JPH0364522B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for modifying propylene-ethylene block copolymerization using an organic peroxide, which has good moldability, excellent impact resistance, high rigidity, and excellent elongation at break. As is well known, crystalline propylene homopolymers have excellent properties and are used in many fields, but their major drawbacks are that they are brittle at low temperatures and lack impact resistance at low temperatures. In order to overcome this drawback, propylene-ethylene block copolymers (hereinafter simply referred to as block copolymers) have been developed. There have been too many proposals regarding this manufacturing method. A typical example is to sequentially polymerize a propylene homopolymer with an ethylene propylene copolymer and/or an ethylene polymer with or without a small amount of propylene, and repeat this operation one or more times on one catalyst. This is a manufacturing method. Furthermore, it is well known that in order to improve impact resistance, it is necessary to make the molecular weight of the ethylene-propylene copolymer part or the ethylene polymer part considerably higher than that of the propylene homopolymer. For example, if the molecular weight is expressed as [η], the propylene homopolymer is usually 0.5 to 3, while the former is about 1 to 15, so the overall average molecular weight
In other words, limitations naturally arise for MFI. Therefore, it is desired to obtain a block copolymer with excellent impact resistance, high rigidity, excellent elongation at break, and excellent moldability (high MFI) from the viewpoint of resource saving and energy saving. Several proposals have been made to improve the moldability of this block copolymer. That is, this is a method called degradation, in which the molecular chains are cut and degraded, for example, by heating or by using oxygen, peroxide, or the like. Many proposals have been made for this, starting with the degradation of propylene homopolymer. Regarding block copolymers, Japanese Patent Publication No. 42-23088 proposes thermal degradation, and Japanese Patent Publications No. 51-30102 and Japanese Patent Application Laid-open No. 55-139447 disclose a method of thermal degradation by adding an organic peroxide. However, although the former method is effective, it requires a large amount of heat and time to cleave the molecular chains, and is therefore not practical from an economic standpoint. The latter is an effective means of easily cleaving molecular chains and lowering the molecular weight compared to the former, but general degradation results in a drop in impact resistance and a sharp drop in elongation at break. The inventors of the present invention have conducted intensive studies to develop a block copolymer that has excellent impact resistance, elongation at break, and excellent moldability. The inventors have discovered that the method for producing the block copolymer that is subjected to degradation has important significance, and have thus arrived at the present invention. The present invention will be explained in detail below. The propylene-ethylene block copolymer (hereinafter referred to as copolymer (c)) used as a raw material in the present invention is preferably 80 to 92% by weight of (a) a propylene polymer containing or not containing 10% by weight or less of ethylene. is 85-92% by weight and (b) propylene and ethylene copolymer 8-20%.
% by weight, preferably 8-15% by weight, and the ethylene content in (b) is 35-60% by weight, preferably 40-55% by weight.
The copolymer (c) consists of % by weight, and the copolymer (c) has a composition such that the MFI ratio is 1.3 to 7, preferably 1.7 to 5, based on the calculation criteria shown in the following formula (). Something is important. MFI ratio = (a) MFI / (c) MFI () If the MFI ratio is less than 1.3, the effect of improving impact resistance will be small, and if it exceeds 7, the appearance of the molded product will deteriorate. Modification of the above copolymer (c) is 10 ppm or more in the above copolymer powder.
Less than 50 ppm, preferably 20 ppm or more and less than 50 ppm of organic peroxide is mixed and dispersed together with normally required stabilizers (heat resistance, aging resistance, weather resistance, etc.), nucleating agents, etc., melted in an extruder, and then pelletized. This is done by In order to obtain a product with excellent physical properties, the MFI of the composition (hereinafter referred to as composition (d)) after each quality test must be
20 to 200 according to the calculation criteria shown in parentheses.
% preferably 30-100% most preferably 40-75%
shall be. MFI improvement rate = MFI of (d) - MFI of (c) / MFI of (c) × 100 () Furthermore, in order to carry out the method of the present invention most effectively, the copolymer ( c) MFI is 5-60
Preferably it is 10-30. The block copolymer of the present application is one in which both components (a) and (b) must be produced on a single catalyst, and an ethylene-based polymer is further addition-polymerized on the same catalyst. It also includes those polymerized separately or mixed by melt-kneading. The content of the present invention will be specifically described below. First, the catalyst used in the polymerization may be one having high activity and stereoregularity, and known catalysts include those based on titanium trichloride, or those containing magnesium, titanium, or halogen as essential components. Preferably, it is based on titanium trichloride, which has higher stereoregularity.
