JP3177169B2 - Wheel cap made of polyolefin resin composition and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to crystalline propylene.
With regard to a wheel cap made of an ethylene block copolymer and a method of manufacturing the same, particularly having good mechanical properties such as strength, impact resistance, heat resistance, and rigidity, and having no molding defects such as warpage, sink mark, and flow mark, The present invention relates to a wheel cap having excellent paintability and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, wheel caps of automobiles have been formed by press-forming an iron plate. However, in recent years, plastic wheel caps have been used to reduce weight and improve design. It has become. As the material of the plastic wheel cap,
Nylon and polyphenylene oxide (PPO) having excellent heat resistance are used, but recently, from the viewpoint of cost reduction, reinforced resin compositions of polyolefin such as polypropylene have been used, and various proposals have been made. I have.

For example, Japanese Utility Model Publication No. 5-20561 discloses a wheel cap made of a polypropylene resin and glass fibers surface-treated with an organic silane compound. The polypropylene-based resin may contain an auxiliary component such as talc, or may contain maleic anhydride-modified polypropylene.

Japanese Patent Publication No. 6-45734 discloses a fiber containing polypropylene, polypropylene having a carboxyl group introduced, silane-treated glass fiber, a two-component pigment comprising zinc sulfide and carbon black, and polyethylene wax. A wheel cap formed by injection molding from a reinforced polypropylene resin composition is disclosed. Furthermore, Japanese Patent Publication No. 6-74365 contains 3 to 12% by weight of ethylene as a resin for wheel caps,
45 to 83% by weight of a crystalline ethylene-propylene block copolymer having a melt flow rate of 20 to 100 g / 10 minutes (the low molecular weight component having a weight average molecular weight of 1,000 to 50,000 is 0.3 to 3.5% by weight). A glass fiber reinforced resin composition comprising 2 to 20% by weight of a polypropylene resin modified with a saturated carboxylic acid or a derivative thereof and 15 to 35% by weight of a glass fiber is disclosed.

[0005] However, in the case of the above-mentioned polypropylene resin composition for a wheel cap, although the purpose of cost reduction has been achieved, the crystallinity of the polypropylene resin is not sufficient in any case, so that the obtained wheel cap molded product is not sufficient. There is a problem that it does not have strength, impact resistance, heat resistance and rigidity. Also, because it contains glass fiber,
There is also a problem that it has a remarkable flow mark on the surface and it is difficult to completely cover it with a coating. Furthermore, if the position and type of gates during wheel cap molding and the design of the wheel cap are not devised, improvement of the resin component alone will result in molding defects such as warpage, sink marks and flow marks. Proved impossible to completely overcome.

Accordingly, it is an object of the present invention to provide a crystalline propylene resin which has sufficient strength, impact resistance, heat resistance and rigidity, is free from molding defects such as warpage, sink marks and flow marks, and has excellent coatability. An object of the present invention is to provide a wheel cap made of an ethylene block copolymer and a method for producing the same.

[0007]

Means for Solving the Problems As a result of intensive studies in view of the above problems, the present inventors have found that a highly crystalline propylene-ethylene block copolymer is molded by a hot runner mold under special injection molding conditions. With excellent strength, impact resistance, heat resistance and stiffness, without forming defects such as warpage, sink marks, flow marks, etc., it was found that a wheel cap excellent in paintability could be obtained, and the present invention was conceived. .

That is, the wheel cap of the present invention comprises:
(a) A propylene homopolymer portion having an isotactic pentad fraction of 97% or more determined by ¹³ C-NMR
70-90% by weight and (b) propylene / ethylene weight ratio
Crystalline propylene-ethylene containing 30 to 10% by weight of a propylene-ethylene random copolymerized portion of 25/75 to 75/25 and having a melt flow rate (230 ° C., load 2.16 kg) of 20 g / 10 min or more It is characterized by being obtained by injection molding a block copolymer.

Further, the method of the present invention for manufacturing the wheel cap uses a hot runner mold so that the gate opening to the cavity of the mold is located within a radius of 70 mm from a center point on the back surface of the wheel cap. Set to
The molding is performed by injecting the crystalline propylene-ethylene block copolymer into the mold cavity. As the type of the gate divided by the opening / closing mechanism, a temperature-controlled gate or a spring-type or mechanical opening / closing type valve gate is preferable.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. [1] Crystalline propylene-ethylene block copolymer [A] Structure The crystalline propylene-ethylene block copolymer basically comprises (a) 70 to 90% by weight of a propylene homopolymer portion,
(b) 30 to 10% by weight of a propylene-ethylene random copolymer portion, and may further contain a small amount of an ethylene homopolymer portion. In addition, each part may exist as a single polymer, or may be in a state where each is bonded. Each of the above-mentioned parts is basically composed of propylene and / or ethylene, but may contain a small amount of another α-olefin, a diene monomer or the like.

(1) Propylene homopolymer part The propylene homopolymer part is characterized in that the isotactic pentad fraction determined by ¹³ C-NMR is 97% or more. Here, the isotactic pentad fraction is measured using the method described in Macromolecules, 6 , 925 (1973), that is, using a ¹³ C-NMR spectrum. As a result, the fraction of the meso bond is determined for the propylene monomer at the center of the five consecutive propylene monomer chains, and the isotactic pentad fraction (IP
F) is obtained. However, the attribution of the peak is Macromolec
ules, 8 , 687 (1975). Specifically, the isotactic pentad fraction is the intensity fraction of the mmmm peak in all the absorption peaks in the methyl carbon region of the ¹³ C-NMR spectrum.

The propylene homopolymer part has an IPF of 97
%, The mechanical properties such as the strength, impact resistance, heat resistance, and rigidity of the crystalline propylene-ethylene block copolymer decrease, and the heat resistance, rigidity, and the like of the obtained wheel cap molded product decrease.

The propylene homopolymer part is ASTM D-1
The melt flow rate (MFR) measured according to 238 (230 ° C., load 2.16 kg) is 10-100 g / 10 min, preferably 20
~ 60g / 10min. If the MFR is less than 10 g / 10 minutes, the moldability is low, while if it exceeds 100 g / 10 minutes, the impact resistance is reduced.

(2) Propylene-ethylene random copolymer portion The propylene-ethylene random copolymer portion is characterized in that the weight ratio of propylene / ethylene is 25/75 to 75/25. When the weight ratio of propylene / ethylene is less than 25/75, the ductility and impact resistance of the crystalline propylene-ethylene block copolymer are low, whereas when the weight ratio of propylene / ethylene exceeds 75/25, the crystalline propylene-ethylene block The elastic modulus of the copolymer decreases. The preferred propylene / ethylene weight ratio is between 35/65 and 65/35.

The intrinsic viscosity [η] of the propylene-ethylene random copolymer portion is 2 to 5 dl / g, preferably 3 to 5 dl / g.
dl / g. When the intrinsic viscosity [η] is less than 2 dl / g,
If the effect of improving the impact resistance is not sufficient, on the other hand, if it exceeds 5 dl / g, the moldability decreases due to an increase in the gel component, and the appearance of the molded product becomes poor.

(3) Ratio Regarding the ratio of each of the above parts, the propylene homopolymer part is 70 to 90% by weight, and the propylene-ethylene random copolymer part is 10 to 30% by weight. Even if it contains a crystalline homopolyethylene portion, its content is 3
% By weight or less. If the propylene homopolymer portion is less than 70% by weight (the propylene-ethylene random copolymer portion exceeds 30% by weight), the rigidity of the crystalline propylene-ethylene block copolymer is low. On the other hand, if the propylene homopolymer portion exceeds 90% by weight (the propylene-ethylene random copolymer portion is less than 10% by weight), the impact resistance is reduced.

