JPH0142285B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for producing a propylene copolymer having a low melting point and excellent moldability. Copolymers of propylene and ethylene and/or other α-olefins are widely used as a way to improve the cold resistance and transparency of polypropylene. In recent years, linear low-density polyethylene (LLDPE) has been in the spotlight as a new material in the film field, and there has been a rapid development of films with excellent transparency and impact resistance. Although this LLDPE has the above properties, the heat resistance and Young's modulus of the film are low.
However, it is completely inadequate when compared with polypropylene film. However, the conventionally known polypropylene film has poor cold resistance, impact resistance, and vertical folding resistance, so it is completely impossible to use it for such film applications, and there has been a desire to develop a new material. One way to improve the cold resistance of polypropylene film is to use a so-called block copolymer with ethylene, but the transparency of the film deteriorates significantly, making it unsuitable for use as a transparent film. . Another method is to increase the content of ethylene, etc. in the random copolymer, but from an industrial scale production perspective, as the content of comonomers such as ethylene increases, the polymerization solvent This increases the solubility of the polymer in purifying solvents, resulting in the adhesion of the polymer to the inner wall of the polymerization reactor, increased production costs due to increased APP, swelling of polymer particles by the purifying solvent, and the accompanying difficulty in solid-liquid separation. In fact, there is a limit to the content of comonomers such as ethylene that can be produced, and ethylene content of Propylene with a melting point of 140℃ or less at % or more.
Ethylene copolymers are difficult to produce by ordinary slurry polymerization, and copolymers with lower crystallinity are usually produced by a solution method. As a means of alleviating these limitations even a little, methods have been proposed in which the polymerization temperature is extremely lowered and a method in which propylene-ethylene-butene ternary copolymerization is performed;
Moreover, it is not very effective. In the latter method, higher α-olefins such as butene have little effect on lowering the melting point, and in order to lower the melting point over the same temperature range, butene is required to be 2 to 3 times (by weight) as ethylene, resulting in a significant increase in cost. Moreover, the effect of expanding the range of production possible with this method is at most 2 to 3 points in terms of the reduction in melting point.
It's only ℃. The present inventors developed a propylene copolymer as a base material for a film that satisfies all of the properties required for a propylene film, such as cold resistance, impact resistance, transparency, crisscross resistance, heat resistance, and Young's modulus. As a result of our intensive efforts, we produced a copolymer with a very low MFI (high molecular weight) and high comonomer content in the polymerization stage, and reduced the molecular weight in the presence of a radical generator, resulting in a narrow molecular weight distribution. A copolymer with a high comonomer content has excellent moldability and is suitable as a base material for a film that satisfies all of the above film properties, and this copolymer can be manufactured without causing any of the process troubles mentioned above. We discovered what we could do and arrived at the present invention. That is, the present invention uses propylene and other olefins under MFI (melt flow index) (230°C, load 2.16 kg) in the presence of a Ziegler type catalyst.
Copolymerized at 0.01 to 0.3 g/10 minutes, then degraded in the presence of a radical generator to give MFI of 0.5 to 100.
