JP2818273B2 - Molding method for syndiotactic polypropylene - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a molded product of syndiotactic polypropylene. In detail, a relatively high tacticity syndiotactic polypropylene homopolymer or a copolymer of propylene and a small amount of other olefins, or a mixture of them and isotactic polypropylene, and a high degree of crystallinity The present invention relates to a method for producing a molded article having excellent physical properties.

[Conventional technology]

The existence of syndiotactic polypropylene has been known for a long time.However, a polymer obtained by polymerizing at low temperature in the presence of a conventional catalyst comprising a vanadium compound, an ether compound and an organoaluminum compound has a syndiotacticity. It was said to have bad, elastomeric properties. However, it is hard to say that this elastomeric physical property has the inherent characteristics of syndiotactic polypropylene. Recently, JAEWEN et al., For the first time, were able to obtain a polypropylene with good tacticity with a syndiotactic pentad fraction exceeding 0.7 using a catalyst composed of a transition metal compound having an asymmetric ligand and an aluminoxane. Was discovered (J. Am. Chem. Soc., 198
8,110,6255-6256).

[Problems to be solved by the invention]

The syndiotactic polypropylene obtained by the above method or a copolymer of propylene having substantially a syndiotactic structure and another olefin, or a mixture thereof with a small amount of a polypropylene having an isotactic structure. It has been found that a molded article molded by a usual molding method has relatively good impact resistance, but does not have sufficient rigidity.

[Means for solving the problem]

Means for Solving the ProblemsThe present inventors have solved the above problem and have intensively searched for a method for producing a syndiotactic polypropylene molded article having excellent rigidity, and found that a molded article having high crystallinity and excellent rigidity can be obtained by a specific molding method. And completed the present invention.

That is, the present invention relates to a homopolymer of propylene having a substantially syndiotactic structure or a copolymer of propylene and a small amount of another olefin, or a copolymer thereof with a small amount of a polypropylene having a substantially isotactic structure. This is a method for syndiotactic polypropylene, which comprises subjecting the mixture to heat-melt molding, stretching, and further subjecting the mixture to a heat treatment at a load equal to or higher than the stretching temperature.

In the present invention, examples of the catalyst used for producing a propylene homopolymer having a substantially syndiotactic structure or a copolymer with a small amount of other olefins include the compounds described in the above-mentioned literatures. Even a catalyst having a structure can be used as long as it is capable of producing a polypropylene having a syndiotactic pentad fraction of 0.7 or more when homopolymerization of propylene is performed.

In the present invention, the homopolymer of propylene having a substantially syndiotactic structure is a syndiotactic that appears in about 20.2 ppm based on tetramethylsilane as measured in ^13C -NMR at 135 ° C. in trichlorobenzene. The peak of the methyl group attributed to the pentad structure is at least 0.5 with respect to the sum of the peaks of all the methyl groups, more preferably
It has a high syndiotactic structure of 0.7 or more, and 10 wt.
% Of crystalline polypropylene. Further, in the copolymer, monomers other than propylene
wt% or less, about 20.2 ppm by ¹³ C-NMR measured in the same manner.
A highly syndiotactic structure having a peak intensity of 0.3 or more, more preferably 0.5 or more, of the peak intensity attributed to the methyl group of all propylene is shown.

Examples of the transition metal compound having an asymmetric ligand useful for producing the polymer described above in the present invention include isopropylene (cyclopentadienyl-1-fluorenyl) hafnium dichloride or isopropyl (Cyclopentadienyl-1-fluorenyl) zirconium dichloride and the like are exemplified. (Wherein R is a hydrocarbon residue having 1 to 3 carbon atoms). In particular, methylaluminoxane wherein R is a methyl group and n is 5 or more, preferably 10 or more is used. You. The use ratio of the aluminoxane to the transition metal compound is 10 to 100,000,000 mole times, usually 50 to 5000.
It is molar times.

The polymerization conditions are not particularly limited, and a solvent polymerization method using an inert medium, a bulk polymerization method in which substantially no inert medium is present, and a gas phase polymerization method can be used. The polymerization temperature is -100 to 200 ° C, and the polymerization pressure is normal pressure to 100 kg /
It is generally performed in cm ² . Preferably -100 to 100
° C, normal pressure ~ 50 kg / cm ² .

Examples of other olefins used for copolymerization with propylene include ethylene and α-olefins having 4 to 20 carbon atoms, and specifically, butene-1, pentene-
1, hexene-1, heptene-1, octene-1, nonene-1, decene-1, undecene-1, dodecene-1,
Tridecene-1, tetradecene-1, pentadecene-
Linear α such as 1, hexadecene-1, octadecene-1, etc.
-Olefin is exemplified, and further 3-methylbutene-
Examples thereof include branched α-olefins such as 1,4-methylpentene-1,4,4-dimethylpentene-1. Polymerization is carried out under the condition that the proportion of propylene and a small amount of other olefins in the copolymer is usually 20% by weight or less, preferably 10% by weight or less. If the content exceeds 20% by weight, the rigidity of the molded body is undesirably reduced. The conditions for the copolymerization are not particularly limited, and known ordinary conditions can be employed.

