JPH073085A - Polyolefin composition - Google Patents

Abstract

PURPOSE:To obtain a polyolefin composition containing a propylene-ethylene block copolymer as a main component and having small shrinkage factor. CONSTITUTION:The composition contains (a) 40-80wt.% of a propylene-ethylene block copolymer having an ethylene content of 1-30wt.% and (b) 20-60wt.% of a polyethylene having a density of >=0.940g/cm<3>. It satisfies the formula (log(R100/R500)+0.80)/log(MFRPP)<0.40 wherein MFRPP is melt flow rate of (a), R100 is the ratio of the melt viscosity of (b) [eta100(b)] to that of (a) [eta100(a)] measured by a rotational viscometer at a frequency of 100rad/sec at 210 deg.C and R500 is the ratio of the melt viscosity of (b) [eta500(b)]to that of (a) [eta500(b)] to that of (a) [eta500(a)] measured by a rotational viscometer at a rotational speed of 500rad/sec at 210 deg.C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyolefin composition containing a propylene-ethylene block copolymer as a main component, and more particularly to a polyolefin composition having a small shrinkage ratio.

[0002]

BACKGROUND OF THE INVENTION Propylene homopolymers and copolymers are lightweight and have excellent mechanical strength and the like, and are therefore widely used in various fields. In particular, the propylene-ethylene block copolymer has high impact strength and rigidity, and is therefore suitable for injection molded products and the like.

However, this propylene-ethylene block copolymer has a problem that it has a large shrinkage ratio and is not necessarily suitable for a field requiring dimensional accuracy. As measures against this, glass fibers, inorganic fillers, and the like have been added to propylene-ethylene block copolymers.

However, when glass fibers, inorganic fillers, etc. are added, since they are dispersed uniformly in the resin component,
There is a problem that it takes time and labor such as addition of various dispersants and high kneading. Further, if the shrinkage ratio can be reduced without adding glass fiber or an inorganic filler, it can contribute to weight reduction of the product and prevention of abrasion of the screw of the molding machine or the extruder.

Therefore, an object of the present invention is to provide a polyolefin composition containing a propylene-ethylene block copolymer as a main component and having a small shrinkage ratio.

[0006]

As a result of earnest research in view of the above objects, the present inventors have found that the propylene-ethylene block copolymer and the melting of the propylene-ethylene block copolymer in the molding shear rate range. If blended with polyethylene whose viscosity ratio satisfies a predetermined relational expression,
The present inventors have found that polyethylene extends as a layered foil on the surface of a molded product and exerts a function of preventing shrinkage, and conceived the present invention.

That is, the polyolefin composition of the present invention comprises (a) 40 to 80% by weight of a propylene-ethylene block copolymer having an ethylene content of 1 to 30% by weight, and (b) 0.
20 to 60% by weight of polyethylene having a density of 940 g / cm ³ or more, the melt flow rate MFR _{PP of} (a) above, and a frequency of 100 rad /
Melt viscosity (η) of the above (a) measured at sec and 210 ℃
₁₀₀ wherein for _(a)] and (b) the melt viscosity [eta _{100 (b)} the ratio of the] (R _100), Frequency 500 rad / sec and a melt viscosity of said measured at 210 ° C. (a) [eta _{500 (a )} ] To the ratio (R ₅₀₀ ) of the melt viscosity [η _{500 (b)} ] of _{(b) to the following} formula: (log (R ₁₀₀ / R ₅₀₀ ) +0.80) / log (MFR
_PP ) <0.40.

The present invention is described in detail below. The polyolefin composition of the present invention comprises a propylene-ethylene block copolymer and polyethylene.

[1] Composition component (a) Propylene-ethylene block copolymer (a) The propylene-ethylene block copolymer used in the present invention has an ethylene content of 1 to 30% by weight.

When the ethylene content of the propylene-ethylene block copolymer is less than 1% by weight, the physical properties such as impact strength deteriorate, while when it exceeds 30% by weight, the physical properties such as rigidity deteriorate. The preferred ethylene content is 2 to 15% by weight.

