NO148222B - SHOCK RESISTANT CHEMICAL MIXED POLYMER MIXTURE - Google Patents

Description

The present invention relates to an impact-resistant, chemically mixed propylene-polymer mixture of the kind specified in the preamble of the claim, suitable for the production of molded articles with improved whitening resistance and gloss.

A method is known from Norwegian patent application no. 77.0051

in the production of an impact-resistant, chemically mixed propylene-polymer mixture consisting of 55-95% by weight crystalline polypropylene containing 0-1 mol-% of another olefin and with an isotacticity index of at least 90, 1-10% by weight of a low-crystalline propylene/ethylene copolymer containing 60-85 mol-% propylene and 1-35 mol-% polypropylene or an ethylene/propylene copolymer, whose intrinsic viscosity over-

rises 2.6.

It has now been shown that if the limiting viscosity for the over-

for the latter polyethylene or ethylene/propylene copolymer has an intrinsic viscosity of at least 0.5 but less than 2.6

a further improvement in the impact resistance of the mixture is achieved. The invention is thus characterized by what is stated in

the claim's characterizing part.

The expression "chemically mixed polymer mixture" as used in the following means that the mixture is not a so-called polymer mixture obtained by first preparing different polymers or copolymers and then physically mixing them.

As mentioned above, the present impact-resistant polymer mixture can be produced by means of the method and the catalyst shown in Norwegian patent application no. 77.0051, which process in summary includes the following steps:

First step

propylene containing 0-1 mol% of another olefin, preferably only propylene, is polymerized in the presence of a catalyst composed of (a) a titanium catalyst supported on a support and wherein the catalyst contains at least magnesium, halogen and titanium on the surface of the support and (b ) an organoaluminum compound, to give crystalline polypropylene with an isotacticity index of at least 90, and which polymer constitutes 55-95% by weight, preferably 60-90% by weight, of the final polymer mixture.

Second step

Propylene and ethylene are polymerized in the presence of the reaction product from the first step and in the presence of the same catalyst at the same time that the propylene content in the gas phase in the polymerization zone is kept at 65 - 90 mol%, preferably 70 - 85 mol%, whereby a low-crystalline propylene/ethylene is formed -copolymer with a propylene content of 60-85 mol%, preferably 60-80 mol%, and which constitutes 1-10% by weight, preferably 2-8% by weight, of the final polymer mixture.

Third step

Ethylene, or both ethylene and propylene, are polymerized in the presence of the reaction product from the second step and in the presence of the same catalyst while keeping the propylene content in the gas phase in the polymerization zone at 0 to 7 mol%, preferably 0-4 mol%, whereby polyethylene is formed or an ethylene/propylene copolymer with a propylene content of up to 7 mol%, preferably up to 3 mol%, especially up to 2 mol%, and which has an intrinsic viscosity of at least 0.5 but less than 2.6, preferably at least 0.5, but not exceeding 2.3, and which polymer constitutes 1-35% by weight, preferably 5-30% by weight, of the final polymer mixture.

In these steps, the reactions are carried out so that the finished polymer mixture has an ethylene content of 3 - 40 mol%, preferably 10 - 35 mol%.

In the present description, the limiting viscosity (h) for polymers is calculated according to the present equation:

wherein the specific viscosity is measured in a decalin solution at 135°C using a "Fitz-Simons" viscometer.

The isotacticity index indicates the content in % by weight of the part of the polymer which is insoluble in boiling n-heptane and which is measured as described later.

Polymer components (A), (B) and (C) in the final chemically blended polymer blend

way can be fractionated by the following methods, and their proportion can be determined according to these methods. (1) The final mixture is dissolved in purified paraffin heated to 150°C, after which the solution is cooled to room temperature.

Thus, the mixture is separated into a fraction soluble in paraffin and a fraction insoluble therein. The fraction which is soluble in paraffin corresponds to component (B) in the final mixture according to the invention. (2) The paraffin-insoluble fraction obtained according to step (1) is further extracted with paraffin at 110°C, and the polymer fraction obtained as paraffin-insoluble at 110°C is polypropylene or propylene-rich propylene/ethylene polymer with high molecular weight. (3) The polymer obtained as the fraction soluble in paraffin at 110°C in step (2) is extracted hot with a mixture of paraffin and butyl carbinol to separate it into polyethylene or ethylene-rich ethylene/propylene copolymer as an insoluble fraction and low molecular weight polypropylene or propylene-rich propylene/ethylene copolymer as a soluble fraction. (4) The sum of the fraction insoluble in paraffin at 110°C obtained in step (2) and the fraction soluble in the mixed solvent in step (3) corresponds to component (A) in the final polymer mixture according to the invention.