In the homopolymerization and copolymerization in the present invention, usually, one-stage polymerization is carried out, the polymer synthesized in this way has a narrow molecular weight distribution, the weight average molecular weight and the number average molecular weight measured at 135 ° C. by gel permeation chromatography. The ratio (hereinafter abbreviated as MW / MN) is usually 1.5 to 3.5
It is effective to use two kinds of transition metal compounds (for example, it is effective to use two kinds of metal such as zirconium and hafnium) or to mix two or more kinds of compounds having different molecular weights. From the above, those having a broad molecular weight distribution of about 15 can be produced and can be used in the present invention.

The preferred molecular weight of the polymer used in the present invention is 0.1 to 20 as an intrinsic viscosity (hereinafter abbreviated as η) measured at 135 ° C. tetralin solution, preferably
It is in the range of 0.5 to 10.0.

In the present invention, a part of the syndiotactic polypropylene or the syndiotactic polypropylene copolymer can be replaced with, for example, polypropylene having an isotactic structure in a range of less than 50% by weight, preferably 40% by weight or less. By doing so, it is also possible to obtain a molded article having higher rigidity. As the isotactic polypropylene used in this case, various brands available on the market can be used, and titanium trichloride or titanium tetrachloride which gives so-called highly stereoregular polypropylene is used as magnesium halide. It can be synthesized as a supported one, and those having an isotactic pentad fraction measured by ¹³ C-NMR of 0.9 or more are preferably used, and η measured under the above conditions is 0.1 to 10, preferably 0.5.
Up to about 5 can be used. In this method, if the amount of the polypropylene having the isotactic structure exceeds 50% by weight, the impact resistance becomes poor.

The above-mentioned polypropylene homopolymer having a substantially syndiotactic structure or a copolymer of propylene and a small amount of other α-olefin of the present invention, or a small amount thereof and a polypropylene having a substantially isotactic structure; Is then melted by heating and formed into a specific shape. There is no particular limitation on the molding method, but since it is necessary to stretch after molding, an extrusion molding method is preferred, and a blow molding method in which extrusion is followed by stretching is preferred.

It is common practice to improve the physical properties such as rigidity by increasing the crystallinity by heating and annealing the crystalline polymer after molding, and the reason is unknown, but for polypropylene with high syndiotacticity, If the temperature is not increased to a temperature close to the melting point by simply heating, not only it takes much time to improve the crystallinity, but also the attained crystallinity is not sufficient. In contrast, stretching before heating was found to be extremely effective.

What is important in the present invention is that the molded article is stretched and then heat-treated after molding, whereby the crystallinity can be improved and the physical properties can be improved.

Stretching is performed at room temperature to heating, but in a molded product formed by quenching after heating and melting, it can be stretched at a relatively low temperature near room temperature, and by doing so, about 7.
Those without 1Å diffraction line can be easily manufactured.
Further, in the case of a film produced by cooling under ordinary conditions, it is preferable to stretch by heating to 100 ° C. or more to the melting point or less, and in this case, the heating temperature after stretching is set higher. After forming by heating and melting, the film can be stretched by cooling to the stretching temperature without cooling completely.

The temperature condition of the heat treatment employed in the present invention is a temperature of 50 ° C. or higher, preferably 80 ° C. or higher and lower than the melting point of the molded product, and a temperature higher than the temperature at the time of stretching. The necessary heating time is not particularly limited because the preferred range varies depending on the melting point and heating temperature of the polymer and the degree of stretching, but the heating time is in the range of several seconds to several tens of hours. The higher the temperature is, the shorter the heating time is sufficient, and if the temperature is 100 ° C. or more, heating for several minutes to several tens minutes is sufficient.

In addition, the degree of stretching is large, and the above-mentioned X-ray diffraction spectrum shows that the diffraction line of about 7.1 ° is greatly reduced by stretching, or that it is heated and melted and then rapidly cooled (about 7.1 ° diffraction line is not observed) Or weak)
When the heating temperature is set to about 100 ° C., it is sufficient to heat for several minutes to several tens minutes. By heating after stretching in this manner, crystallization is sufficiently advanced even if the heating time is short, and the physical properties are improved. The heat treatment is preferably performed in a state where the stretched product is fixed and under a load, so that deformation of the molded product can be avoided.