The melt flow rate (MFR _PP , 230 ° C., 2.16 kg load) of the propylene-ethylene block copolymer is preferably 5 to 100 g / 10 minutes, and particularly preferably 20 to 80 g / 10 minutes. If the MFR _PP value is less than 5 g / 10 min, the moldability of the resulting composition, particularly the injection moldability, will decrease, and
If it exceeds g / 10 minutes, the mechanical strength decreases, which is not preferable.

The propylene-ethylene block copolymer has a melt viscosity [η _{100 (a)} ] (measured by a rotational viscometer _{) at} a frequency of 100 rad / sec and a temperature of 210 ° C. of from 800 to 50.
00, particularly preferably 1000-3000, frequency 500 ra
The melt viscosity [η _{500 (a)} ] (measured by a rotational viscometer _{) at} d / sec and 210 ° C. is preferably 500 to 1100, particularly preferably 600 to 1000.

Examples of the propylene-ethylene block copolymer as described above include: (1) First, only propylene is polymerized to produce a propylene polymerized portion, and then ethylene is supplied to cause copolymerization. A product obtained by repeating once or twice or more, and (2) a propylene-ethylene block copolymer synthesized by multistage polymerization can be used.

The propylene-ethylene block copolymer synthesized by multistage polymerization comprises a substantially crystalline propylene polymerized portion and a propylene-ethylene copolymerized portion.
It is composed of a crystalline ethylene polymerized portion, and each portion may be present as a single polymer or may be in a state where they are bonded.

Examples of the crystalline propylene polymerized portion include a homopolymer of propylene or a propylene copolymer containing a small amount (about 3 mol% or less) of a comomer component. As the comonomer component, butene-1, octene-
Other α-olefins and diene-based monomers such as 1 may be mentioned.

The propylene-ethylene copolymerized portion is a low crystalline portion having an ethylene content of 30 to 60% by weight. Ethylene content is less than 30% by weight or
If it exceeds 60% by weight, ductility is insufficient. Further, the propylene-ethylene copolymer part may also contain a small amount (about 3 mol% or less) of a comonomer component.

Examples of the crystalline ethylene polymerized portion include an ethylene homopolymer or an ethylene copolymer containing a small amount (about 3 mol% or less) of a comonomer component.

The content of the crystalline propylene-polymerized portion, the propylene-ethylene-copolymerized portion, and the ethylene-polymerized portion of the whole multistage polymerized propylene-ethylene block copolymer containing each of the above-mentioned portions is ++. If the total is 100% by weight, the crystalline propylene polymerized portion is 6
0-96% by weight, 1 part of propylene-ethylene copolymerization
-20% by weight and crystalline ethylene polymerized portion is preferably 1-20% by weight.

The multi-stage polymerized propylene-ethylene block copolymer as described above is produced by first polymerizing propylene in the presence of a Ziegler catalyst or the like to form a crystalline propylene homopolymer portion, and then ethylene + propylene in the next step. To produce a propylene-ethylene copolymerization moiety (a trace amount of an ethylene homopolymer moiety is also generated in this step), and in some cases, by further polymerizing ethylene, a crystalline ethylene homopolymer moiety is generated. Can be synthesized.

Of these propylene-ethylene block copolymers, the multistage polymerized propylene-ethylene block copolymer (2) is particularly preferable.

(B) Polyethylene The polyethylene used in the present invention is 0.940 g / cm ³ or more,
It preferably has a density of 0.950 to 0.980 g / cm ³ . When the density is 0.940 g / cm ³ or less, the rigidity of the composition decreases.

The polyethylene is 5-80 g / 10.
Min, especially 10-40g / 10min melt index (MI, 19
It preferably has a temperature of 0 ° C. and a load of 2.16 kg. If the melt index value is less than 5 g / 10 minutes, the fluidity of the resulting composition will be poor, while if it exceeds 80 g / 10 minutes, the mechanical strength of the resulting composition will be reduced.