The molar ratio between ethylene and propylene in each polymer can be determined in the usual way by a melting infrared spectrophotometric method or by NM R spectrophotometric method.

The following examples and comparative examples show the invention in more detail.

EXAMPLE 1

Preparation of a titanium catalyst component

1 kg of commercially available, anhydrous magnesium chloride, 0.23

1 ethylene benzoate and 0.15 1 methyl polysiloxane (viscosity 20 centi-poise at 25°C) were introduced under a nitrogen atmosphere into a stainless steel (SUS 32) vibrating ball mill containing 36 kg of stainless steel balls and pulverized at 7.8 g for 80 h. solid product of the pulverization treatment was suspended in 10 1 titanium tetrachloride and stirred at 80°C for 2 h. The solid product was collected by filtration and washed with purified hexane until no more titanium could be detected in the washing liquid. Drying of the obtained product gave a titanium-containing solid catalyst component containing 2.0 wt% titanium as atom, 65.0 wt% chlorine as atom and 8.0 wt% ethylene benzoate.

Preparation of a polymer mixture

The apparatus used consisted of three polymerization reactors A,

B and C, each with a volume of approx. 18 1. 18 1 and 25 1, and as connected in series and with a flushing tank (D) (volume 3 1) arranged between the polymerization reactors B and C. Reactor A was filled with 0.079 mmol/h, calculated as titanium atom, with the titanium catalyst component prepared as described above in the form of a hexane suspension, 3.95 mmol/h triethylaluminum in the form of a hexane solution and 1.49 mmol/h methyl-p-toluate in the form of a hexane solution.

The total supply of hexane was 2.10 l/h. Propylene was introduced continuously in an amount of 0.714 NM<*>Vh, and hydrogen was added in an amount of 1.8 Nl/h, so that the hydrogen concentration in the gas phase was 3.5 mol%. The propylene was thus polymerized at 60°C, and the pressure inside the reactor A was at this time 7.2 kg/cm .

In reactor A, polypropylene was formed with a melt index (measured at 190°C under a load of 216 kg) of 4.83 and an isotactic index of 92.5 (as a result of extraction with n-heptane) in an amount of 989 kg/h.

The suspension carried out from reactor A was introduced into reactor B, and 40.0 Nl/h propylene, 58.4 Nl/h ethylene and 3 l/h hexane were introduced into reactor B. The propylene and ethylene were thus copolymerized, and the pressure inside the reactor B was 2.0 kg/cm , and the propylene content in the monomer mixture in the gas phase was 84.3 mol%. A copolymer was obtained in reactor B in an amount of

292 g/h.

The suspension from reactor B was then taken to the flushing tank D to remove unreacted monomers and hydrogen and then introduced into reactor C. The ethylene was introduced into reactor C in an amount of 306.4 Nl/h and hydrogen was added so that the hydrogen content in the gas phase amounted to 45.8 mol% (nitrogen 7.5%). The ethylene was polymerized in reactor C under a polymerization pressure of 1.5 kg/cm 2 , and a polymer quantity of o 409 g/h was obtained.

Upon depressurization, unreacted monomer and hydrogen were removed from the effluent coming from reactor C. The resulting polymer was separated by filtration and dried to give a white powdery polymer mixture in an amount of 1.511 g/h. The polymer blend had a melt index of 3.02 and an intrinsic viscosity of 2.58. The ethylene content of the polymer mixture was 35.2 mol%.

The polymer formed in reactor C had an intrinsic viscosity of 1.80.

Part of the polymer mixture was dissolved in paraffin at 150°C

and cooled to room temperature. The precipitated polymer was separated and an amorphous polymer containing 67 mol% propylene was obtained from the paraffin solution. The proportion of amorphous polymer was 4.85% by weight calculated on the polymer mixture.

An antioxidant was added to the polymer mixture and test pieces were prepared from the mixture. The properties of the test pieces were measured and the results are shown in table 1.

The properties of the polymer mixture were determined using the following test methods:

Breaking strength at the yield point

According to ASTM D638-64T. The test pieces were produced according to new JIS K-7113. The stretching speed was 50 mm/min.

Extension in case of breakage

Same as yield strength.

Izod impact strength

Per ASTM D256-56."Notched". 23°C.

Shine

According to ASTM D523. Angle of incidence 20°.

a

Whitening

A weight (diameter=1.27 cm) of a specified shape was allowed to fall

a height of 50 cm on a specified test piece (120 x 130 x 2

mm) and the degree of whitening was determined visually. The results were graded according to the following scale:

A: No change took place

B: A pale white pattern with a diameter of approx. 1 cm

was formed

C: A white pattern with a diameter of 2 - 3 cm became

formed.

