JP3255021B2 - Thermoplastic elastomer composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic elastomer composition having excellent balance between rigidity and low-temperature impact resistance, tensile properties, melt fluidity, appearance of a molded article, and the like. More specifically, the present invention relates to a thermoplastic elastomer composition comprising a specific crystalline polypropylene and an ethylene-α-olefin copolymer rubber.

[0002]

2. Description of the Related Art Thermoplastic elastomers are widely used in automobile parts, home electric appliances parts, daily necessities and the like because of their excellent properties, but the parts to which they are applied are becoming larger and more sophisticated. Therefore, there is a demand for a thermoplastic elastomer composition having excellent balance between rigidity and low-temperature impact resistance, tensile properties, melt fluidity, appearance of a molded article, and the like.

For the purpose of improving these properties, a number of crosslinked TPE compositions have been proposed in which a peroxide is added by an extruder or the like to dynamically crosslink a rubber component. Crosslinked TP
E composition has a tensile property by crosslinking rubber,
Although it was excellent in low-temperature impact properties, it was not always satisfactory in terms of appearance and melt fluidity, such as surface roughness of the molded product due to crosslinked rubber having a large particle diameter.

[0004] As a method of improving the melt fluidity,
A method of adding paraffin oil, silicone oil, or the like has been proposed. However, the thermoplastic elastomer obtained by such a method has problems such as stickiness on the surface of the molded article and bleeding of the oil at a high temperature.

[0005] Non-crosslinked TPE is a thermoplastic elastomer having good melt fluidity and appearance of a molded article. However, conventional thermoplastic elastomers are suitable for low-temperature impact resistance and tensile properties of automobile parts and home electric parts. Is still insufficient.

[0006]

SUMMARY OF THE INVENTION In view of the state of the prior art, the present invention provides a thermoplastic elastomer composition which is excellent in balance between rigidity and low-temperature impact resistance, tensile properties, melt fluidity, appearance of molded articles, and the like. The purpose is to do.

[0007]

That is, the present invention provides (A) crystalline polypropylene: 48 to 10% by weight, and (B) ethylene-α-olefin copolymer rubber: 52 to 90% by weight ((A ) + (B) = 100% by weight.), And the crystalline polypropylene of (A) is a propylene homopolymer or a copolymer of propylene and 1 mol% or less of ethylene or an α-olefin having 4 or more carbon atoms. The composition of the crystalline polypropylene portion and ethylene and propylene is ethylene / propylene = 20 / 80-60 / by weight ratio.
(1) the crystalline polypropylene portion has an intrinsic viscosity [η] p of 0.8 to 2.0 dl / g, and the molecular weight ratio Q value measured by GPC (1) Weight average molecular weight Mw / number average molecular weight M
N) is 3.0 to 5.0, and the xylene-soluble component at 20 ° C is 1.5.
% By weight or less, (2) the intrinsic viscosity [η] EP of the ethylene-propylene random copolymer portion is 3.5 to 8.5,
(3) The thermoplastic elastomer composition according to (1), wherein the ethylene-propylene random copolymer portion is an ethylene-propylene block copolymer having 5 to 20% by weight of the whole polymer.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The ethylene-propylene block copolymer of crystalline polypropylene (A) used in the present invention is usually prepared in two steps in the presence of a Ziegler-Natta catalyst in combination with titanium trichloride and an alkylaluminum compound. In carrying out the present invention, it is preferable to use a catalyst comprising a complex of titanium trichloride and magnesium, a trialkylaluminum compound and an electron-donating organic compound. The method for producing this catalyst is described in detail, for example, in JP-A-61-218606.