[2] Blending Ratio The blending ratio of the above-mentioned (a) propylene-ethylene block copolymer and (b) polyethylene is 40 to 80% by weight of (a) propylene-ethylene block copolymer, It is preferably 60 to 80% by weight, the total of (b) is 20 to 60% by weight,
It is preferably 20 to 40% by weight. If the propylene-ethylene block copolymer is less than 40% by weight (polyethylene
When it exceeds 60% by weight), the rigidity and moldability are deteriorated, while when the propylene-ethylene block copolymer exceeds 80% by weight (when polyethylene is less than 20% by weight), a composition having a sufficiently low shrinkage ratio is obtained. Hard to get.

[3] Melt Viscosity Ratio In the present invention, the melt flow rate (MFR _PP , 230 ° C.) of the (a) propylene-ethylene block copolymer described above is used.
2.16 kg load, unit g / 10 minutes) and the melt viscosity [η _{100 (a)} ] of the above ( _a) measured by a rotational viscometer at a frequency of 100 rad / sec and 210 ℃ [b]. η _{100 (b)} ] ratio ([η _{100 (b)} ] / [η _{100 (a)} ]: R
₁₀₀ ) and the above measured at a frequency of 500 rad / sec and 210 ° C
The ratio of the melt viscosity [eta _{500 (b)]} of the relative melt viscosity of (a) [eta _{50 0 (a)]} (b) ([eta _{500 (b)]} / [eta _{500 (a)]:} R
_500), but the following formula (1): (log (R 100 / R 500) +0.80) / log (MFR PP) < it should satisfy 0.40 (1).

In the above equation, when the left side is 0.40 or more, the melt viscosity of polyethylene at the molding temperature is high,
Polyethylene does not extend as a layered foil on the surface of the molded product, making it difficult to sufficiently reduce the shrinkage of the composition.

Particularly, it is preferable that the following formula (2) (log (R ₁₀₀ / R ₅₀₀ ) +0.80) / log (MFR _PP ) ≦ 0.35 (2) is satisfied.

[4] Other Components The polyolefin composition of the present invention has other additives such as fillers, heat stabilizers, antioxidants, light stabilizers, flame retardants, and plasticizers for the purpose of modification. Agents, antistatic agents, release agents and the like can be added as appropriate.

[5] Production Method The polyolefin composition of the present invention can be obtained by mixing the above-mentioned components by various blending methods. Examples of the blending method include blending by multistage polymerization, post-reactor blending, powder blending, pellet blending, dry blending, and the like.
The above-mentioned (a) component and (b) component are polymerized respectively, and these powders are mixed in-line at a predetermined mixing ratio,
A so-called post-reactor is used, in which the above-mentioned various additives are blended, if necessary, and then melt-kneaded at 170 to 260 ° C, preferably 180 to 230 ° C, and pelletized using an extruder, particularly preferably a twin-screw extruder. It is preferably produced by blending. Further, in some cases, the components (a) and (b) may be mixed by a reactor blend.

[0029]

The polyolefin composition of the present invention is formed by blending a propylene-ethylene block copolymer and polyethylene having a predetermined melt viscosity in the molding shear rate range at a specific ratio, so that the mechanical strength is maintained. The shrinkage rate has been reduced.

Although the reason why such an effect is obtained is not always clear, polyethylene is obtained by blending propylene-ethylene block copolymer with polyethylene whose melt viscosity at the molding temperature satisfies a predetermined relational expression. Is present as a layered foil in the sea structure of the propylene-ethylene block copolymer, and exerts an action of preventing shrinkage of the entire composition.

[0031]

The present invention will be described in more detail by the following examples. The following resins and talc were used as raw materials.