g/10 min, melting point below 140℃ and propylene content
A method for producing a propylene copolymer having a copolymer content of 85 to 95% by weight. According to the findings of the present inventors, a high molecular weight copolymer with an MFI of 0.3 g/10 minutes or less surprisingly has a significantly reduced dissolution rate in a polymerization solvent or a purification solvent. For example, we investigated the solubility of a propylene copolymer with an ethylene content of 9.3% by weight in hexane, an example of a hydrocarbon that is a typical polymerization solvent, and isobutanol, an example of an alcohol that is a typical purification solvent. As shown in the figure, the amount dissolved rapidly decreases in the region of MFI of 0.3 g/10 minutes or less. Furthermore, even if the average molecular weight of the copolymer is increased, the molecular weight of the component dissolved in isobutanol used as a purification solvent does not increase. Therefore, the copolymer slurry and the copolymer-alcohol slurry during purification do not become viscous, and solid-liquid separation becomes easy, and there is no lumping or clogging in the subsequent drying or transfer process. Does not occur. When the thus obtained copolymer with an MFI of 0.3 g/10 minutes or less is granulated or molded by adding a commonly used antioxidant, etc., it cannot be granulated or molded at all due to its high molecular weight. In other cases, the resin temperature rises and discoloration occurs, and normal injection molding, film molding, etc. may not be able to properly mold the resin. However, if a radical generator such as peroxide is added at the same time and pelletized while degrading at 180° to 300°C, a moldable low melting point product with an arbitrary MFI depending on the amount of radical generator added. This makes it possible to produce copolymers. The Ziegler type catalyst used in the present invention is a known catalyst system that provides isotactic polypropylene consisting of a transition metal compound component and an organometallic compound, and preferred examples of the transition metal compound are trivalent and/or tetravalent. A titanium compound or a titanium compound complex modified with an organic compound or an inorganic compound, such as a titanium compound containing a halogen, a complex consisting of a magnesium compound and, if necessary, an electron-donating compound, a titanium trichloride eutectic, etc. I can give it to you. On the other hand, examples of the organometallic compound include trialkylaluminum such as triethylaluminum and triisobutylaluminum, and dialkylaluminum halides such as diethylaluminum monochloride and diisobutylaluminum monobromide. Suitable examples of such catalysts include (1) a catalyst system in which so-called AA type titanium trichloride and diethylaluminum monochloride are combined; (2) a system in which an electron-donating compound is added to the catalyst (1); ( 3) The above catalyst system in which the titanium trichloride component is activated by treatment with an electron-donating compound, (4) A catalyst in which β-type titanium trichloride as the titanium component is activated by treatment with an atom-donating compound and a Lewis acid. (5) A catalyst system obtained by combining an electron-donating compound, a tetravalent titanium compound, a magnesium compound, and a trialkylaluminium compound with an aromatic ester, etc., but crystalline polypropylene is preferable. Any known catalyst that provides the following can be used. Polymerization may be carried out continuously or batchwise, and the polymerization tank may be one or multiple tanks. Further, polymerization may be performed in multiple stages with different hydrogen concentrations and/or comonomer concentrations. Although there is no particular restriction on the form of the polymerization reactor, a ring reactor is particularly suitable because it can easily achieve a high stirring rate and thus less polymer adheres to the inner wall of the reactor. In the present invention, the olefin copolymerized with propylene is represented by the general formula CH ₂ =CHR (R represents hydrogen or an alkyl group having 2 to 10 carbon atoms), such as ethylene, butene-
Examples include 1,4-methylpentene-1, hexene-1, octene-1, or mixtures thereof. For the purpose of obtaining a low melting point copolymer, it is preferable to include ethylene. The comonomer concentration may be adjusted so that the propylene content in the copolymer is 80% by weight or more, preferably 85 to 95% by weight of the polymerization system. Random copolymerization of propylene and the above olefin can be carried out by a slurry method in the presence of an inert hydrocarbon such as hexane, heptane, kerosene, or a liquefied α-olefin solvent such as propylene, or by a gas phase polymerization method in the absence of a solvent. Room temperature to 100℃, preferably 40℃ to 70℃
It can be carried out at a polymerization temperature of Slurry polymerization is preferably carried out using a hydrocarbon having a boiling point of 70°C or lower. In particular, a method of slurry polymerization in which a predetermined amount of comonomer is present in liquefied propylene is preferred because it has high polymerization activity and a small amount of soluble polymer in the polymerization solvent. The MFI of the copolymer can be easily adjusted to 0.01 to 0.3 g/10 min by, for example, adding hydrogen as a chain transfer agent to the polymerization zone according to a conventional method. of the copolymer before degradation