The ethylene-propylene block copolymer used in the present invention comprises the following components (I) and (II). (I) The crystalline polypropylene part has (1) an intrinsic viscosity [η] p in tetralin of 135 ° C. of 0.8 to 2.0 dl.
/ G, preferably 0.8 to 1.7 dl / g, more preferably 0.85 to 1.5 dl / g, and (2) G
Q value (weight average molecular weight Mw / number average molecular weight MN) measured by PC is 2.5 to 5.5, preferably 3 to 5,
And (3) occupies 95 to 80% by weight of the total copolymer amount, and (II) the ethylene-propylene random copolymer portion has (1) intrinsic viscosity [η] EP in tetralin at 135 ° C.
Is 3.5-8.5 dl / g, preferably 3.5-7.0 dl / g
dl / g, (2) the composition ratio of ethylene and propylene is 20/80 to 60/40 (weight ratio), and
(3) It accounts for 5 to 20% by weight of the total copolymer amount.

The ethylene-propylene block copolymer is produced by two steps of the above (I) and (II) by a slurry polymerization method or a gas phase polymerization method. The slurry polymerization method is preferred.

If [η] p of (I) is less than 0.8 dl / g, the mechanical strength is reduced. If it is 2.0 dl / g or more, the melting of the ethylene-propylene block copolymer and the composition thereof is reduced. Fluidity decreases. If the Q value is 5.5 or more, a weld line of an ethylene-propylene block copolymer and an injection-molded product obtained from the composition appears strongly, and if it is 3 or less, a flow mark occurs.

The intrinsic viscosity [η] EP of (II) is 3.5 dl
/ G or less, the impact resistance is low, and 8.5 dl / g
If it is more than the above, the melt fluidity is reduced, and the impact resistance is lowered due to poor dispersion of the constituent components of the composition. Ethylene-
When the ethylene content in the propylene random copolymer is 20
If the content is less than 60% by weight or less than 60% by weight, the impact resistance of the molded product is deteriorated.

The method for producing the ethylene-propylene block copolymer used in the present invention is described in, for example,
94685 and the like. The thermoplastic elastomer of the present invention has heat resistance, rigidity, scratch resistance,
When used for applications requiring gloss etc., ethylene-
The crystalline polypropylene portion polymerized in the first stage of the propylene block copolymer has an isotactic pentad fraction of the boiling heptane-insoluble portion of 0.970 or more and the content of the boiling heptane-soluble portion of 5.0% by weight. It is preferable to use a highly crystalline polypropylene having a content of the xylene-soluble portion of 20 ° C. or less of 1.5% by weight or less.

The isotactic pentad fraction of the boiling heptane-insoluble part, the content of the boiling heptane-soluble part and the content of the polymer soluble in xylene at 20 ° C. are as follows.
It is determined as follows. After completely dissolving 5 g of crystalline polypropylene in 500 ml of boiling xylene, the temperature is lowered to 20 ° C. and left for 4 hours. Thereafter, this is separated by filtration, and the xylene-insoluble portion at 20 ° C. is separated. The filtrate was concentrated and dried to evaporate xylene, and further dried under reduced pressure at 60 ° C.
To obtain a polymer soluble in xylene. The value obtained by dividing the dry weight by the charged sample weight is expressed as a percentage of 2
It is the content of the xylene-soluble portion at 0 ° C. After the xylene-insoluble part at 20 ° C. is dried, it is subjected to Soxhlet extraction with boiling n-heptane for 8 hours. This extraction residue is referred to as a boiling heptane-insoluble part, and a value obtained by dividing the value obtained by subtracting the dry weight from the charged sample weight (5 g) by the charged sample weight and expressing the result in percentage is the content of the boiling heptane-soluble part. is there.

The isotactic pentad fraction is
A. Macromolec by Zambelli et al.
Ules, 6, 925 (1973), i.e., an isotactic linkage in pentad units in a crystalline polypropylene molecular chain measured using 13C-NMR, in other words, a propylene monomer unit having 5 propylene monomer units.
It is the fraction of propylene monomer units at the center of a chain of meso-bonds that are continuously formed. However, regarding the assignment of NMR absorption peaks, Macromole published afterwards
cules, 8, 687 (1975). Specifically, the isotactic pentad fraction is measured as the area fraction of the mmmm peak in all the absorption peaks in the methyl carbon region of the 13 C-NMR spectrum.
In this way, the UK National Physica
L LABORATORY NPL Reference Material CRM N
o. M19-14 Polypropylene PP
When the isotactic pentad fraction of / MWD / 2 was measured, it was 0.940.

