JPH0678406B2 - Propylene / ethylene copolymer for injection molding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a propylene block copolymer for injection molding, which is excellent in the balance of transparency, rigidity, impact resistance and injection moldability.

Since polypropylene injection-molded products have excellent mechanical, optical or thermal properties, they are used in various parts and containers for industrial, household, food and medical use.

However, depending on the application, these performances are not sufficiently satisfied, and their use is limited.

In particular, it was difficult to satisfy all the performances of rigidity, impact resistance and transparency.

(Prior Art) Conventionally, in order to improve transparency and impact resistance, a method of randomly copolymerizing propylene with a small amount of α-olefins such as ethylene, butene-1, and hexene-1 has been adopted.
Rigidity is remarkably reduced, and when the amount of comonomer is increased to improve the degree of improvement in transparency and impact resistance, the amount of by-product of amorphous polymer, which has poor commercial value, is increased. There was a problem.

Further, the recent increase in molding speed is not always satisfied.

(Summary of the Invention) In view of such a situation, the inventors of the present invention have conducted extensive studies, and as a result, by using a propylene / ethylene copolymer having a specific structure, a balance between transparency, rigidity, and impact resistance, and injection molding. The present invention has been accomplished by finding that a polypropylene / ethylene copolymer having excellent properties can be obtained.

That is, the propylene / ethylene copolymer for injection molding of the present invention comprises (a) 5 to 95 parts by weight of a propylene homopolymer block (A) and a propylene / ethylene random copolymer block (B) having an ethylene content of 2 to 15% by weight. ) 95 to 5 parts by weight (however, the total of the block (A) and the block (B) is 100 parts by weight).

(B) Density of propylene single block (A) part is 0.90
80g / cm ³ or more.

(C) The final propylene / ethylene copolymer melt flow rate (230 ° C / load 2.16 kg) is 0.1 to 100 g / 10 minutes, and the final propylene-only block (A) melt flow rate (MFR _A ) and final Ratio of melt flow rate (MFR _{A + B} ) of propylene / ethylene copolymer, (MFR _A ) /
(MFR _{A + B} ) should be within the range of 10 to 0.1.

(Detailed Description of the Invention) Propylene / Ethylene Copolymer Composition The copolymer according to the present invention comprises 5 to 95 parts by weight of a propylene homopolymer block (A) and a propylene / ethylene random copolymer having an ethylene content of 2 to 15% by weight. Polymer block (B)
95 to 5 parts by weight.

Here, “parts by weight” of block (A) and block (B)
Is 100 parts by weight in total for both blocks.

The block (A) in the copolymer of the present invention is 5 to 95.
Parts by weight (preferably 10 to 90 parts by weight, more preferably 15 to 90 parts by weight)
Propylene / ethylene random copolymer block (B) having an ethylene content of 2 to 15 parts by weight (preferably 2.5 to 13 parts by weight, more preferably 3 to 10 parts by weight).
Is from 95 to 5 parts by weight (preferably 90 to 10 parts by weight, more preferably 85 to 20 parts by weight), and the ethylene content of the propylene / ethylene random copolymer block (B) is within the above range. As long as the content is within the range, it is possible to select a desired physical property balance without substantially decreasing the transparency, but in general, in order to obtain a physical property balance that emphasizes rigidity, the ethylene content should be adjusted. When the balance is low and the physical property balance is focused on impact resistance, set the ethylene content high.

Generally, when the ethylene content in the propylene / ethylene random copolymer block is constant, impact resistance can be significantly improved by increasing the amount of the propylene / ethylene random copolymer block relative to the propylene single block. However, the rigidity decreases in parallel with this. However, as will be described later, by setting the density of the propylene homopolymer block to 0.9080 g / cm ³ or more, it is possible to improve the impact resistance without substantially reducing the rigidity.

If the ratio of the propylene homoblock (A) and the propylene / ethylene random copolymer block (B) deviates from the above range, the balance between the rigidity and the impact resistance will be lost.

