JPH0827238A - Propylene based block copolymer composition - Google Patents

Abstract

PURPOSE:To obtain a propylene-based block copolymer composition suitable for producing a molding excellent in transparency, shrinkage factor and resistance to whitening on impact and bending. CONSTITUTION:This propylene-based block copolymer composition has a value of 0.2-2.0 of a [([eta]RC/[eta]PP)X(WPP/WRC)] and 0.3-4 ratio of the melt flow of a homopolymer component to the melt flow of a copolymer component and a value of <=6.5 of the ([eta]RC), when the intrinsic viscosity of the homopolymer component is ([eta]PP), the intrinsic viscosity of the copolymer component is (WPP) and weights of the homopolymer component and the weight of the copolymer component are each (WPP) and (WRC) The composition is excellent in whitening resistance to both of impact and bending and has 61-36% haze (1mm).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention has transparency, impact whitening property,
The present invention relates to a propylene-based block copolymer composition by vapor phase polymerization, which is excellent in molding shrinkage and bending whitening resistance.

[0002]

2. Description of the Related Art Polypropylene resin is relatively inexpensive and has been used in various fields due to its excellent properties. However, in general, propylene homopolymer has high rigidity, but on the other hand, it has a drawback that it has poor impact resistance, especially at low temperature. Many proposals have been made to improve the impact resistance of propylene homopolymer at low temperature. These proposals have generally produced propylene-based block copolymers that first produce a propylene homopolymer component and then introduce an ethylene-propylene random copolymer component.
Propylene-based block copolymers are widely used in various industrial fields such as automobiles and home appliances due to their excellent impact resistance at low temperatures. However, although conventional propylene block copolymers have excellent impact resistance, they have drawbacks such as being easily whitened when subjected to impact or bending, and having poor transparency and higher molding shrinkage compared to homopolymers. there were. As a method for improving the stress whitening defect of a propylene-based block copolymer, the intrinsic viscosity of the propylene homopolymer component and ethylene-
Although a proposal has been made of a polymer composition that defines only the ratio of the intrinsic viscosity of the propylene random copolymer component, the present inventors have conducted an impact whitening test and a bending whitening test of an injection molded article of the proposed polymer composition. As a result, the effect was insufficient in the impact whitening test, but the effect was insufficient, and particularly the effect was insufficient in the bending test. Further, an olefin elastomer obtained by blending a homopolymer or a propylene block copolymer with ethylene-propylene rubber (hereinafter referred to as EPR) or a linear low-density polyethylene has been proposed, but the price of the EPR is high. And the blending process are required, and thus there are problems in terms of economy and performance degradation due to poor dispersibility such as EPR in the final product.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As a result of intensive investigations aimed at solving the above-mentioned problems, the present inventors have found that after the homopolymer component is polymerized in the gas phase polymerization, the ethylene-propylene copolymer is continuously produced. In the propylene block copolymer composition obtained by polymerizing the components, the product of the polymerization production ratio of the homopolymer component and the ethylene-propylene copolymer component and the intrinsic viscosity ratio of each component is controlled within a certain range. In addition, by controlling the melt flow rate ratio of the homopolymer component and the ethylene-propylene copolymer component and the melt flow rate of the ethylene-propylene copolymer component, excellent transparency, molding shrinkage and impact whitening property as well as bending are obtained. The inventors have invented a propylene-based block copolymer having excellent whitening resistance. As is apparent from the above description, an object of the present invention is to provide a propylene-based block copolymer excellent in transparency, molding shrinkage, impact whitening property and bending whitening property.

[0004]

The propylene block copolymer of the present invention is (1) a block copolymer comprising a propylene homopolymer component and an ethylene-propylene copolymer component, wherein the homopolymer component has an intrinsic viscosity [ η] _PP and copolymer component intrinsic viscosity [η] _RC and its homopolymer component weight and copolymer component weight are W _PP and W, respectively.
_{When RC} , the product of the ratio of the intrinsic viscosity of the copolymer component and the homopolymer component and the weight ratio of the homopolymer component and the copolymer component (([η] _RC / [η] _PP ) × (W _PP / W _RC ))
Is in the range of 0.2 to 2.0, and the ratio of the melt flow rate of the homopolymer component to the melt flow rate of the copolymer component is in the range of 0.3 to 4, and the [η] _{RC of the} copolymer component is A propylene-based block copolymer composition characterized by being 6.5 or less. (2) The ethylene content of the copolymer component is 25 wt% to 6
The composition according to (1) above, which is in the range of 5 wt%. (3) The weight of the copolymer component is 30 wt% to 80 wt%
(1) The composition according to (1) or (2) above, which is in the range of (4) The composition according to (1), (2) or (3) above, wherein the propylene block copolymer is a gas phase polymer. . Is characterized in that.

