JPS6312086B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing a crystalline propylene-α-olefin copolymer containing less amorphous polymer even if the α-olefin content is high. This improved propylene-α-olefin copolymer has good transparency and is suitable for use as a film with improved heat sealability. Biaxially stretched films made of highly crystalline polypropylene are excellent packaging materials in terms of transparency, rigidity, etc., but cannot be applied to automatic packaging machines as they are because of their poor heat-sealability. That is, since the heat-sealing temperature of a stretched polypropylene film is usually higher than the stretching temperature, the heat during heat-sealing causes the film to shrink as it tries to return to its unstretched state, impairing its appearance and reducing its sealing strength. Furthermore, polypropylene film has a higher melting point than polyethylene film, etc., and requires a high heat sealing temperature during bag making, making it impossible to increase the sealing speed. Therefore, since propylene and a small amount of ethylene, crystalline α-olefin copolymer such as butene-1 has better low-temperature heat-sealability than polypropylene, it is widely used by laminating it on a polypropylene film to compensate for these drawbacks. It is. The higher the α-olefin content of these copolymers, the lower the heat-sealing temperature, which is economically advantageous because the bag-making speed of the composite film can be increased. However, when attempting to copolymerize a large amount of α-olefin, the higher the content, the more low-molecular-weight, amorphous copolymers are produced as by-products. Generally, in the production of crystalline polyolefin, if the ratio of these worthless low molecular weight, amorphous copolymers to the target crystalline olefin copolymer increases, not only will it result in a loss of the raw material olefin; Various problems arise in production. For example, when manufacturing by polymerization in an inert solvent or by polymerization in a liquid phase monomer that does not substantially contain a solvent, the dispersion state or flow properties of the suspension may be poor, resulting in increased viscosity, This causes problems such as a decrease in the heat transfer rate, and the bulk specific gravity of the resulting polymer decreases, resulting in a worsening of the dispersion state. Sometimes it is impossible to extract the polymer from the polymerization tank. In addition, when polymerizing in the gas phase, heat transfer decreases due to amorphous polymer adhering to the polymerization tank, and the stickiness of the powder increases, resulting in insufficient powder flow and increased stirring power. A problem occurs. When these propylene copolymers with a high α-olefin content are made into a film, it contains a fairly large amount of amorphous polymer that is soluble in xylene at 20°C (hereinafter referred to as cold xylene soluble portion). Inconvenient problems such as increased blocking and deterioration of transparency occur due to whitening caused by bleeding to the surface of the film. Therefore, conventional propylene-ethylene copolymers have only been produced with an ethylene content of 6 to 7 mol%. Also propylene
Even with α-olefin copolymers such as butene-1, copolymers with a high α-olefin content and little amorphous polymer have not been produced to date. As a result of various studies, the inventors found that in the production of a crystalline propylene-α-olefin copolymer with a high α-olefin content, the amount of useless amorphous polymer is small, the bulk density of the powder is high, and the fluidity is improved. We have invented a method for industrially advantageously producing a good crystalline propylene-α-olefin copolymer powder. Therefore, according to the present invention, it is possible to obtain a film having good blocking properties, good transparency, and good low-temperature heat-sealing properties that were hitherto unanticipated.The above-mentioned problems can be overcome and the film is economically far more advantageous. That is, the present invention reduces titanium tetrachloride with an organoaluminum compound, and then produces a catalyst comprising an activated titanium trichloride composition and an organoaluminum compound of the general formula R ₂ AlX (R is a hydrocarbon group, X is a halogen). After previously polymerizing 0.01 to 50 parts by weight of propylene per unit weight of titanium trichloride using a system, α-olefin having 4 to 10 carbon atoms and propylene are supplied, and the polymerization temperature is set to T=−. 1/
60・C ² −3/2・C+85 (T is temperature expressed in °C,
C is a crystalline propylene-α with an α-olefin content of 8 to 25 mol%, characterized in that it is polymerized at less than mol% of α-olefin in the copolymer;
- A method for producing an olefin copolymer. According to the production method of the present invention, even if the α-olefin content is 8 to 25 mol%, the amorphous polymer is surprisingly small and has a low melting point, so it can be used in blow molded products and sheets in addition to films. It also has good impact resistance and transparency. The titanium compound used as a catalyst in the present invention is obtained by reducing titanium tetrachloride with an organoaluminum compound, using titanium trichloride as a starting material for producing an activated titanium compound, and treating it with a complexing agent. , organoaluminum compound treatment,
Alternatively, it is characterized by using a catalyst highly activated with titanium tetrachloride or a combination thereof. This catalyst can be prepared by simply reducing titanium trichloride obtained by heat treatment or other known methods (for example,
It has higher activity and stereoselectivity than that obtained by the method described in Publication No. 20501). More specifically, it is possible to use solid catalysts obtained by methods described in, for example, Japanese Patent Application Laid-Open No. 74595/1982 and Japanese Patent Application No. 108276/1983. In addition, when carrying out the present invention, Japanese Patent Application Laid-Open No. 47-34478
A highly active catalyst obtained by the method described in , ie, by treating β-type titanium trichloride with a complexing agent such as ether and then treating it with titanium tetrachloride, can also be used satisfactorily in this method. Catalysts other than those essential to the present invention, such as titanium tetrachloride currently on the market, reduced with metal aluminum and activated by pulverization (for example, titanium trichloride manufactured by Toho Titanium Co., Ltd.)
