Highly crystalline polypropylene

Abstract: A highly crystalline polypropylene (PP) from which highly stiff molded products can be produced and also which can be used for use applications for which con­ ventional PP could not have been used is provided, which PP is chracterized by the following conditions (A) and (B): (A) its melt flow rate (MFR) and absorbance ratio according to the method of infrared absorption spectra (IRτ; an absorbance ratio of a wave-number of infrared rays of 997 cm⁻¹ to that of 973 cm⁻¹) satisfy an equation of IR-τ≧0.0203 log MFR + 0.950 and its MFR is in the range of 0.1 to 200; and (B) when a dilute solution of the PP dissolved in xylene is slowly cooled with stirring, an initially deposited component in 2 to 3% by weight has an IR-τ value of 0.97 or more and the weight average M.W. (M w1 ) of the deposited components and that (M wo ) of the PP have a ratio of 3 or more.

Description: 1. Field of the Invention This invention relates to a highly crystalline polypropylene. More particularly it relates to a polypropylene having an extremely high crystallinity even when any additive for secondarily enhancing its crystallinity such as nucleating agent is not added. 2. Description of the Related Art Crystalline polypropylene (hereinafter referred to as "PP") as a thermoplastic resin is provided with general-purpose properties due to which it is usable as parts of automobiles, domestic appliances, fibers, food-packaging materials, etc. and excellent physical properties (such as mechanical strength, stiffness, heat resistance, chemical resistance and electrical properties, and also high impact resistance can be imparted thereto in addition to the above physical properties by block-copolymerization; hence in recent years its demand has been being remarkably increasing. However, these properties have not yet been fully satisfactory depending on its use applications and its use has been restricted. For example, the stiffness of injection-molded products obtained from PP, particularly the stiffness thereof in a high temperature region in the vicinity of 80°C, is inferior to those of molded products obtained from polystyrene, ABS resin, etc. and also its heat deformation-resistant temperature is low. Further, in the fields of film and fibers, too, polyester resins are superior to PP in the aspect of nerve. Thus, if it is possible to impart to a very cheap PP, the same extent of properties in the aspect of stiffness as that of these resins or impart thereto stiffness filling in the gap between PP and these resins, then it can be expected that use of PP to industrial products or industrial parts around automobiles, domestic appliances will be more extended. By enhancing the stiffness, it is possible to make its molded products having a thinner thickness while the same strength is retained, which serves resources-saving. In the field of packaging of foods, since highly stiff materials have small shrinkage even at high temperatures, it is possible to shorten the drying time of printing ink on the surface of a film by raising its secondary processing temperature to thereby improve the operation efficiency due to speed-up on the production line. In the field of fibers such as cotton for bed-cloths or carpets by increasing the bulkiness of fibers, such effects can be expected that the feeling of fibers is improved, the elastic recovery properties are enhanced and the decrease in resilience are reduced. Any of these matters can be achieved by enhancing the stiffness of PP. As to the prior art for enhancing the stiffness of molded products of PP, for example, there is a process of adding an organic nucleating agent such as aluminum p-tert.-butylbenzoate, 1,3,2,4-dibenzylidene-sorbitol to PP, followed by molding the mixture. Further, there is another process of adding various inorganic fillers such as talc, calcium carbonate, mica, barium sulfate, asbestos, calcium silicate followed by molding. However, the former process has drawbacks that the cost not only becomes high, but also luster, impact strength, tensile strength and elongation are reduced, while the latter process has drawbacks that the light-weight properties and transparency each specific of PP are not only damaged, but also the impact strength, luster, appearance, tensile elongation and processability are reduced. Further, processes of obtaining highly stiff PP without adding any nucleating agent, inorganic filler are disclosed in Japanese patent application laid-open Nos. Sho 57-47305/ 1982, Sho 59-22131/1984, but any of the PPs disclosed therein are poor in the crystallinity enough to be able to develop a high stiffness. GB-A-2124240 describes an isotactic polypropylene for molding in which a similar catalyst system is used as in the present invention. However the polymerization process employed in GB-A-2124240 is different and therefore also the properties of the polypropylene obtained by the different processes are different. This becomes obvious by the comparative examples of the present specification. Thus the present inventors have made extensive research on production of a PP whose molded products have a high stiffness even when a high stiffness-effecting promoter such as fillers e.g. talc or additives e.g. nucleating agent is not added and even when conventional molding conditions, not particular molding conditions, are applied, namely a PP having a primary structure exhibiting a high crystallinity. As a result, we have found that a PP having specified properties exhibits a never observed high crystallinity and when molded into various molded products, developing a high stiffness, and have completed the present invention based on this finding. Apparent