107989, the general formula TiCl ₃ (AlRn
X _3-o ) _x・(c) _y (In the formula, R is a hydrocarbon group having 1 to 20 carbon atoms, X is a halogen atom, n is a number of 0≦n≦2, and C is a complexing agent. Yes x is a number less than 0.15, y is
A number greater than or equal to 0.001. ) Titanium trichloride is most preferred. Also, as a cocatalyst, AlRnX _3-o
(R is a hydrocarbon group with 1 to 20 carbon atoms, n is a number of 1 to 3)
Among the compounds represented by the above, dialkylaluminum monochlorides represented by diethylaluminum monochloride, di-n-propylaluminum monochloride, di-n-hexylaluminum monochloride, and mixtures thereof are particularly preferably used. Also, generally known electron-donating compounds are used as stereoregularity improvers. In the method for producing a block copolymer using the catalyst system, the polymerization is carried out in two stages,
In the first step, propylene is homopolymerized in the presence of liquefied propylene, and in the second step, ethylene-propylene random copolymerization is carried out in the presence or absence of liquefied propylene, in the so-called gas phase. In the first step, propylene is homopolymerized in the presence of liquefied propylene. Here, in order to supply the solid titanium trichloride catalyst complex and organoaluminum compound into the polymerization tank, aliphatic hydrocarbons such as hexane and heptane, alicyclic hydrocarbons such as cyclohexane, and aromatic hydrocarbons such as benzene and toluene are used. It is preferred to use small amounts of inert liquid hydrocarbons as diluents, such as. In propylene homopolymerization, small amounts, for example up to 1% by weight, may
A copolymer containing a very small amount of other olefin, such as 5% by weight or less of other olefin, obtained by coexisting with ethylene, but exhibiting substantially the properties of a propylene homopolymer, is also considered a propylene homopolymer in the present invention. include. The polymerization temperature and time are selected so that the amount of propylene homopolymer is 80 to 92% by weight of the total polymer produced. Polymerization temperature is usually
The temperature is selected from the range of 40 to 100°C, preferably 55 to 80°C. The polymerization pressure is the sum of the vapor pressure of liquefied propylene determined by the polymerization temperature, the pressure of hydrogen used as a molecular weight regulator, and the vapor pressure of a small amount of the inert liquid hydrocarbon used as a diluent for the catalyst component, but usually 30 ~50Kg/ ^cm2 . The melt flow index of the propylene homopolymer obtained in the first stage (extrusion rate g/10 min at 230°C and load 2.16 kg, according to ASTM D1238-70) is 10.
Select the polymerization temperature and amount of molecular weight regulator so that the molecular weight is ~200. Examples of the molecular weight modifier include hydrogen, dialkylzinc, etc., but hydrogen is preferred.
Typically, the hydrogen concentration in the gas phase is about 1 to 30 mole percent. Next, in the second step, propylene-ethylene random copolymerization is performed in the presence of the propylene homopolymer produced in the first step. When polymerization is carried out in liquefied propylene, the propylene/propylene+ethylene ratio in the gas phase is 60 to 80 mol%, preferably 63 to 75
selected from the range of mol%. Propylene/propylene + ethylene ratio is 60-80
The mol% is the condition in which the amount of by-product of amorphous polymer is maximized, but it is also the condition in which the impact strength of the final polymer is improved the most, and even under these conditions, the solid trichloride According to the method using a titanium-based catalyst complex, a block copolymer powder with high bulk density and excellent free-flowing properties can be obtained with almost no adhesion to the walls of the reaction tank. Outside the above range, the improvement in impact strength is insufficient and is not preferred. When polymerization is carried out at a propylene/propylene+ethylene ratio of 60 to 80 mol%, the resulting propylene-ethylene random copolymer contains approximately 35% ethylene.
60% by weight, more preferably 42 to 55% by weight. The amount of propylene-ethylene random copolymer is 8 to 20% by weight of the total polymer production.