[B] Physical properties The melt flow rate of the crystalline propylene-ethylene block copolymer used in the present invention (MFR, 230 ° C., load 2.
(Measured at 16 kg) is 20 g / 10 min or more, preferably 20 to 50 g / 10 min, from the viewpoints of moldability, impact resistance and heat resistance.

[C] Production Method The method for producing the propylene-ethylene block copolymer includes a mechanical blending method or a reactor blending method of a propylene homopolymer portion and a propylene-ethylene random copolymer portion. In the case of mechanical blending,
After separately preparing a propylene homopolymer portion and a propylene-ethylene random copolymer portion, they are uniformly blended by a super mixer or the like. In the case of the reactor blending method, a propylene homopolymer portion is prepared, and then a propylene-ethylene random copolymer portion is continuously prepared in the same reactor.
In the multistage polymerization method, the propylene homopolymer portion and the propylene-ethylene random copolymer portion are in a state of being substantially uniformly blended.

Therefore, the multi-stage polymerization method will be described in detail below. (1) Formation of propylene homopolymer part (a) Pre-polymerization (i) Pre-polymerization catalyst The pre-polymerization catalyst is a solid component whose olefin is (A) magnesium, titanium, halogen and the first electron-donating compound as essential components. , (B) an organoaluminum compound, (C) an organosilicon compound, and (D) an optional second electron-donating compound. As olefins, in addition to propylene, ethylene, 1-butene, 1-hexene, 4-methyl-1-
And the like. Details of each of the above components of the prepolymerization catalyst are as follows.

(A) Solid component The solid component (hereinafter referred to as component (A)) contains magnesium, titanium, halogen and a first electron-donating compound as essential components, and usually contains a magnesium compound, a titanium compound and a first compound. It can be prepared by bringing into contact with an electron donating compound (in the case where each of the compounds has no halogen, a halogen-containing compound).

Magnesium compound The magnesium compound is represented by the general formula MgR ¹ R ² .
Provided that R ¹ and R ² are the same or different hydrocarbon groups, OR
³ groups (R ³ is a hydrocarbon group) or a halogen atom. Specifically, as the hydrocarbon group for R ¹ and R ² , an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group, an aryl group,
An aralkyl group, and as the R ³ group, a C 1 -C 1
Examples include 12 alkyl groups, cycloalkyl groups, aryl groups, and aralkyl groups, and examples of the halogen atom include chlorine, bromine, iodine, and fluorine.

Specific examples of these compounds include MgMe ₂ , Mg
(I-Pr) ₂ , MgBu ₂ , MgOct ₂ , MgPh ₂ , MgcyHe ₂ , Mg
(OEt) ₂ , Mg (OHe) ₂ , Mg (OPh) ₂ , EtMgCl, He
MgCl, i-BuMgCl, PhMgCl, EtOMgCl, PhOMgCl, EtOMg
Br, EtOMgI, MgCl ₂ , MgBr ₂ , MgI ₂ (where Me:
Methyl, Et: ethyl, Pr: propyl, Bu: butyl, He:
Hexyl, Ph: phenyl, cyHe: cyclohexyl. ).

The above-mentioned magnesium compound can also be prepared from metallic magnesium or other magnesium compounds when preparing the component (A). As an example,
Magnesium metal, a halogenated hydrocarbon and the general _{^{formula: X 1 n M (OR 4}} ) mn ( provided that X ¹ is a hydrogen atom, 1 to halogen atoms or carbon atoms
20 hydrocarbon groups, M is a boron, carbon, aluminum, silicon or phosphorus atom, and R ⁴ has 1 to 20 carbon atoms
Hydrocarbon groups, m is the valence of M, m> n
≧ 0. A) contacting an alkoxy group-containing compound.

X ^{1 in} the general formula of the alkoxy group-containing compound
And hydrocarbon groups of R ⁴ include methyl (Me), ethyl (Et), propyl (Pr), i-propyl (i-Pr), butyl (Bu), i-butyl (i-Bu), hexyl ( He), an alkyl group such as octyl (Oct), a cycloalkyl group such as cyclohexyl (cyHe) and methylcyclohexyl, an alkenyl group such as allyl, propenyl and butenyl, and phenyl (P
h), aryl groups such as tolyl and xylyl, phenethyl, 3
-An aralkyl group such as phenylpropyl.
Among these, an alkyl group having 1 to 10 carbon atoms is particularly preferable.

As specific examples of the alkoxy group-containing compound, when M is carbon, C (OEt) ₄ , C (OP
r) ₄ , C (OBu) ₄ , HC (OMe) ₃ , HC (OEt)
₃ , HC (OBu) ₃ , HC (OPh) ₃ , MeC (OE
t) ₃ , PhC (OEt) ₃ , CH ₂ ClC (OEt) ₃ , Cl
C (OMe) ₃ , ClC (Oi-Bu) ₃ , BrC (OEt) _{3 and the} like. When M is silicon, Si (OEt) ₄ , Si
(OHe) ₄ , HSi (OEt) ₃ , HSi (OPh) ₃ , MeSi
(OBu) ₃ , PhSi (OEt) ₃ , CHCl ₂ Si (OEt) _{3 and the} like. When M is boron, B (OEt) ₃ , B
(OBu) _{3 and the} like. When M is aluminum, Al (OMe) ₃ and Al (OEt) _{3. When} M is phosphorus, P (OMe) ₃ and P (OEt). ₃ ) and the like.

As the magnesium compound, a metal (M ') of Group II or Group IIIa of the periodic table represented by the general formula: MgR ¹ R ² · p (M′R ⁵ _q )
Complexes with organic compounds of the formula (1) can also be used. The metal M ′ is aluminum, zinc, calcium or the like, and R ⁵ has 1 to 1 carbon atoms.
12 alkyl groups, cycloalkyl groups or aralkyl groups. Q represents the valence of the metal M ′, and p represents 0.1 to
Indicates the number 10. Specific examples of the compound represented by M′R ⁵ _q include AlMe ₃ , AlEt ₃ , Al (i-Bu) ₃ , AlPh ₃ , ZnMe
₂ , ZnEt ₂ , ZnBu ₂ , ZnPh ₂ , CaEt _{2 and the} like.

Titanium compound As the titanium compound, divalent, trivalent and tetravalent titanium compounds can be used. For example, titanium trichloride, titanium tetrachloride, titanium tetrabromide, trichloroethoxy titanium, trichlorobutoxy titanium, dichlorodiethoxy titanium, dichlorodibutoxy titanium, dichlorodiphenoxy titanium and the like can be mentioned. Of these, titanium tetrachloride is particularly preferred.

First electron donating compound The first electron donating compound includes carboxylic acids, carboxylic anhydrides, carboxylic esters, carboxylic halides, alcohols, ethers, ketones, and the like.
Amines, amides, nitriles, aldehydes, alcoholates, phosphorus, arsenic or antimony compounds bonded to an organic group via carbon or oxygen, phosphoamides,
And thioethers, thioesters, carbonates and the like. Of these, carboxylic acids, carboxylic anhydrides, carboxylic esters, carboxylic halides, alcohols, and ethers are preferred.