from the foregoing, an object of the present invention is to provide a highly crystalline PP from which molded products having a high stiffness can be produced. Another object of the present invention is to provide a highly crystalline PP which can be used for use applications for which conventional PPs could not have been used. The present invention resides in: a highly crystalline polypropylene characterized by satisfying the following conditions (A) and (B): (A) its melt flow rate (MFR) and absorbance ratio according to the method of infrared absorption spectra (IR- τ ; the absorbance ratio of the wave-number of infrared rays of 997 cm⁻¹ to that of 973 cm⁻¹, i.e. A₉₉₇/A₉₇₃) satisfy the equation of IR- τ ≧ 0.0203 log MFR + 0.950 and its MFR is in the range of 0.1 to 200; and (B) when a dilute solution of said polypropylene dissolved in xylene in a concentration of 0.2 wt/vol.% is slowly cooled at a rate of 5°C/hr with stirring, at a revolution number of 300 rpm, an initially deposited component in 2 to 3 % by weight has an IR- τ value of 0.97 or more and the weight average molecular weight (M wl ) of the deposited component and that (M wo ) of said polypropylene have a ratio (M wl /M wo ) of 3 or more. The present invention will be described in more detail. The present highly crystalline PP has a melt flow rate (MFR, g/10 minutes, 230°C) is in the range of 0.1 to 200. If the MFR is less than 0.1, the fluidity of PP at the time of melting is insufficient, while if it exceeds 200, molded products obtained therefrom is insufficient in the strength. The greatest features of the highly crystalline PP of the present invention consist in that it has a high IR-τ value and also has a specified component described later. One of the indications of the primary structure of PP employed for defining the highly crystalline PP is IR-τ. Any of the prior art such as Japanese patent application laid-open Nos. Sho 58-104905/1983, Sho 59-22913/1984 mentions as a condition of obtaining a highly stiff PP, a condition that the isotactic ratio as measured by means of ¹³C NMR is to be on a high level. This ratio refers to an isotacticity expressed by 5 isotactic chains (5 isotactic chains as counted in terms of monomer unit), (whereas IR-τ refers to an isotacticity expressed by 10 or more isotactic chains as described below. As compared with the isotactic pentad ratio by means of ¹³C NMR, IR-τ as an indication of the quantity of a longer isotactic chain present is a most adequate indication for defining the primary structure of a highly crystalline pp. This IR-τ refers to the ratio of the absorbance at a wave-number of 997 cm⁻¹ or infrared spectrum to that at a wave-number of 973 cm⁻¹ thereof (A₉₉₇/A₉₇₃). The relationship between this IR-τ and the helix structure·primary structure, particularly the isotactic chain has already been elucidated as follows: Isotactic PP crystallizes taking a helix structure, and the higher the isotacticity of PP is (i.e. the larger the quantity of long isotactic chain present is), the less the helix structure is disturbed; hence its crystallinity is more raised. The infrared absorption at 997 cm⁻¹ has the following specific feature: The above absorption spectrum is attributed mainly to the skeletal C-C stretching vibration (H. Tadokoro et al, J. Chem. Phys., 42 , 1432 ('65)), which absorption spectrum develops in solid state in the case of isotactic PP, while it is extinct in molten state in that case. On the other hand, in the case of atactic PP, it does not develop even in solid state. In view of these facts, the above absorption has been employed as an indication relating directly to the content of the isotactic helix (T. Miyazawa, Polym. letter, 2 , 847 ('64)). Further, it has also been confirmed that this absorption spectrum develops when the length of the isotactic chain reaches 10 or more (T. Miyazawa and H. Inagaki, J. Polym. Sci., A-2 , 7 , 963 ('69)). The absorption spectrum at 973 cm⁻¹ has the following specific feature and reflects neither specified stereoregularity nor helix structure and hence it is employed as the internal standard absorption spectrum for IR-τ: This absorption spectrum is attributed to the stretching vibration of C-C as skeletal carbons of PP, but unlike the absorption spectrum at 997 cm⁻¹, it is not extinct even in the molten state of PP (T. Miyazawa and H. Inagaki, J. Polym. Sci., A-2 , 7 , 963 ('69)). Further, as to this absorption spectrum, it has also been confirmed that the propylene chains link in head-to-tail manner and the absorption spectrum develops when the chain length reaches 5 or more (T. Miyazawa and H. Inagaki, J. Polym. Sci., A-2 , 7 , 963 ('69)). In order to relate IR-τ to the the content of long isotactic chain, it is necessary that the isotactic chain in a sample take a helix structure as much as possible and hence it is important to make the crystallization conditions at the time of sample preparation definite and sufficiently carry out annealing (R.H. Hughes, J. Appl. Polym. Sci, 13 , 417 ('69)). As to the measurement conditions according to the IR-τ measurement method of the present invention, the conditions have been sufficiently taken into consideration. Further, since the IR-τ varies depending on MFR, it is necessary for the highly crystalline PP of the present invention to satisfy the relationship of IR-τ ≧ 0.0203 log MFR + 0.950 . IR-τ values less than the above one are in the range of IR-τ values exhibited by PP having conventional crystallinity. The upper limit has no particular limitation, but if the IR-τ values are too high, the stretching property is insufficient in the case of PP grade for stretching processing. Further, the highly crystalline PP