The polymerization temperature and time are selected so that If this amount is less than 8% by weight, the effect of improving impact strength etc. will be small, and if it exceeds 20% by weight, the bulk density and free flow properties of the resulting polymer powder will deteriorate, resulting in stiffness and
This is not preferable because it tends to cause a large decrease in transparency and a large shrinkage rate of the molded product. Polymerization temperature is usually 25-70
The temperature is preferably selected from the range of 25 to 65°C. 70℃
If it exceeds this amount, the resulting block copolymer will have poor free flow properties and agglomeration between polymer particles will occur, which is unfavorable in terms of slurry properties. The polymerization pressure is the sum of the vapor pressure of liquefied propylene determined by the polymerization temperature, the pressure of hydrogen, the pressure of ethylene, and the vapor pressure of a trace amount of inert liquid hydrocarbon,
Usually it is 10-40Kg/ ^cm2 . And propylene-
The MFI of the ethylene random copolymer is preferably 1 or less, and the polymerization temperature is adjusted such that the ratio of the MFI of the propylene homopolymer to the MFI of the entire block copolymer (MFI ratio) is 1.3 to 7, preferably 1.7 to 5. Select the amount of hydrogen, which is a molecular weight regulator. Normally, the hydrogen concentration in the gas phase is determined by the hydrogen/propylene + ethylene ratio.
The amount should be 0.1 to 30 mol%. When carrying out so-called gas phase polymerization in the substantial absence of liquid hydrocarbons, propylene/
By setting the propylene+ethylene ratio in the range of 60 to 90 mol%, the ethylene contained in the copolymer will be in the range of approximately 35 to 60% by weight. As before, the amount of propylene-ethylene random copolymer should be 5 to 20% by weight of the total polymer production. Polymerization temperature is usually 40-100℃, preferably 60-90℃
℃, and the polymerization pressure is usually 10 to 50 Kg/ ^cm2 . Further, the polymerization temperature and the amount of hydrogen are selected so that the MFI of the propylene/ethylene random copolymer is 1 or less and the AFI ratio is 1.3 to 7, preferably 1.7 to 5, as described above. When the MFI ratio is less than 1.3, the effect of improving impact resistance is small and the polymer targeted by the present application cannot be obtained. On the other hand, if it is 7 or more, the effect of improving impact resistance is good, but the molecular weight of the copolymer part is too high, resulting in poor moldability, and the dimensional stability of the molded product deteriorates, which is undesirable and leads to continuous polymerization. In this case, insoluble matter, so-called phisheye, occurs, which is undesirable. The hydrogen concentration in the gas phase is usually about 0.01 to 30 mol% in terms of hydrogen/propylene+ethylene ratio. The total amount of ethylene introduced and the amount of hydrogen are adjusted so that the ethylene content in the total block copolymer is 3 to 15% by weight and the MFI is 5 to 100, preferably 10 to 60.
Polymerization is carried out continuously or batchwise, and the amount of block copolymer produced is 10,000 ml per gram of titanium trichloride.
preferably 16,000g or more, more preferably 16,000g or more
It is said to be over 20,000g. When a block copolymer is produced by the above method, the amount of amorphous polymer produced is small. It also has excellent impact strength, rigidity, and low-temperature brittleness even without removing the amorphous polymer. Furthermore, since the polymer (c) can be obtained in the form of a powder with excellent free-flowing properties, stable operation for a long period of time is possible. The organic peroxide used to modify the obtained copolymer (c) is not particularly limited, but one whose decomposition temperature required to obtain a half-life of 1 minute is preferably 150°C to 200°C. For example, 2,5-dimethyl-2,5
- ditertiary butyl peroxyhexane,
Examples include 2,5-dimethyl-2,5-ditertiarybutylperoxyhexine-3α,α'-bistershaributylperoxyisopropylbenzene. In addition, this mixing method includes mixing the copolymer (c) powder with a known method such as stirring or dissolving the organic peroxide in a diluted liquid, spraying the mixture, and drying, etc., to uniformly mix the organic peroxide with the polymer. Any method is fine as long as it is possible. If the MFI improvement rate is 200% or more during degradation, the drop in impact strength and elongation at break will be noticeable and the desired polymer of the present invention cannot be obtained, and if it is less than 20%, the effect of degradation will be small and the moldability will deteriorate. Little improvement. The temperature and time required for heat treatment are preferably selected appropriately in conjunction with the amount of organic peroxide added so that the target MFI improvement rate is achieved.The heat treatment temperature is preferably 180 to 250°C and the time is 10 seconds or more5. This can be achieved by appropriately selecting the temperature and time so that the temperature is within minutes. The heating container used can be a screw extruder, a Banbury mixer, a roll mixer, or other known methods. Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, the meanings of the abbreviations in the examples and various measurement methods are as follows. Catalyst efficiency CE (g/g) is the amount of copolymer produced in grams per gram of titanium trichloride. The ethylene content [E]IR (wt%) in the copolymer was determined from an infrared absorption spectrum. Melt flow index MFI (g/10min)
According to ASTM D1238−70, 230℃, load 2.16Kg
It shows the amount of polymer extruded when . First yield point strength YS (Kg/cm ² ) and elongation at break
UE (%) was determined by tensile testing of dumbbell pieces punched from press sheets in accordance with ASTM D638-72. Unless otherwise specified, values are measured at 20°C. Izotsu impact strength (Kg-cm/cm) is
According to ASTM D256, a notched strip cut out from a press sheet is heated at 20°C.