The ethylene-α of (B) used in the present invention
-The olefin copolymer rubber has an ethylene content of 85.
% To 40% by weight, preferably 85% to 65% by weight, the Mooney viscosity ML1 + 4 measured at 121 ° C. is 15 to 80, preferably 20 to 70, and the iodine value is 0 to 1
Five are preferably used. If the ethylene content is 40% by weight or less, the rigidity of the molded article is greatly reduced, and if the ethylene content is 85% by weight or more, the effect of improving the impact resistance is small. If the Mooney viscosity exceeds 70, the fluidity of the composition will decrease, or the impact strength will decrease due to poor dispersion of the rubber particles. On the other hand, if the Mooney viscosity is 10 or less, the dispersion particle size of the rubber in the composition is too small, so that the effect of improving the impact resistance is small, and the surface of the injection molded article is not preferred.

Specific examples of the α-olefin copolymerized with ethylene include propylene, 1-butene, 4-methyl-pentene-1, 1-hexene and the like.
Propylene or 1-butene is preferred. The ethylene-α-olefin random copolymer rubber is copolymerized with a small amount of a non-conjugated diene monomer such as ethylidene norbornene, dicyclopentadiene, 1,4-hexadiene in an iodine value of 0 to 15, preferably about 0 to 10. It may be. These ethylene-α-olefin copolymer rubbers can be used alone or in admixture of two or more according to the respective purposes such as fluidity of the composition, impact strength and hardness of the molded article. The used amount is 52 to 90% by weight, preferably 52 to 70% by weight. This ethylene-α
-When the olefin-based copolymer is 52% by weight or less, the effect of improving the impact resistance is small, and when it exceeds 70% by weight, the melt fluidity is greatly reduced, which is not preferable.

The ethylene-α-olefin random copolymer rubber is usually polymerized in a hydrocarbon solvent in the presence of a catalyst comprising a vanadium compound and an organoaluminum compound. As the vanadium compound, vanadium oxytrichloride, vanadium tetrachloride, vanadate compound, and as the organic aluminum compound, ethyl aluminum sesquichloride, diethyl aluminum chloride or the like is used, and polymerized in a solvent such as hexane or heptane. Manufactured.

The thermoplastic elastomer composition of the present invention comprises a crystalline ethylene-propylene block copolymer
%, And 52 to 90% by weight of an ethylene-α-olefin copolymer rubber. However, the total of each component is 100% by weight.

The composition of the present invention is prepared by mixing an ethylene-propylene block copolymer and an ethylene-α-olefin copolymer rubber with a tumbler, a Henschel mixer, a ribbon blender, etc., followed by a single-screw extruder, a twin-screw extruder. It can be manufactured by melt-kneading with a machine, Banbury mixer, kneader or the like.

By using an extruder having excellent kneading performance, such as a twin-screw extruder, a Banbury mixer, or a kneader, a high-quality composition in which the components are uniformly dispersed can be obtained. The kneading of each component may be performed simultaneously, or may be performed separately.

Further, in addition to the basic components of these compositions, antioxidants, ultraviolet absorbers, lubricants, antistatic agents, copper damage inhibitors, flame retardants, neutralizing agents, nucleating agents, foaming agents, plasticizers ,
Additives such as pigments and dyes can be blended according to the purpose. Among these additives, it is desirable to add an antioxidant or an ultraviolet absorber in order to improve heat resistance, weather resistance, and oxidation stability.