When the MFI exceeds 0.3 g/10 minutes, the effect of reducing the amount eluted into the above-mentioned polymerization solvent or purification solvent is poor, and a copolymer with a sufficiently low melting point cannot be produced. On the other hand, the MFI of the copolymer before degradation is
It is preferable to set it to 0.01g/10 minutes or more. this
Even if it is lower than 0.01 g/10 min, there is no particular advantage in reducing the elution amount to the solvent mentioned above, and the amount of radical generator required to reduce the molecular weight to a molecular weight that has useful formability will only increase. This makes homogeneous degradation difficult. As a method for degrading the copolymer, in the presence of a radical generator described below,
It can be carried out at 300°C, preferably from 220° to 270°C, using a conventional single-screw or twin-screw extruder. In the method of the present invention, the radical generator used in the degradation of the copolymer is one whose half-life is longer than 1 second at the melting point (115° to 140°) of the copolymer, and whose decomposition rate is longer than 1 second at 300°C. Selected from those whose decomposition rate is shorter than 10 minutes in half-life. Even if a radical generator with a decomposition rate outside this range is used, the MFI of the resulting product will be uneven or unstable, making it difficult to use industrially. Preferred examples of such radical generators include hydroperoxides, alkyl peroxides,
Compounds with the above decomposition rate among organic peroxides such as acyl peroxides, ketone peroxides, alkyl peresters, peroxydicarbonates, and silicon peroxides,
For example, t-butyl hydroperoxide, dicumyl peroxide, 1,3-bis(t-butylperoxyisopropyl)benzene, benzoyl peroxide, methyl isobutyl ketone peroxide, t-butyl perbenzoate, diisopcopyl peroxydi Carbonate, vinyltris(t-butylperoxy)silane, etc. can be mentioned.Furthermore, there are azo compounds having the above-mentioned decomposition rate, such as azobisisobutyronitrile, 2,2'-azobis(2,4 -dimethylvaleronitrile), etc. The amount of the radical generator used varies depending on the molecular weight before and after degradation, but is generally used in the range of 0.002 to 0.5 parts by weight per 100 parts by weight of the copolymer. Additionally, known antioxidants, lubricants, ultraviolet deterioration inhibitors, and the like can be used as additives added during kneading. The propylene content in the copolymer according to the present invention is 85
~95% by weight. The melting point of the resulting copolymer is
The copolymer with a melting point higher than 140℃ is
It can be manufactured using conventional methods, and the advantages of using the method of the present invention are limited. In particular, the method of the present invention is suitable for obtaining copolymers having a melting point of 115 DEG to 135 DEG C. The MFI of the product after molecular weight reduction is 0.5 to 100 g/10 min, but if the MFI is smaller than this range, the moldability is poor and it is difficult to use it for normal purposes;
If the MFI exceeds 100, it becomes difficult to pelletize, which is not preferable. The copolymer of the present invention has a reduced molecular weight, has a narrow molecular weight distribution, and has a flow rate ratio MLMFI/MFI of 8 to 18, preferably 10 to 18. It is 16. This ratio can also be used as a measure of the degree of molecular weight loss. MFI and MLMFI after molecular weight reduction when changing the usage amount
The changes in MFI are shown in the table below. MFI MLMFI/MFI 0.09* 20.1 0.18 18.6 0.56 15.8 1.8 13.1 3.4 12.8 8.2 12.6 12.3 12.3 28.6 11.6 *Before molecular weight reduction
The ratio of MLMFI/MFI is 19.5 to 2.5 even if the MFI is changed.
is within the range of One of the physical properties of the copolymer of the present invention is an improvement in low-temperature impact resistance, as seen in the difference between Example 1 and Comparative Example 1, which will be described later.
When MLMFI/MFI exceeds 18, this effect is poor and a product with excellent moldability cannot be obtained. Furthermore, if this ratio is less than 8, the degree of molecular weight degradation will be excessive,
Radical generators cause color and odor. The effects of implementing the present invention are (1) a low melting point copolymer of 140°C or less can be produced steadily in slurry polymerization without any trouble in the polymerization purification system drying system transfer system; (2) Copolymers with arbitrary moldability (MFI) can be produced easily and with almost no migration, and (3) they contain very little solvent soluble content and are economical. (1) It is a low melting point copolymer that has not been available on an industrial scale in the past, and (a) It can be used as a film base material when laminated on biaxially oriented polypropylene film or as a laminating film at very low temperatures. (b) Improves low-temperature impact resistance; (2) Due to narrow molecular weight distribution and being a copolymer with reduced molecular weight, (b) high MFI.