AA), and those using conventionally known catalysts in which titanium tetrachloride is reduced with an organoaluminum compound and heat treated are insufficient and cannot be used. When these catalysts are used, copolymers with a high α-olefin content may have a low bulk specific gravity of the powder, increasing the amount of amorphous polymer produced, or may not be powder-like, but may be block-like or It produces a gel-like polymer and is difficult to manufacture industrially. The organoaluminum compound that can be used next needs to be a monohalide represented by the general formula R ₂ AlX (R is a hydrocarbon group, X is a halogen). The catalyst system of the present invention contains the above-mentioned activated titanium compound and organoaluminium compound, but also contains compounds such as amines, ethers, esters, sulfur, halogens, benzene, azulene derivatives, organic and inorganic nitrogen, phosphorus, etc. It may also contain a known third component such as. Although it is essential to use the above catalyst system,
These catalyst systems must then be pretreated with propylene. The pretreatment of the propylene polymerization catalyst system itself is already known, for example,
4992. That is, the catalyst system used to initiate the copolymerization of propylene and α-olefin is a polymerization catalyst in which 0.01 to 50 parts by weight of propylene is polymerized to titanium trichloride in the catalyst system. be. This pretreatment of the catalyst may be carried out in a separate tank before charging the catalyst into the reactor, or if the polymerization is carried out batchwise, it may be carried out in the same reactor in which the polymerization will be carried out, before starting the polymerization. Then, a certain ratio of propylene and α-olefin may be supplied for polymerization. If this catalyst is not pretreated, the amorphous copolymer will be eluted into the inert solvent or liquid phase monomer, and the powder will solidify into blocks or gels, making production virtually impossible. becomes. In addition to the catalyst system and catalyst pretreatment mentioned above, the polymerization temperature is also important, and is determined by the following formula: T=-1/60C ² -3/2C+85 (T is the temperature in degrees Celsius, C is α in the copolymer
The temperature must be below the temperature specified by (mol% of olefin). If the polymerization temperature is higher than that shown by the formula, the powder properties will be extremely deteriorated and become block-like or gel-like, making production impossible. However, when polymerized at a temperature below the temperature indicated by the formula, a high-quality propylene-α-olefin copolymer with good powder properties even with a high α-olefin content and a small amount of cold xylene soluble portion in the polymer can be obtained. can be manufactured. Generally, to reduce amorphous polymers,
It is known that polymerization can be carried out at a fairly low temperature. However, it has been difficult to industrially produce α-olefin copolymers with a high content because productivity per catalyst and per hour comes at a cost. However, if the catalyst system described above is used and the catalyst is further pretreated, a high α-olefin content, i.e., 8 to 25 mol% of crystalline propylene-α-olefin can be obtained only when the polymerization occurs at a temperature below the temperature shown by the formula. A copolymer of high quality can be produced industrially advantageously and without any problems in production. It was extremely difficult to predict that it would be possible to produce a product having an α-olefin content of 8 to 25 mol % in the manner described above, and this is surprising. The polymerization temperature below the temperature shown in the formula is an experimental value found by us. α-olefin copolymerized with propylene is
Specific examples of hydrocarbons with 4 to 10 carbon atoms include 1-butene, 1-pentene, and 1,4-hexene.