The thermoplastic elastomer composition of the present invention comprises:
It has excellent balance of rigidity and low-temperature impact resistance, excellent tensile properties and melt fluidity, and because of its good appearance, it is molded by injection molding and press molding, and is used for automobile interior parts, home appliances parts, and daily necessities. It is preferably used. Among automotive interior parts, it is suitably used for instrument panel parts and airbag covers.

[0024]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by the following examples.

The following raw materials were used to obtain the compositions of the examples and comparative examples. (A) Crystalline polypropylene The following abbreviations are used below. [Η] P: the intrinsic viscosity Q _P of the crystalline polypropylene portion: the ratio Q value of the molecular weight of the crystalline polypropylene portion (weight average molecular weight Mw / number average molecular weight MN) CXS: weight of xylene solubles of the polypropylene portion [ η] EP: Intrinsic viscosity of ethylene-propylene random copolymer part C2inEP: Weight% of ethylene in ethylene-propylene random copolymer part EP content: Weight% of ethylene-propylene random copolymer part to total polymer A- 1: [η] P = 1.0 (dl / g), Q _P = 3.
5, CXS = 0.71 (wt%) [η] EP = 6.0 (dl / g), C2inEP = 25 (wt%), EP
Content = 13 (wt%) MI at 230 ° C and 2.16 kg load is 30 (g)
/ 10 min) block polypropylene A-2: [η] P = 1.8 (dl / g), Q _P = 4.
0, CXS = 0.71 (wt%) [η] EP = 3.0 (dl / g), C2inEP = 42 (wt%), EP
Content = 18 (wt%) MI of 30 (g / 230 ° C, 2.16 kg load)
Block polypropylene A-3: [η] P = 1.1 (dl / g), Q _P = 3.
8, CXS = 0.77 (wt%) [η] EP = 4.0 (dl / g), C2inEP = 40 (wt%), EP
Content = 17 (wt%) MI at 230 ° C and 2.16 kg load is 65 (g /
A 10min) block polypropylene A-4: [η] P = 1.4 (dl / g) , Q P = 5.
5. CXS = 3.0 (wt%) [η] EP = 2.7 (dl / g), C2inEP = 38 (wt%), EP
Content = 15 (wt%) MI at 230 ° C and 2.16kg load is 65 (g /
10 min) block polypropylene

(B) Ethylene-α-olefin copolymer rubber B-1: Mooney viscosity (ML _{1 + 4} 121 ° C.) is 2
5. Ethylene propylene rubber having a propylene content of 22% B-2: MI at 230 ° C. under a load of 2.16 kg of 17 (g / 10 mi)
n) Ethylene butene rubber having a butene content of 17% B-3: Mooney viscosity (ML _{1 + 4} 121 ° C.) of 3
3. Ethylene propylene rubber having a propylene content of 27% B-4: EPDM-1 (ethylene-propylene-ethylidene norbornene (ENB) copolymer rubber, iodine value = 10, propylene content = 30
wt%, ML _{1 + 4} 100 ° C. = 143) in a 5% by weight hexane solution per 100 parts by weight of EPDM-1 mineral oil based softener (“Diana Process Oil PW manufactured by Idemitsu Kosan Co., Ltd.)
-380 "), and then the solvent was removed by steam stripping to obtain an oil-extended EPDM-1 (M
L _{1 + 4} 100 ° C = 78)

In each of the following Examples and Comparative Examples, the additive formulation is constant as described below. Antioxidant: Sumilizer BP-101 (manufactured by Sumitomo Chemical Co., Ltd.) 0.2% Light stabilizer: Sanol LS770 (manufactured by Ciba Geigy) 0.05% based on 100 parts by weight of resin part (including oil): Sumisorb 300 (manufactured by Sumitomo Chemical Co., Ltd.) 0.1% Lubricant: oleic acid amide 0.1% About the obtained composition, cylinder temperature 220 ° C,
A test piece was prepared by injection molding at a mold temperature of 50 ° C., and the physical properties were evaluated.