Specific examples of the carboxylic acid include aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, and acrylic acid; aliphatic dicarboxylic acids such as malonic acid, succinic acid, adipic acid, and maleic acid; and tartaric acid. Aliphatic oxycarboxylic acid, cyclohexene monocarboxylic acid, cis-1,2-
Examples thereof include alicyclic carboxylic acids such as cyclohexanedicarboxylic acid, aromatic monocarboxylic acids such as benzoic acid and toluic acid, and aromatic polycarboxylic acids such as phthalic acid, naphthalic acid and trimellitic acid. Carboxylic anhydrides are anhydrides of the above carboxylic acids.

As the carboxylic acid ester, mono- or polyvalent esters of the above carboxylic acids can be used. Specific examples thereof include butyl formate, ethyl acetate, isobutyl pivalate, ethyl acrylate, methyl methacrylate, and benzoate. Methyl acrylate, ethyl benzoate, methyl p-toluate, ethyl p-anisate, ethyl cinnamate, monomethyl phthalate, dibutyl phthalate, diisobutyl phthalate, diallyl phthalate, diphenyl phthalate, diethyl terephthalate, etc. Can be

As the carboxylic acid halide, acid halides of the above carboxylic acids can be used.
As specific examples, acetate chloride, acetate bromide,
Propionic acid chloride, butyric acid chloride, butyric acid bromide, acrylic acid chloride, acrylic acid bromide,
Methacrylic acid chloride, methacrylic acid bromide, crotonic acid chloride, malonic acid chloride, malonic acid bromide, succinic acid chloride, succinic acid bromide,
Examples include adipic acid chloride, adibic acid bromide, maleic acid chloride, maleic acid bromide, tartaric acid chloride, and tartaric acid bromide. Also, monoalkyl halides of dicarboxylic acids such as adipic acid monomethyl chloride and maleic acid monoethyl chloride can be used.

Alcohols are represented by the general formula R ⁶ OH. Here, R ⁶ is an alkyl group having 1 to 12 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, or an aralkyl group. Specific examples include methanol, propanol,
Isobutanol, pentanol, hexanol, cyclohexanol, phenol and the like.

Ethers are represented by the general formula R ⁷ OR ⁸ . Here, R ⁷ and R ⁸ are an alkyl group, alkenyl group, cycloalkyl group, aryl group or aralkyl group having 1 to 12 carbon atoms, which may be the same or different. Specific examples include diethyl ether, diisopropyl ether,
Diisoamyl ether, di-2-ethylhexyl ether, diallyl ether and the like can be mentioned.

Halogen-containing compounds Examples of the halogen-containing compound include halogenated hydrocarbons, halogen-containing alcohols, silicon halide compounds having a hydrogen-silicon bond, groups IIIa, IVa and Va of the periodic table.
Halides of group elements (hereinafter referred to as metal halides)
And the like.

Halogenated hydrocarbons include those having 1 to 1 carbon atoms.
Mono- and polyhalogen substituents of 12 saturated or unsaturated aliphatic, cycloaliphatic and aromatic hydrocarbons are mentioned. Specific examples of those compounds include aliphatic compounds such as methyl chloride, methylene chloride, chloroform, iodoform, carbon tetrachloride, tetrachloroethylene, pentachloroethane, hexachloroethane, and hexachloropropylene, and alicyclic compounds. Examples include chlorocyclopropane and hexachlorocyclopentadiene, and aromatic compounds include chlorobenzene, p-dichlorobenzene, hexachlorobenzene, and hexabromobenzene. One or more of these compounds may be used.

The halogen-containing alcohol is a compound in which a mono- or polyhydric alcohol having one or more hydroxyl groups in one molecule is obtained by substituting one or more hydrogen atoms other than a hydroxyl group with a halogen atom. As a halogen atom,
Examples thereof include chlorine, bromine, iodine and fluorine atoms, and a chlorine atom is particularly preferable. Illustrating these compounds,
Chloroethanol, 1-chloro-2-propanol, 5-chloro-1-pentanol, 3-chloro-1,2-propanediol, 2-chlorocyclohexanol, 2-bromoethanol, 1-bromo-2-butanol, 2-bromo-p-cresol, 1-bromo-2-naphthol and the like.

Examples of the silicon halide compound having a Si—H bond include HSiCl ₃ , H ₂ SiCl ₂ , H ₃ SiCl and H (C
_{2 H 5) SiCl 2, H} (t-C 4 H 9) SiCl 2, H (C 6 H
₅ ) SiCl ₂ , H (CH ₃ ) ₂ SiCl, H (i-C ₃ H ₇ ) ₂
SiCl and the like.

As metal halides, B, Al, Ga, In,
Ti, Si, Ge, Sn chlorides, fluorides, bromides, iodides, especially BCl ₃ , BBr ₃ , BI ₃ , AlC
_{l 3, AlBr 3, GaCl 3} , GaBr 3, InCl 3, TiCl 3, SiCl
₄ , SnCl _{4 and the} like are preferred.

Magnesium compound, titanium compound,
The first electron-donating compound and, if necessary, the halogen-containing compound are mixed and stirred in the presence or absence of an inert medium or mechanically co-milled to obtain a 40 to 15
Contact at 0 ° C. As the inert medium, saturated aliphatic hydrocarbons such as hexane, heptane and octane, saturated alicyclic hydrocarbons such as cyclopentane and cyclohexane, and aromatic hydrocarbons such as benzene, toluene and xylene can be used.

Specifically, the component (A) is composed of magnesium metal, a halogenated hydrocarbon and a general formula: X ¹ _nM (O
R ⁴ ) contacting the magnesium-containing solid obtained by contacting the compound of _mn (which may be the same as the aforementioned alkoxy group-containing compound) with a halogen-containing alcohol;
Then, a method of contacting with an electron-donating compound and a titanium compound (JP-A-63-264607), contacting a magnesium dialkoxide with a silicon halide compound having a hydrogen-silicon bond, followed by contacting the titanium halide compound, Then, a method of contacting with an electron donating compound (and further contacting with a titanium halide compound if necessary) (JP-A No. 62-146904), contacting a magnesium dialkoxide with a silicon halide compound having a hydrogen-silicon bond. After that, it can be prepared by a method of contacting with an electron donating compound and then with a titanium compound (Japanese Patent Application Laid-Open No. 58-198503). Ingredient (A)
May be washed with the above-mentioned inert medium as needed.

[0041] (B) The organoaluminum compound organoaluminum compound represented by the general ^{_{formula: R 9 r AlX 2 3-}} r ( provided that, R ⁹ is an alkyl group or an aryl group, X ² is a halogen atom, an alkoxy group or a hydrogen atom And r is an arbitrary number from 1 to 3), and the number of carbon atoms is preferably 1 to 18, more preferably 2 to 6.

Specifically, trimethylaluminum,
Trialkylaluminums such as triethylaluminum and triisobutylaluminum, dialkylaluminum monohalides such as dimethylaluminum chloride and diethylaluminum bromide, monoalkylaluminum dihalides such as methylaluminum dichloride and ethylaluminum dibromide, and alkylaluminums such as ethylaluminum sesquichloride Examples include dialkylaluminum monoalkoxides such as sesquihalide, diethylaluminum ethoxide and diethylaluminum phenoxide, and dialkylaluminum hydrides such as dimethylaluminum hydride and diethylaluminum hydride. Among these, triethylaluminum, triisobutylaluminum and the like are particularly preferred.