That is, if the proportion of the propylene single block (A) is less than the above range, the rigidity becomes weak, and if the proportion of the propylene / ethylene random copolymer block (B) is too small, the impact resistance becomes weak.

Molecular weight The molecular weight of the copolymer of the present invention has a melt flow rate of 0.1 to 1
It is necessary to be in a range corresponding to 00g / 10 minutes (230 ° C / 2.16kg load). Below this range, injection molding will be difficult and the rigidity of the resulting product will be weak. Also,
When the melt flow rate exceeds the above range, transparency is deteriorated and impact resistance is deteriorated.

In order to obtain a better balance between moldability, product rigidity, and impact resistance, it is preferable that the melt flow rate be in the range of 1 to 50 g / 10 minutes.

The ratio of the melt flow rate (MFR _A ) of the propylene homopolymer block (A) to the melt flow rate of the final propylene-ethylene copolymer (MFR _{A + B} ) MFR _A / MFR
_{A + B} needs to be in the range corresponding to 10 to 0.1.

If the range is deviated to either side, the quality balance of transparency, rigidity, impact strength of the product and the moldability (insufficient injection amount) during injection molding are impaired.

That is, when the content is below this range, the transparency and rigidity are deteriorated, and the moldability at the time of injection molding, especially the injection amount is decreased (poor fluidity of the material).

Also, when it exceeds the above range, the transparency, impact strength and the moldability are deteriorated.

In order to obtain better injection moldability and processing stability, it is preferable that MFR _A / MFR _{A + B} is in the range of 2 to 0.5.

Density of Propylene-Only Block (A) In order for the copolymer of the present invention to have an excellent balance of physical properties as described below, the density of the propylene-only block (A) must exceed a certain value. That is, the density of the block (A) was 0.9080 g /
cm ³ or more, preferably 0.9085 g / cm ³ or more, more preferably
It should be 0.9090 g / cm ³ or more. If this density is below this value, an excellent balance of physical properties cannot be expected.

Production of Copolymer The propylene / ethylene copolymer for injection molding of the present invention is
It is obtained by preliminarily homopolymerizing propylene to produce block (A), and then copolymerizing propylene / ethylene at random in the presence of this block (A) to produce block (B).

The copolymer of the present invention is usually produced by using a stereospecific polymerization catalyst mainly composed of a titanium component and an organoaluminum compound. Titanium components include α, β, γ
Alternatively, a titanium compound supported on a carrier such as δ type titanium trichloride or magnesium chloride is preferable.

As the titanium trichloride, titanium tetrachloride obtained by reducing titanium tetrachloride with metallic aluminum can be used. In the case of organoaluminum-reduced titanium trichloride, titanium trichloride obtained by extracting and removing aluminum chloride from a reduction product with a complexing agent is often used after activation treatment by a suitable method.

The propylene homoblock (A) of the copolymer of the present invention
Since a density of 0.9080 or more is required, it is preferable that the following various stereoregularity improvers be co-ground with titanium trichloride or added at the time of polymerization.

The stereoregularity improver used in the present invention includes aliphatic or aromatic carboxylic acid esters. Specific examples thereof include methyl methacrylate, ethyl acetate, butyl formate,
Amyl acetate, vinyl butyrate, vinyl acetate, ethyl benzoate, propyl benzoate, butyl benzoate, octyl benzoate, 2-ethylhexyl benzoate, methyl toluate, ethyl toluate, toluyl 2-ethylhexyl,
Methyl anisate, ethyl anisate, propyl anisate,
There are esters such as ethyl cinnamate, methyl naphthoate, ethyl naphthoate, propyl naphthoate, butyl naphthoate, 2-ethylhexyl naphthoate, and ethyl phenylacetate.

