, nacrite, kaolinite, anoxite, metahalloysite, and halloysite, whose main constituent layers are 1:1 type structures, and serpentine group such as chrysotile, lizardite, and antigorite.
(a) Smectite group such as montmorillonite, sauconite, beidellite, nontronite, saponite, hectorite, stevensite, etc., vermiculite group such as vermiculite, mica group such as mica, illite, sericite, glauconite, attapulgite, sepiolite, palygorskite, bentonite, pyrophyllite, talc, chlorite group, which have a 2:1 type structure as their main constituent layer.

The silicate used in the present invention may be a layered silicate having a mixed layer of the above (a) and (b).
In the present invention, the silicate as the main component is preferably a silicate having a 2:1 type structure, more preferably a smectite group silicate, and particularly preferably montmorillonite.

The activity of these silicates can be improved by chemically treating them with an acid, a salt, an alkali, an oxidizing agent, a reducing agent, an organic solvent, or the like.
The acid treatment removes impurities on the surface of the ion-exchange layered silicate particles, exchanges interlayer cations, and also dissolves some or all of the cations such as Al, Fe, and Mg in the crystal structure.
The acid used in the acid treatment includes hydrochloric acid, nitric acid, sulfuric acid, etc., but inorganic acids are preferred, and sulfuric acid is particularly preferred.
The acid treatment conditions are not particularly limited, but are preferably conditions in which a 5 to 50 wt % aqueous acid solution is reacted at a temperature of 60 to 100°C for 1 to 24 hours, and the acid concentration may be changed during this period. After the acid treatment, washing is usually carried out. Washing is an operation in which the acid contained in the treatment system is separated and removed from the ion-exchanged layered silicate.

The salts used in the salt treatment are preferably selected to contain specific cations, preferably monovalent to tetravalent metal cations, and more preferably Li, Ni, Zn, or Hf cations.
Specific examples of salts include the following:
Examples of compounds with a Li cation include LiCl, LiBr _{, Li2SO4} , _Li3 ( _PO4 ), Li( _ClO4 ) _{, Li2} ( _C2O4 ), _{LiNO3 ,} Li( _OOCCH3 ), and _Li2 ( _C4H4O4 ) _.
Examples of those having Ni as a cation include _NiCO3 , Ni _{( NO3} ) ₂ , _NiC2O4 , Ni( _ClO4 ) ₂ , _NiSO4 , _NiCl2 , and _NiBr2 .
Examples of compounds with a Zn cation include Zn( _OOCH3 ) ₂ , Zn _{( CH3COCHCOCH3} ) ₂ , ZnCO3, Zn( _NO3 ) ₂ , Zn( _ClO4 ) ₂ , _Zn3 ( _PO4 ) ₂ , _ZnSO4 , _ZnF2 , _ZnCl2 , _ZnBr2 , _{and ZnI2} .
Examples of compounds having a cation of Hf include Hf( _OOCCH3 ) ₄ , Hf( _CO3 ) ₂ , Hf( _NO3 ) ₄ , Hf( _SO4 ) ₂ , _HfOCl2 , _HfF4 , _HfCl4 , _HfBr4 , and _HfI4 .

After chemical treatment, the material is dried. Generally, drying temperatures between 100 and 800°C are acceptable, and high temperatures that could cause structural destruction (for example, 800°C or higher, depending on the heating time) are not recommended. Even if the structure is not destroyed, the properties can change depending on the drying temperature, so it is preferable to change the drying temperature depending on the application. Drying times are typically between 1 minute and 24 hours, preferably between 5 minutes and 4 hours, and the atmosphere is dry air, dry nitrogen, dry argon, or under reduced pressure. There are no particular limitations on the drying method, and various methods are possible.

Component [C] Organoaluminum Compound The organoaluminum compound of component [C] is a component that is optionally used as needed, and is most preferably a compound represented by the following formula [II]:
(AlR ⁴ _p X _3-p ) _q ...[II]
In formula [II], ^R4 represents a hydrocarbon group having 1 to 20 carbon atoms, X represents a halogen atom, a hydrogen atom, an alkoxy group, or an amino group, p represents an integer of 1 to 3, and q represents an integer of 1 or 2.
^R4 is preferably an alkyl group, and when X is an alkoxy group, it is preferably an alkoxy group having 1 to 8 carbon atoms, and when X is an amino group, it is preferably an amino group having 1 to 8 carbon atoms.
Of these, preferred are trialkylaluminums where p = 3 and q = 1 and dialkylaluminum hydrides where p = 2 and q = 1. More preferred are trialkylaluminums where R ⁴ has 1 to 8 carbon atoms.

Organoaluminum compounds can be used alone, in combination with other compounds, or in combination. Furthermore, organoaluminum compounds can be added not only during catalyst preparation, but also during prepolymerization or main polymerization.

(iv) Method for Producing Propylene-Based Copolymer (a) Examples of methods for producing the propylene-based copolymer (a) include a slurry polymerization method using an inert solvent in the presence of the catalyst, a solution polymerization method, a gas phase polymerization method using substantially no solvent, and a bulk polymerization method using a polymerization monomer as a solvent.
For example, in the case of a slurry polymerization method, the polymerization can be carried out in an inert hydrocarbon or liquid monomer such as n-butane, isobutane, n-pentane, isopentane, hexane, heptane, octane, cyclohexane, benzene, toluene, or xylene. The polymerization temperature is usually −80 to 150°C, preferably 40 to 120°C. The polymerization pressure is preferably 1 to 60 atmospheres (0.10 to 6.08 MPa), and the molecular weight of the resulting propylene-based copolymer (a) can be adjusted with hydrogen or other known molecular weight modifiers. The polymerization can be carried out by a continuous or batch reaction, and the conditions may be those typically used. Furthermore, the polymerization reaction may be carried out in one stage or multiple stages.
When a metallocene catalyst is used, it is desirable to carry out a prepolymerization treatment before carrying out the main polymerization. As the monomer to be subjected to the prepolymerization, an α-olefin such as ethylene, propylene, 1-butene, 1-hexene, etc., a diene compound such as 1,3-butadiene, etc., or a vinyl compound such as styrene, divinylbenzene, etc. can be used.
This prepolymerization is preferably carried out in an inert solvent under mild conditions, and is desirably carried out so as to produce 0.01 to 1,000 g, preferably 0.1 to 100 g, of polymer per 1 g of solid catalyst (total of component [A] and component [B]).