EXAMPLE 2

The apparatus used consisted of three polymerization reactors

A, B and C, each with a volume of 18 1 and connected in series and

while flushing tank D (with a volume of 3 1) arranged between the reactor

pure B and C.

0.079 mmol/h, calculated as titanium atoms, was added to reactor A,

of the titanium catalyst component prepared according to example 1 in the form of a hexane suspension, 4.23 mmol/h methyl p-toluate in the form of a hexane solution, and 11.85 mmol/h triethylaluminum in the form of a hexane solution, and where the total volume of added hexane was 2.1 l/h. Propylene and hydrogen were continuously introduced into reactor A in an amount of approx. 0.717 NM<3>/h and 3.2 Nl/h. The ion temperature of the polymerisation was 60°C, and the absolute pressure in the reaction

2

tore A was 7 kg/cm .

In reactor A, polypropylene was obtained with a melt index of

14.4 and an isotacticity index of 91.5 in an amount of 1,025 g/h.

The polymer suspension was produced by reactor A and fed into reactor B. Ethylene and propylene were introduced into reactor B in an amount of 35.2 Nl/h and 24.1 Nl/h, respectively, together with hexane in an amount of 3 l/h. Ethylene and propylene were thus copolymerized and the pressure in reactor B was 1.6 kg/cm 2 , and the propylene content in the monomer mixture in the gas phase was 85.7 mol%.

In reactor B, a polymer was formed in an amount of 198 g/h. The polymer obtained in reactor B had an intrinsic viscosity of 3.29.

Subsequently, the polymer suspension was carried out from reactor B and fed

to the flushing tank D, and after unreacted monomers and hydrogen had been removed, ethyl n was introduced in an amount of 197.6 Nl/h. The ethylene content of the monomer mixture in the gas phase was 97.8 mol%. Hydrogen was added so that it amounted to 22.6 mol% (nitrogen 42.2%)

calculated on the gas phase. The polymerization was carried out at a pressure of 2.5 kg/cm 2 . In reactor C, an ethylene polymer with an intrinsic viscosity of 1.43 was obtained in a quantity of 266 g/h.

The effluent from reactor C was treated in the same way as stated in example 1 and gave a polymer mixture with a melt index of 8.88 and an ethylene content of 26.9 mol% in an amount of 1.377 g/h.

The polymer mixture was extracted with paraffin in the same manner as stated in Example 1 and was found to contain 4.0% by weight of an amorphous ethylene/propylene copolymer with a propylene content of 68 mol%.

The properties of the obtained polymer mixture were determined in the same way as stated in example 1 and the results are shown in the following table.

EXAMPLE 3

An apparatus consisting of three polymerization reactors A, B and

C (with a volume of 18 1, 18 1 and 25 1, respectively) were connected in series and a flushing tank D (volume 3 1) was arranged between reactors B and C.

0.079 mmol/h, calculated as titanium atoms, was introduced to reactor A,

of the titanium catalyst component prepared according to example

column 1 in the form of a hexane suspension, 3.95 mmol/h triethylaluminum in the form of a hexane solution and 1.49 mmol/h methyl p-toluate in the form of a hexane solution, and the total amount of hexane added was 2.1 l/h .

Propylene and hydrogen were introduced continuously respectively in an amount of 0.713 NM 3/h and 1.3 Nl/h and propylene was polymerized, the pressure inside reactor A this time being kept at 7.0 kg/cm 2. It was obtained polypropylene with an isotacticity index of 93.0

in an amount of 986 g/h in reactor A.

The polymer suspension produced from reactor A was introduced into the reactor

B. Ethylene and propylene were introduced into reactor B in an amount of

58.4 Nl/h and 40.0 Nl/h, and ethylene and propylene were copolymerized. Propylene content of the monomer mixture in the gas phase in reactor B

was 84.3 mol%.

The polymer was formed in an amount of 278 g/h in reactor B.

The polymer suspension carried out from reactor B was introduced

to flushing tank D and unreacted propylene was removed, after which the suspension was introduced into reactor C. The ethylene was introduced in an amount of 13 2 Nl/h into reactor C and polymerized. The amount of hydrogen in reactor C was adjusted to 33.4 mol% (nitrogen 19.8%), calculated on the gas phase.

The ethylene polymer obtained in reactor C had a limiting viscosity

of 0.9.

The effluent from reactor C was treated in the same way as in example

pel 1 and a polymer mixture was obtained in an amount of

1,281 g/h. The mixture had an ethylene content of 21.0 mol%.

