JPS6251287B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an industrially advantageous method for producing propylene block copolymers having excellent hot-tack properties. More specifically, we are developing a propylene block copolymer that has excellent hot-tack and heat-sealing properties, as well as a good balance of physical properties required for propylene copolymer films, such as transparency, rigidity, slipperiness, and blocking properties, for industrial and economical purposes. It relates to an advantageous manufacturing method. Isotactic polypropylene produced with stereoregular catalysts has excellent rigidity, strength, moldability, appearance of molded products, and heat resistance, and is therefore widely used in various molded products. Furthermore, polypropylene films are highly valued for their transparency and stiffness, and are widely used as various packaging materials. One of the drawbacks of polypropylene is that its impact strength is highly dependent on temperature, and its impact strength rapidly decreases from room temperature to 0°C, that is, it has poor cold resistance. Another drawback is that the heat-sealing temperature of the film and the shrinkage temperature of the stretched film are too high. For example, if you try to heat-seal a biaxially stretched film at a temperature that provides sufficient heat-sealing strength, heat shrinkage will occur. Heat sealing is virtually impossible because the appearance of the film is impaired. Hot-tack properties are very important physical properties required for films. Films are widely used to package various products such as potato chips, rice crackers, biscuits, foods such as sugar, rice, wheat, and flour, grains, bolts, nuts, nails, screws, etc. After packaging and sealing the above-mentioned products, the load of the product is immediately applied to the sealed portion without sufficiently cooling the sealed portion, so that the sealed portion is likely to be damaged or punctured. Therefore,
Even if the heat-sealability is good, if the hot-tackiness is poor, it cannot be used practically. In order to improve these drawbacks of polypropylene, random copolymers such as propylene-ethylene, propylene-butene-1, and propylene-ethylene-butene-1, which are copolymerized with a small amount of α-olefin such as ethylene or butene-1, have been produced. It is used alone or blended with other resins or rubbers as a heat-sealing layer for biaxially oriented polypropylene films, shrink wrapping films, cold-resistant polypropylene films, etc. The method for producing these propylene copolymers is as follows:
Slurry polymerization (hereinafter referred to as solvent polymerization) using an inert solvent such as hexane or heptane is common, but in solvent polymerization, many worthless amorphous polymers are dissolved in the solvent, resulting in loss of monomers. This is not only economically disadvantageous, but also tends to cause productivity problems such as an increase in stirring power due to an increase in slurry viscosity and a decrease in heat transfer in the polymerization tank. This phenomenon becomes more pronounced as the attempt is made to produce a copolymer containing a high comonomer (α-olefin such as ethylene and butene-1) with excellent hot-tack and heat-sealing properties. In addition, propylene copolymers have major drawbacks in terms of physical properties. Copolymers of propylene and ethylene have insufficient heat-sealability, stiffness, slipperiness, and blocking properties. α of propylene and butene-1 etc.
-Copolymers with olefins have very poor hot-tack properties and poor impact strength at low temperatures, that is, cold resistance. Copolymers of propylene, ethylene, butene-1, etc. have been improved to some extent in physical properties such as heat sealability, but they are inferior in hot-tack properties and stiffness, and the balance of physical properties when processed into a film is still insufficient. It is not something we should be satisfied with. Block copolymers of propylene and ethylene or α-olefin are also known, and although they can improve cold resistance without significantly reducing rigidity, transparency deteriorates. In particular, the transparency when made into a film is extremely poor, and the heat-sealing temperature cannot be lowered. As described above, a propylene copolymer that has excellent hot-tack properties and heat-sealing properties and has an excellent balance of other physical properties has not yet been found, and has not been stably produced. In order to overcome the manufacturing disadvantages and physical property disadvantages of propylene copolymers as described above, we
As a result of intensive research, we have arrived at the present invention. That is, the present invention uses a Ziegler-Natsuta catalyst to copolymerize propylene and ethylene in the first stage of copolymerization, and in the second stage to copolymerize propylene and an α-olefin having 4 to 8 carbon atoms. In the method for producing a propylene block copolymer, the composition of the monomers supplied to the first stage copolymerization is 90 to 99.5% by weight of propylene,
Ethylene is 0.5 to 10% by weight, the amount of copolymer produced in the first stage copolymerization is 20 to 90% by weight of the total amount of copolymer, and the second stage copolymerization The composition of the monomer supplied to is propylene 60
~98% by weight, 2 α-olefins with 4 to 8 carbon atoms
~40% by weight, and the amount of copolymer produced in the two-stage copolymerization is 10~40% by weight of the total amount of copolymer produced.