The polymerization reaction is carried out in the presence or absence of a solvent, such as an inert hydrocarbon such as butane, pentane, hexane, heptane, toluene, or cyclohexane, or a liquefied α-olefin. In the present invention, it is desirable to maximize the amount of polymer produced per solid catalyst (if the solid catalyst has been prepolymerized, this does not include the polymer produced in the prepolymerization). To maximize the amount of polymer produced, it is desirable to set both the polymerization temperature and pressure relatively high.

Typically, the polymerization temperature is selected from 60 to 90°C, and the polymerization pressure is selected from about 1.5 to 4 MPa. In particular, in the case of bulk polymerization, it is preferable that the polymerization temperature is selected from 60 to 80°C, and the polymerization pressure is selected from about 2.5 to 4 MPa in correlation with the temperature. On the other hand, in the case of gas-phase polymerization, it is preferable that the polymerization temperature is selected from 70 to 90°C, and the polymerization pressure is selected from about 1.5 to 4 MPa.
Furthermore, the polymer production amount per solid catalyst can be increased by extending the residence time of the solid catalyst, but an excessively long residence time affects productivity. A preferred residence time is 1 to 8 hours, more preferably 1 to 6 hours. It is desirable to set the polymerization conditions so that the polymer production amount per gram of solid catalyst including the carrier is 20 kg or more, preferably 25 kg or more, more preferably 30 kg or more.
Hydrogen may be present in the polymerization system as a molecular weight modifier. Furthermore, the polymerization may be carried out in multiple stages by changing the polymerization temperature, the concentration of the molecular weight modifier, etc.

In the present invention, after the completion of the polymerization, the resulting propylene-based copolymer (a) is preferably washed with an inert saturated hydrocarbon solvent such as propane, butane, pentane, hexane, or heptane, or a liquid α-olefin, more preferably with an inert hydrocarbon solvent having 3 or 4 carbon atoms or a liquid α-olefin.
The washing method is not particularly limited, and known methods such as decantation of the supernatant after contact treatment in a stirring tank, countercurrent washing, and separation from the washing liquid using a cyclone can be used.
A deactivator may be added before or at the same time as washing. The deactivator is not particularly limited, and examples thereof include water, alcohols such as methanol, ethanol, and isopropanol, ketones such as acetone and methyl ethyl ketone, and mixtures thereof.
As such a propylene copolymer (a), commercially available products can be used, such as those available from Japan Polypropylene Corporation under the trade names WINTEC and NOVATEC PP.

(v) Molecular weight distribution (Mw/Mn) and weight average molecular weight (Mw) of the propylene copolymer (a)
The molecular weight distribution [weight average molecular weight (Mw)/number average molecular weight (Mn)] of the propylene copolymer (a) used in the present invention, as determined by gel permeation chromatography (GPC), is preferably 1.5 to 7.0.
The lower limit of the molecular weight distribution is more preferably 2.0 or more, and even more preferably 3.0 or more, and the upper limit is more preferably 6.0 or less, and even more preferably 5.0 or less.
When the lower limit of the molecular weight distribution is not less than a certain level, the range of conditions for producing and purifying the propylene copolymer (a) is widened, which is preferable, and thus the production efficiency is improved. On the other hand, when the upper limit is not more than a certain level, it indicates that the length of the molecular chain is very uniform, which is preferable, because the content of relatively low molecular weight components such as unreacted monomers, dimers, low molecular weight compounds, amorphous components, and oligomers, which are thought to cause the generation of volatile components, is reduced.

The weight-average molecular weight (Mw) of the propylene-based copolymer (a) used in the present invention is preferably in the range of 100,000 to 600,000. A weight-average molecular weight Mw of 600,000 or less facilitates molding. On the other hand, a weight-average molecular weight Mw of 100,000 or more is practical because it reduces low-crystalline components, suppresses mold contamination, bleed-out, solvent elution, etc., and improves the impact resistance of molded products.

(vi) Average elution temperature (T ₅₀ ) and elution dispersity (σ) of the propylene copolymer (a)
When a metallocene catalyst is used, the propylene copolymer (a) used in the present invention preferably has an average elution temperature (T ₅₀ ) of 90 to 105°C and an elution dispersity (σ) of 9°C or less.
Here, the average elution temperature is a value based on the elution curve of the polymer obtained by temperature rising elution fractionation using o-dichlorobenzene as a solvent, and represents the temperature at which the cumulative mass of the eluted polymer reaches 50% by mass. The elution dispersity is the value of σ when the cumulative mass elution amount I(t) is defined as being expressed by the following mathematical formula (1), assuming that the elution amount obtained by temperature rising elution fractionation follows a normal probability distribution with respect to the elution temperature.

...Equation (1)
Specifically, the dissolution dispersity is σ=T ₅₀ −T _15.9 , where T _15.9 indicates the temperature at which the cumulative mass becomes 15.9 mass %.
By setting the average elution temperature to 90 to 105° C., the molecular weight and melting point of the propylene-based copolymer (a) can be made appropriate for molding, thereby improving dimensional accuracy. When the average elution temperature is 90° C. or higher, the molecular weight and melting point of the propylene-based copolymer (a) do not become too low, and the dimensional accuracy of the molded product becomes good. When the average elution temperature is 105° C. or lower, the molecular weight and melting point of the propylene-based resin do not become too high, which is preferable.
Furthermore, by having an elution dispersity (σ) of 9° C. or less, it is possible to suppress elution of components due to an increase in temperature and to improve dimensional accuracy. The elution dispersity (σ) is more preferably 7° C. or less, and even more preferably 6° C. or less.
As such a propylene-based copolymer (a) using a metallocene catalyst, a commercially available product can be used, for example, a product under the trade name WINTEC manufactured by Japan Polypropylene Corporation.