Further, in order to obtain a high yield of the block copolymer with respect to the catalyst, it is preferable to use titanium trichloride or titanium tetrachloride supported on magnesium chloride or the like. Also in this case, the density of the propylene-only block (A) needs to be 0.9080 g / cm ³ or more, and therefore the selection of the catalyst constitution for that purpose is important. For example, as a solid catalyst component, an aromatic polyvalent carboxylic acid halide such as phthaloyl chloride as an electron donor which is a constituent element thereof, JP-A-57-63310 and JP-A-58-830.
As described in each of JP-A No. 16 and 1,1-diphenyldimethoxymethane or 1,1-diphenyl as an electron donor to be used in combination with the phthalic acid ester compound and the solid catalyst and the organoaluminum compound. Specific sterically hindered ethers such as -1-methoxyethane, or alkoxysilanes described in the above publication are suitable for use as a catalyst for obtaining the copolymer of the present invention.

As the organoaluminum compound, it is preferable to use a compound represented by the general formula AlRaY _3- a. a is an arbitrary number satisfying 0 <a ≦ 3, Y is a halogen atom, and R is a hydrocarbon residue having about C _{1 to 18} , preferably an alkyl group or an annealing group. Specifically, triethyl aluminum, diethyl aluminum chloride and the like are preferable.

The ratio of the melt flow rate (MFR _A ) of the propylene homopolymerization block (AFR) of the propylene / ethylene copolymer for injection molding of the present invention to the melt flow rate (MFR _{A + B} ) of the final propylene / ethylene copolymer. MFR _A / MFR _{A + B} is 10
Since it is necessary to fall within the range corresponding to 0.1 to 0.1, a molecular weight control agent for controlling the melt flow rate during the polymerization of both propylene homopolymerization block (A) and ethylene / propylene random copolymer block (B). It is necessary to control hydrogen as a control feed.

The polymerization conditions can be any which is purposeful depending on the given catalyst and monomer composition, but for example the polymerization temperature is usually
30-100 ℃, preferably 40-85 ℃, most preferably 50-7
It is in the range of 5 ℃.

Example 1 A stainless steel reactor having an internal volume of 200 liters equipped with a stirring blade was sufficiently replaced with propylene gas, and then 80 liters of heptane was added as a polymerization solvent. Keep the temperature inside the chamber at 50 ° C and use diethyl aluminum chloride (DE
AC) 50 g and titanium trichloride ("T" manufactured by Marubeni Solvay Chemical Co., Ltd.
RL23 ") 15 g was added. Furthermore, 2.2 g of methyl benzoate was added as a stereoregularity improver.

Subsequently, propylene was fed at a rate of 5.83 kg / hour for 15 minutes. During this period, hydrogen was supplied so that the concentration in the vapor phase portion would be 9.0% by volume. Next, the internal temperature was raised to 65 ° C, the hydrogen concentration was adjusted to 12% by volume, and propylene was continuously supplied for 180 minutes at a rate of 5.83 kg / hour. During this period, the propylene supply amount was 17.5 kg. The density of the propylene homopolymer obtained at this point was 0.9092 g / cm ³ , and the melt flow rate was 12 g / min.

(The above is a propylene homopolymer block (A)) While maintaining the temperature inside the vessel, the hydrogen concentration and the propylene supply rate, ethylene is newly supplied at a rate of 0.320 kg / hour,
Propylene and ethylene were fed over 180 minutes each.

During this period, the supplied amounts of propylene and ethylene were 17.5 kg and 0.96 kg. At this point, the internal pressure was 3.6 kg / cm ² G, but at this point the supply of propylene and hydrogen was stopped, and ethylene was supplied at a rate of 0.190 kg / hr while maintaining the internal pressure at 2.0 kg for 40 minutes. The reaction was completed after lowering to kg / cm ² G.
During this period, the supply amount of ethylene was 0.13 kg.

(The above propylene / ethylene random copolymer block (B)) 1.8 was added to the obtained block copolymer with butanol, the catalyst was decomposed at 70 ° C. for 3 hours, and then the catalyst was removed by washing with water.

After further centrifugation and drying steps, product block copolymer 3
I got 3.0 kg. The amount of the amorphous copolymer solubilized in the polymerization solvent was 1.1 kg.

The melt flow rate of the resulting product block copolymer is
It was 10.5g / 10min.