80% by weight of a propylene block copolymer. By producing in this way, the production of amorphous copolymers that dissolve in polymerization solvents, which have no utility value, is minimized, and the yield of the highly crystalline propylene block copolymer product is significantly increased. At the same time, a propylene block copolymer having particularly excellent hot-tack and heat-sealing properties and improved stiffness, transparency, slipperiness, blocking properties, etc. can be obtained. The catalyst used in the production of the propylene block copolymer in the present invention is a so-called Ziegler catalyst.
This is Natsuta Catalyst. That is, as is well known, it is a catalyst consisting of a system containing an organometallic compound of Groups 1 to 1 of the Periodic Table and a transition metal compound of Groups 1 to 2 as essential components, and its various modifying agents are also well known. Titanium compounds, especially halogenated titanium compounds, are preferably used as the transition metal compound component. Titanium compounds are often used supported on a suitable carrier. Specifically, titanium tetrahalides such as titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, and low-valent titanium halides such as titanium trichloride, titanium tribromide, titanium tetraiodide, and titanium dichloride are used. be.
Particularly preferred are titanium tetrachloride and titanium trichloride. Various methods for producing titanium trichloride are known. Titanium tetrachloride reduced with hydrogen, metallic aluminum, metallic titanium, organometallic aluminum, etc.
These are pulverized by methods such as heat treatment or ball milling, and in this case, ether compounds,
Titanium trichloride obtained by reduction is treated with a complexing agent such as an ether compound, titanium trichloride obtained by treatment with a complexing agent is further treated with halogen, organic Those treated with a halogen compound or a halogen compound such as titanium tetrahalide, those treated with a complexing agent and a halogen compound at the same time, and those treated with an organoaluminum compound and reduced with a complexing agent and a halogen compound at the same time. It is also known as something that has become a summer.
Among these, those reduced with metallic aluminum and further pulverized, and those produced using an organic aluminum compound as a reducing agent are preferably used. Japanese Patent Application Publication 1977
-34478, JP-A-51-46598, JP-A-52-
No. 107294, JP-A-53-33289, JP-A-53-51285
The titanium trichloride catalysts described in each specification of the above patent are particularly preferred because they have high activity and can produce propylene block copolymers in high yields. Inorganic solid particles (e.g. MgCl ₂ ; MgOHCl,
SiO ₂ , Al ₂ O _{3 ,} etc.) and/or compositions of these inorganic solid particles pretreated with a Lewis base and a tetravalent or trivalent halogenated titanium compound are also preferably used. It is equally preferred that these compositions be milled or treated with various modifiers such as metal halides, halogenated hydrocarbons, alkylene oxides, ethers, esters, ketones, amines, phosphorous compounds, and the like. Methods for producing these catalysts are described, for example, in JP-A-49-86482 and JP-A-51-92885.
No., JP-A-52-151691, JP-A-53-21093,
JP-A-53-146292, JP-A-54-2292, JP-A-Sho
Although described in publications such as No. 54-112983, catalysts supported on titanium tetrachloride produced by these methods are preferred. Although organometallic compounds such as beryum, magnesium, and aluminum are known as organometallic compounds of groups 1 to 10 of the periodic table, it is preferable to use aluminum compounds. As an organoaluminum compound, AlR _o X _3-o (R is a hydrocarbon group, X is a halogen, hydrogen or alkoxy group, n is 1 to
3) is preferably used. When the transition metal compound component is titanium tetrachloride or a supported catalyst,
Organoaluminum compounds in which n is 2 to 3, for example,
Triethylaluminum, triisobutylaluminum, etc. are preferably used. When the transition metal compound component is titanium trichloride, organic aluminum compounds in which n is 1 to 3, such as diethylaluminum chloride, ethylaluminum sesquichloride, triethylaluminum, etc., are preferably used. Furthermore, Lewis bases such as ethers, thioethers, esters, cyclic esters, phosphines, phosphites, phosphates, ke∽, amines, etc. may be added as a third component to the catalyst system consisting of these transition metal compounds and organometallic compounds during polymerization. can be used. In the copolymerization of the present invention, in the first stage copolymerization, the composition of the monomers supplied to the copolymerization is propylene.