(vii) Melting peak temperature (Tm) of the propylene copolymer (a)
The melting peak temperature (Tm) of the propylene copolymer (a) used in the present invention is in the range of 126°C to 152°C, preferably 126 to 148°C. When the melting peak temperature (Tm) is 126°C or higher, the rigidity and moldability are good, and when it is 152°C or lower, the impact strength is good.
The specific method for measuring the melting peak temperature (Tm) is to use a differential scanning calorimeter (DSC) to take a 5.0 mg sample, hold it at 200°C for 5 minutes, crystallize it to 40°C at a temperature decrease rate of 10°C/min, and then melt it at a temperature increase rate of 10°C/min. The peak position of the curve drawn when this is done is taken as the melting peak temperature Tm (°C).

(2) Biomass polyethylene (b)
Plant-derived ethylene, which is a raw material monomer for the biomass polyethylene (b) used in the present invention, can be obtained by fermenting plant materials such as sugarcane with microorganisms to produce ethanol, which is then heated in the presence of a catalyst to cause an intramolecular dehydration reaction.
Biomass polyethylene (b) is a polymer obtained by polymerizing a monomer containing plant-derived ethylene as a main component. The raw material monomer for biomass polyethylene (b) does not have to contain 100% plant-derived ethylene. This is because environmental impact can be reduced by using plant-derived ethylene as part of the monomer.
The biomass polyethylene (b) may be a homopolymer obtained by homopolymerizing plant-derived ethylene or a copolymer obtained by copolymerizing plant-derived ethylene with an α-olefin. The number of carbon atoms in the α-olefin is not particularly limited, but 1-butene, 1-hexene, or 1-octene is preferred. Furthermore, petroleum-derived ethylene may also be included.

Examples of polyethylenes that can be used as the biomass polyethylene (b) include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE). These polyethylenes can be used alone or in combination of two or more.
The density of high-density polyethylene is preferably 0.940 to 0.965 g/ ^cm3 , and within this range, rigidity is improved, which is preferable. The density of medium-density polyethylene is preferably 0.925 to 0.940 g/ ^cm3 , and within this range, rigidity is improved, which is preferable.
Among the above polyethylenes, it is preferable to use at least one of low-density polyethylene and linear low-density polyethylene, as this will provide a sufficient transparency-improving effect.
The density of the low-density polyethylene is preferably 0.910 to 0.920 g/cm ³ , and more preferably 0.913 to 0.917 g/cm ^3. A density of 0.910 g/cm ³ or more is preferred because rigidity is improved, and a density of 0.920 g/cm ³ or less is preferred because transparency improvement effect is sufficient.
The density of the linear low-density polyethylene is preferably 0.895 to 0.925 g/cm ³ , and more preferably 0.900 to 0.917 g/cm ^3. A density of 0.895 g/cm ³ or more is preferred because rigidity is improved, and a density of 0.925 g/cm ³ or less is preferred because transparency improvement effect is sufficient.

The proportion of plant-derived carbon to the total carbon in biomass polyethylene (b) is called the biomass percentage, and can be determined by measuring the concentration of ^14C contained in biomass polyethylene (b). That is, while a certain percentage of ^14C is contained in the atmosphere, the carbon in petroleum-derived resins does not contain ^14C . Therefore, the biomass percentage can be determined by measuring the concentration of ^14C contained in biomass polyethylene (b). Specifically, if all the carbon in biomass polyethylene (b) is petroleum-derived, the biomass percentage is 0%, and if all the carbon in biomass polyethylene (b) is plant-derived, the biomass percentage is 100%. ASTM D6866 is an example of a test method for measuring the ^14C concentration.
The biomass polyethylene (b) preferably has a melt flow rate in the range of 0.21 to 72 g/10 min according to ASTM D1238 (190° C., 2.16 kg load).

The weight proportion of the biomass polyethylene (b) used in the propylene-based copolymer is 10 to 49 parts by weight, preferably 15 to 40 parts by weight. When the amount is 10 parts by weight or more, an environmental load reduction effect can be expected, and when the amount is 49 parts by weight or less, sufficient rigidity of the product can be obtained. (Here, a propylene-based polymer composition containing 51 to 90 parts by weight of the propylene-based polymer (a) and 10 to 49 parts by weight of the biomass polyethylene (b) is 100 parts by weight.)
An example of such biomass polyethylene (b) is "Green PE" (trade name manufactured by Braskem).

(3) Biomass Degree The biomass degree (%) in the present invention is a numerical value calculated by the following formula.
Biomass ratio (%) = [{A × (B ÷ 100)} / C] × 100 ... Formula (2)
A: Weight of biomass polyethylene (b) B: Bio content (%) of biopolyethylene used
C: Weight of propylene-based polymer composition The bio content (%) of the biomass polyethylene (b) can be measured and calculated according to ASTM D6866.

(4) Nucleating Agent The propylene polymer composition of the present invention may contain a nucleating agent in an amount of preferably 0.01 to 0.6 parts by weight per 100 parts by weight of the propylene polymer composition.
Various common known nucleating agents can be used, such as sterically hindered amide compounds, metal salts of organic dicarboxylic acids, metal salts of organic monocarboxylic acids, sorbitol or its derivatives, nonitol or its derivatives, metal salts of diterpenic acids, or polymer nucleating agents.
Among these, it is particularly preferable to contain a nucleating agent represented by the following formula (1) in order to achieve transparency.