of the present invention has a novel primary structure containing a component exhibiting a surprising nucleating effectiveness. This has been confirmed from a fact that a first deposited component (hereinafter referred to as "first fraction") is separated from the highly crystalline PP according to a stirring fractionation technique mentioned later and when this first fraction is added to PP exhibiting a conventional crystallinity, the crystallinity of the conventional PP is notably improved although the level of the resulting crystallinity does not reach that of the highly crystalline PP of the present invention. The specific feature of this component in the aspect of the primary structure is as follows: Namely, the first fraction in 2 to 3% by weight based on the total weight of a sample, initially obtained in the determination according to the stirring fractionation technique mentioned later has an IR-τ of 0.97 or more, and the ratio (M wl /M wo ) of the weight average molecular weight (M wl ) of the first fraction to that (M wo ) of the original unfractionated PP is 3 or more. If the Ir-τ value of the first fraction is less than 0.97, the resulting PP is a PP exhibiting a conventional crystallinity. Further, the upper limit has no particular limitation, and it is unclear what extent the upper limit is to (the IR-τ value of 100% isotactic PP has never been reported). Further, if the first fraction has a ratio of the weight average molecular weight (M wl ) of the first fraction to that (M wo ) of the original unfractionated sample of less than 3, addition of such a first fraction to conventional PP exhibits no effect of improving the crystallinity of the resulting PP. The upper limit of the ratio of M wl to M wo has no particular limitation, and it is unclear what extent the upper limit is to. To the highly crystalline PP of the present invention may be added various additives added to conventional PP such as antioxidant, heat stabilizer, UV absorber, antiblocking agent, antistatic agent, metal deactivator, neutralizing agent such as metal soaps, dispersing agent, coloring agent, lubricant, various inorganic fillers (e.g. talc and mica), polyethylene (according to low, medium or high pressure process), ethylene-propylene rubber (EPR), ethylenepropylene block copolymer. The highly crystalline PP may be produced for example by using the so-called Ziegler-Natta catalyst i.e. a combination of a Ti-containing solid component (a solid compound composed mainly of TiCℓ₃ or a solid compound having TiCℓ₄ supported on a carrier such as MgCℓ₂) with an organoaluminum compound or in some cases, a combination of the above-mentioned two components with an electron donor as a third catalyst component, and also by employing a polymerization process comprising a part of the stages where propylene is polymerized under specified conditions i.e. at a relatively low polymerization temperature (such as room temperature to about 60°C) and substantially in the absence of a molecular weight modifier (usually hydrogen gas), according to slurry polymerization carried out in an inert solvent, bulk polymerization using propylene itself as solvent, gas phase polymerization using mainly propylene gas. Further, a process wherein a large amount of an aromatic carboxylic acid ester such as methyl p-toluylate and methyl p-anisate is used as a third catalyst component may also be employed. In this case, the process comprises a stage wherein propylene is polymerized at relatively high temperature such as 60° to 75°C and in the presence of a certain quantity of a molecular weight modifier. According to this process, it is presumed that addition of the aromatic carboxylic acid ester broaden the molecular weight distribution of the resulting PP and also improve its stereoregularity to a large extent. The highly crystalline PP of the present invention is constituted by a novel primary structure with which conventional PP has never been provided, and this primary structure exhibits an extremely high crystallinity which has never been observed. For example, the highly crystalline PP of the present invention exhibits the following characteristic melting and crystallization behaviors: (i) the crystallization rate is high; (ii) the number of crystalline nuclei generated is large; (iii) the growth rate of spherulite is high; (iv) the crystallinity is high and the density of solids is high; (v) the melting point is high; and (vi) the crystallization on-set temperature at the time of temperature-lowering and the peak top temperature measured by means of DSC apparatus are high. When the PP having such high crystallinity is molded and processed, it is possible to notably improve the mechanical properties of the resulting molded products and also notably reduce the cost of molding and processing as follows, as compared with the case where conventional PP is used: (i) the molded and processed products are stiff and a firm feeling can be secured; (ii) it is possible to make the molded products thinner; (iii) the thermal deformation and thermal softening at high temperatures are reduced; (iv) the surface has a high hardness and a superior resistance to surface scratching; (v) deformation under load is difficult to occur; (vi) the chemical resistance is improved; (vii) the linear thermal expansion coefficient is small; (viii) the stretching-molded and processed products have a low percentage of heat shrinkage; and (ix) at the time of secondary processing accompanied with heating, processing at higher temperatures than those employed so far is possible; hence it is possible to make the production cycle faster. Due to the above-mentioned improvement in the performances of molded and