90 to 99.5% by weight, preferably 94 to 99.0% by weight, and 0.5 to 10% by weight, preferably 1 to 10% by weight of ethylene.
It is 6% by weight. As a catalytic modification treatment to further increase the yield of crystalline copolymers, for example, when used in the early stage of copolymerization to the extent that it does not adversely affect the physical properties of the entire copolymer finally obtained. Copolymerization may be carried out by supplying propylene or α-olefin alone so as to give a polymer of 10 g or less per 1 g of transition metal compound catalyst or 1% or less of the total copolymer finally obtained. If the weight percent of ethylene supplied in the first stage polymerization is less than 0.5 weight percent, the effect of lowering the heat-sealing temperature of the film will be small when a film is formed from the finally obtained copolymer. Moreover, if the weight percent of ethylene exceeds 10 weight percent, the amount of components dissolved in the polymerization solvent of the copolymer to be produced increases, which is undesirable because the yield of the crystalline copolymer decreases. The amount of copolymer produced in the first stage copolymerization is 20 to 90% by weight, preferably 30% by weight of the total copolymer.
~80 weight. If the amount of copolymer produced in the first step exceeds 80% by weight of the total amount of copolymer produced, the yield of the crystalline copolymer that does not dissolve in the polymerization solvent of the entire copolymer will be improved. If no effect is found and the amount of copolymer produced in the first step is less than 10% by weight of the total amount of copolymer produced, the effect of improving physical properties by the copolymer obtained in the second step cannot be expected. . In the present invention, the composition of the monomers supplied to the second stage copolymerization is 60 to 98% by weight of propylene, preferably 70 to 97% by weight, and 2 to 40% by weight of α-olefin having 4 to 8 carbon atoms. %, preferably 3 to 30% by weight. By copolymerizing α-olefin, the hot tack properties, heat seal properties, transparency, rigidity, slip properties, blocking properties, etc. of the entire copolymer can be effectively improved. Here α−
If the olefin content is less than 2% by weight, the effect of improving the physical properties of the copolymer will be small;
If it exceeds 40% by weight, the yield of the crystalline copolymer will be markedly reduced, and when the copolymer is processed into a film, blocking properties, transparency, etc. will deteriorate. The amount of copolymer produced in the second stage of polymerization is 10 to 80% by weight, preferably 20 to 70% by weight of the total amount of copolymer produced, but the copolymer produced in this second stage is If the amount exceeds 80% by weight, the effect of improving physical properties by the copolymer produced in the second stage is small, and if the amount of the copolymer produced in the second stage exceeds 10% by weight,
If it is less than % by weight, the yield of the crystalline copolymer of the entire copolymer will decrease, which is not preferable. The propylene block copolymer of the present invention has a 74.0
~99.7% by weight propylene units, 0.2-18% by weight
alpha-olefin units, 0.1-8% by weight of ethylene units, particularly preferably 80.0-99.0% by weight of propylene units, 0.5-15.0% by weight of alpha-olefin units, 0.5-5% by weight of ethylene units. . The polymerization conditions in the present invention can be arbitrarily selected and carried out. That is, polymerization involves aliphatic hydrocarbons such as butane, puntane, hexane, heptane, etc., alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, aromatic hydrocarbons such as benzene, toluene, xylene, or mixtures thereof. It can be carried out in the presence of an activated hydrocarbon, or it can be carried out using the polymerization monomer itself as a polymerization solvent. Furthermore, it can also be carried out in a medium in which the polymerized monomer is in a gaseous state. Each monomer may be supplied to the reaction system continuously or in parts, but
It must be ensured that the monomers fed in each of the stages result in a copolymer having a substantially random composition. α-olefin having 4 to 8 carbon atoms is butene-
1, pentene-1, hexene-1,4-methyl