...(1)
(In the formula, n is an integer of 0 to 2; R ¹ to R ⁵ are each independently the same or different and represent hydrogen, halogen, alkyl having 1 to 20 carbon atoms, alkenyl having 2 to 20 carbon atoms, alkoxy having 1 to 20 carbon atoms, alkoxycarbonyl having 1 to 20 carbon atoms, or phenyl; and R ⁶ is alkyl having 1 to 20 carbon atoms.)
Among the nucleating agents represented by formula (1), a representative commercially available product is Milad NX8000J (manufactured by Milliken & Company). Its chemical structural formula is as shown in formula (1-1) below. The molecular weight of this nucleating agent is 484. This substance has the excellent characteristic of being extremely stable thermally and chemically, and therefore hardly undergoing thermal decomposition even at molding temperatures. This is highly preferable because it does not cause the problem of decomposition products bleeding out onto the surface of molded articles and deteriorating their appearance.

... (1-1)

The content of the nucleating agent represented by formula (1) contained in the propylene-based polymer composition of the present invention is preferably in the range of 0.1 to 0.6 parts by weight, more preferably 0.2 to 0.4 parts by weight, and even more preferably 0.3 to 0.4 parts by weight, per 100 parts by weight of the propylene-based polymer composition. When the content of the nucleating agent represented by formula (1) is 0.1 parts by weight or more, rigidity and transparency can be expected to be exhibited, while when it is 0.6 parts by weight or less, there is less concern about bleeding onto the surface of the molded article, which is advantageous in terms of cost-effectiveness (cost performance) in terms of rigidity and transparency, and elution.

(5) Other Additives In addition to the above-mentioned components, the propylene polymer composition of the present invention may contain additives such as various antioxidants used as stabilizers for propylene polymers, ultraviolet absorbers, light stabilizers, and neutralizers.
Specifically, examples of the antioxidant include phosphorus-based antioxidants such as bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, di-stearyl-pentaerythritol diphosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, tris(2,4-di-t-butylphenyl)phosphite, tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite, and tetrakis(2,4-di-t-butyl-5-methylphenyl)-4,4'-biphenylene diphosphonite. antioxidants, phenolic antioxidants such as 2,6-di-t-butyl-p-cresol, tetrakis[methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)]methane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene and tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, and thio antioxidants such as di-stearyl-β,β'-thio-di-propionate, di-myristyl-β,β'-thio-di-propionate and di-lauryl-β,β'-thio-di-propionate.

Examples of ultraviolet absorbers include 2-hydroxy-4-n-octoxybenzophenone, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole, and 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole.

Light stabilizers include n-hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate, 2,4-di-t-butylphenyl-3',5'-di-t-butyl-4'-hydroxybenzoate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, dimethyl succinate-2-(4-hydroxy-2,2,6,6-tetramethyl-1-piperidyl)ethanol condensate, poly{[6-[(1,1,3,3-tetramethylbutyl)acetate] Examples of light stabilizers include N,N'-bis(3-aminopropyl)ethylenediamine-2,4-bis[N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino]-6-chloro-1,3,5-triazine condensate.

Further examples include amine-based antioxidants represented by the following formula (2) and formula (3), which have good resistance to NOx gas discoloration, lactone-based antioxidants such as 5,7-di-t-butyl-3-(3,4-di-methyl-phenyl)-3H-benzofuran-2-one, and vitamin E-based antioxidants such as those represented by the following formula (4).

... (2)

...(3)

...(4)

Examples of the neutralizing agent include metal fatty acid salts such as calcium stearate, zinc stearate, and magnesium stearate, hydrotalcite (trade name: DHT-4A, manufactured by Kyowa Chemical Industry Co., Ltd., a magnesium aluminum composite hydroxide salt represented by the following formula (5)), and Mizuka Lack (trade name, manufactured by Mizusawa Industrial Chemicals Co., Ltd., a lithium aluminum composite hydroxide salt represented by the following formula (6)).
Mg _1-x Al _x (OH) ₂ (CO ₃ ) _x/2・mH ₂ O…(5)
[In the formula, x is 0<x≦0.5, and m is a number of 3 or less.]
[ _Al2Li (OH) ₆ ] _nX・_mH2O ...(6)
[In the formula, X is an inorganic or organic anion, n is the valence of the anion (X), and m is 3 or less.]

In addition, various known additives, such as antistatic agents, lubricants, dispersants such as fatty acid metal salts, dyes, pigments, etc., can be added as long as they do not impair the objectives of the present invention.

As long as the properties, functions, and other characteristics of the propylene-based polymer composition of the present invention are not impaired, 1 to 30 parts by weight of other polymers besides the propylene-based copolymer (a) and biopolyethylene (b), such as mono-, bi-, or terpolymers such as polyethylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-1-butene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, and acrylate polymer, can be added per 100 parts by weight of the propylene-based polymer composition. Similarly, it is also possible to blend elastomers such as natural rubber, butyl rubber, diene rubber, EPR, and EPDM. Furthermore, it is also possible to use general-purpose inorganic fillers such as talc, calcium carbonate, silica, alumina, gypsum, and mica in combination.

(6) Flexural Modulus of Propylene-Based Polymer Composition The flexural modulus of the propylene-based polymer composition of the present invention is preferably 500 MPa or more, and when the flexural modulus is 500 MPa or more, the strength of a molded article is sufficient, more preferably 800 MPa or more, and even more preferably 1000 MPa or more.

(7) Charpy Impact Strength of Propylene-Based Polymer Composition The Charpy impact strength of the propylene-based polymer composition of the present invention is preferably 3.0 kJ/ ^m2 or more. When the Charpy impact strength is 3.0 kJ/ ^m2 or more, breakage of a molded article during transportation is suppressed. The Charpy impact strength is more preferably 3.5 kJ/m2 or ^more , and even more preferably 4.8 kJ/m2 or ^more .

(8) Haze of Propylene-Based Polymer Composition The haze of the propylene-based polymer composition of the present invention at a product thickness of 2 mm is preferably 50% or less. When the haze is 50% or less, the visibility of the contents improves and the design becomes better. The haze is more preferably 45% or less, and even more preferably 35% or less.