However, it has advantages such as high low-temperature impact, (b) greatly improved vertical laying properties, and (c) good transparency. Furthermore, the low melting point copolymer of the present invention has properties such as high transparency, impact resistance, heat resistance, and flexibility, so it can be used for household appliance parts, automobile parts, etc. by injection molding, extrusion molding, and blow molding. It can be used for a wide range of purposes, including parts, toys, and household goods. Next, the present invention will be explained in more detail with reference to Examples. In the following examples, "%" indicates "% by weight" unless otherwise specified. In addition, various physical properties in the following Examples and Comparative Examples were measured by the following methods. (1) Melting point After preheating the sample at 230℃ for 5 minutes, melting point was heated to 50℃ using a pressure press.
Kg/cm ² for 5 minutes, 25° to 30°C and 100°C in a cooling press
A film with a thickness of 100 to 1000μ that was pressed at Kg/ ^cm2 for 5 minutes was placed in a DSC (PerkinElmer type) pan and held at 500° for 5 minutes, cooled at 20°C/min, and then heated at 323° for 5 minutes. The melting point (Tm) is measured at the temperature of the endothermic peak when the temperature is increased at 20°C/min. (2) Hexane soluble content of crude polymer The crude polymer taken out from the polymerization tank was dried overnight in a vacuum dryer, and 5 g of this sample was extracted using a Soxhlet extractor at the boiling point of n-hexane for 6 hours. Minutes. (3) IBA soluble content of crude polymer The soluble content when the dried sample of the crude polymer obtained in (2) above was extracted with isobutanol (IBA) for 6 hours using a Soxhlet extractor. (4) Molecular weight of IBA soluble component Weight average molecular weight of the above IBA soluble component measured using GPC. (5) Liquid content of polymer after centrifugation The IBA content contained in the polymer was determined from the difference in weight before and after drying of the polymer after centrifugation. (6) MFI and MLMFI JIS-K-6758 compliant, load is MFI at temperature 230℃
2.16Kg for MLMFI and 10Kg for MLMFI. (7) Particle size of copolymer The copolymer was sieved in accordance with JIS-Z-8801, and the particle sizes corresponding to the integrated values of weight fraction of 10, 50 and 90% were ₁₀ and _50, respectively. and ₉₀ . (8) Film impact strength Measured using a pendulum impact tester (manufactured by Toyo Seiki) with a 1/2 inch ball at the tip. (9) Film haze value Compliant with ASTM-D-1003 law. Example 1 A titanium trichloride composition (obtained by co-pulverizing 5.0 kg of commercially available AA type titanium trichloride and 0.75 kg of γ-butyrolactone in a vibrating mill with a vibration mill width of 8 mm for 30 hours) was placed in a 290 mm continuous ring reactor. Powder 39g/HEt ₂ AlCl in heptane solution (2mol/) 0.30/H propylene
91 Kg/H, ethylene 4 Kg/H and H ₂ 4.1 Nl/H were supplied, and polymerization was carried out continuously at 60° C. Propylene 52 Kg/H and propylene-ethylene copolymer 43 Kg/H were extracted from the outlet. Even after continuous polymerization for 24 hours, no decrease in the heat transfer coefficient U of the reactor and no change in the amplitude of the stirring pump power were observed. Approximately 200 kg of this crude polymer was placed in a tank, followed by 2 m ³ of isobutanol and stirred at 95°C for approximately 30 minutes. Next, this slurry was applied to a horizontal centrifuge (Super Decanter P-660 manufactured by Tomoe Kogyo Co., Ltd.), and then heated to 100°C.