The present invention is described in detail below. The propylene-based block copolymer composition of the present invention has the constitutional characteristics of the relational expression ([η] _RC / [η] _PP ) × (W _PP / W _RC ) of the content of the homopolymer component and the copolymer component and the intrinsic viscosity.
) Is in the range of 0.2 to 2.0, more preferably 0.3 to
The ratio of the melt flow rate of the homopolymer component to the melt flow rate of the copolymer component is in the range of 0.3 to 4, more preferably 0.3 to 3.5. The intrinsic viscosity [η] _{RC of the} component is 6.
It is 5 or less, more preferably 5.0 or less.
The propylene-based copolymer composition in the above range has excellent transparency, molding shrinkage, impact whitening property and bending whitening property. Outside the above range, for example, when the ratio of the intrinsic viscosity [η] _RC / [η] _PP of the homopolymer component and the copolymer component is outside the range of 0.2 to 2.0, the impact whitening property of the propylene block copolymer is obtained. However, it is inadequate, and especially the bending whitening property is inadequate.

Regarding the content of each of the above components, it is preferable that the copolymer component is in the range of 30 wt% to 80 wt%. More preferably, it is in the range of 35 wt% to 75 wt%. Outside the above range, the impact whitening property and the bending whitening property are insufficient. If it is 30 wt% or less, the impact resistance at low temperature is insufficient, and if it is 80 wt% or more, the fluidity of the powder produced by the polymerization is poor, and there is a problem in the production of the propylene-based block copolymer.

The ethylene content of the copolymer component is 25 wt.
% To 65 wt% is preferable. More preferably, it is in the range of 30 wt% to 65 wt%. When the ethylene content of the copolymer component is 25 wt% or less, transparency is good, but impact resistance is insufficient, and when it is 65 wt% or more, bending whitening resistance is insufficient.

In the propylene block copolymer of the present invention, a homopolymer component is first produced from crystalline polypropylene, and the intrinsic viscosity ([η] _PP ) and melt flow rate (MFR _PP ) of the polymer component are directly measured. It
The intrinsic viscosity ([η] _RC ) and melt flow rate (MFR _RC ) of the subsequently produced copolymer component, which is a propylene-ethylene random copolymer, cannot be measured directly.
Therefore, the intrinsic viscosity [η] _PP of the entire copolymer composition was measured, and from the intrinsic viscosity ([η] _WHOLE ) of the entire composition, the intrinsic viscosity [η] of the homopolymer component was calculated from the weight fraction of the homopolymer component. The intrinsic viscosity [η] _RC of the copolymer part is determined by subtracting the product of _PP and dividing this by the total composition, that is, the quotient of the copolymer components. That is, the following formula (1)

[0009]

(Equation 1)

The melt flow rate (MFR _RC ) of the copolymer component is determined by measuring the melt flow rate (MFR _WHOLE ) of the entire copolymer composition and the melt flow rate (MFR _PP ) of the homopolymer, and the following formula (2) More demanded.

[0011]

(Equation 2)

Where the fraction of the copolymer component (W _RC / 100)
Can be determined by a conventionally known infrared analysis method or the like.

The propylene block copolymer of the present invention may be obtained by any method. For example, it may be a blend obtained by adding EPR having an intrinsic viscosity ratio defined in the present invention to a homopolymer. Further, a blended product in which an ethylene-propylene random copolymer polymerized using a titanium-containing solid catalyst component is added to a homopolymer may be used. However, the method of adding EPR is disadvantageous from the economical aspect such as the high price of EPR and the need for a blending step. Further, the method of adding EPR has a problem that the quality cannot be stabilized due to poor dispersibility of EPR. A preferred method for obtaining the propylene block copolymer of the present invention is a method for producing by polymerization. The propylene block copolymer composition of the present invention obtained by the polymerization is E
It is desirable because it does not require PR and is inexpensive, and because it does not require a blending step, it can be obtained with stable quality. The production method by polymerization is illustrated below.

That is, the production amount of the olefin polymer of the pre-activated catalyst treated with a small amount of olefin in the presence of the titanium-containing solid catalyst component, the organoaluminum compound and, if necessary, the electron donor is the titanium-containing solid catalyst. Ingredient 1
Prepolymerization is carried out to give 0.1 to 100 grams per gram, and then propylene is subjected to main polymerization in the presence of the organoaluminum and, if necessary, an electron donor in the presence of the preactivation catalyst. Random copolymerization of propylene and ethylene is preferably carried out to obtain a propylene block copolymer powder. The organoaluminum and electron donor used in the preactivation and main polymerization can be the same or different types.