processed products, the highly crystalline PP can be applied concretely to fields of industrial parts and products around automobiles and domestic appliances. Further, by replacing polystyrene or ABS resin so far used in these fields by the cheap highly crystalline PP, it is possible to reduce the cost of the final products. One of the effects of the present invention consists in that it has become possible to elevate the level of stiffness of PP up to that of polystyrene or ABS resin which conventional PP could not have attained, and also broaden the use applications of PP towards those of these resins. Namely, it can be expected to use the PP as heat-resistant parts, thin and highly stiff parts as enumerated below: (i) housing for car heater, distributor cap as automobile parts and back cover for TV set, light body, cover for an electric rice cooker in appliances; (ii) ceiling plate, vegetables box of refrigerator, highly stiff parts such as tank, cover, control box, pulsator of an electric washing machine; (iii) parts needing heat resistivity or high stiffness such as propeller fan as general industrial parts, bath corner, caps, compact case, vessel for an electronic range, painting pallet and parts for daily commodities sanitary fixtures, e.g. toothbrush handle and hairbrush handle, toilet seat and toiletry goods; (iv) biaxially oriented film, cast film, flat yarn, monofilaments, band and sheets for food tray. The present invention will be described in more detail by way of Examples. The measurement of the above-mentioned primary sturcture and the measurement of physical properties of the resulting molded products were carried out according to the following methods: 1) Measurement method of IR-τ: A sample was molded into a film by preheating it for one minute and pressing for one minute by means of a press-molding machine at 200°C, followed by immediately water-cooling the film down to 20°C to obtain a film of about 40 µm thick. This film was then placed in an annealing tube, followed by sucking in vacuo and thereafter annealing in an oil bath at 135°C for one hour. Three small films were cut out of the annealed film, followed by measuring the absorbance ratios (A₉₉₇/A₉₇₃) at 997 cm⁻¹ and 973 cm⁻¹ with the respective small films as samples to render the average value of the ratios as IR-τ value. The measurement of the average value was carried out by means of an infrared spectrophotometer of Perkin-Elmer 783 type. 2) Fractionation method of the "first fraction": In a 1 ℓ three-neck flask was placed PP (1.8 g) and xylene (900 mℓ), followed by adding a phenolic antioxidant (0.9 g), heating the mixture with stirring (agitating blades: half round shape blades made of Teflon) to completely dissolve it, gradually cooling it after dissolution at a revolution number of 300 rpm and lowering the temperature of the xylene solution at a temperature-descending rate of 5°C/hr when the solution temperature reached 100°C or lower. Polymer deposition on agitating blades began and when the percentage by weight of the deposits reached 2 to 3%, agitation was stopped and the deposits adhered onto the agitating blades were recovered. 3) Measurement method of weight average molecular weight: The weight average molecular weight was measured by means of gel permeation chromatograph (150C type (tradename) manufactured by Waters Company; measurement temperature, 135°C; mobile phase, orthodichlorobenzene; column, TSK gel GMH 6-HT). 4) MFR: according to JIS K 6758. 5) Pelletization of PP powder: As to the pelletization of PP powder obtained by polymerization, blending and granulation were carried out using the following formulation of additives unless otherwise indicated: A phenolic heat stabilizer (4 g) and calciumstearate (4 g) were added to PP powder (4 Kg), followed by blending the mixture at room temperature for 5 minutes by means of a high speed agitating mixer (Henschel mixer (tradename)) and pelletizing the resulting blend by means of a single screw extruder having a screw bore diameter of 40 mm, to obtain pellets. 6) Preparation of test pieces for measuring the physical properties of injection-molded products: The sample obtained by the above pelletization was molded by means of a screw in-line type injection molding machine manufactured by Nippon Seikosho Company at a temperature of 230°C and a mold-temperature of 50°C to prepare a definite test piece, followed by subjecting the test piece to conditioning in a chamber of a constant humidity (RH 50%) and a constant temperature (room temperature, 23°C) for 72 hours and using the resulting test piece for measurement of physical properties. 7) Method of measuring the physical properties of injection-molded products: i) Flexural modulus: according to JIS K 7203 (unit: [(MPa)(Kgf/cm²)] ii) Flexural strength: according to JIS K 7203 (unit: [(MPa)(Kgf/cm²)] iii) Tensile strength: according to JIS K 7113 (unit: [(MPa)(Kgf/cm²)] iv) Rockwell hardness (R scale): according to JIS K 7202 v) Heat distortion temperature (HDT) : at 4.6 x 10⁻⁴Kg/m² according to JIS K 7207 (4.6 Kg/cm²) (unit:°K) vi) Izod impact strength: according to JIS K 7110 (23°C) (unit: N. m/m) 8) Method of measuring the physical properties of films: i) Young's modulus: according to ASTM D-888 (unit: [(MPa)(Kgf/cm²)] ii) Tensile yield strength: according to ASTM D-882 (unit: [(MPa) Kgf/mm²)] iii) Haze: according to ASTM D-1003 (unit: %) iv) Punching impact strength: according to ASTM D-781 (unit: [(MPa)(Kgf/mm²)] 9) Method of measuring the physical properties of fibers: Fineness: according to JIS Z 1533-1970 Tenacity: according to JIS Z 1533-1970 (unit: N/d) Elongation: according to JIS Z 1533-1970 (unit: %) 10% Young's modulus: according to JIS Z 1533-1970 (unit: N/d) Percentage heat shrinkage: (1) A filament to be measured is loaded on a metal measure or a measuring tape placed horizontally; one end of the filament is fixed, thereafter a weight of 30 to 50 g is attached onto another end and vertically hung down in inverted L manner; and in a state where the filament is stretched in the horizontal direction, gage marks are attached onto the filament at a distance of 1 m between the gage marks. (2) The filament having the gage marks attached thereonto is placed in an oven adjusted to a definite testing temperature and heated for 15 minutes. (3) The resulting filament taken out of the oven is cooled down to room temperature, followed by again measuring the distance between the gage marks of the filament according to the abovementioned method (1) and calculating the reduction proportion of the lengths before and after heating in the oven. wherein A: distance between the gage marks before the heating (1,000 mm) B: distance between the gage marks after the heating (mm) The highly crystalline PP of the present invention may be produced according to various processes. Embodiments are shown in Examples 1 - 9. Example 1 (1) Preparation of catalyst: n-Hexane (600 mℓ), diethylaluminum monochloride (DEAC) (0.50 mol) and diisoamyl ether (1.30 mol) were mixed at 25°C for one minute, followed by reacting these at the same temperature for 5 minutes to obtain a reaction liquid (I) (the molar ratio of diisoamyl ether/DEAC: 2.6). TiCℓ₄ (4.5 mols) was placed in a nitrogen gas-purged reactor, followed by heating it to 35°C, dropwise adding thereto the total quantity of the above reaction liquid (I) over 300 minutes, keeping the mixture at the same temperature for 60 minutes, raising the temperature up to 85°C, further reacting the mixture for one hour, cooling the resulting material down to room temperature, removing the supernatant, adding n-hexane (4,000 mℓ), removing the supernatant by decantation, four times repeating the washing operations to obtain a solid product (II) (190 g), suspending the whole of the product (II) in n-hexane (3,000 mℓ), adding to the suspension, diisoamyl ether (290 g) and TiCℓ₄ (350 g) at 20°C over about one minute, reacting the mixture at 75°C for one hour, cooling the resulting material down to room temperature (20°C) after completion of the reaction, removing the supernatant by decantation, adding n-hexane (4,000 mℓ), agitating the mixture for 10 minutes, allowing it to stand still, five times repeating the operations of removing the supernatant and drying the resulting material under reduced pressure to obtain a solid product (III). (2) Preparation of preactivated catalyst: Into a 20 ℓ capacity stainless reactor equipped with slant blades and purged with nitrogen gas were added n-hexane (15 ℓ), diethylaluminum monochloride (42 g) and the solid product (III) (30 g) obtained above at room temperature (20°C), followed by feeding propylene (30 g) at a rate of 0.5 g/min. over 60 minutes, further agitating the mixture for 8 hours, removing unreacted propylene and n-hexane under reduced pressure to obtain a preactivated catalyst (IV) (about 1 g of propylene per g of the solid product (III), reacted). (3) Propylene polymerization: Into a 250 ℓ capacity stainless polymerization vessel equipped with turbine type agitating blades and purged with nitrogen gas were fed n-hexane (100 ℓ) and then diethylaluminum monochloride (20 g), the preactivated catalyst (IV) (40 g) obtained above and methyl p-toluylate (40,0 g) as an aromatic carboxylic acid ester, followed by raising the temperature up to 40°C, feeding propylene to raise the total pressure up to (0,98 MPa·G) (10 Kg/cm²G), polymerizing it at 40°C, under (0,98 MPa·G) (10 Kg/cm²G) and for 15 minutes, and further as a second stage polymerisation, adding hydrogen (250 Nℓ), raising the temperature up to 50°C and continuing polymerization for 3 hours and 45 minutes, thereafter feeding methanol (25 ℓ), raising the temperature up to 90°C, after 30 minutes, adding a 20% by weight NaOH aqueous solution (100 g), agitating the mixture for 20 minutes, adding purified water (50 ℓ), discharging residual propylene, Withdrawing the resulting aqueous layer, adding purified water (50 ℓ), water-washing the mixture with stirring for 10 minutes, withdrawing the aqueous layer, again adding purified water (50 ℓ), water-washing the mixture with stirring for 10 minutes, withdrawing the aqueous phase, then withdrawing a PP-n-hexane slurry, filtering it and drying to obtain PP powder (MFR=1.4, yield 35 Kg). Comparative example 1 Propylene was polymerized under the preparation conditions indicated in Table 1 mentioned later to obtain PP powder (32 Kg). With PP powder obtained in the above Example 1 and Comparative example 1, MFR, IR-τ, IR-τ of the first fraction and M wl /M wo were measured. Further, with the PP powder, pellets were prepared and with the pellets, definite test pieces for measuring the physical properties of injection-molded products were prepared to measure their mechanical physical properties. The results are collectively shown in Table 1. Examples 2, 3, 4, 5 and 6 In Examples 2 to 5, Example 1 was repeated except that among the preparation conditions of Example 1, the quantity of hydrogen at the time of the second stage polymerization was varied as indicated in Table 1. Further, in Example 6, Example 1 was repeated except that among the preparation conditions of Example 1, the quantity of the preactivated catalyst was made half, addition of the carboxylic acid ester was omitted and the quantity of hydrogen was varied as indicated in Table 1. With the thus obtained PP powder, MFR, IR-τ, IR-τ of the first fraction