The properties described in the examples and comparative examples were measured by the following methods. (1) GPC measurement conditions The measurement was carried out by gel permeation chromatography (GPC) under the following conditions. The calibration curve was prepared using standard polystyrene. Model: 150CV type manufactured by Millipore Waters Co., Ltd. Column: Shodex M / S 80 Measurement temperature: 145 ° C, solvent ortho-dichlorobenzene Sample concentration: 5 mg / 8 ml Note that NBS (National Bureau of Standard) was used under these conditions.
s) Standard Reference Material 706 (Mw / M
As a result, the molecular weight distribution (Q value) Mw / Mn = 2.1 was obtained. (2) MI: JIS K7112 (3) Hardness: ASTM D2240 (4) Bending test: JIS K7203 (5) Tensile test: A test was performed using a JIS K6301 No. 3 dumbbell at a pulling speed of 200 (mm / min). . (6) Izod impact test: ASTM D256 The test piece was 12 mm thick, with a notch.

Example 1 Block PP of A-1 40 wt%, EPR60 of B-1
The wt% and additives were kneaded with a twin-screw extruder set at a cylinder temperature of 200 ° C. to produce pellets. The obtained composition was subjected to injection molding to prepare test pieces, and the physical properties were evaluated.

Examples 2 to 5 and Comparative Examples 1 to 4 The compositions shown in Tables 1 and 2 were carried out in the same manner as in Example 1.

Example 6 45% by weight of block PP of A-3 and EPR19 of B-3
wt%, 36 wt% of EPDM of B-4 and additives were kneaded at 170 to 200 ° C. with a Banbury mixer, and then pelletized by using an extruder. The obtained composition was subjected to injection molding to prepare test pieces, and the physical properties were evaluated.

The following can be seen from the results. Examples 1 and 2 satisfying the conditions of the present invention are excellent in fluidity and low-temperature impact resistance as compared with Comparative Examples 1 and 2 in which the crystalline polypropylene (A) does not satisfy the conditions of the present invention, Similarly, Examples 3 and 4 are excellent in tensile properties as compared with Comparative Examples 3 and 4, respectively.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

As described above, according to the present invention, the balance between rigidity and low-temperature impact resistance, tensile properties, melt fluidity,
It was possible to provide a thermoplastic elastomer composition having excellent molded article appearance and the like.

Claims (3)

(57) [Claims] (A) crystalline polypropylene: 48 to 10% by weight and (B) ethylene-α-olefin-based copolymer rubber: 52 to 90% by weight ((A) + (B) = 100% by weight) The crystalline polypropylene of (A) comprises a propylene homopolymer or a crystalline polypropylene portion obtained by copolymerizing propylene and ethylene or an α-olefin having 4 or more carbon atoms of 1 mol% or less, and ethylene and propylene. Of ethylene / propylene in a weight ratio of 20/80 to 60 /
(1) the intrinsic viscosity [η] p of the crystalline polypropylene portion is 0.8 to 2.0 dl / g, and the ratio Q value of the molecular weight measured by GPC ( (Weight average molecular weight Mw / number average molecular weight MN) is 3.
0-5.0, 1.5% by weight or less of xylene solubles at 20 ° C., (2) intrinsic viscosity [η] EP of the ethylene-propylene random copolymer portion is 3.5-8.5, and (3) A thermoplastic elastomer composition characterized in that the ethylene-propylene random copolymer portion is an ethylene-propylene block copolymer having 5 to 20% by weight of the whole polymer. 2. The thermoplastic elastomer composition according to claim 1, wherein (B) is an ethylene-α-olefin copolymer rubber or an ethylene-α-olefin-nonconjugated diene copolymer rubber. 3. The thermoplastic elastomer composition according to claim 2, wherein (B) is an ethylene-propylene copolymer rubber and / or an ethylene butene copolymer rubber.