[2] Method for producing propylene-based polymer composition The propylene-based polymer composition of the present invention can be obtained by mixing predetermined amounts of the propylene-based copolymer (a), the biomass polyethylene (b), and, if necessary, other additives in a Henschel mixer (trade name), a super mixer, a ribbon blender, or the like, and then melt-kneading the mixture in a temperature range of 190 to 260°C using a conventional single-screw extruder, a twin-screw extruder, a Banbury mixer, a plavender, a roll, or the like.

[3] Molded Article Obtained Using Propylene-Based Polymer Composition To produce a molded article using the propylene-based polymer composition of the present invention, the propylene-based polymer composition is molded into a molded article having a desired shape by injection molding or the like.
The uses of the molded articles are not particularly limited, but they can be used in a wide variety of applications, such as various industrial materials, automobile-related parts, various containers for medical and cosmetic use, daily necessities, films, and fibers.

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.
In the following examples and comparative examples, the physical properties of the propylene copolymer (a) and the propylene polymer composition were measured according to the following methods.
<1. Measurement method>

(1) Melt flow rate (MFR):
Measurement was carried out in accordance with JIS K7210 (230°C, 2.16 kg load).

(2) Calculation of the ethylene content of the propylene copolymer (a)
The ethylene content in the random copolymer was measured by infrared spectroscopy using a characteristic absorption band at 733 cm ^-1 , using an ethylene-propylene random copolymer whose composition had been verified by ^C -NMR as a standard material. The pellets were press-molded into a film with a thickness of approximately 500 μm.

(3) Measurement of molecular weight and molecular weight distribution:
The molecular weight distribution Mw/Mn of the propylene copolymer (a) was calculated by measuring the weight average molecular weight Mw and the number average molecular weight Mn by gel permeation chromatography (GPC) under the following conditions:
Apparatus: GPC (ALC/GPC 150C) manufactured by WATERS
Detector: FOXBORO MIRAN 1A IR detector (measurement wavelength: 3.42 μm)
Column: Showa Denko AD806M/S (3 columns in series)
Mobile phase solvent: o-dichlorobenzene
Measurement temperature: 140℃
Flow rate: 1.0ml/min
Injection volume: 0.2ml

(4) Melting peak temperature (melting point) (Tm, unit: ° C.):
Using a differential scanning calorimeter (DSC), a 5.0 mg sample was taken, the temperature was raised to 200°C once to erase the thermal history, and then the sample was held at 200°C for 5 minutes. The temperature was then lowered to 40°C at a rate of 10°C/min to crystallize the sample, and the temperature was then raised again at a rate of 10°C/min to melt the sample. The temperature at the top of the endothermic peak was taken as the melting peak temperature (melting point) (Tm).

(5) Flexural modulus (rigidity)
Measurement was carried out in accordance with JIS K7171.

(6) Charpy impact strength (impact resistance)
The Charpy impact strength at 23°C was measured in accordance with JIS K7111.
(7) Haze Value: Measured in accordance with JIS K7136 using a sheet piece having a thickness of 2 mm.

(9) Crack test in MD and TD directions Test pieces of 120 mm x 120 mm x 2 mm were injection molded (molding temperature: 200°C, mold temperature: 40°C), and as shown in Figure 1, a cut of about 3 cm in length was made in each piece with pruning shears so that the cut was 1.5 cm wide. The cut part was then bent by hand, and the cracking was evaluated according to the following criteria.
◎: No splits (fissures, cracks) or separation into several pieces even when bent more than 90 degrees (no splits)
○: Even when bent more than 90 degrees, a split (crack) occurs, but the film does not separate into several parts (does not split).
×: When bent more than 90 degrees, it separates into several parts (cracks).

<2. Resins and Additives>
2-1. Production of Propylene-Based Copolymer (a) (1) Production Example 1
<Preparation of solid titanium catalyst component>
A 10 L autoclave equipped with a stirrer was thoroughly purged with nitrogen, and 2 L of purified toluene was introduced. To this, 200 g of Mg(OEt) ₂ and 1 L of _TiCl4 were added at room temperature. The temperature was raised to 90°C, and 50 ml of di-n-butyl phthalate was introduced. The temperature was then 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, and the total liquid volume was adjusted to 2 L. 1 _L of TiCl4 was added at room temperature, and 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, and the total liquid volume was adjusted to 2 L. 1 _L of TiCl4 was added at room temperature, and 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. Furthermore, toluene was replaced with n-heptane using purified n-heptane, and a slurry of solid components was obtained. A portion of this slurry was sampled and analyzed, and the Ti content of the solid component was found to be 2.7% by weight.
Next, a 20 L autoclave equipped with a stirrer was thoroughly purged with nitrogen, and 100 g of the above solid component slurry was introduced as a solid component. Purified n-heptane was introduced to adjust the solid component concentration to 25 g/L. 50 ml of _SiCl4 was added, and the reaction was carried out at 90°C for 1 hour. The reaction product was thoroughly washed with purified n-heptane.
Thereafter, purified n-heptane was introduced to adjust the liquid level to 4 L. To this was added 30 ml of dimethyldivinylsilane, 30 ml of (i-Pr) ₂ Si(OMe) ₂ , and 80 g of a solution of Et ₃ Al diluted in n-heptane (as Et ₃ Al), and the reaction was carried out at 40°C for 2 hours. The reaction product was thoroughly washed with purified n-heptane, and a portion of the resulting slurry was sampled, dried, and analyzed. The solid components contained 1.2 wt% Ti and 8.8 wt% (i-Pr) ₂ Si(OMe) ₂ .
Further, using 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. Next, the slurry was cooled to 10°C, and 10 g of a diluted n-heptane solution of Et ₃ Al was added as Et ₃ Al, and 280 g of propylene was fed over 4 hours. After the propylene feed was completed, the reaction was continued for another 30 minutes. Next, the gas phase was thoroughly purged with nitrogen, and the reaction product was thoroughly washed with purified n-heptane. The obtained slurry was extracted from the autoclave and vacuum dried to obtain solid catalyst component (c). This solid catalyst component contained 2.5 g of polypropylene per 1 g of the solid component. Furthermore, analysis revealed that the portion of this solid catalyst component (c) excluding polypropylene contained 1.0 wt% Ti and 8.2 wt% (i-Pr) ₂ Si(OMe) ₂ .