An organic alnium compound in which two or more aluminum atoms are bonded via an oxygen atom or a nitrogen atom can also be used. Such compounds include, for example,

Embedded image Etc. can be exemplified.

(C) Organosilicon Compound The organosilicon compound has the following general formula:

Embedded image (However, R ¹⁰ is a cyclic substituent containing an ether bond or a thioether bond in the ring, an oxy group having a cyclic substituent containing an ether bond in the ring, a cyclic substituent containing a ketone bond in the ring, or a heterocyclic substituent containing a nitrogen atom. Group, a silicon-containing heterocyclic substituent, or a substituent having a lactone skeleton structure, wherein R ¹¹ is a hydrocarbon group having 1 to 10 carbon atoms, R ¹³ O—, R ^13
14 ₃ Si— or R ¹⁵ ₃ SiO— (where R ¹³ is a hydrocarbon group having 3 to 10 carbon atoms, R ¹⁴ and R ¹⁵ are each a hydrocarbon group having 1 to 10 carbon atoms, May be the same or different), R ¹² is a methyl group or an ethyl group,
x is 1 or 2, y is 0 or 1, z is 2 or 3, and x + y + z = 4. ).

[0045] Specific examples of R ^10, the following can be listed (indicating respective R ¹⁰ groups RA, in RB · · · and the like.).

Embedded image

The hydrocarbon group represented by R ¹¹ , R ¹³ , R ¹⁴ and R ^{15 in} the above general formula includes an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, a cycloalkadienyl group, an aryl group and an aralkyl group. And the like. Examples of the alkyl group include ethyl, i-propyl, s-butyl, t-butyl, etc., and the alkenyl group includes
Vinyl, allyl, propenyl, 1-hexenyl and the like; cycloalkyl groups include cyclopentyl and methylcyclohexyl groups; cycloalkenyl groups include cyclopentenyl and cyclohexenyl; Examples of the enyl group include cyclopentadienyl and methylcyclopentadienyl groups, and examples of the aryl group include phenyl, tolyl, and xylyl groups, and examples of the aralkyl group include a benzyl and phenethyl group. .

As a specific example of the component (C), [RA] ₂ Si (OM
e) ₂ , [RB] (i-Pr) Si (OMe) ₂ , [RC] (t-Bu) Si
_{(OMe) 2, [RC]} (Me 3 SiO) Si (OMe) 2, [RA] (i-
Pr) Si (OEt) ₂ , [RA] Si (OMe) ₃ , [RD] Si (OME)
₃ , [RB] Si (OEt) ₃ , [RE] MeSi (OME) ₂ , [RF]
(I-PrO) Si (OME) ₂ , [RG] (i-Pr) Si (OEt) ₂ ,
[RH] Si (OMe) ₃ (provided that [RA], [R
B] · · is equivalent to the sign of R ¹⁰ in the general formula (II)).

(D) Second electron-donating compound The second electron-donating compound (component (D)) includes an organosilicon compound (excluding the same compound as component (C)), nitrogen, and sulfur. Although electron donating compounds containing a hetero atom such as oxygen, phosphorus, and the like can be used, organosilicon compounds are preferred. The component (D) may be added when the organoaluminum compound is combined with the prepolymerization catalyst, or may be added after being brought into contact with the organoaluminum compound in advance.

As the organosilicon compound, a compound in which a total of four alkoxy groups (a part of which may be substituted with an alkyl group or an aryl group) is bonded to a silicon atom is preferable. These alkyl groups and alkoxy groups may be chain or cyclic. The alkyl group or the aryl group may be substituted with a halogen element. Specific examples of the organosilicon compound include tetramethoxysilane, tetraisobutoxysilane, tetraphenoxysilane, tetrabenzyloxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriphenoxysilane, ethyltriethoxysilane, butyltriethoxysilane. Examples thereof include silane, butyltriphenoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, dimethyldiisopropoxysilane, dimethyldiphenoxysilane, and diethyldiethoxysilane.

As specific examples of the heteroatom-containing electron donating compound, compounds containing a nitrogen atom include 2,2,6,
6-tetramethylpiperidine, 2,6-diethylpiperidine,
2,6-diisobutyl-4-methylpiperidine, 3-methylpyridine, 2,6-diisobutylpyridine, 2,5-dimethylpiperidine, imidazole, benzoamide, acetonitrile, aniline, toluidine, triethylamine, and the like, and a sulfur atom As a compound containing, thiophenol, thiophene, ethyl 2-thiophenecarboxylate, methyl mercaptan and the like, and as a compound containing an oxygen atom, tetrahydrofuran, 2-methyltetrahydrofuran, 2,2,5,5-tetraethyltetrahydrofuran and the like Examples of the compound containing a phosphorus atom include triphenylphosphine and triphenylphosphite.

(Ii) Prepolymerization conditions The solid component (component (A)) is brought into contact with the olefin in the presence of an organoaluminum compound (component (B)) and an organosilicon compound (component (C)) to obtain an olefin. Is prepolymerized. At this time, it is preferable to add a second electron-donating compound (component (D)) as necessary together with the components (B) and (C). The prepolymerization is carried out in the presence of an inert medium (which may be the same as that used for preparing the magnesium-containing solid), usually at a temperature of 100 ° C or lower, preferably -30 ° C to +
It is carried out at a temperature of 30 ° C, more preferably -20 ° C to + 15 ° C. As the polymerization system, either a batch system or a continuous system may be used.
Moreover, you may perform in two or more steps. When performing in multiple stages,
The polymerization conditions may be changed for each stage.

Component (B) has a concentration of 10 to 50 in the prepolymerized system.
0 mmol / liter, preferably 30-200 mmol /
Liter, and titanium 1 in component (A)
1 to 50,000 moles per gram atom, preferably 2 to 1,000
Used to be molar. Component (C) has a concentration in the prepolymerized system of 5 to 1,000 mmol / l, preferably 10 to 10 mmol / l.
Use to make 200 mmol / l. The component (D) used as needed has a concentration of 1 to 3 in the prepolymerized system.
100 mmol / l, preferably 5-50 mmol / l
Use to make up liters. Component (A) by pre-polymerization
The olefin polymer is incorporated into the mixture, and the amount of the polymer is 0.1 to 200 g, particularly 0.5 to 50 g, per 1 g of the component (A).
It is preferred that The catalyst component prepared as described above is preferably washed in order to prevent deterioration of the catalyst component during storage. The catalyst component is preferably stored at a temperature as low as possible, preferably in the temperature range of -50 ° C to + 30 ° C, especially -20 ° C to + 5 ° C.

(Ii) Main polymerization The prepolymerization catalyst obtained as described above is combined with an organometallic compound and, if necessary, an electron-donating compound to form a main polymerization catalyst, and propylene homopolymerization is carried out. To obtain a propylene homopolymer moiety.

Examples of the organometallic compounds include organic compounds of metals of Groups I to III of the periodic table. lithium,
Organic compounds of magnesium, zinc or aluminum are preferred, and organic aluminum compounds are particularly preferred. The organoaluminum compound may be the same as the component (B) used when preparing the prepolymerization catalyst. Examples of the organic compound of a metal other than aluminum include diethyl magnesium, ethyl magnesium chloride, and diethyl zinc. As an organic compound of aluminum and another metal, LiAl (C ₂ H
₅ ) _{4 and the} like.