It was dried with a dryer while circulating _N2 to obtain a white powder. Even during continuous polymerization for 24 hours, no troubles occurred in the polymerization system. In addition, purification centrifugation,
No phenomena such as clogging, clumping, or coarse graining were observed during each drying process. MFI of crude polymer is 0.08
g/10 minutes, the n-hexane soluble content was 10.3%, the IBA soluble content was 1.4%, the propylene content was 91.5% by weight, the weight average molecular weight of the IBA soluble content was 7800, and Tm was 125.6°C. The particle size of the copolymer is ₉₀ = 950μ ₅₀ =
540μ and ₁₀ = 180μ. Immediately after centrifugation
The IBA liquid content was 32%, and the particle diameters of the fluff after purification and drying were ₉₀ = 910μ, ₅₀ = 440μ, and ₁₀ = 150μ, and no agglomeration occurred at all, but on the contrary, they became slightly finer. The angle of repose was 35°, and the bulk density (hereinafter expressed as ρ _B ) was 0.3 g/cc. To this dry refined fluff, 0.08% of 2,6 di-tertiary butyl-4-methylphenol, stearyl-
β-(3,5 di-tert-butyl-4-hydroxyphenyl) propionate 0.1%, calcium stearate 0.15%, dimyristyl thiodipropionate 0.1%, cyclic neopentane tetraru bis(octadenphosphite) ) and 0.06% of 1,3-bis-(tert-butylperoxyisopropyl)benzene as a peroxide were added, and the temperatures of C ₁ , C ₂ and D were adjusted to 190°C, respectively, using a 40mmφ extruder. Pelletization was carried out at 230°C and 240°C. The MFI of this pellet is 8.6
g/10 min, Tm is 127.2℃, propylene content is 91.7
It was in weight%. Also, MLMFI/MFI was 12.3. Comparative Example 1 Polymerization was carried out under exactly the same conditions as in Example 1, except that the amount of H ₂ supplied to the reactor was 51 Nl/H. Six hours after the start of polymerization, a decrease in U (heat transfer coefficient) and an increase in the amplitude of swing of the stirring pump power began, and after 12 hours, the decrease in U reached 20% or more. This is due to polymer adhesion to the inner walls of the reactor.
(Fist-sized polymer lumps were also observed at the bottom of the flash hopper.) The MFI of the obtained crude polymer was 8.1 g/10 min, n-
Hexane soluble content is 25.4%, IBA soluble content is 5.0%, propylene content is 91.8%, weight average molecular weight of IBA soluble content is 7400, Tm is 126.1°C, particle size is D ₉₀ =
1420μ, ₅₀ = 760μ, ₁₀ = 200μ, and contained 26% fluff with a particle size of 5000μ or more. This crude polymer was washed with IBA and centrifuged in the same manner as in Example 1. The IBA slurry becomes very viscous and
The IBA liquid content immediately after centrifugation was as high as 58%. This creates a lump that does not flow at the bottom of the dryer.
The polymer lumps that could not be continuously extracted amounted to more than 10% of the total amount, and stable operation was completely impossible. The particle size distribution of the polymer powder after drying is ₉₀ =
3040μ, ₅₀ = 1020μ, ₁₀ = 210μ, 5000μ
The proportion of these polymer particles was 4.2%.
Also, the angle of repose was 52° and ρ _B = 0.28. This powder was petitized in the same manner as in Example 1, but without adding peroxide, to obtain product pellets. of this pellet
MFI was 8.3 g/10 min, Tm was 126.7°C, and propylene content was 91.9%. Examples 2 to 6 Using the fluff obtained by purification and drying in Example 1, the type and amount of the radical generator were varied as shown in Table 1 below, and the physical properties of the resulting pellets were measured.

[Table] Comparative Example 2 The purified dried fluff of Example 1 was pelletized in an extruder in the same manner as in Example 1, but without using a radical generator. In this case, not only was the fluidity necessary for molding not obtained, but the pellets were also intensely colored. Comparative Example 3 Continuous polymerization was carried out at 60° C. in exactly the same manner as in Example 1, except that the amount of H ₂ supplied during polymerization was 12 Nl/H. As in Comparative Example 1, U began to decrease after about 10 hours, and after 18 hours, the decrease in U reached 20%, and the fluctuation range of the stirring pump power became large, indicating that the polymer was attached to the inner wall of the reactor. crude polymer
MFI is 0.86g/10min, propylene content is 91.7%,
The n-hexane soluble content was 23.8%. This crude polymer fluff was purified and dried in exactly the same manner as in Example 1. The IBA liquid content after centrifugation was 48%, and a lump that did not flow occurred inside the dryer, forcing the operation to be stopped. Example 1 Same as Example 1, except that in addition to ethylene 4Kg/H, butene-1 was added at 4.3Kg/H and the amount of _H2 feed was changed.