These include pentene-1, heptene-1, octene-1, etc., and a mixture of these can also be used. It is preferable to carry out the reaction in the presence of hydrogen as a molecular weight regulator in the reaction system. The amount of hydrogen supplied is determined by the application in which the propylene block copolymer product is used. 1st stage and 2nd stage
The supply balance of hydrogen in the stage polymerization varies depending on the polymerization conditions, the desired molecular weight of the copolymer, etc., and it is necessary to adjust the supply balance accordingly. Normally, in each of the first and second stage polymerizations, the hydrogen concentration in the polymerization gas phase, excluding the vapor partial pressure of the inert solvent, is
It is carried out in the range of 0.1 to 15% by volume. The polymerization reaction may be carried out under the same or different conditions in each of the first and second stages, but the polymerization temperature is usually 30 to 90°C, preferably 45 to 80°C,
The polymerization pressure ranges from around normal pressure to 100 kg/cm ² G. The amounts of the uncatalyzed component, the transition metal compound A, and the organometallic compound B are not particularly limited, but the concentration of component B in the polymerization tank is preferably in the range of 1 to 100 mmol/. The polymerization may be carried out batchwise using one or more polymerization tanks, or may be carried out continuously. The present invention will be specifically explained below with reference to Examples, but the scope of the present invention is not limited thereby. In addition, the physical property values in the following examples were measured by the following method. (1) Powder polymer yield Powder polymer yield Weight of polymerization solvent insoluble portion / Weight of polymerization solvent insoluble portion + Weight of polymerization solvent soluble portion x 100 (2) Melt index (MI) Based on JIS K6758. (3) Heat sealing temperature A sample with a width of 25 mm obtained by pressing films together using a heat sealer at a specified temperature for 2 seconds under a load of 2 kg/cm ² was peeled at a peeling speed of 200 mm/min and a peeling angle of 180°. The peel resistance obtained by doing this is 300
The temperature when g/25 mm was taken as the heat sealing temperature. (4) Hot-tack properties Measurements were made using a partially modified heat sealer manufactured by Toyo Seiki. Fix the top of the film with a width of 25 mm and a length of 300 mm. Apply a 35g load to the bottom of the film. The film was folded in half and pressed using a heat sealer at a predetermined temperature with a load of 1 kg/cm ² for 0.5 seconds (seal width 20 mm), and then the length (mm) of peeling under a constant peeling load was measured. (See Figure 1) (5) Transparency (Haze) According to ASTM D1003. (6) Opening properties (blocking) Test pieces were blocked by treatment at 60° C. for 3 hours under a load of 40 g/cm ² and measured using a blocking tester manufactured by Shimadzu Corporation. (7) Stiffness Based on ASTM D747. haze, heat seal temperature, hot tackiness,
Blocking is an antioxidant, anti-blocking agent,
A powder copolymer to which a lubricant was added was pelletized using a granulator, and a 30 micron thick film formed using a T-die molding machine was measured. Example 1 (1) Preparation of catalyst () Preparation method (preparation of ring-based product) After replacing the reaction vessel in step 5 with argon,
Add 1 ml of dry hexane and 250 ml of titanium tetrachloride and keep this solution at -5°C. Add a solution consisting of 750 ml of dry hexane and 580 ml of ethylaluminum sesquichloride under conditions such that the temperature of the reaction system is kept below -3°C. Drip. Then, stirring was continued for 2 hours at the same temperature. After the reaction, the resulting reduced product was allowed to stand for solid-liquid separation at 0° C. and washed twice with hexane (1) to obtain 400 g of reduced product. () Preparation method The reduction product obtained by the preparation method was slurried in n-decalin, and the slurry concentration was 0.2
It was heat treated at 140°C for 2 hours as g/cc. After the reaction, the supernatant liquid was extracted and washed twice with hexane (1) to obtain titanium trichloride composition A. () Preparation method 400 g of titanium trichloride composition A prepared according to the preparation method was slurried in 2 toluene, and A/I ₂ /diisoamyl ether =
Titanium trichloride solid catalyst B was added by adding iodine and diisoamyl ether at a molar ratio of 1/0.1/1.0, reacting at 80°C for 1 hour, and then washing with 1 hexane 5 times.