As the titanium-containing solid catalyst in the above-mentioned method for producing a propylene-based block copolymer, any known one can be used as long as the titanium compound is supported on the magnesium compound. For example, a titanium-containing solid catalyst component obtained by spraying a magnesium compound-alcohol solution, partially drying the solid component, and then treating the dried solid component with titanium halide and an electron-donating compound (JP-A-3-119003). Is mentioned. Further, a titanium-containing solid catalyst component obtained by dissolving a magnesium compound in tetrahydrofuran / alcohol / electron donor and treating TiCl ₄ alone or a magnesium carrier precipitated with a combination of electron donors with titanium halide and an electron-donating compound. (JP-A-4-103604).

The organoaluminum compound used in the polymerization of the present invention has a general formula of AlR ⁵ _M R ⁶ _N X _{3- (M + N).}
(In the formula, R ⁵ and R ⁶ represent a hydrocarbon group or an alcohol group, X represents a halogen, and M and N are 0 <M + N.
Represents an arbitrary number of ≦ 3. ) An organoaluminum compound represented by Specifically, trimethyl aluminum, triethyl aluminum, tri-n-propyl aluminum, tri-n-butyl aluminum,
Tri-i-butyl aluminum, dimethyl aluminum chloride, diethyl aluminum chloride, methyl aluminum sesquichloride, di-n-propyl aluminum monochloride, ethyl aluminum sesquichloride, ethyl aluminum dichloride, diethyl aluminum iodide, ethoxydiethylaluminum and the like. be able to. These organoaluminum compounds may be used alone or in admixture of two or more.

The organosilicon compound (C ') used in the polymerization according to the present invention has a general formula of R ² _X R ³ _Y Si.
(OR ⁴ ) _Z (wherein R ² _X and R ⁴ are hydrocarbon groups, R ³ is a hydrocarbon group or a hydrocarbon group containing a hetero atom,
X + Y + Z = 4, 0 ≦ X ≦ 2, 1 ≦ Y ≦ 3, 1 ≦ Z ≦ 3
) Can be used. Specifically, methyltrimethoxysilane, t-butyltrimethoxysilane, t-butyltriethoxysilane, phenyltriethoxysilane, methylethyldimethoxysilane, methylphenyldiethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diisopropyldimethoxy. Silane, diisobutyldimethoxysilane,
Examples thereof include di-t-butyldimethoxysilane, diphenyldimethoxysilane, trimethylmethoxysilane, and trimethylethoxysilane. Preferred are diisobutyldimethoxysilane, diisopropyldimethoxysilane, di-t-butyldimethoxysilane and diphenyldimethoxysilane. These organosilicon compounds may be used alone or in admixture of two or more.

Polymerization of propylene for producing the homopolymer component of the propylene block copolymer of the present invention may be carried out by any of the slurry polymerization method, the bulk polymerization method and the gas phase polymerization method using the above titanium-containing solid catalyst. However, the polymerization method of the copolymer component in the latter stage is preferably a gas phase polymerization method. In the slurry polymerization method or the bulk polymerization method, the copolymer component is dissolved in the solution, and it is difficult to continue stable operation, and the effects of the present invention are not sufficiently exhibited. The improving effect of the present invention is remarkable in the combination of the gas phase polymerization method and the gas phase polymerization method.

Although the polymerization conditions vary depending on the polymerization mode, in the case of the gas phase polymerization method, the titanium-containing catalyst component, the organoaluminum component and the organosilicon compound are polymerized at a temperature of 20 to 120 ° C., preferably while mixing and stirring a certain amount of powder. 40-1
Polymerization pressure atmospheric pressure to 100 kg / cm ² under the condition of 00 ° C
The homopolymer component is polymerized by feeding under the condition of G, preferably 5 to 50 kg / cm ² G. It is effective to control the molecular weight of the homopolymer component by adding a molecular weight regulator such as hydrogen during the polymerization. After polymerizing the homopolymer component, extract a part of the produced powder and measure the intrinsic viscosity, MF
It is used to measure R and determine the polymerization yield per unit weight of catalyst. Following the polymerization of the homopolymer component, the copolymer component is polymerized at a polymerization temperature of usually 20 to 120 ° C., preferably 40 to 100 ° C., and a polymerization pressure of atmospheric pressure to 100 kg.
/ Cm ² G, preferably 5 to 50 kg / cm ² G is polymerized to produce a propylene-based random copolymer. The ethylene content in the copolymer component of the present invention is controlled by controlling the gas molar ratio of ethylene monomer and propylene monomer in the comonomer gas.
The ethylene content in the copolymer component is 25 wt% to 65 w
It is adjusted to be t%. The weight of the copolymer component relative to the weight of the homopolymer component is 30 wt% to 30 wt% by controlling the polymerization time and using a polymerization activity regulator of a catalyst such as carbon monoxide or hydrogen sulfide.
It is adjusted to be 80 wt%. Furthermore, the molecular weight of the copolymer component depends on the intrinsic viscosity and MFR of the copolymer component.
Is adjusted by adding a molecular weight modifier such as hydrogen during the copolymerization so as to satisfy the requirements of the present invention. The polymerization may be carried out batchwise, anti-continuously or continuously, but industrially continuous polymerization is preferred.