The electron donating compound to be combined with the prepolymerization catalyst and the organometallic compound, if necessary, may be the same as the electron donating compound or the components (C, D). The electron donating compound may be added when the organometallic compound is combined with the prepolymerization catalyst, or may be added after being brought into contact with the organometallic compound in advance.

The amount of the organometallic compound to be used for the prepolymerization catalyst is usually 1 to 2,000 gmol, particularly preferably 20 to 500 gmol, per 1 g of titanium in the catalyst component. When an electron donating compound is used, the amount of the organometallic compound is 0.1 to 40 g atoms (as aluminum), preferably 1 to 25 g atoms, per mole of the electron donating compound. Select the ratio of the sex compounds.

The propylene polymerization reaction may be carried out in a gas phase or a liquid phase. When the polymerization is carried out in the liquid phase, an inert carbon such as normal butane, isobutane, normal pentane, isopentane, hexane, cyclohexane, benzene, toluene and xylene is used. It can be carried out in hydride or in a liquid monomer. The polymerization temperature is usually from -80 ° C to + 150 ° C, especially 40 ° C.
It is in the temperature range of ℃ to 120 ℃. The polymerization pressure may be from 1 to 60 atm. The molecular weight of the polymer is adjusted with a molecular weight regulator such as hydrogen. The polymerization reaction is performed continuously or batchwise under ordinary conditions.

(2) Production of Propylene-Ethylene Random Copolymer Part After producing the propylene homopolymer part, the mixture is switched to (ethylene + propylene) in the presence of the catalyst to produce a propylene-ethylene random copolymer part. As long as the polymerization conditions in the propylene-ethylene random copolymerization reaction satisfy the requirement of the ethylene / propylene weight ratio,
It can be appropriately selected from the above range of polymerization conditions for the propylene homopolymer portion. In addition, the ethylene content of the propylene-ethylene random copolymer portion is determined by sampling the reaction mixture and measuring an NMR spectrum.

[2] Other Components The crystalline propylene-ethylene block copolymer for a wheel cap of the present invention may contain other additives (for example, heat stabilizers, antioxidants, light stabilizers) for the purpose of modification. ,Flame retardants,
Plasticizer, antistatic agent, release agent, foaming agent, coloring agent, pigment, etc.)
Can be added.

[3] Injection molding [A] Hot runner mold Injection molding of a wheel cap free from molding defects such as warpage, sink mark and flow mark using the above crystalline propylene-ethylene block copolymer. Requires the use of a hot runner mold as the injection mold.
The hot runner mold is an injection molding mold that heats the sprue and runner portions of the mold and keeps the molding material in the molten state at all times, and cools and removes only the molded product. It is a mechanism that can do it.

The gate system of the hot runner is roughly classified into a system in which the gate is sealed by a valve, and a system in which the gate is melted or semi-molten by heat balance to cut the gate. Further, there are two types of valve gates: a spring type and a mechanical opening / closing type. Gates using a seal based on heat balance include a hot edge sealing type and a temperature control type. Gate seal systems suitable for the injection molding of the wheel cap of the present invention include a temperature control system (regardless of a heating system such as electromagnetic induction and direct energization), a spring system, and a mechanical opening and closing valve gate system. . In particular, a mechanical opening / closing valve gate system is preferable.

[B] Gate Position The gate position of the injection mold is set so as to be located near the center of the back surface of the wheel cap. Here, the vicinity of the center of the rear surface of the wheel cap refers to a case where the radius r is 70 mm from the center point C of the wheel cap 10 as shown in FIG.
Within the range. Gate 11 is the wheel cap
If it is not near the center of the back surface of the gate 10, it is located downstream of the gate 11 and / or
Alternatively, there is a possibility that a flow mark is generated around the periphery. In the case where the mark can be hidden by attaching a mark, center cap, etc. of another part on the design surface, the gate can be provided at the same position on the wheel cap surface side (design surface side) as described above. The same effect can be obtained.

[C] Injection molding conditions The temperature of the crystalline propylene-ethylene block copolymer injected into the cavity through the gate is preferably 170 to 280 ° C. If the injection temperature is lower than 170 ° C., a flow mark or the like is likely to occur due to defective resin flow. If the injection temperature exceeds 280 ° C., the crystalline propylene-ethylene block copolymer may be deteriorated. The preferred injection temperature is 190-260 ° C. The injection pressure is preferably about 400 to 1000 kgf / cm ² . As a material of the injection mold, a commonly used plastic mold steel may be used. However, beryllium copper alloy (high conductivity alloy BeAll)
) Is preferred. Thereby, appearance quality such as suppression of sink of molded products, reduction of warpage and distortion, and
It is possible to achieve improvement in productivity and cost reduction by shortening the cooling time at the time of molding, as well as improving the releasability.

[4] Shape of Wheel Cap As shown in FIGS. 1 (a) and 1 (b), the wheel cap 10 of the present invention has a gate mark 11 near the center of the rear surface 10b and a continuous gate mark on the rear surface 10b. It has targeted or intermittent ribs 12. The rib 12 may be formed as a part of the locking portion (claw portion) 13 of the wheel cap, or may be provided for reinforcing the claw portion 13. The rib 12 may have various shapes such as an annular shape, and at least one rib may be used. Also ribs 12
Is preferably provided near the outer periphery.

As shown in FIG. 1C, the thickness t of the rib 12
The ratio (t / T) between the thickness (measured at the rib base 12a) and the thickness T of the wheel cap 10 body is preferably 0.4 or less.
If t / T exceeds 0.4, sink marks are likely to occur. The more preferable t / T is 0.3 or less. Generally, the thickness T of the wheel cap body is preferably about 2 to 3 mm, and the draft of the rib 12 is preferably 0.5 ° or more.

The surface (design surface) 10a of the wheel cap 10
In the case where the recess 14 is provided, it is preferable that the depth D is 2 mm or less, as shown in FIG. If the depth D of the recess 14 exceeds 2 mm, the flow of the resin is also hindered, and flow marks, hair lines, and the like are generated on the surface. Further, in order to improve the appearance quality, the chamfer radius (the radius of curvature of the corner) R of the concave portion 14 is preferably 1 mm or more. Further, the draft of the concave portion 14 (the angle between the normal to the design surface and the side surface of the concave portion) is preferably 2 ° or more, more preferably 5 ° or more.

[5] Coating [A] Pretreatment The wheel cap made of the above-mentioned crystalline propylene-ethylene block copolymer exhibits good coating film adhesion without a primer treatment. Therefore, the manufacturing cost of the wheel cap can be reduced.

In order to further improve coating film adhesion,
Pretreatment with an organic solvent such as xylene or isopropyl alcohol, or plasma discharge treatment, corona discharge treatment, pure water treatment, or the like is preferable. The primer treatment is not essential, but the primer treatment further improves the coating film adhesion.

[B] Paint As the paint applied to the wheel cap of the present invention, it is preferable to use an acrylic urethane-based two-pack paint containing a chlorinated polyolefin. As a preferred example,
A two-pack paint containing acrylic polyol containing 5 to 50% by weight, more preferably 10 to 20% by weight, of a chlorinated polyolefin as a main component and an isocyanate compound as a curing agent at a predetermined ratio is exemplified. By containing the chlorinated polyolefin, the affinity with the polyolefin resin composition is improved, and a coating film having excellent adhesion can be obtained. When the content of the chlorinated polyolefin exceeds the upper limit, the gloss of the coating film is lost.

[0070]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but the present invention is not limited thereto.