Measured at -20°C. The comb-shaped flow length (mm) was determined by using a 1-ounce injection molding machine and using a comb-shaped flow mold with a thickness of 0.2 mm, 0.4 mm, and 0.6 mm, a width of 5.0 mm, and a length of 70 mm.
The flow length at 480Kg/cm ² was determined and the results are shown at a thickness of 0.4mm. This is a measure of moldability in injection molding, and naturally the larger the value, the better the moldability. In addition, the gas phase propylene concentration is expressed as the concentration of propylene relative to the sum of propylene and ethylene in the gas phase in mol%, and the gas phase hydrogen concentration is the concentration of hydrogen relative to the sum of propylene and ethylene in the gas phase.
Expressed in mol%. Catalyst Production Example 1 (Production of solid titanium trichloride-based catalyst complex) (A) Production of homogeneous titanium trichloride solution In a 500 mL flask with a sufficiently dry argon atmosphere, add 120 mL of n-heptane and titanium tetrachloride.
89 mmol was charged, and further 83 mmol of di-n-octyl ether was added. While stirring this and keeping it at 25℃, add diethylaluminum monochloride.
When 33 mmol of titanium trichloride dissolved in 50 ml of n-heptane was gradually added dropwise, a greenish-black homogeneous solution of titanium trichloride in n-heptane was obtained. (B) Formation of precipitate of titanium trichloride and production of catalyst When the homogeneous solution of titanium trichloride obtained in step (A) above was heated to 95°C, a precipitate of purple titanium trichloride was formed during the heating process. Admitted. After stirring at 95°C for 30 minutes, the precipitate was separated and washed twice with 100 ml of n-heptane and then three times with 100 ml of toluene to obtain a finely granular purple solid titanium trichloride catalyst complex. Elemental analysis showed that the catalyst complex had a composition of the formula TiCl ₃ (AlCl ₃ ) 0.003 [(n-C ₃ H ₁₇ ) ₂ O] 0.10. In addition, using CuKα radiation, the X
When the line diffraction spectrum was measured, it had a halo with maximum intensity at 2θ = 32.9°. The specific surface area determined by nitrogen adsorption method (BET method) was 3 m ² /g. Production of Block Copolymer 1 A 10 induction stirring autoclave was sufficiently dried, vacuumed and purged with purified nitrogen gas, then replaced with sufficiently purified propylene gas, and 10 mmol of di-n-propyl aluminum monochloride was charged therein. After charging 3.5Kg of liquefied propylene and raising the temperature to 70℃
Pressurely inject _H2 and place the solid titanium trichloride complex shown in the catalyst production example in the autoclave at 70 °C while stirring.
80 mg of TiCl ₃ was injected under pressure. At this time, the first stage polymerization reaction was started, and the polymerization was continued at 70°C for 3.5 hours.
After 3.5 hours, unreacted propylene and H ₂ gas were immediately purged under cooling, and the internal pressure was reduced to 0 Kg/cm ² . While a small amount of propylene gas was flowing, about 10 g of powdered polypropylene was collected from the siphon by pneumatic transport and exposed to fluorescent X-rays. The Ti content was measured and the CE, MFI, and [η] of the polymer in the first stage were determined. Then, after charging H ₂ gas and 2.5 kg of liquefied propylene
Adjust the temperature to 40℃ and adjust the concentration of propylene in the gas phase to 68 mol% of propylene and ethylene.