and ratio of M wl /M wo were measured and with pellets prepared from the PP powder, definite test pieces were prepared to measure the mechanical physical properties of injection-molded products, in the same manner as in Example 1. The results are shown in Table 1. Comparative examples 2, 3 and 4 Three kinds of PP powder for commercially available grades manufactured by Chisso Corporation (Comparative example 2: PP powder (A) for a grade A 5012, MFR=2.2; Comparative example 3: PP powder (B) for a grade K 1016, MFR= 5.8; and Comparative example 4: PP powder (C) for a grade K 1800, MFR=21.5) were pelletized and test pieces were prepared therefrom. With the above kinds of PP powder, MFR, IR-τ, IR-τ of the first fraction and ratio of M wl /M wo were measured in the same manner as in Example 1. Further, with pellets prepared therefrom, definite test pieces were prepared according to injection-molding process to measure their mechanical physical properties. The results, are shown in Table 2. Examples 7 and 8 and Comparative example 5 In Example 7, into a 50 ℓ capacity stainless polymerization vessel equipped with turbine type agitating blades and purged with nitrogen gas were fed propylene (18 Kg), diethylaluminum chloride(6g) having H₂S (0.0008 mol) and collidine (0.0008 mol) mixed therein in advance and the preactivated catalyst of Example 1 (5 g) at room temperature, followed by raising the temperature up to 45°C, polymerizing the mixture for 15 minutes while keeping the temperature, further adding hydrogen (80 Nℓ), polymerizing the resulting material for 3 hours and 45 minutes, thereafter discharging unreacted propylene, feeding isobutanol (15 ℓ), agitating the mixture at 90°C for one hour, adding a 20% by weight NaOH aqueous solution (40 mℓ), agitating the mixture for 20 minutes, adding purified water (10 ℓ) , agitating the mixture for 10 minutes, withdrawing the resulting aqueous layer, further twice repeating washing with purified water (10 ℓ) and withdrawal, thereafter withdrawing a PP-isobutanol slurry, filtering and drying to obtain PP powder (6.1 Kg). Example 8 was carried out in the same manner as in Example 7 except that among the conditions of Example 7, diethylaluminum monochloride containing neither H₂S nor collidine was used and the conditions indicated in Table 2 were employed. Comparative example 5 was carried out in the same manner as in Example 8 except that among the conditions of Example 8, the quantity of propylene was changed to 16 Kg, the first stage polymerization was omitted and the conditions indicated in Table 2 were employed. With the respective PP powders obtained in such Examples and Comparative example, MFR, IR-τ, IR-τ of the first fraction and ratio of M wl /M wo were measured. Further, the respective PP powders were pelletized and test pieces for measuring the physical properties of definite injection-molded products were prepared from the resulting pellets to measure their mechanical physical properties. The results are collectively shwon in Table 2. Example 9 and Comparative example 6 Into a 50 ℓ capacity stainless polymerization vessel equipped with anchor type agitating blades and purged with nitrogen gas was fed PP powder (300 g) obtained in Comparative example 1, followed by five times repeating pressurizing of propylene gas (0,49 MPa·G) (5 Kg/cm²·G) and pressure-dropping thereof (MPa·G) (0 Kg/cm²·G), thereafter feeding diethylaluminum chloride (6 g), the preactivated catalyst of Example 1 (4 g) and methyl p-anisate (2 g) at room temperature, raising the temperature up to 60°C, pressurizing the contents with propylene gas up to 1.96 MPa·G (20 Kg/cm²·G) carrying out polymerization at 60°C for 20 minutes. Hydrogen gas (45 Nℓ) was then added, followed by further carrying out polymerization at 60°C, under 1.96 MPa·G (20 Kg/cm²·G) for 3 hours and 45 minutes, thereafter discharging unreacted propylene gas, feeding propylene oxide (10 g) and water (30 g), agitating the mixture at 95°C for 30 minutes, passing nitrogen gas for drying, cooling the resulting material down to room temperature and taking out PP powder. Comparative example 6 was carried out in the same manner as in Example 9 except that the first stage polymerization was omitted and preparation conditions were varied as shown in Comparative example 6 of Table 2. With the respective PP powders of the Example and Comparative example, MFR, IR-τ, IR-τ of the first fraction and ratio of M wl /M wo were measured. Further, the respective PP powders were pelletized and test pieces for measuring the mechanical physical properties of definite injection-molded products were prepared from the resulting PP pellets to measure their mechanical physical properties. The results are collectively shown in Table 2. As apparent from the results of Tables 1 and 2, molded products obtained from the highly crystalline PP of the present invention have not only a superior stiffness at room temperature but also a far superior stiffness particularly at 80°C. Examples 10 and 11 and Comparative examples 7 and 8 In Examples 10 and 11, homo PP part was first obtained in the same manner as in Examples 1 to 5, followed by preparing an ethylene-propylene random copolymer part (RC part) by polymerization so that the random copolymer part could have a composition consisting of 60% by weight of ethylene and 40% by weight of propylene and also the content of the total ethylene in the resulting block copolymer as a final polymer could be 8% by weight, to obtain powder of the block copolymer. In Comparative examples 7 and 8, homo PP part was first obtained in the same manner as in Comparative example 1, followed by successively preparing an ethylene-propylene random copolymer (RC part) by polymerisation so that the RC part could have a composition consisting of 60% by weight of ethylene and 40% by weight of propylene and also the content of the total ethylene in the resulting block copolymer as a final polymer could be 8% by weight, to obtain powder of the block copolymer. The respective portions of the homo-PPs of these Examples and Comparative examples were withdrawn, followed by purification and drying as in Example 1 to obtain PP powders, which were then subjected to measurements of MFR, IR-τ, IR-τ of the first fraction and ratio of M wl /M wo . Further, MFRs of powders of block copolymers obtained from the above PP powders were measured. Further, the block copolymers were pelletized and test pieces for measuring the physical properties of definite injection-molded products were prepared from the pellets to measure their mechanical physical properties. The results are shown in Table 3. As apparent from Table 3, it has so far been difficult for block copolymers to raise their stiffness without lowering their impact properties. As apparent from the results of Table 3, the block copolymers of the present invention containing a highly crystalline PP as its homo-PP part have overcome the above difficulty, and the block copolymers of Examples 10 and 11 are not only superior in the stiffness at room temperature to those of Comparative examples 7 and 8, but also particularly they are far superior therein at high temperatures. Examples 12, 13 and 14 PP powder obtained in Example 5 was pelletized, and in this pelletization, aluminum p-tert.-butylbenzoate (0.3% by weight) (Example 12) as a nucleating agent or talc (20% by weight) (Example 13) or calcium carbonate (20% by weight) (Example 14) was additionally added to the additive used in the pelletization. Test pieces were prepared according to injection molding. The results of measurements of physical properties are shown in Table 4. Comparative examples 9, 10 and 11 PP powder used in Comparative example 4 was pelletized, but in this pelletization, the additionally added additives and their quantities added were as follows: Comparative example 9: aluminum p-tert.-butylbenzoate (0.3% by weight) Comparative example 10: talc (30% by weight); and Comparative example 11: CaCO₃ (40% by weight). The measurement results of mechanical physical properties are shown in Table 4. As apparent from the results of Example 5 of Table 1 and those of Examples 12, 13 and 14 of Table 4, nucleation effectiveness and addition effectiveness of filler upon the highly crystalline PP are clearly observed as in the case of conventional PP, and by adding these, it is possible to further improve the stiffness of the highly crystalline PP. Further, as apparent from comparison of Example 13 with Comparative example 10 and that of Example 14 with Comparative example 11, when the highly crystalline PP is used, it is possible to achieve stiffness to the same extent as that of conventional PP only by adding a less quantity of filler. Examples 15, 16 and 17 Powder of ethylene-propylene block copolymer obtained in Example 11 was pelletized, and in this case, the additionally added additives and their quantities added were as follows: Example 15: aluminum p-tert.-butylbenzoate (0.3% by weight); Example 16: talc (20% by weight); and Example 17: CaCO₃ (20% by weight). The measurement results of mechanical physical properties are shown in Table 4. Comparative examples 12, 13 and 14 Powder of ethylene-propylene block copolymer obtained in Comparative example 8 was pelletized, and in this case, the additionally added additives and their quantities added were as follows: Comparative example 12: aluminum p-tert.-butylbenzoate (0.3% by weight); Comparative example 13: talc (30% by weight); and Comparative example 14: CaCO₃ (40% by weight). The measurement results of physical properties are shown in Table 4. Comparative example 15 A commercially available high-impact polystyrene (trademark: Stylon 492) was injection-molded and test piece was prepared, followed by measurement of physical properties. The measurement results are shown in Table 4. In the case of the block copolymers containing the highly crystalline PP as homo-PP part, it is also possible to further make the stiffness higher without damaging impact properties due to nucleation effectiveness and filler addition effectiveness (see the measurement values of physical properties of Example 11 in Table 3 and Examples 15, 16 and 17 in Table 4). Further, by using these block copolymers, it is also possible to notably reduce the quantity of filler added while keeping the strength to nearly the same extent as that of conventional block copolymers. Namely, it is possible to reduce the quantity of talc added by 10% by weight (see Example 16 and Comparative example 13), and it is possible to reduce the quantity of CaCO₃ added by 20% by weight (see Example 17 and Comparative example 14). Further, the block copolymers of the present invention have a far higher flexural strength and flexural modulus at high temperatures (e.g. 80°C) than those of conventional block copolymers. The firm feeling under heating extends the use applications of PP to a large extent. For example, it is possible to extend its use applications as far as those in the fields of high-impact polystyrene and ABS. The polymer shown in Comparative example 15 is a high-impact polystyrene. The highly crystalline PP of the present invention has nearly the same stiffness at 23°C as that of the polystyrene (see Examples 1 to 5 and Comparative example 15), and in the case of the block copolymer of the present invention composed basically of the highly crystalline PP, filler addition makes