<Production of Propylene-Ethylene Random Copolymer>
The production of a propylene-ethylene random copolymer will be described using the flow sheet shown in Figure 2. Two gas-phase polymerization reactors were used. The two polymerization reactors 1 and 10 were continuous horizontal gas-phase polymerization reactors (length/diameter = 5.2) equipped with an agitator, with an inner diameter D of 2100 mm, a length L of 11000 mm, and an internal volume of 40 ^m3 .
After thoroughly purging the interior of the polymerization vessel 1 with nitrogen, polypropylene powder from which polymer particles having a particle size of 500 μm or less had been removed was charged, and 120 g/hour of the solid catalyst component (c) and a 15 wt % hexane solution of triethylaluminum were continuously fed so that the molar ratio per mole of Ti atoms in the catalyst component (c) was 350. Furthermore, hydrogen was fed into the polymerization vessel 1 so that the ratio of the hydrogen concentration to the propylene concentration in the polymerization vessel 1 became 0.095, ethylene was fed so that the ratio of the ethylene concentration to the propylene concentration became 0.020, and propylene monomer was fed into the polymerization vessel 1 so that the pressure and temperature in the polymerization vessel 1 were maintained at 2.10 MPa and 61° C., respectively. The reaction heat was removed by the heat of vaporization of the raw material liquefied propylene fed through the raw material mixed gas feed pipe 3. The unreacted gas discharged from the polymerization vessel 1 was withdrawn to the outside of the reactor system through the unreacted gas withdrawal pipe 4, cooled and condensed, and refluxed to the polymerization vessel 1 through the recycle gas pipe 2.
The propylene-ethylene random copolymer (first stage) produced in the polymerization reactor 1 was continuously withdrawn from the polymerization reactor 1 through a polymer withdrawal pipe 5 so that the polymer retention level became 45% by volume of the reaction volume, and was supplied to a polymerization reactor 10 for the second polymerization step.
The polymer from the first polymerization step, hydrogen so that the ratio of the hydrogen concentration to the propylene concentration in the polymerizer 10 was 0.021, ethylene so that the ratio of the ethylene concentration to the propylene concentration in the polymerizer 10 was 0.068, and propylene monomer so that the pressure and temperature in the polymerizer 10 were maintained at 2.05 MPa and 70°C, respectively. A polymerization activity inhibitor for adjusting the polymerization amount of the propylene-ethylene random copolymer (second stage) was supplied through a polymerization activity inhibitor addition pipe 11. Reaction heat was removed by the heat of vaporization of the liquefied propylene feedstock supplied through a raw material gas mixture supply pipe 6. The unreacted gas discharged from the polymerizer 10 was withdrawn to the outside of the reactor system through an unreacted gas withdrawal pipe 8, cooled and condensed, and refluxed to the polymerizer 10 through a recycle gas pipe 7. The propylene copolymer produced in the second polymerization step was continuously withdrawn from the polymerization vessel 10 through a polymer withdrawal pipe 9 so that the polymer retention level was 50% by volume of the reaction volume. The withdrawn powder was separated into gases in a gas recovery machine 12, and the powder portion was withdrawn to a recovery system and granulated in a granulation system.
The production rate of the propylene copolymer was 9.6 T/hour, the average residence time in the polymerizer 1 was 1.9 hours, and the average residence time in the polymerizer 10 was 1.3 hours. The catalyst efficiency was calculated by dividing the production rate by the feed rate of the solid catalyst component (c), and was found to be 88,900 g-PP/g-catalyst.
Furthermore, analysis of the resulting propylene copolymer, the second-stage polymer, revealed that it had an MFR of 38.9 g/10 min, an ethylene content of 5.0 wt%, and a Tm of 148° C. The PP component (first stage) had an MFR of 71.9 g/10 min and an ethylene content of 2.5 wt%. Calculation of the index for the PP component (second stage) revealed that it had an MFR of 8.0 g/10 min and an ethylene content of 11.3 wt%.
Here, the MFR of the PP component (second stage) was calculated from the MFR of the PP component (first stage), the MFR of the propylene-based copolymer, and the weight ratio of the PP component (first stage) to the PP component (second stage) according to an empirical formula known as the logarithmic additivity rule of viscosity. The ethylene content was calculated from the ethylene content of the PP component (first stage), the ethylene content of the propylene-based copolymer, and the weight ratio of the PP component (first stage) to the PP component (second stage). The weight ratio of the PP component (first stage) to the PP component (second stage) was calculated from the amount of liquefied propylene supplied to the polymerization reactor, and the amount of the PP component (second stage) produced was 28 wt% of the total weight.

2-2. Production of Propylene-Based Copolymers Other than Propylene-Based Copolymer (a) (1) Production Example 2
(i) Preparation of solid catalyst A 100-liter reactor equipped with a stirring blade, thermometer, jacket, and cooling coil was charged with 30 mol of Mg(OEt) ₂ , and then Ti(OBu) ₄ was charged so that the ratio of Ti(OBu) ₄ /Mg was 0.60 (m.r. (molar ratio)) relative to the magnesium in the charged Mg(OEt) _2. Furthermore, 19.2 kg of toluene (TOL) was charged, and the temperature was raised while stirring. After reacting at 139°C for 3 hours, the temperature was lowered to 130°C, and a toluene solution of MeSi(OPh) ₃ was added so that the ratio of MeSi(OPh) ₃ /Mg was 0.67 (m.r.) relative to the magnesium in the charged Mg(OEt) _2. The amount of toluene used here was 7.8 kg. After the addition was completed, the mixture was reacted at 130°C for 2 hours, then cooled to room temperature, and Si(OEt) ₄ was added. The amount of Si(OEt) ₄ added was adjusted so that the ratio of Si(OEt) ₄ /Mg was 0.056 (m.r.) relative to the magnesium in the Mg(OEt) ₂ previously charged.