Methylpentene-1, octene-1, decene-1
etc. The α-olefin is not limited to a single substance and may be a mixture of two or more of these, but among these α-olefins, butene-1 is particularly desirable since it has a small amount of amorphous copolymer. In the present invention, if ethylene is used instead of α-olefin having 4 to 10 carbon atoms, a large amount of amorphous copolymer is produced, which not only lowers the powder polymer yield but also reduces the amount of amorphous copolymer in the powder polymer. Polymer builds up significantly. Therefore, when this crystalline propylene-ethylene copolymer is made into a film, blocking is extremely large even if the heat sealing temperature is low, and the economical decrease in transparency due to whitening caused by bleeding of the amorphous copolymer onto the film surface is significant. You can only get things that have no commercial value. This is truly surprising since it is only by using α-olefin having 4 to 10 carbon atoms as a comonomer as in the present invention that a film with sufficiently low heat-sealing temperature and good blocking properties can be obtained. It is. In the present invention, ethylene cannot be used in place of α-olefin, but it is possible to add a small amount of ethylene to propylene or α-olefin for polymerization. In this case, even if the propylene content is kept constant, as the ethylene content increases, the above-mentioned qualities such as blocking will deteriorate, so there is an upper limit to the ethylene content that can be added, and it must be kept at 7 mol% or less. Must be. A crystalline propylene-α-olefin copolymer having an α-olefin content of less than 8 mol % can be produced by a conventionally known method without using the production method of the present invention. On the other hand, a crystalline propylene-α-olefin copolymer containing more than 25 mol % of α-olefin cannot be produced industrially even by the method of the present invention. The catalyst system and pretreatment of the catalyst system described above are carried out at a polymerization temperature below the temperature expressed by the formula α
- Conditions for producing a crystalline propylene copolymer with an olefin content of 8 to 25 mol % and a small amount of amorphous copolymer. These three points are essential, and if even one is missing, manufacturing becomes impossible. As long as these conditions are met, the polymerization can be carried out by known methods. Batch or continuous polymerization can be carried out, for example in an inert solvent or in liquid phase monomers. As a result, the present invention can increase the comonomer content and reduce the amount of amorphous copolymer compared to conventionally known crystalline propylene copolymers, which improves film quality, such as blocking and bleed whitening. It is possible to industrially advantageously produce a propylene copolymer suitable for a film that can be heat-sealed at a lower temperature than before without any adverse effects. In order to explain the method of the present invention more clearly, comparative examples and examples are described below, but the present invention is not limited only by these examples.
In addition, the characteristic values in the following examples were measured by the following method. (1) Powder polymer yield Powder polymer yield = Polymerization solvent insoluble part / Polymerization solvent soluble part + Polymerization solvent insoluble part x 100 (2) Cold xylene soluble part After dissolving 5g of polymer in 500ml of boiling xylene, After slowly cooling to room temperature and leaving at 20°C for 4 hours, the precipitated polymer was separated, xylene was evaporated from the liquid, and the solution was dried at 60°C under reduced pressure to recover the cold xylene-soluble polymer. The percentage of the recovered polymer to the sample polymer was defined as cold xylene soluble portion %. (3) Heat sealing temperature A sample with a width of 25 mm obtained by pressing two films together using a heat sealer at a predetermined temperature for 2 seconds under a load of 2 kg/cm ² was peeled off at a peeling speed of 200 mm/min and at a peeling angle.
The peel resistance obtained by performing T-shaped peeling at 180 was 300.
Temperature at g/25mm. (4) Transparency (haze) Based on ASTMD 1003. (5) Opening properties (blocking) Test pieces that were blocked by treatment at 60° C. for 3 hours under a load of 40 g/cm ² were measured using a blocking tester manufactured by Shimadzu Corporation. Example 1 (1) Preparation of catalyst 1 Preparation method I (preparation of reduction product) After replacing the 200 reaction vessels with argon,
Add 40% dry hexane and 10% titanium tetrachloride, keep this solution at -5℃ and add 30% dry hexane.
, ethylaluminum sesquichloride
A solution consisting of 23.2 was prepared at a temperature of -3°C.
It was applied under the following conditions. Stirring was then continued at the same temperature for 2 hours. After the reaction, the resulting reduced product was allowed to stand still and was subjected to solid-liquid separation at 20°C, and washed twice with 40 kg of hexane to obtain 16 kg of reduced product. 2 Preparation method The reduction product obtained in Preparation method I was slurried in n-decalin, and the slurry concentration was adjusted to 0.2.
It was heat treated at 140°C for 2 hours as g/cc. After the reaction, remove the supernatant and dilute with 40% hexane.
After washing twice, a titanium trichloride composition (A) was obtained. 3 Preparation method 11 kg of titanium trichloride composition (A) prepared according to the preparation method was slurried in 55% toluene,
Iodine and diisoamyl ether were added at a molar ratio of titanium trichloride composition (A)/I ₂ /diisoamyl ether = 1/0.1/1.0, and heated at 80°C.