The resulting polymer mixture was extracted with paraffin on it

the same way as stated in Example 1. It was found that the polymer mixture contained 3.72% by weight of a non-crystalline copolymer of ethylene and propylene with a propylene content of 67 mol%.

The properties of the polymer mixture were determined in the same way as stated in example 1 and the results are shown in the following table 1.

Comparative example 1

This comparison shows that the limiting viscosity of the ethylene polymer in the polymer mixture markedly affects the gloss of the polymer mixture.

In example 1, the polymer suspension carried out from reactor B was taken to the flushing tank D where unreacted monomers were removed, and then taken to reactor C. The ethylene was introduced into reactor C in an amount of 216.0 Nl/h and polymerized at the same time as hydrogen was introduced so that the hydrogen concentration was 15.5 mol% (nitrogen 32.9%) in the gas phase.

After the polymerisation, the polymer suspension was treated in the same way as stated in example 1 and a polymer mixture with an ethylene content of 31.5 mol% and an intrinsic viscosity of 3.06 was obtained. Extraction of the mixture with paraffin showed that the polymer mixture contained 4.44% by weight of an amorphous copolymer with a propylene content of 67 mol%.

The ethylene polymer obtained in reactor C had an intrinsic viscosity of 4.48.

The obtained polymer mixture had a gloss of 17.5% and the degree of whitening was determined to be A.

Comparative example 2

An apparatus consisting of four polymerization reactors A, B, C and E was connected in series and a flushing tank D arranged between reactors C and E.

Polymerization was carried out under the following conditions.

To reactor A (19 1) was added 0.087 mmol/h, calculated as titanium atoms, of the titanium catalyst component prepared in example 1 in the form of a hexane suspension, 13.05 mmol/h triethylaluminum as a hexane solution and 5.22 mmol/h methyl p- toluate as a hexane solution, the total hexane feed rate being 2.1 l/h. Propylene and hydrogen were introduced in an amount of approx. 864 Nl/h and 2.6 Nl/h, and propylene was polymerized at 60°C and

2

at a pressure of 10.0 kg/cm in reactor A.

The polymer suspension produced from reactor A was introduced into reactor B (18 1 in volume), and propylene was further polymerized at a total pressure of 6.3 kg/cm 2. In reactors A and B, polypropylene was obtained with an isotacticity index of 90.5 formed in an amount of 1.2 59 g/h.

The polymer suspension from reactor B was fed to reactor C (volume 25 1).

Ethylene and propylene were introduced into reactor C in an amount of 107.2 Nl/h and 16.7 Nl/h and copolymerized. The propylene content in the monomer mixture in the gas phase in reactor C was 62.8 mol%.

In reactor C, a polymer was obtained in an amount of 268 g/h.

The polymer suspensions from reactor C were taken to the flushing tank D (volume 3 1) where part of unreacted monomers were removed and then taken to reactor E (volume 18 1), and ethylene was introduced in an amount of 105.6 Nl /h and polymerized.

When the concentrations of hydrogen, nitrogen, ethylene and propylene

in reactor E was adjusted to acc. 1.1 mol%, 46.9 mol%, 20.7 mol% and 2.6 mol%, calculated on the gas phase, a

ethylene/propylene copolymer with an intrinsic viscosity of 1.64 in reactor E.

The polymer suspensions produced from reactor E were treated in the same way as in example 1 and a polymer mixture was obtained with an ethylene content of 15.2 mol%, a melt index of 7.91 and an intrinsic viscosity of 2.41 in an amount of 1,450 g/h

The polymer mixture was extracted with paraffin in the same manner as stated in Example 1, and an amorphous copolymer of ethylene and propylene with a propylene content of 65 mol% was obtained. The proportion of the amorphous copolymer was 8.89% by weight, calculated on the polymer mixture.

The polymer blend had a gloss of 4 3.6, and the degree of whitening was determined to be C.

Claims (1)

Impact-resistant, chemically mixed propylene polymer with an ethylene content of 3 - 40 mol-% and consisting of (A) 55-95% by weight of crystalline polypropylene containing 0-1 mol-% of another olefin and having an isotacticity index of at least 90, (B) 1-10% by weight of a low-crystalline propylene/ethylene copolymer containing 60-85 mol-% propylene, and (C) 1-35 mol-% polyethylene or an ethylene/propylene- copolymer containing up to 7 mol% propylene, characterized in that component C has an intrinsic viscosity of at least 0.5, but less than 2.6, and where the total proportions of (A), (B) and (C) are 100 weight -%.