Synthesis Example 1 Crystalline propylene-ethylene block copolymer (BPP
Synthesis of 1) (1) Preparation of Component (A) for Producing Propylene Homopolymer Part In a 1-liter reaction vessel equipped with a reflux condenser, chip-shaped metallic magnesium (purity 99.5) was placed under a nitrogen gas atmosphere.
%) And 250 ml of n-hexane were added, stirred at 68 ° C for 1 hour, taken out of metallic magnesium, and dried at 65 ° C under reduced pressure to obtain preactivated metallic magnesium.

To pre-activated magnesium metal, 140 ml of n-butyl ether and a solution of n-butyl magnesium chloride in n-butyl ether (1.75 mol / l) were added to a volume of 0.1%.
5 ml was added, the resulting suspension was kept at 55 ° C., and a solution of 38.5 ml of n-butyl chloride dissolved in 50 ml of n-butyl ether was added dropwise over 50 minutes. After performing the reaction at 70 ° C. for 4 hours with stirring, the reaction solution was kept at 25 ° C.

To the reaction solution was added 55.7 ml of HC (OC ₂ H ₅ ) _3.
The mixture was added dropwise over a period of time, and the mixture was reacted at 60 ° C. for 15 minutes.
The obtained solid was washed six times with 300 ml of n-hexane and dried under reduced pressure at room temperature for 1 hour to obtain 31.6 g of a magnesium-containing solid containing 19.0% of magnesium and 28.9% of chlorine.

Under a nitrogen gas atmosphere, 6.3 g of a magnesium-containing solid and 50 ml of n-heptane were put into a 300 ml reaction vessel equipped with a reflux condenser, a stirrer and a dropping funnel to form a suspension. , 2,2-trichloroethanol
A mixed solution of 20 ml (0.02 mmol) and 11 ml of n-heptane was added dropwise from a dropping funnel over 30 minutes, and the mixture was further stirred at 80 ° C. for 1 hour. The obtained solid was filtered off, and n-hexane at room temperature was added.
The solid was washed four times with 100 ml and twice with 100 ml of toluene each to obtain a solid component.

To the solid component was added 40 ml of toluene, and titanium tetrachloride was added so that the volume ratio of titanium tetrachloride / toluene was 3/2, and the temperature was raised to 90 ° C. A mixed solution of 2 ml of di-n-butyl phthalate and 5 ml of toluene was added dropwise with stirring, followed by stirring at 120 ° C. for 2 hours. The obtained solid substance was separated by filtration at 90 ° C and washed at 90 ° C twice with 100 ml each of toluene. Titanium tetrachloride was further added so that the volume ratio of titanium tetrachloride / toluene was 3/2, and the mixture was stirred at 120 ° C. for 2 hours, and stirred at room temperature with 100 ml of n-hexane.
After washing twice, 5.5 g of the component (A) was obtained.

In a 500 ml reactor equipped with a pre-polymerization stirrer, 3.5 g of the above-mentioned component (A) and 300 ml of n-heptane were put under a nitrogen gas atmosphere, and cooled to 5 ° C. with stirring. Next, a solution of triethylaluminum (TEAL) in n-heptane (2.0 mol / l) and
2,3,4-trimethyl-3-azacyclopentyltrimethoxysilane is reacted with TEAL and 2,3,4-trimethyl-3 in the reaction system.
-Azacyclopentyltrimethoxysilane was added so that the concentration became 100 mmol / L and 10 mmol / L, respectively, and the mixture was stirred for 5 minutes.

After the pressure in the system was reduced, propylene gas was continuously introduced, and propylene was polymerized for 2.2 hours. After the polymerization, propylene in the gas phase was purged with nitrogen gas,
The solid phase was washed three times with ml of n-hexane at room temperature. The solid phase was dried under reduced pressure at room temperature for 1 hour to prepare a prepolymerized catalyst. As a result of measuring the amount of magnesium in the prepolymerized catalyst, the amount of prepolymerized was 3.1 g per 1 g of the component (A).

[0078] This polymerization under nitrogen gas atmosphere TEAL in n- heptane solution (0.3 mol /
4) and 3 ml of a solution of t-butoxycyclopentyldimethoxysilane in n-heptane (0.08 mol / l) were mixed, kept for 5 minutes, and then placed in a 5-liter stainless steel autoclave equipped with a stirrer. After charging 22.5 mg of the obtained prepolymerized catalyst into the reaction system, 18 liters of hydrogen gas (normal temperature and normal pressure) and 3.0 liters of liquid propylene were injected as a molecular weight controlling agent, and the reaction system was heated to 70 ° C. The polymerization of propylene was carried out for one hour. After the polymerization was completed, unreacted propylene and hydrogen gas were purged until the pressure in the vessel reached 0.2 kgf / cm ² G.

(2) Production of Propylene-Ethylene Random Copolymerized Part After introducing 0.2 liter of hydrogen gas into the vessel, a mixed gas having a molar ratio of propylene to ethylene of 1.03 was supplied, and the pressure in the vessel was increased to 6.0. While maintaining the pressure at kgf / cm ² G, copolymerization of propylene and ethylene was performed for 1.5 hours. The unreacted gas was purged to obtain 840 g of a white powdery propylene-ethylene block copolymer (BPP1). Table 1 shows the manufacturing conditions.

Analysis of the obtained crystalline propylene-ethylene block copolymer (BPP1) revealed that the proportion of propylene homopolymer was 87.0% by weight and that of propylene-ethylene random copolymer was 13.0% by weight. The isotactic pentad fraction of the propylene homopolymer portion was measured by ¹³ C-NMR method and found to be 97.5%. Also, the melt flow rate (MFR, 230 ° C., load 2.16 kg) of the propylene homopolymer portion was measured and found to be 50 g / 10 minutes. On the other hand, for the propylene-ethylene random copolymer portion, the weight ratio of propylene / ethylene is 60/40, and the intrinsic viscosity [η] (135 ° C.)
Measured in decalin) was 3 dl / g. Furthermore, the MFR of the whole propylene-ethylene block copolymer (BPP1)
Was 25 g / 10 minutes. Table 2 shows the measurement results.

Synthesis Example 2 The first-stage and second-stage polymerizations were performed immediately without the prepolymerization under the same conditions as in Synthesis Example 1 except for the conditions shown in Table 1 to obtain a propylene-ethylene block copolymer (BPP2). Was. The properties of the obtained propylene-ethylene block copolymer (BPP2) were measured in the same manner as in Synthesis Example 1. Table 2 shows the results.

Synthesis Example 3 Prepolymerization, first-stage polymerization and second-stage polymerization were carried out under the same conditions as in Synthesis Example 1 except for the conditions shown in Table 1, to obtain a propylene-ethylene block copolymer (BPP3). The properties of the obtained propylene-ethylene block copolymer (BPP3) were evaluated using Synthesis Example 1.
It measured similarly to. Table 2 shows the results.

Synthesis Example 4 Prepolymerization, first-stage polymerization and second-stage polymerization were carried out under the same conditions as in Synthesis Example 1 except for the conditions shown in Table 1 to obtain a propylene-ethylene block copolymer (BPP4). The properties of the obtained propylene-ethylene block copolymer (BPP4) were evaluated using Synthesis Example 1.
It measured similarly to. Table 2 shows the results.