I added it so that In this case, the ethylene content in the second stage ethylene-propylene copolymer is 49%.
It is. This time was defined as the start of the second stage polymerization. After that, additional ethylene was supplied so that the pressure remained constant, and 40
Polymerization was carried out for 45 minutes at °C. Immediately after the polymerization was completed, unreacted propylene, ethylene, and hydrogen were purged, and 1920 gr of free-flowing white powdery propylene-ethylene block copolymer was obtained from the autoclave. The analysis results of this block copolymer are summarized in Table-1.

[Table] Next, BHT (2,6-di-t-butyl-p-cresol) was added to 0.1% Irganox as a stabilizer.
1010 (stabilizer trade name, manufactured by Geigi), 0.2% dilaurylthiopropionate, and 0.2% calcium stearate were uniformly added to the polymer powder to prepare Examples-1 to 3 and Comparative Examples-1 to 3. It was used as a sample. Block copolymer production method 2 A block copolymer was produced in the same manner as block copolymer production method-1. However, the concentration of propylene in the second stage gas phase relative to propylene and ethylene is
60% and the ethylene content in the copolymer is 52%
It was hot. The analysis results of the obtained block copolymer were as shown in Table 2 below. A stabilizer was also added in the same manner.

[Table] Examples 1 to 3, Comparative Examples 1 to 2 The polymer obtained by block copolymer production method-1 (stabilizer added) was divided into 5 parts, and the organic peroxide 2,5-dimethyl was divided into 5 parts as shown in Table 3. -2,5-di-(t-butylperoxy)hexane (hereinafter abbreviated as PH25B)
Pelletization was carried out at a resin temperature of 220°C using a 30% m/mφ single-screw extruder while changing the amount of addition. Note that the organic peroxide was diluted with acetone and uniformly blended into the polymer.

[Table] In Examples 1 to 3, although the MFI was improved by 24%, 47%, and 75%, respectively, compared to the powdered polymer before degradation by peroxide, there was almost no decrease in Izot impact strength. There is also sufficient elongation. This is done by using the same MFI as in Example 3 with a higher degree of degradation (MFI
In comparison with Comparative Example-4, which obtained a change rate of 259%, the effectiveness of the method defined in the present application is clear. Examples 4 to 6, Comparative Examples 3 to 4 The polymer obtained by block copolymer production method-2 was treated with a stabilizer and peroxide PH25B in the same manner as in Examples 1 to 3.
A degradation test was conducted by changing the amount of and resin temperature, and the results are shown in Table 4.

[Table] Comparative Examples 5 and 6 In order to show that the physical properties of the modified product differ depending on the difference in the block copolymer used as the raw material, the following block copolymers were manufactured and treated with organic filtrate in the same manner as in Example 1. Degradation using oxides was performed. Production example 3 (comparative example 5) is MFI in formula ()
This is an example in which the ratio is less than 1.3, and in Production Example 4 (Comparative Example 6), the ethylene content in the ethylene-propylene copolymer in the second stage polymerization of the block copolymer is
In 71% of cases, the concentration of propylene in the gas phase relative to propylene and ethylene corresponds to 45%.

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Claims (1)

[Scope of Claims] 1 (a) 80 to 92% by weight of a propylene homopolymer or a propylene-ethylene random copolymer having an ethylene content of 10% by weight or less; (b) an ethylene content of 35 to 60% by weight % of a propylene-ethylene random copolymer (c), the melt flow index of (a) is 1.3 of that of (c). In the method of adding an organic peroxide and melt-kneading a propylene-ethylene block copolymer (c) having a melt flow index of 5 to 7 times that of (c) and a melt flow index of 5 to 60 g/10 min, The amount of peroxide added is 10 ppm or more and less than 50 ppm relative to the block copolymer, and the melt flow index improvement rate expressed by the following formula is controlled to be 20 to 200%. A method for modifying propylene-ethylene block copolymers. MFI improvement rate = MFI after modification - MFI of (c) / MFI of (c) × 100