Continuous polymerization was carried out at 2.0 Nl/H. The MFI of the crude polymer powder was 0.05 g/10 min, the ethylene content was 8.3%, the butene-1 content was 2.9%, the n-hexane soluble content was 10.5%, and the IBA soluble content was 1.7%. As in Example 1, there were no troubles in polymerization and purification, and continuous operation for 24 hours was possible. Example 1
Add additives and radical generator A in the same manner as above and pelletize to obtain a MFI of 12.4 g/10 minutes and a Tm of 122.4°C.
I obtained pellets with MLMFI/MFI of 11.9. Example 8 A solid catalyst in which an equimolar complex of titanium tetrachloride and hexamethyldisiloxane was supported at 70°C in heptane on a carrier prepared by co-pulverizing 0.9 kg of pensoyl chloride and 3.0 kg of magnesium chloride with a 100-vibration mill, and triethylaluminum. Continuous polymerization was carried out in the same manner as in Example 1 using a catalyst system using ethyl benzoate and ethyl benzoate. However, instead of the titanium trichloride composition, an n-heptane solution ( ₁ mol/
) and a solution of ethyl benzoate in n-heptane (0.3 mol/) in equal amounts 0.7/H, propylene 94 Kg/H, ethylene 5.7 Kg/H and H ₂ 0.2 Nl/H
was supplied, polymerized continuously at 60℃, and 40kg/propylene-ethylene random copolymer was released from the outlet.
Extracted with H. The copolymer dried with a paddle dryer had a propylene content of 88.0% by weight, a Tm of 121.4°C, and an MFI of 0.04 g/
10 minutes, n-hexane soluble content 14.2%, IBA soluble content 2.0
%, and stable continuous operation for 24 hours was possible. Example 9 MFI of Example 1=8.2g/10min, Tm=127.2°C
Using pellets with MLMFI/MFI = 12.3 to which silica was added as an anti-blocking agent and erucic acid amide as a lubricant, the pellets were water-cooled at a cooling temperature of 25°C, a die temperature of 220°C, and a 40mmφ extruder (die diameter: 10mm). Thickness under the condition of rotation speed 80 rpm
A 20μ inflation film was obtained. The blow-up ratio at this time was 1.2. The impact strength of the obtained film at -5°C and 20°C was 90 and 500 Kg cm/mm, respectively.
Further, the haze value was 3.9%. Comparative example 4 MFI=8.5, Tm=140.4℃ and MLMFI/MFI
= 21 propylene-ethylene copolymer directly produced without molecular weight reduction (propylene content 95.1
%) of a 20μ film treated in exactly the same manner as in Example 9 and formed by inflation at -5°C.
and impact strength at 20℃ are 10 and 390, respectively.
Kg·cm/mm, and the haze value was 5.0%. Example 10 Same as Example 1 except that the hydrogen supply amount was 6Nl/H, MFI was 0.15g/10min, propylene content was 91.9%, n-hexane soluble content was 12.1%, and IBA soluble content was A 1.6% crude polymerized powder was obtained. As in Example 1, there were no troubles in the polymerization and purification steps, and 24
Continuous operation for hours was possible. Additives and radical generators (however, the amount added was 0.03%) were added to this polymerized powder in the same manner as in Example 1, and the powder was pelletized. of the obtained pellets
MFI is 9.7g/10min, Tm is 128.1℃, MLMFI/
MFI was 13.6.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the MFI of an ethylene-propylene copolymer having an ethylene content of 9.3% by weight, and the hexane soluble content and isobutanol soluble content. In FIG. 1, curve A shows the hexane soluble content, and curve B shows the isobutanol soluble content.

Claims (1)

[Claims] 1 Copolymerize propylene and other olefins in the presence of a Ziegler-type catalyst using MFI (melt flow index) (230°C, load 2.16 kg) at a rate of 0.01 to 0.3 g/10 minutes, and then in the presence of a radical generator. 1. A method for producing a propylene copolymer, which comprises the steps of: producing a copolymer having an MFI of 0.5 to 100 g/10 min, a melting point of 140° C. or lower, and a propylene content of 85 to 95% by weight.