Synthesis Example 5 Prepolymerization, first-stage polymerization and second-stage polymerization were carried out under the same conditions as in Synthesis Example 1 except for the conditions shown in Table 1, to obtain a propylene-ethylene block copolymer (BPP5). The properties of the obtained propylene-ethylene block copolymer (BPP5) were evaluated using Synthesis Example 1.
It measured similarly to. Table 2 shows the results.

Table 1 Synthesis Example No. 1 2 3 4 5 Polymerization conditions BPP1 BPP2 BPP3 BPP4 BPP5 First stage ( Homopolymerization of propylene) Liquid propylene (liter) 3.0 3.0 3.0 3.0 3.0 Hydrogen gas amount (liter) 18.0 12.5 6.6 17.0 10.0 Second stage (copolymerization of propylene / ethylene) C ₃ / C ₂ ⁽¹⁾ 1.03 0.84 0.84 0.84-Hydrogen gas volume (liter) 0.2 0.3 0.15 0.2-Pressure in container (kgf / cm ² G) 6.0 6.1 6.0 6.0 -Polymerization time (h) 1.5 1.5 1.5 1.5-Note (1) Molar ratio of propylene to ethylene.

Table 2 Synthesis Example No. 1 2 3 4 5 Characteristics BPP1 BPP2 BPP3 BPP4 BPP5 Propylene homopolymer portion Content (% by weight) 87.0 88.0 85.0 91.0 100.0 IPF (%) ⁽¹⁾ 97.5 96.0 97.5 97.5 97.5 MFR (g) / 10 min) 50 47 9.5 48 20 Propylene-ethylene random copolymerized portion Content (% by weight) 13.0 12.0 15.0 9.0 0.0 C ₃ / C ₂ weight ratio ⁽²⁾ 60/40 50/50 50/50 50/50 − [Η] (dl / g) 3.0 3.0 3.5 3.0-Overall block copolymer MFR (g / 10 min) 25 20 5 30-Notes: (1) Isotactic pentad fraction. (2) Propylene / ethylene weight ratio.

Example 1 and Comparative Examples 1 to 4 Crystalline propylene-ethylene block copolymer BPP1: manufactured in Synthesis Example 1 BPP2: manufactured in Synthesis Example 2 BPP3: manufactured in Synthesis Example 3 BPP4: manufactured in Synthesis Example 4 BPP5: manufactured in Synthesis Example 5

2. Kneading and injection molding method The above crystalline propylene-ethylene block copolymer (BP
P1 to BPP5) are twin-screw extruders (Ikegai Co., Ltd., PCM-
45) Melt kneading in step 45.
° C., and injection molded at an injection pressure of 900 kgf / cm ² and mold temperature of 60 ° C., to obtain a test piece.

3. Measurement of Physical Properties The following mechanical properties were measured for each test piece. Table 3 shows the measurement results.

Flexural modulus (kgf / cm ² ): Measured at 23 ° C. using a 110 mm × 10 mm × 4 mm test piece according to JIS K7203.

Izod impact strength (kgf · cm / cm):
It was measured at 23 ° C. using a notched test piece of 80 mm × 10 mm × 4 mm from JIS K7110.

Heat distortion temperature (HDT): According to JIS K7207, a test piece of 120 mm × 12.7 mm × 4 mm was used at 23 ° C. and 4.
It was measured under a load of 6 kgf / cm ² .

Injection moldability: A 1.5 mm-thick product model was injection-molded, and the injection moldability was evaluated by examining the fluidity of the resin and the appearance and deformation of the product model.

Primerless paintability: After washing each test piece with isopropyl alcohol (IPA), an acrylic / urethane two-pack paint for automobile exterior (based on acrylic polyol containing 20% by weight of chlorinated polyolefin) 1.2 mol of liquid B based on the isocyanate compound per 1 mol of liquid A (expressed as a functional group molar ratio)
Formulated. ) Was applied, and the coating film adhesion was evaluated.

Table 3 Example Comparative Example Resin Types and Properties 1 1 2 3 4 Resin Types BPP1 BPP2 BPP3 BPP4 BPP5 Flexural Modulus (kgf / cm ² ) 15000 13000 14000 17500 22000 Heat Deformation Temperature (° C.) 125 115 120 130 142 Izod impact strength ⁽¹⁾ 9.0 9.0 9.5 6.0 2.5 Injection moldability ○ ○ △ ○ ○ Paintability ⁽²⁾ ○ ○ ○ △ × Remarks Rigidity, rigidity, impact resistance Shock resistance Heat resistance Heat resistance Lack Lack Lack Lack Lack Note: (1) Unit: kgf · cm / cm. (2) Primerless paintability.

As is clear from Table 3, BPP1 has a good balance of rigidity, impact resistance and heat resistance, and is excellent in injection moldability and paintability.

Examples 2 and 3 and Comparative Examples 5 and 6 BPP1 was injection-molded with a hot runner mold to obtain a wheel cap (radius R 196 mm, thickness T2 to T2) shown in FIG.
3 mm). The presence or absence of molding defects at various thicknesses t of the rib 12 (measured at the rib base 12a) was observed. Table 4 shows the results
Shown in

Table 4 Example No. Comparative Example No. Item 2 3 5 6 Thickness of body ⁽¹⁾ T (mm) 2.0 3.0 2.0 2.0 Rib thickness t (mm) 0.8 0.9 1.0 1.6 Rib / body ratio (t / T) ⁽²⁾ 0.4 0.3 0.5 0.8 △ △ × Evaluation Sink is almost not Sink Sink is slightly Sink is very inconspicuous. Inconspicuous. Stand out practical. This is a problem. Note: (1) Wheel cap body. (2) The ratio of the rib thickness to the wheel cap body thickness.

As is evident from the results in Table 4, the ratio (t / T) of the thickness of the rib to the thickness of the wheel cap main body was 0.1.
If it is 4 or less, the appearance of the formed wheel cap surface is good.

Example 4 and Comparative Examples 7 to 9 BPP1 was injection-molded using a hot runner mold and the wheel cap shown in FIG. 1 (radius R 196 mm, thickness T3 mm)
Was obtained, the shape of the design surface concave portion was changed, and the presence or absence of molding failure was observed. Table 5 shows the results.

Table 5 Example No. Comparative Example No. Item 4 7 8 9 Thickness of body ⁽¹⁾ T (mm) 3.0 3.0 3.0 3.0 Depth of recess ⁽²⁾ D (mm) 1.5 3.0 2.0 2.0 R (mm) of design recess ⁽³⁾ 1.0 1.0 0.2 1.0 recess Draft angle of ⁽²⁾ (°) 5.0 5.0 5.0 0.5 Appearance ⁽⁴⁾ ◎ × △ △ Evaluation Molding defect is excellent without concave design of concave design. The-mark is broken and the-mark is damaged. Generate. Generated slightly. Was. Note: (1) Wheel cap body. (2) The recess 14 in the design surface 10a of the wheel cap. (3) The radius of curvature of the design surface concave portion 14 of the wheel cap. (4) The appearance of the design surface 10a of the wheel cap.

As is clear from the results shown in Table 5, when the depth D of the concave portion 14 is 2 mm or less, a wheel cap free from molding defects can be obtained. In addition, the radius of curvature of the design surface concave portion 14 is 1 mm.
If it is less than the above, it can be seen that even when the depth D of the concave portion 14 is 2 mm, a slight flow mark is generated (Comparative Example 8). Further, it is found that when the draft angle of the concave portion 14 is less than 2 °, molding failure occurs (Comparative Example 9).