A titanium trichloride solid catalyst (B) was obtained by reacting for 1 hour. (2) Pretreatment of catalyst system After purging a reaction vessel with an internal volume of 5 with a stirrer with argon, 11 g of dry n-heptane, 16 g of the above titanium trichloride solid catalyst (B), and 70 g of aluminum diethyl monochloride were added. . Next, the inside of the reactor was replaced with propylene, the temperature was raised to 50° C., and 300 g of propylene was fed and reacted with stirring to obtain a catalyst system (C). (3) Copolymerization of propylene-α-olefin After a polymerization vessel with an internal volume of 200 and equipped with a stirrer was sufficiently replaced with propylene, 68 of industrial heptane was introduced. The entire amount of the catalyst system (C) was added and washed with industrial heptane until the final amount of industrial heptane was 70. Next, 6.5 kg of propylene and 17 kg of butene were added, and the temperature was raised to 50° C. and the gauge pressure was 4 kg/cm ² . By strictly controlling the gas phase composition of butene-1 and propylene under an appropriate hydrogen partial pressure, 7.0 kg of butene-1 and 22.5 kg of propylene were continuously fed. The slurry after polymerization was purified after decomposing and removing the catalyst with isobutanol to obtain 31 kg of powdered polymer.
The intrinsic viscosity of this product was determined to be 1.49 as measured in a tetralin solution at 135°C, and the content of butene-1 determined by infrared spectroscopy was 16.6 mol %. Table 1 shows the powder polymer yield, bulk specific gravity, cold xylene soluble content, and measured quality results of the obtained copolymer. Example 2 The polymerization temperature was 47°C, butene in the crystalline copolymer
A copolymer was produced in the same manner as in Example 1 except that the 1 content was changed to 20.5 mol%.
The results are shown in Table-1. Example 3 A copolymer was produced in the same manner as in Example 1, except that the composition of ethylene, propylene, and butene-1 in the crystalline polymer was changed as shown in Table 1. The results are shown in Table-1. Comparative Examples 1, 2, 3 Copolymers were produced in the same manner as in Examples 1, 2, and 3 except that titanium trichloride AA manufactured by Toho Titanium Co., Ltd. was used. However, in both cases, the polymer swelled in the polymerization solvent, making it impossible to obtain a powdery copolymer and making it impossible to extract it from the polymerization vessel. Comparative Example 4 A copolymer was produced in the same manner as in Example 1, except that polymerization was performed without pre-polymerization treatment. In this case, the powder polymer content was 65%, and the obtained polymer was a mixture of gel-like materials and had a bulk specific gravity of 0.3 or less. Comparative Example 5 A copolymer was produced in the same manner as in Example 1 except that the polymerization temperature was 60°C. The powder polymer yield in this case was 53%, and the obtained polymer was a mixture of gel-like materials and had a bulk specific gravity of 0.3 or less. The polymerization conditions and results of Examples 1, 2, and 3 and Comparative Example 5 are shown in Table 1 for comparison. It was produced in the same manner as Comparative Example 1 except that the butene-1 and ethylene contents in the crystalline copolymer were as shown in Table 1. The results are shown in Table-1. Comparative Example 8 Copolymerization was carried out in the same manner as in Example 1 except that titanium trichloride AA manufactured by Toho Titanium Co., Ltd. was used and the polymer composition was as shown in Table 1, and the polymerization was carried out at a temperature of 60°C. The results are shown in Table-1. Comparative Example 9 A copolymer was produced in the same manner as in Example 1, except that the ethylene content in the crystalline copolymer was as shown in Table 1. The results are shown in Table-1. 【table】

[Brief explanation of the drawing]

FIG. 1 is a flowchart to aid in understanding the present invention.

Claims (1)

[Claims] 1 Titanium trichloride composition obtained by reducing titanium tetrachloride with an organic aluminum compound and further activating it and the general formula R ₂ AlX (R is a hydrocarbon group, X is a halogen)
per unit weight of titanium trichloride.
After polymerizing 0.01 to 50 parts by weight of propylene, α-olefin having 4 to 10 carbon atoms and propylene are supplied, and the polymerization temperature is set to T=-1/60・C ² −3/2・
The content of α-olefin is 8 to 25, characterized by polymerization at C+85 (T is temperature expressed in °C, C is mol% of α-olefin in the copolymer) or less.
A method for producing a crystalline propylene-α-olefin copolymer that is mol%.