I got it. () Production of propylene block copolymer. 100 g of purified heptane, 8.0 g of titanium trichloride solid catalyst B obtained by the preparation method, and 50 g of diethylaluminum chloride were added to a polymerization tank with an internal volume of 200 g that was purged with nitrogen, and the temperature was raised to 50°C. Then, in the presence of hydrogen, a mixed gas of propylene and ethylene was supplied to keep the pressure in the polymerization tank constant, and polymerization was carried out until the amount produced in the first stage reached 10 kg. Then,
A mixed gas of propylene and butene-1 was supplied to keep the pressure in the polymerization tank constant, and polymerization was carried out until the amount produced in the second stage reached 10 kg. After the polymerization was completed, the solvent and copolymer were separated and dried to obtain a propylene block copolymer. The polymerization conditions and polymerization results are shown in Table 1, and the physical properties of the propylene block copolymer are shown in Table 2. Example 2 A propylene block copolymer was produced in the same manner as in Example 1, except that the mixed gas composition of propylene, ethylene, and butene-1 was changed and the amounts produced in the first and second stages were changed. The results are shown in Tables 1 and 2. Example 3 The mixed gas composition of propylene, ethylene, and butene-1 was changed, the amount of production in the first and second stages was changed, and 5.2 g of methyl methacrylate was added to the polymerization tank.
A propylene block copolymer was produced in the same manner as in Example 1 except that . Results 1st and 2nd
Shown in the table. Comparative Example 1 A copolymer was produced in the same manner as in Example 1 except that only propylene was supplied in the first step. The results are shown in Tables 1 and 2. Comparative Examples 2 to 4 In the first stage, random copolymerization of propylene-butene-1, propylene-ethylene, and propylene-ethylene-butene-1 was carried out, and the second stage copolymerization was not carried out. The results are shown in Tables 1 and 2. Examples 4 and 5 A propylene block copolymer was produced in the same manner as in Example 1 except that a TiCl ₃ AA catalyst (manufactured by Toho Titanium Co., Ltd.) was used. The results are shown in Tables 1 and 2. Comparative Example 5 Random copolymerization of propylene-ethylene-butene-1 was performed in the first stage using a TiCl ₃ AA catalyst and no second stage copolymerization was performed. The results are shown in Tables 1 and 2. Example 6 A propylene block copolymer was produced by continuous copolymerization using a TiCl ₃ AA catalyst and two 200 polymerization tanks. TiCl ₃ AA catalyst was added at 4.7 g/hr, diethylaluminium chloride was added at 10 g/hr, and purified heptane was added at 20 g/hr in the first polymerization tank in which hydrogen coexisted.
hr, propylene 5.5Kg/hr, ethylene 0.16Kg/hr
was continuously supplied for copolymerization at 50°C, and the polymerization slurry was extracted while keeping the liquid phase level in the first tank constant. The second polymerization tank, which coexists with hydrogen, receives the polymerization slurry from the first tank, as well as propylene 2.5Kg/hr and butene-1 0.52Kg/hr.
The polymerization slurry was drawn out while continuously supplying hr and keeping the level of the polymerization tank constant. Through the above operations, the composition of monomers supplied to the second polymerization tank was as follows. Propylene 5.25Kg/hr (90.83wt%) Ethylene 0.01Kg/hr (0.17wt%) Butene-1 0.52Kg/hr (9.0wt%) The composition of the obtained propylene block copolymer was as follows. Propylene 92.6wt% Ethylene 2.6wt% Butene-1 4.8wt% The ratio of the amount of copolymer produced in the first tank to the amount of copolymer produced in the second tank is 1st tank/2nd tank. Eye =
It was 49/51. Table 2 shows the physical properties of the propylene block copolymer obtained.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 shows how the peeling length is measured in the measurement of hot tackiness. However, a indicates the seal width and b indicates the peeling length.

Claims (1)

[Claims] 1 Using a Ziegler-Natsuta catalyst, in the first stage of copolymerization, propylene and ethylene are copolymerized, and in the second stage, propylene and α having 4 to 8 carbon atoms are copolymerized.
- In a method for producing a propylene block copolymer by copolymerizing with olefin, the composition of the monomers supplied to the first stage copolymerization is 90 to 99.5% by weight of propylene and 0.5 to 10% of ethylene.
% by weight, the amount of copolymer produced in the first stage copolymerization is 20 to 90% by weight of the total amount of copolymer produced, and the monomer supplied to the second stage copolymerization The composition is 60 to 98% by weight of propylene and 2 to 40% by weight of α-olefin having 4 to 8 carbon atoms,
A method for producing a propylene block copolymer, characterized in that the amount of copolymer produced in the second stage of copolymerization is 10 to 80% by weight of the total amount of copolymer produced.