Examples 5 to 7 and Comparative Examples 10 and 11 BPP1 was injection-molded with a hot runner mold to obtain a wheel cap (radius R 196 mm, thickness T3 m) shown in FIG.
In obtaining m), the type and position of the gate of the hot runner mold were changed, and the presence or absence of molding defects was observed. Table 6 shows the results.

Table 6 Example No. Item 5 6 7 Gate position Back center point Back center point 1 point shifted 50 mm from back center point Gate type Mechanical open / close Spring type Direct current heating type Valve gate Gate ⁽¹⁾ Gate ⁽²⁾ Exterior ⁽³⁾ ◎ ○ ○ Remarks There is no molding failure. Setting of molding conditions. Setting of molding conditions is excellent. However, the gate sea has a wide range of molding conditions with good sealing properties and good sealing properties. Less likely to occur. Less likely to occur. Note: (1) Pragate. (2) Samocomgate. (3) The appearance of the wheel cap design.

Table 6 (Continued) Comparative Example No. Item 10 11 Gate position 3 points on the outer circumference Center point on the back side Gate type Open gate Cold gate Appearance ⁽¹⁾ △ × Remarks Setting molding conditions Skill required outside the gate, poor visual quality, weld line, Post-processing of gates It takes time and effort to balance gates. Deficiencies are likely to occur due to inadequacies. Note: (1) Design appearance of wheel cap.

As is clear from the results in Table 6, unless the gate is provided at the center of the back surface of the wheel cap or in the vicinity thereof, a wheel cap having a good appearance cannot be obtained (Comparative Example 10). Also, in the case of a cold gate, even if the gate is provided at the center of the back surface of the wheel cap or in the vicinity thereof, it is understood that molding failure or deformation occurs (Comparative Example).
11).

Examples 8 and 9 and Comparative Examples 12 and 13 Using the wheel cap mold of Example 5, a molded product obtained by injection molding of BPP1 was used without pretreatment (Example 8). ) And isopropyl alcohol (I
PA) When washing was performed (Example 9, Comparative Examples 12 and 13)
For each of the samples, the following coating materials were used to evaluate coating film adhesion. Table 7 shows the results. 1. Composition of acrylic / urethane-based two-pack paint A two-pack paint for automobile exteriors comprising the following liquid A and liquid B. Liquid A: based on acrylic polyol containing 20% by weight of chlorinated polyolefin. Solution B: Based on isocyanate compound. The mixing ratio of solution A / solution B expressed by an equimolar ratio of functional groups is 1 /
1.2. 2. Acrylic / melamine paint. Melamine resin cured acrylic resin for automotive exterior. 3. Polyester / melamine paint. Melamine resin-curable polyester resin for automotive exterior.

Table 7 Example No. Comparative Example No. Item 8 9 12 13 Pretreatment None IPA cleaning IPA cleaning IPA cleaning Type of paint ⁽¹⁾ Acr / Ure Acr / Ure Acr / Mel PET / Mel Coating appearance ◎ ◎ ○ ○ Coating adhesion 100/100 100/100 80 / 100 0/100 Evaluation Coating quality, dense coating quality, dense coating adhesion Good coating adhesion Both good adhesion Good adhesion Slightly poor. Notably inferior. Good. Good. Note: (1) Acr / Ure: Acrylic / urethane two-pack paint. Acr / Mel: Acrylic / melamine paint. PET / Mel: polyester / melamine paint.

As is evident from the results in Table 7, the wheel cap of the present invention shows good coating film adhesion in the case of the acrylic / urethane-based two-pack type paint regardless of the presence or absence of the pretreatment. On the other hand, in the case of a melamine resin-containing paint, good coating film adhesion cannot be obtained even after pretreatment.

[0110]

As described in detail above, the wheel cap of the present invention is formed by injection molding a crystalline propylene-ethylene block copolymer under a special condition using a hot runner mold. It has impact resistance, heat resistance, rigidity, etc., has no molding defects such as warpage, sink marks and flow marks, and has good coating film adhesion.

[Brief description of the drawings]

1 shows a wheel cap according to an embodiment of the present invention, (a) is a longitudinal sectional view, (b) is a rear view, (c) is a cross-sectional view of a main part thereof, (d) is a cross-sectional view of the relevant part.

[Description of Signs] 10 ··· Wheel cap 10a · · · Design surface (front surface) 10b · · · Back surface 11 · · · Gate mark 12 · · · Rib 13 · · · Locking portion (claw portion) 14 ・ ・ ・ ・ Recess

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08K 7/14 C08K 7/14 C08L 23/12 C08L 23/12 53/00 53/00 // (C08L 23/12 23:16 23:26) B29K 23:00 B29L 31:56 (72) Inventor Masao Sakaizawa 3-1 Chidoricho, Kawasaki-ku, Kawasaki-ku, Kanagawa Prefecture East Fuel Chemical Co., Ltd. Technology Development Center (72) Inventor Shintaro Kikuchi Kawasaki-shi, Kanagawa Prefecture 3-1 Chidori-cho, Kawasaki-ku Tohoku Chemical Co., Ltd. Technology Development Center (72) Inventor Yuji Fujita 3-1 Chidori-cho, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Tonen Chemical Co., Ltd. Technology Development Center (72) Inventor Yasuhide Narita No. 1 Noda, Toyoda, Oguchi-machi, Oguchi-machi, Niwa-gun, Aichi Prefecture Inside the Tokai Rika Electric Machinery Works, Ltd. (56) References JP-A-7-32401 (JP, A) JP-A-4-146962 (JP, A) JP-A-2-150444 (JP, A) JP-A-3-137150 (JP, A) JP-A-6-57063 (JP, A) JP-A-5-4502 (JP, A) JP-A-5 −32885 (JP, A) Japanese Utility Model Application Hei 2-63203 (JP, U) Japanese Utility Model Application Hei 1-62333 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60B 7/02 B29C 45/00 C08F 297/08 C08K 3/34 C08K 7/14 C08L 23/12 C08L 53/00 C08L 23/12

Claims (5)

(57) [Claims] (1) 70-90% by weight of a propylene homopolymer portion having an isotactic pentad fraction of 97% or more as determined by ¹³ C-NMR, and (b) a weight ratio of propylene / ethylene of 25%. A crystalline propylene-ethylene block containing 30 to 10% by weight of a propylene-ethylene random copolymerized portion having a melt flow rate (230 ° C., a load of 2.16 kg) of 20 g / 10 min or more. A wheel cap obtained by injection molding a copolymer. 2. The wheel cap according to claim 1, wherein a gate mark is located near the center of the rear surface of the wheel cap. 3. The wheel cap according to claim 1, further comprising at least one rib on a back surface, wherein a ratio (t / T) of a thickness t of the rib to a thickness T of the wheel cap body is set. Wheel cap characterized by being 0.4 or less. 4. The wheel cap according to claim 1, wherein the depth of the concave portion in the front design surface is 2 mm or less, the chamfer radius is 1 mm or more, and the normal line of the design surface. The angle between the groove and the side surface of the recess is not less than 2 °. 5. The method for manufacturing a wheel cap according to claim 1, wherein a hot runner mold is used, and a gate opening to a cavity of the mold is radiused from a center point on a rear surface of the wheel cap. A method for producing a wheel cap, characterized in that the mold is set by positioning so as to be within 70 mm, and the crystalline propylene-ethylene block copolymer is injected into the mold cavity.