The proportion of the propylene homopolymer block (A) and the propylene / ethylene random copolymer block (B) in the block copolymer was calculated by subtracting the amount of unreacted monomer and the amount of by-produced amorphous polymer from the total amount of monomer supplied. The rest
It was calculated by allocating it to the ratio of the amounts of the monomers supplied to produce each copolymer block. The ethylene content of the propylene / ethylene random copolymer block (B) is the ratio of both blocks calculated as described above,
It was calculated from the ethylene content in the product block copolymer.

The results are summarized in Table 1.

100 parts by weight of the block copolymer powder thus obtained, 0.15 parts by weight of 2,6 di-t-butyl-p-cresol as an antioxidant, 0.05 part by weight of calcium stearate as a neutralizing agent, and transparent core As an agent, 0.2 parts by weight of aluminum p-t-butylbenzoate was added, mixed and pelletized. Using this pellet, using an in-line type 8 oz injection molding machine, the flexural modulus of the shape defined by JIS under the temperature condition of 240 ° C, the Izod impact strength test piece and the transparency of 1 × 100 × 100 mm shape A sheet was created and used for measurement.

Regarding the moldability during injection molding, a sheet of 2 x 80 x 300 mm shape with a 1-point gate with a diameter of 1 mm, injection pressure of 60 kg / cm ² G,
Molded at a rotation speed of 100 rpm and a molding cycle of 45 seconds,
The injection amount at this time was measured. The results are shown in Table-1.

Example 2 Example 1 except that 1.9 g of butyl benzoate was added instead of methyl benzoate as a stereoregularity improver, which was added at the time of polymerization to change the density of propylene-only block (A). A block copolymer was produced by the same method.

In addition, an injection molded product was produced using the resulting block copolymer under the same conditions as in Example 1 and the physical properties and moldability were evaluated.

The results are as shown in Table 1.

Example 3 Preparation of Solid Catalyst Component 75 ml of purified heptane in a three-necked glass flask (with thermometer and stir bar) having an inner volume of 500 ml and purged with nitrogen gas, 75 ml of purified heptane
Titanium tetrabutoxide, 10 g of anhydrous magnesium chloride are added. Then, the temperature of the flask is raised to 90 ° C., and magnesium chloride is completely dissolved in 2 hours. Next, the flask is cooled to 40 ° C., and 15 ml of methylhydrogen polysiloxane is added to precipitate magnesium chloride and titanium tetrabutoxide complex. After washing this with purified heptane, 8.7 ml of silicon tetrachloride and 1.8 ml of phthaloyl chloride are added, and the mixture is kept at 50 ° C. for 2 hours. After this, wash with purified heptane and add 25 ml of titanium tetrachloride to add 25
Hold at ℃ for 2 hours. This was washed with purified heptane to obtain a solid catalyst component.

The titanium content in the solid catalyst component was 3.0% by weight.

Polymerization After adding 80 liters of heptane as a polymerization catalyst, keep the internal temperature at 60 ° C and use triethylaluminum as a catalyst.
A block copolymer was prepared in the same manner as in Example 1 except that 25 g, 1,1-diphenyldimethoxymethane (5.0 g), and the above solid catalyst component (2.5 g) were charged so that the hydrogen concentration was 2.5% by volume. Manufactured.

The results are summarized in Table 1.

An injection-molded article was produced using the resulting block copolymer under the same conditions as in Example 1, and its moldability and physical properties were evaluated.

The results are shown in Table 1.

Comparative Example 1 A block copolymer was produced in the same manner as in Example 1 except that the stereoregularity improver, which was added at the time of polymerization to change the density of the propylene homologous block (A), was not added.

An injection-molded article was produced using the resulting block copolymer under the same conditions as in Example 1, and its moldability and physical properties were evaluated.

The results are shown in Table 1.

Comparative Example 2 Propylene / Ethylene Random Copolymer Block (B)
At the time of production, the ethylene feed rate and feed rate were each 0.05
A block copolymer was produced under the same conditions as in Example 1 except that 6 kg / hr and 0.17 kg were used.

An injection-molded article was produced using the resulting block copolymer under the same conditions as in Example 1 and its moldability and physical properties were evaluated.