[1] Propylene-ethylene block copolymer BPP-1: [BJ540A Tonen Kagaku KK, ethylene content 7.5% by weight, MFR _PP (230 ° C., 2.16 kg load)
40 g / 10 min, log (MFR _PP ) = 1.602, melt viscosity measured by rotational viscometer: [η _{100 (a)} ] (at ₁₀₀ rad / sec and 210 ° C.) = 2000, [η _{500 (a)} ] ( ₅₀₀ rad / sec
And 210 ° C.) = 900, multistage polymerized product) BPP-2: [BJ510 Tonen Kagaku KK, ethylene content 7.5% by weight, MFR _PP (230 ° C., 2.16 kg load) 1
0 g / 10 min, log (MFR _PP ) = 1, melt viscosity measured by rotational viscometer: η _{100 (a)} (at ₁₀₀ rad / sec and 210 ° C.) = 4100, η _{500 (a)} ( ₅₀₀ rad / sec and 210) (In ° C) = 980] [2] Polyethylene-PE-1: [J6331 Tonen Chemical Co., Ltd., density 0.
955 g / cm ³ , melt index (190 ℃, 2.16 kg load) 30 g / 10 min, melt viscosity measured by rotational viscometer:
[Η _{100 (b)} ] (at ₁₀₀ rad / sec and 210 ℃) = 160
0, [η _{500 (b)} ] (at ₅₀₀ rad / sec and 210 ℃) = 9
00] PE-2: [J6211 Tonen Chemical Co., Ltd., density 0.
957 g / cm ³ , melt index (190 ℃, 2.16 kg load) 12 g / 10 min, melt viscosity measured by rotational viscometer:
[Η _{100 (b)} ] (at ₁₀₀ rad / sec and 210 ° C) = 280
0, [η _{500 (b)} ] (at ₅₀₀ rad / sec and 210 ℃) = 1
800] PE-3: [J6170 Tonen Chemical Co., Ltd., density 0.
961 g / cm ³ , melt index (190 ° C, 2.16 kg load) 7.5 g / 10 minutes, melt viscosity measured by rotational viscometer: [η _{100 (b)} ] (at ₁₀₀ rad / sec and 210 ° C) =
3900, [η _{500 (b)} ] (at ₅₀₀ rad / sec and 210 ° C)
= 2700] ・ PE-4: [Y6111 Tonen Chemical Co., Ltd., density 0.
953 g / cm ³ , melt index (190 ℃, 2.16 kg load) 1.2 g / 10 min, melt viscosity measured by rotational viscometer: [η _{100 (b)} ] (at ₁₀₀ rad / sec and 210 ℃) =
10200, [η _{500 (b)} ] (at 500rad / sec and 210 ° C) = 6000] [3] Filler / talc: [Micron White 5000A Hayashi Kasei Co., Ltd.]
Made] -Glass fiber: [TP-527 Central Glass Co., Ltd.
Made)

Examples 1-5 and Comparative Examples 1-5 Propylene-ethylene block copolymers (BPP-1, BPP-2) and polyethylene (PE-1 to PE- in the proportions shown in Table 1).
4) and were dry-blended with a super mixer, then charged into a twin-screw extruder (65 mmφ) and kneaded at 200 ° C. and a screw rotation speed of 180 rpm to obtain pellets of the composition.

The above-mentioned propylene-ethylene block copolymer (BPP-1, BPP-2) and polyethylene (PE-1 to PE-4)
The melt viscosity ratio R ₁₀₀ ([η _{100 (b)} ] / [η
_{100 (a)])} and, R ₅₀₀ ([eta _{500 (b)]} / [eta _{500 (a)])}
From the following equation: (log (R ₁₀₀ / R ₅₀₀ ) +0.80) / log (MFR _PP ) ... (I) (wherein MFR _PP is the value of the melt flow rate of BPP (unit: g / 10 Value) was calculated. The results are shown in Table 1 together with the composition.

The pellets thus obtained were used to measure the melt flow rate (MFR), and an injection molding machine was used for injection temperature 210 ° C., injection pressure 300 kg / cm ² and mold temperature 60 ° C. for the test described later. The test piece of was produced.