After the completion of the main polymerization, the monomer can be removed from the polymerization system to obtain a particulate polymer. The obtained polymer is subjected to measurement of intrinsic viscosity, MFR, ethylene content, and polymerization yield per unit weight of catalyst.

The propylene block copolymer composition of the present invention can be molded into various shapes by various molding methods such as injection molding and extrusion molding. Upon molding, the propylene block copolymer composition of the present invention may optionally be added with known antioxidants, neutralizing agents, antistatic agents, weathering agents and the like used in conventional polyolefins. Good.

[0022]

EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

The measuring methods used in Examples and Comparative Examples will be described below.

The intrinsic viscosity described in the present invention means a viscosity at a predetermined temperature of a polymer and an infinite dilution of the polymer in a given solvent. In the case of the present invention,
Under a temperature condition of 135 ° C., tetralin (tetrachloronaphthalene) was used as a solvent, and the viscosity was measured using an automatic viscosity measuring device AVS2 type manufactured by Mitsui Toatsu. (Unit: dl / g)

The melt flow rate is JISK 6710.
According to the above method, it was measured at 230 ° C. and a load of 2160 g.
(Unit: g / 10 min.)

The Izod impact value complies with JIS K 6758. (Unit J / m)

Examples 1-8, Comparative Examples 1-8 4 kg of propylene block copolymer powder having each MFR and each ethylene composition shown in Table 1 below, 0.004 kg of phenolic heat stabilizer and 0 calcium stearate. Add 0.004 kg and mix with a high-speed stirring mixer (Note, Henschel mixer, trade name) for 10 minutes at room temperature,
The mixture was granulated using an extruder having a screw diameter of 40 mm. Then, the granulated product was made into a JIS type test piece at a molten resin temperature of 230 ° C. and a mold temperature of 50 ° C. by an injection molding machine, and the test piece was kept in a room at a humidity of 50% and a room temperature of 23 ° C. for 72 hours. It was adjusted. The impact whitening test was carried out by using a DuPont impact tester manufactured by Toyo Seiki Co., Ltd. on the adjusted 50 × 50 × 20 mm flat plate sample, the load was dropped under the following conditions, and the diameter of the white spot generated on the flat plate by the impact was measured. It was measured. The results are shown in Tables 1 to 6. Hammer tip 0.635 cm R Cradle inner diameter 3.81φ Load 500 g Load drop height 1 m Bending whitening test was adjusted under the above conditions 25 × 50
It is good to have a flat sample of × 1 mm that is folded in half from the center while supporting both ends with your fingers and that does not whiten at that time.
The whitened product was evaluated as defective. The results are shown in Tables 1 to 6
Shown in The haze is 25 × 50 adjusted under the above conditions.
A × 1 mm flat plate-shaped sample was measured according to ASTM D1003. The results are shown in Tables 1 to 6. The Izod impact value was measured according to JISK 6758. The results are shown in Tables 1 to 6. The molding shrinkage ratio was measured under the above conditions from the entire length of the mold of the molding machine (JIS K7
(113 tensile test piece) was obtained by the following formula (3) in which the ratio of the length obtained by subtracting the total length of the test piece from the length of the mold was multiplied by 100.
The results are shown in Tables 1 to 6.

[0028]

(Equation 3)

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

[Table 5]

[0034]

[Table 6]

EFFECT OF THE INVENTION By using the propylene block copolymer of the present invention, a molded article having excellent transparency, molding shrinkage and impact whitening property as well as bending whitening property can be obtained.

Claims (4)

[Claims] 1. In a block copolymer comprising a homopolymer component of propylene and a copolymer component of ethylene-propylene, an intrinsic viscosity [η] _PP of the homopolymer component, an intrinsic viscosity [η] _{RC of the} copolymer component and the homopolymer component thereof. And the weight of the copolymer component are W _PP respectively
And W _RC , the product of the ratio of the intrinsic viscosity of the copolymer component and the homopolymer component and the weight ratio of the homopolymer component and the copolymer component (([η] _RC / [η] _PP ) × (W _PP / W
_RC )) is in the range of 0.2 to 2.0, and the ratio of the melt flow rate of the homopolymer component to the melt flow rate of the copolymer component is in the range of 0.3 to 4, and [η of the copolymer component is ] _RC is 6.5 or less, The propylene block copolymer composition characterized by the above-mentioned. 2. The ethylene content of the copolymer component is 25 w.
The composition of claim 1 in the range of t% to 65 wt%. 3. The weight of the copolymer component is 30 wt% to 8%.
The composition according to claim 1, which is in the range of 0 wt%. 4. The composition according to claim 1, wherein the propylene block copolymer is a gas phase polymer.