Next, toluene was added to the resulting reaction mixture so that the magnesium concentration became 0.58 (mol/L-TOL). Furthermore, diethyl phthalate (DEP) was added so that the DEP/Mg ratio was 0.10 (m.r.) relative to the magnesium in the Mg(OEt) ₂ previously charged. The resulting reaction mixture was cooled to 10°C while continuing to stir, and TiCl ₄ was added dropwise over 2 hours to obtain a homogeneous solution. Note that TiCl ₄ was added so that the TiCl 4 /Mg ratio was 4.0 (m.r.) relative to the magnesium in the Mg(OEt) ₂ previously charged. After _{the TiCl 4 addition} was completed, the mixture was heated to 15°C at 0.5°C/min while stirring and maintained at the same temperature for 1 hour. Next, the mixture was again heated to 50°C at 0.5°C/min and maintained at the same temperature for 1 hour. The mixture was then heated to 118°C at 1°C/min and treated at the same temperature for 1 hour. After the treatment was completed, stirring was stopped, the supernatant liquid was removed, and the residue was washed by decantation with toluene to a residual liquid ratio of 1/73 (volume ratio of toluene/solid component) to obtain a slurry of solid component.

Next, toluene and _TiCl4 were added to the slurry obtained here at room temperature. The _TiCl4 was adjusted so that _TiCl4 /Mg(OEt) ₂ = 5.0 (m.r.) relative to the magnesium in the Mg(OEt) ₂ that had been charged earlier. The toluene was also adjusted so that the _TiCl4 concentration was 2.0 (mol/L-TOL). The slurry was heated with stirring, and the reaction was carried out at 118°C for 1 hour. After the reaction was completed, the stirring was stopped, the supernatant liquid was removed, and the mixture was washed by decantation with toluene so that the residual liquid ratio = 1/150 (volume ratio of toluene/solid component), and a slurry of solid components was obtained.

(ii) Preparation of Solid Catalyst Component (A) 400 g of the solid component obtained in (i) was transferred to another reactor equipped with a stirring blade, a thermometer, and a cooling jacket, and normal hexane was added to dilute the solid component to a concentration of 5.0 (g/L). While stirring the resulting slurry, trimethylvinylsilane, TEA, and TBMDES were added at 15°C. TEA represents triethylaluminum, TBMDES represents t-butylmethyldiethoxysilane, and t-butyl represents a tertiary butyl group. The amounts of TEA, trimethylvinylsilane, and TBMDES added were 0.475 g, 0.137 g, and 0.167 g, respectively, per gram of the solid component in the solid catalyst component (A). After the addition was completed, the mixture was maintained at 15°C for 1 hour while continuing to stir, and then the temperature was raised to 30°C and stirred at the same temperature for 2 hours. Next, the temperature was lowered again to 15°C, and while maintaining the same temperature, 4.8 kg of propylene gas was fed at a constant rate into the gas phase of the reactor over 8 hours to carry out prepolymerization. After completion of the feed, stirring was stopped, the supernatant liquid was removed, and then washing was carried out by decantation using normal hexane to obtain a slurry of solid catalyst component (A). The residual liquid rate was 1/12 (volume ratio of normal hexane/solid catalyst component (A)). The obtained solid catalyst component (A) had 12.0 g of propylene polymer per 1 g of solid catalyst component (A).

(iii) Production of Propylene-Ethylene Copolymer Continuous production of propylene-ethylene copolymer was carried out using a process incorporating a degassing system consisting of a double-pipe heat exchanger and a fluidized flash tank downstream of a 0.4 ^m3 liquid-phase polymerization vessel equipped with an agitator. Liquefied propylene, ethylene, hydrogen, TEA, and TBEDMS were continuously fed into the liquid-phase polymerization vessel. TBEDMS represents t-butylethyldimethoxysilane, and t-butyl represents a tertiary butyl group. The feed rates of liquefied propylene, TEA, and TBEDMS were 163 kg/hr, 8.86 g/hr, and 1.37 g/hr, respectively. Hydrogen and ethylene were fed to a gas-phase concentration of 6.15 mol% and 0.74 mol%, respectively. Furthermore, the solid catalyst component (A) obtained in (ii) above was fed at a rate of 0.13 g/hr as the solid component contained in (A). The liquid-phase polymerization vessel was cooled so that the polymerization temperature became 70°C. The slurry polymerized in the liquid-phase polymerization vessel was heated by a double-pipe heat exchanger and discharged into a fluidized flash vessel. The discharge rate of the slurry was adjusted so that the polypropylene particles contained in the slurry were approximately 24 kg/hr. The average residence time of the polypropylene particles in the liquid-phase polymerization vessel was 1.4 hours. Analysis of the discharged polypropylene revealed that it had an MFR of 25.0 g/10 min, an ethylene content of 0.7 wt%, a molecular weight distribution (Mw/Mn) of 5.6, and a Tm of 156°C.

(2) Production Example 3
A propylene-ethylene copolymer was produced in the same manner as in Production Example 2, except that the feed amount was changed so that the concentration of ethylene in the gas phase was 0.85 mol %. Analysis of the obtained polypropylene revealed that it had an MFR of 21.0 g/10 min, an ethylene content of 0.8 wt %, a molecular weight distribution (Mw/Mn) of 5.7, and a Tm of 159°C.