For the test piece thus obtained,
The shrinkage rate, specific gravity, and flexural modulus were measured. The results are also shown in Table 1.

Table 1 Composition (parts by weight) Example 1 Example 2 Example 3 Example 4 BPP-1 60-40 60 BPP-2-80-80 PE-1 40-60 PE-2-20 - - PE-3 - - - 40 value 0.36 0.19 0.36 0.38 product contraction rate of the melt viscosity ratio _{R 100 0.80 0.68 0.80 1.95 R 500} 1.00 1.84 1.00 3.00 formula ^{(I) (1) MD 0.98} 0.95 0.93 1.12 TD 1.17 1.02 1.05 1.25 Specific gravity ⁽²⁾ 0.91 0.91 0.91 0.91 Flexural modulus ⁽³⁾ 12400 13700 12300 13100

Table 1 (continued) Composition (parts by weight) Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 BPP-1 100 90 80-80-30 BPP-2--85-PE-2 − − − 15 − PE − 4 − − − − 70 Talc − 10 − − − Glass fiber − − 20 − − Melt viscosity ratio R ₁₀₀ − − − 0.68 5.10 R ₅₀₀ − − − 1.84 6.67 Value of formula (I) − − − 0.19 0.42 Physical Property Shrinkage ⁽¹⁾ MD 1.52 1.23 1.21 1.25 1.52 TD 1.63 1.35 1.38 1.30 1.60 Specific gravity ⁽²⁾ 0.91 1.08 1.12 0.91 0.91 Flexural modulus ⁽³⁾ 14500 21800 32200 13800 9800

(1) Shrinkage rate: injection molding (resin temperature 250 ° C.,
At holding pressure 200 ~400 kg / cm ^2), to produce a 153 × 153 × 2 mm molded article, after a two-day aging, and the dimensions were measured, the injection molded article injection direction (TD), the width direction (MD)
The shrinkage rate was measured (unit:%). (2) Specific gravity: Measured by JIS K7112 (unit: g / cm ³ ) (3) Flexural modulus: Measured by JIS K7203 (Unit: kg
f / cm ² ).

As is clear from Table 1, Examples 1-5
The injection-molded product of the polyolefin composition of No. 1 has a shrinkage ratio of 1.3% or less in both MD and TD directions, has a lower value than Comparative Examples 2 and 3 in which talc, glass fiber, etc. are added, and has a specific gravity. Significantly smaller.

[0041]

As described above in detail, in the present invention, the ratio of the melt viscosity in the molding shear rate range to the propylene-ethylene block copolymer and the propylene-ethylene block copolymer is predetermined. Since it is made by blending polyethylene with the relational expression at a specific ratio,
The shrinkage is reduced while maintaining the mechanical strength.

Such a polyolefin composition of the present invention is suitable for injection molded articles such as automobile interior and exterior products, home electric appliances, medical equipment, various miscellaneous goods, stationery and industrial products.

Claims (1)

[Claims] 1. (a) 40 to 80% by weight of a propylene-ethylene block copolymer having an ethylene content of 1 to 30% by weight.
And (b) polyethylene having a density of 0.940 g / cm ³ or more
A polyolefin composition containing 20 to 60% by weight, wherein the melt flow rate MFR _{PP of} (a) above and the melting of (a) measured at a frequency of 100 rad / sec and 210 ° C. by a rotational viscometer. the ratio of the melt viscosity [eta _{100 (b)]} of the relative viscosity [eta _{100 (a)]} (b) and (R _100), frequency 500 rad / s
Melt viscosity of _(a) (η _{500 (a)} ] measured at ec and 210 ° C against melt viscosity of _(b) [η _{500 (b)} ]
The ratio (R ₅₀₀ ) is expressed by the following formula: (log (R ₁₀₀ / R ₅₀₀ ) +0.80) / log (MFR
_PP ) <0.40 is satisfied, The polyolefin composition characterized by the above-mentioned.