In the molding of the above-mentioned polymer of the present invention, additives usually used in the molding of polyolefin, for example,
An antioxidant, an ultraviolet absorber, a crystallization nucleating agent and the like may be mixed and used. As the crystallization nucleating agent used at this time,
Any material can be used as long as it can raise the crystallization temperature of the syndiotactic polypropylene, and usually has a higher melting point than the syndiotactic polypropylene, and a small contact energy with the syndiotactic polypropylene. The crystallization nucleating agent for isotactic polypropylene can also be used. For example, salts of benzoic acid, benzylidene sorbitols, salts of phosphates, quinacridone or polyvinylcyclohexane, poly 3-methylbutene, crystalline polystyrene, polyolefins having a high melting point such as trimethylvinylsilane can be preferably used,
In addition, inorganic compounds such as talc, kaolin, and mica can also be preferably used. The amount of the crystallization nucleating agent varies depending on the type of the crystallization nucleating agent, but is usually about 0.001 ppm to 1 wt% based on the polymer.

〔Example〕

 Hereinafter, the present invention will be described with reference to Examples.

Example 1 10 mg of isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride obtained by lithiating isopropylcyclopentadienyl-1-fluorene synthesized by an ordinary method in an autoclave having an internal volume of 2 and reacting with zirconium tetrachloride. And 1.36 g of methylaluminoxane having a degree of polymerization of about 15 obtained by reacting copper hexahydrate and trimethylaluminum in toluene were dissolved in toluene 1 at a polymerization pressure of 2 kg / cm ² -G at 50 ° C. for 1 hour. Polymerized. After the reaction, unreacted propylene was purged, the slurry was taken out, filtered at 30 ° C., and washed five times with 500 ml of toluene. Then, the powder obtained by drying under reduced pressure at 80 ° C. was 28 g, and according to ¹³ C-NMR, the syndiotactic pentad fraction was 0.902, η was 0.88, and MW /
MN was 2.2. Pressing this powder at 250 ° C
After producing a 1 mm sheet, the sheet was cooled to 20 ° C. in 5 minutes, and then stretched twice at 100 ° C. According to the X-ray diffraction spectrum, the diffraction line observed at about 7.1 ° in this stretching had about 1/2 intensity. Physical properties of this stretched product were measured as follows.

Haze:% Tensile strength according to ASTM D1003 Tensile strength: kg / cm ² A test piece of 50 mm × 20 mm was cut out from the stretched film, and the strength at the time of tensile breaking at a tensile speed of 200 mm / min was determined using a tensile tester.

Elongation:% Elongation of the test piece at the time of fracture when determining tensile strength.

The tensile strength of the sheet before stretching is 580 kg / cm ² , the elongation is 420%,
The haze was 15.2%. The tensile strength after stretching is 660kg /
cm ² , elongation 85%, haze 22.6%.

After measuring the physical properties after keeping the stretched product at 130 ° C. for 30 minutes in a stretched state, the tensile strength was 780 kg / cm ² , and the elongation was 55.
%, The haze was 26%, and the crystallinity determined from the X-ray diffraction spectrum was 78%. On the other hand, the crystallinity before and after the stretching was 52% before the stretching, and in the stretched one, broad diffraction lines were observed and it was not clear, but was about 40%. By performing the heat treatment in this manner, the crystallinity is significantly improved, and the physical properties are also improved.

Example 2 The physical properties of the film obtained in the same manner as in Example 1 except that the heat treatment was performed at 110 ° C. and the treatment time was changed to 1 hour, the tensile strength was 760 kg / cm ² , the elongation was 48%, and the haze was 28. % And X
The degree of crystallinity determined from the-line diffraction spectrum was 72%.

Example 3 Calcium stearate and 2,6-di-t-butylphenol were added to the syndiotactic polypropylene obtained in Example 1 with 10/10000 and 10/10000 talc, respectively, and granulated. Use a 14-hole die with a temperature of 22
Spinning was performed at 0 ° C. and a screw rotation speed of 64 rpm. The strand exiting the die was air cooled. The resulting fiber thickness is 370 D / 14
This book was subjected to a tensile test and found that the maximum strength was 480 g and the elongation was
150%. Although the film was stretched twice at 60 ° C., the maximum strength in a tensile test was 560 g and the elongation was 40%. According to the X-ray diffraction spectrum, the diffraction line observed at about 7.1 ° in this stretching had about 1/2 intensity. Further, the yarn was stretched and treated at 100 ° C. for 2 hours, but the maximum strength in a tensile test was 620 g, the elongation was 15%, and the crystallinity was
72%.

〔The invention's effect〕

A molded article having excellent physical properties can be obtained by the method of the present invention, which is extremely valuable industrially.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B29C 55/00-55 / 30,71 / 02 D01F 6 / 06,6 / 46 C08J 5 / 00,5 / 18 C08J 7/00

Claims (2)

(57) [Claims] 1. A propylene homopolymer having a substantially syndiotactic structure, a copolymer of propylene with a small amount of another olefin, or a copolymer thereof with a small amount of a polypropylene having a substantially isotactic structure. A method for molding syndiotactic polypropylene, which comprises subjecting a mixture to heat-melt molding, stretching, and further subjecting the mixture to a heat treatment at a stretching load or higher with an applied load. 2. The method according to claim 1, wherein the stretching is carried out under such conditions that the diffraction image observed at a plane spacing of about 7.1 ° in the X-ray diffraction spectrum is reduced.