it possible to develop a stiffness which is the same as or higher than that of the above-mentioned polystyrene. Example 18 and Comparative example 16 In Example 18, PP powder obtained in Example 4 was used, and in Comparative example 16, PP powder of commercially available grade manufactured by Chisso Corporation (grade name: K1008, MFR=10.3). To the respective PP powders (5 Kg) were added a phenolic heat stabilizer (0.005 Kg), calcium stearate (0.005 Kg) and fine powder of silica (average particle diameter: 0.1 µm) (0.01 Kg), followed by pelletization. The respective pellets were subjected to film-making by means of a film-making machine manufactured by Yamaguchi Seisakusho Company (tradename: CYT), at a die temperature of 215°C and at a cooling water temperature of 20°C to prepare an inflation film having a folded width of 150 mm and a thickness of 30 µm. The film was subjected to conditioning in a chamber of constant temperature (room temperature 23°C) and constant humidity (RH 50%) for 72 hours, followed by measuring the physical properties indicated in Table 5. The measurement results of film are shown in Table 5. The Young's modulus in Example 18 is seen to be much more improved than that in Comparative example 16. Example 19 and Comparative example 17 In Example 19, PP powder obtained in Example 1 was used, and in Comparative example 17, PP powder of commercially available grade manufactured by Chisso Corporation (grade name: A5012; MFR=2.2). To the respective PP powders (5 Kg) were added a phenolic heat stabilizer (0.005 Kg), calcium stearate (0.005 Kg) and fine powder of silica (average particle diameter: 0.1 µm) (0.0075 Kg), followed by pelletization. The resulting pellets were extruded by a T die type film-making machine at a resin temperature of 250°C, followed by quenching by means of a cooling roll at 20°C to prepare sheets of 1 mm thick, heating the sheets by hot air at 150°C for 70 seconds, stretching them by means of a biaxially stretching machine to 7 times the original lengths at the same time in both the longitudinal and lateral directions to obtain biaxially oriented films of 20 µm thick, Subjecting the films to conditioning in a chamber of constant temperature (room temperature, 23°C) and constant humidity (RH 50%) for 72 hours, and measuring the physical properties of the films indicated in Table 5. The measurement results of the physical properties of the films are shown in Table 5. Even when the highly crystalline PP of the present invention is applied to biaxially oriented films, the Young's modulus is notably improved and also the secondary percentage of heat shrinkage at high temperatures is reduced to a large extent; hence it is possible to raise the drying temperature at the stage of secondary processing such as printing, etc. to thereby shorten the processing time. Example 20 and Comparative example 18 In Example 20, PP powder obtained in Example 3 was used, and in Comparative example 18, PP powder of commercially available grade manufactured by Chisso Corporation (grade name: K1016; MFR=5.8) was used. The respective PP powders (4 Kg) were pelletized, followed by extruding the resulting pellets by means of an extruder having a bore diameter of 40 mm, a nozzle diameter of 0.5 mm and a hole number of 150, to obtain unstretched filaments of 15 d/f, followed stretching these filaments by means of a usual stretching machine at stretching ratios of 5 times, 6 times and 7 times the original length, successively subjecting the stretched filaments to heat treatment of 5% relaxing while heating them on a hot plate having a surface temperature of 130°C to obtain filaments of 3 to 6 d and measuring the tenacity and the percentage of heat shrinkage indicated in Table 6. The measurement results are shown in Table 6. The percentages of heat shrinkage in Example 20 is lower than those in Comparative example 18, and particularly as the temperature rises, the difference therebetween is notable. Further, the tenacity and Young's modulus are also higher. The filament according to the present invention refers collectively to filament staple and filament of odd-shaped cross-section obtained by melt-spinning PP, stretched filament, heat-treated filament, and products converted from the foregoing, and since the percentage of heat shrinkage is improved to a large extent, it is possible to carry out heat treatment at higher temperatures at the drying step in the production process of products such as carpet; hence improvement in productivity can be expected.

Claims: A highly crystalline polypropylene characterized by satisfying the following conditions (A) and (B): (A) its melt flow rate (MFR) and absorbance ratio according to the method of infrared absorption spectra (IR- τ ; the absorbance ratio of the wave-number of infrared rays of 997 cm⁻¹ to that of 973 cm⁻¹, i.e. A₉₉₇/A₉₇₃) satisfy the equation of IR- τ ≧ 0.0203 log MFR + 0.950 and its MFR is in the range of 0.1 to 200; and (B) when a dilute solution of said polypropylene dissolved in xylene in a concentration of 0.2 wt/vol.% is slowly cooled at a rate of 5°C/hr with stirring, at a revolution number of 300 rpm, an initially deposited component in 2 to 3 % by weight has an IR- τ value of 0.97 or more and the weight average molecular weight (M wl ) of the deposited component and that (M wo ) of said polypropylene have a ratio (M wl /M wo ) of 3 or more.

Inventors: CHIBA HIROMASA, HANARI TOHRU, MATSUDA KIYOSHI, MORI KINYA, NAMIKI ICHIRO, CHIBA, HIROMASA, HANARI, TOHRU, MATSUDA, KIYOSHI, MORI, KINYA, NAMIKI, ICHIRO
Applicants: CHISSO CORP, CHISSO CORPORATION
Application year: 1988
Main classification: C08F10
IPC codes: C08L23, C08F10, C08F110, C08F8, C08F297, C08F4