The results are shown in Table 1.

Comparative Example 3 Propylene / Ethylene Random Copolymer Block (B)
The ethylene feed rate and feed rate during production were 1.46 each.
A block copolymer was produced under the same conditions as in Example 1 except that kg / hour and 4.38 kg were used.

An injection-molded article was produced using the resulting block copolymer under the same conditions as in Example 1 and its moldability and physical properties were evaluated.

The results are shown in Table 1.

Comparative Example 4 Propylene was supplied over a period of 10 minutes with a propylene supply amount of 0.97 kg during the production of the block (A), and a propylene supply amount of 34.03 kg during the production of the propylene / ethylene random copolymer block (B). A block copolymer was produced under the same conditions as in Example 1 except that ethylene was supplied over a period of 350 minutes with the amount of ethylene being 1.87 kg.

An injection-molded article was produced using the resulting block copolymer under the same conditions as in Example 1 and its moldability and physical properties were evaluated.

The results are shown in Table 1.

Comparative Example 5 Propylene-only block (A) was supplied over a period of 340 minutes with a propylene supply amount of 33.0 kg, and a propylene-ethylene random copolymer block (B) was supplied with a propylene supply amount of 2.0 kg, Supplying ethylene for 0.11 kg over 20 minutes,
A block copolymer was produced in the same manner as in Example 1 except for the above.

An injection-molded article was produced using the resulting block copolymer under the same conditions as in Example 1 and its moldability and physical properties were evaluated.

The results are shown in Table 1.

Comparative Example 6 The hydrogen supply concentration during the production of propylene-only block (A) was set to 0% by volume, and the hydrogen supply concentration during the production of propylene / ethylene random copolymer block (B) was measured.
A block copolymer was produced in the same manner as in Example 1 except that the content was 38% by volume.

An injection-molded article was produced using the resulting block copolymer under the same conditions as in Example 1, and its moldability and physical properties were evaluated.

The results are shown in Table 1.

Comparative Example 7 The hydrogen supply concentration at the time of producing propylene single block (A) was
A block copolymer was produced in the same manner as in Example 1 except that the content of hydrogen was 35% by volume and the hydrogen supply concentration during production of the propylene / ethylene random copolymer block (B) was stopped.

An injection-molded article was produced using the obtained block copolymer in the same manner as in Example 1 and its moldability and physical properties were evaluated.

The results are shown in Table 1.

Experimental Method In the above Examples and Comparative Examples, unless otherwise indicated, the test methods used for evaluation of each product are as follows.

(1) Melt flow rate (MFR) (230 ° C., 2.16 kg) ASTM-D-1238 (condition L) g / 10 minutes (2) Density Determined according to JIS K7112 D method.

(3) Transparency (injection molding 1 mm sheet) Compliant with JIS K6714 (4) Bending elastic modulus Compliant with JIS K7203 (5) Izod impact strength Compliant with JIS K7110 (6) Moldability (injection amount) Moldability during injection molding , Especially as an evaluation method of flowability, 2
The weight ratio of the × 80 × 100 mm sheet at the time of the full shot was set to 100% as the injection amount, and the sheet weight ratio of the short shot molded under the above conditions was determined.

Claims (1)

[Claims] 1. A propylene / ethylene copolymer for injection molding, which is defined by the following (a) to (c), (b) 5 to 95 parts by weight of a propylene homopolymer block (A) and ethylene. Including 95 to 5 parts by weight of a propylene / ethylene random copolymer block (B) having a content of 2 to 15% by weight (however, the total of the block (A) and the block (B) is 100 parts by weight). ] (B) Propylene single block Density of part (A) is 0.9080
g / cm ³ or more, (c) the final propylene / ethylene copolymer melt flow rate (230 ° C / load 2.16 kg) is 0.1 to 100 g / 10 minutes, and the propylene single block (A) Ratio (MFR _A ) / (MF of melt flow rate (MFR _A ) and melt flow rate (MFR _{A + B} ) of final propylene-ethylene copolymer
R _{A + B} ) should fall within the range of 10 to 0.1.