2-3. Propylene-based copolymer (a)
(PP-1) Japan Polypropylene Corporation, trade name "WINTEC WFW4M", MFR = 7.0 g/10 min, ethylene content = 1.9 wt%, Tm = 133°C
(PP-2) Japan Polypropylene Corporation, trade name "WINTEC WSX03", MFR = 25 g/10 min, ethylene content = 3.4 wt%, Tm = 126°C
(PP-3) Product name "NOVATEC-PP MG03BD" manufactured by Japan Polypropylene Corporation, MFR = 30 g/10 min, ethylene content = 2.2 wt%, Tm = 152°C
(PP-4) Propylene-based resin obtained by polymerization in Production Example 1 2-4. Propylene-based copolymer other than propylene-based copolymer (a) (PP-5) Propylene-based resin obtained by polymerization in Production Example 2 (PP-6) Propylene-based resin obtained by polymerization in Production Example 3

2-5. Biomass polyethylene (b)
Low-density polyethylene (LDPE)
(PE-1) Product name “Green PE SPB608” manufactured by Braskem
Density: 0.915 g/cm ³ , melt flow rate according to ASTM D1238 (190°C, 2.16 kg load) is 30 g/10 min, bio content: 95% (all properties are listed in the manufacturer's catalogue).
Linear low density polyethylene (LLDPE)
(PE-2) Product name “Green PE SLL118” manufactured by Braskem
Density: 0.916 g/cm ³ , melt flow rate according to ASTM D1238 (190°C, 2.16 kg load) is 1 g/10 min, bio content: 87% (all properties are listed in the manufacturer's catalogue).
High density polyethylene (HDPE)
(PE-3) Braskem product name “Green PE SGM9450F”
Density: 0.952 g/cm ³ , melt flow rate according to ASTM D1238 (190°C, 5 kg load) is 0.33 g/10 min, bio content: 96% (all properties are listed in the manufacturer's catalogue).

2-6. Other Additives (A-1) Hindered phenol-based antioxidant "IR1010"tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxylphenyl)propionate]methane, manufactured by BASF Japan Ltd., trade name "IRGANOX1010".
(A-2) Phosphorus-based antioxidant "IF168" tris(2,4-di-t-butylphenyl)phosphite, manufactured by BASF Japan Ltd., trade name "IRGAFOS168".
(B-1) Neutralizer "CAST" calcium stearate, manufactured by NOF Corporation.
(N-1) Nucleating agent "NX8000J" 1,2,3-trideoxy-4,6:5,7-bis-[(4-propylphenyl)methylene]-nonitol, manufactured by Milliken & Company, trade name "Milad NX8000J".

3. Examples 1 to 11 and Comparative Examples 1 to 4
Each polymer and additive were prepared in the blending ratio (parts by weight) shown in Table 1, dry-blended in a Super Mixer, and then melt-kneaded and pelletized in a nitrogen atmosphere at a die outlet temperature of 220°C using a TEM-35B twin-screw extruder manufactured by Toshiba Machine Co., Ltd. The resulting pellets were used to measure physical properties. The evaluation results are shown in Table 1.

As is clear from Table 1, Examples 1 to 11 contain the specified amounts of the propylene-based copolymer (a) and biomass polyethylene (b) according to the present invention, and are materials that can reduce environmental impact. They are excellent in rigidity and impact resistance and do not crack. Examples 1 to 4 contain the specified amounts of LDPE as the biomass polyethylene (b), and are also excellent in transparency. Example 5 has the same composition as Example 1, but with an increased content of LDPE as the biomass polyethylene (b). This increases the biomass content while improving impact resistance, demonstrating superiority in terms of environmental impact. Example 6 has the same composition as Example 1, but with a reduced content of LDPE as the biomass polyethylene (b). This shows that the rigidity and transparency are even superior to those of Example 1. Example 7 uses LLDPE as the biomass polyethylene (b). Although the content is the same as Example 1, the impact resistance is further improved compared to Example 1. In Example 8, HDPE was used as the biomass polyethylene (b), and although the content ratio was the same as in Example 1, the rigidity was further improved compared to Example 1. In Example 9, LLDPE was used as the biomass polyethylene (b), and the content ratio was the same as in Example 2, and both the rigidity and impact resistance were similar to those of Example 2. In Example 10, HDPE was used as the biomass polyethylene (b), and although the content ratio was the same as in Example 2, the rigidity was further improved compared to Example 2. In Example 11, the nucleating agent was not contained in the composition of Example 1, and it can be seen that the rigidity and impact resistance of Example 1 were further improved compared to Example 11 due to the nucleating action of the nucleating agent contained.
On the other hand, Comparative Example 1 is slightly superior to Example 1 in rigidity and transparency, but is found to crack in a TD cracking test. Comparative Examples 2 and 3 are excellent in both rigidity and impact resistance and have sufficient cracking resistance, but the content of biomass polyethylene (b) LDPE is low and they do not have a sufficient biomass content. Comparative Example 4 is excellent in both rigidity and impact resistance, being comparable to Example 1, but is found to crack in a TD cracking test.

The propylene-based polymer composition of the present invention produces molded articles that are superior in rigidity and impact resistance and do not crack, even when containing biomass polyethylene. With a biomass content of 8.4 to 49%, it is useful for reducing environmental impact.

Figure 2
1. Polymerization vessel (first polymerization step)
2. Recycle gas pipe 3. Raw material mixed gas supply pipe 4. Unreacted gas vent pipe 5. Polymer vent pipe 6. Raw material mixed gas supply pipe 7. Recycle gas pipe 8. Unreacted gas vent pipe 9. Polymer vent pipe 10. Polymerizer (second polymerization step)
11. Pipe for adding polymerization inhibitor 12. Gas recovery machine

Claims (3)

A propylene-based polymer composition for injection molding contains 51 to 90 parts by weight of a propylene-based copolymer (a) that satisfies the following conditions (A-i) to (A-iv) and 10 to 49 parts by weight of a biomass polyethylene (b), totaling 100 parts by weight, and having a biomass content of 8.4 to 49%.
(Ai) Propylene-α-olefin random copolymer.
(A-ii) The α-olefin content is in the range of 1 to 5% by weight.
(A-iii) The melt flow rate according to JIS K7210 (230°C, 2.16 kg load) is in the range of 0.5 to 100 g/10 min.
(A-iv) The melting peak temperature (Tm) is in the range of 126 to 152°C. 2. A propylene polymer composition for injection molding, comprising 0.01 to 0.6 parts by weight of a nucleating agent per 100 parts by weight of the propylene polymer composition for injection molding according to claim 1. A molded article obtained by using the propylene polymer composition for injection molding according to claim 1 or 2.