JP2003514049A - Expandable polypropylene polymers and their uses - Google Patents

Abstract

  (57) [Summary] The present invention relates generally to expandable polypropylene polymers and, more particularly, to expandable isotactic polypropylene homopolymers derived from metallocene catalysis, methods for their preparation, and articles formed therefrom. The expandable polypropylene polymer has a molecular weight distribution and density falling within a wide range. This expandable polypropylene polymer can be prepared in a multi-stage polymerization process using the same metallocene component in at least two stages.

Description

Detailed Description of the Invention

FIELD OF THE INVENTION The present invention relates generally to polypropylene polymers, their uses, and methods of making them.

Background Polyethylene (PE), polystyrene (PS), and polypropylene (PP)
Of the three most versatile commodity plastics, polypropylene is believed to have the most favorable property profile of these three for various applications. These applications include, for example, stretched and unstretched films, woven fibers, nonwovens, and various injection molded parts. Comparing these properties, it is well known that polypropylene has a higher modulus and heat deflection temperature (HDT) than polyethylene. The higher the modulus and HDT, the more suitable the polymer is for permanent use in appliances and automotive parts. In addition, polypropylene is non-polar and therefore resists degradation, typically by solvents such as acids and alkalis. Compared to polystyrene, polypropylene has good organoleptic performance, high barrier properties, and an integral living hinge.
It is preferable in applications that require the "hinge" characteristic. Finally, the preferred and impact-modified forms of polypropylene blends with various other polymers are the predominant automotive industry in the area of bumpers, side panels, floor mats, dashboards and instrument panels. Occupy a position.

However, there are some polymer applications where polypropylene is not the preferred plastic of choice. Examples of areas of application for such polymers include thermoforming and foaming. Foamed polymers find use in automotive, marine, electrical, and packaging applications because of their good insulating and structural properties at low added weights. Thermoforming is a commonly used fabrication method that advantageously competes with injection molding in the manufacture of thin walled containers. Polypropylene defects in foaming and thermoforming are believed to be associated with their generally poor melt strength and rapid melt viscosity loss, poor sheet sag, and relatively slow crystallization rates. For example, in order to successfully foam a product molded from a polyolefin, it is desirable that the polyolefin selected for foaming have a high melt strength. The high melt strength allows controlling the growth rate of bubbles within the polyolefin without premature rupture. Control of foam growth rate is also important to ensure a uniform distribution of cell size resulting in higher product uniformity. In addition, a wider polymer processing temperature window is desirable when the polymer is used in the product forming process to reduce the harm to the fabrication of high quality products due to temperature variations along the process line.

Further development and research are needed in the area of polypropylene compositions and manufacturing methods as plastic product manufacturing and consumers can more fully benefit from the use of polypropylene in more applications. This is especially the case, as mentioned above, when the manufacturing process of the product requires that the polymer be foamed.

[0005] was prepared in a multistage reactor illustrating the outline broad molecular weight distribution of the invention, formed from a polypropylene polymer foam and the desired polypropylene homopolymer foams products,
It has been found to have superior foam control as compared to foamed products formed from traditional polypropylene polymers.

More specifically, the present invention provides a molecular weight distribution in the range of 2.5 to 20.0,
Hexane extractables less than 1.0 wt%, melt flow rates in the range 0.2 dg / min to 30.0 dg / min, and foams in the range 0.1 to 1.0 g / cm ³ inclusive. It relates to a foamed polypropylene polymer comprising an isotactic propylene homopolymer having a density. The expanded polypropylene polymer may further include a blend of first and second propylene homopolymers.
The first propylene homopolymer has a melt flow rate in the range of 0.15 dg / min to 4.0 dg / min and a molecular weight distribution in the range of 1.8 to 2.5.
The second propylene homopolymer has a melt flow rate in the range of 5 dg / min to 1000 dg / min and a molecular weight distribution in the range of 1.8 to 2.5.

In another aspect, there is provided a method of forming a foamed isotactic polypropylene polymer comprising the steps of: Propylene is a metallocene-based catalyst, and preferably a single metallocene-based catalyst, and 0.15 dg /
A first concentration of chain transfer sufficient to produce a first propylene homopolymer having a melt flow rate in the range of minutes to 4.0 dg / min and a molecular weight distribution in the range of 1.8 to 2.5. It is homopolymerized in the presence of the agent. The catalyst based on the first propylene homopolymer and the metallocene comprises a second propylene homopolymer having a molecular weight distribution in the range of 1.8 to 2.5 and a melt flow rate in the range of 5 dg / min to 1000 dg / min. Homopolymerized with propylene in the presence of a second concentration of chain transfer agent sufficient to produce. Isotactic polypropylene is 2.
Is a blend of first and second homopolymers having a molecular weight distribution in the range of 5 to 20, wherein the first homopolymer comprises 40% to 80% by weight of the isotactic polypropylene polymer, and The second homopolymer comprises 20% to 60% by weight of the isotactic polypropylene polymer. Desirably, the chain transfer agent in at least one of the steps is hydrogen. The isotactic polypropylene polymer thus formed is then treated such that when the isotactic polypropylene polymer is contacted with a blowing agent, a foamed isotactic polypropylene polymer is formed.

[0008] DETAILED DESCRIPTION polypropylene polymers polypropylene polymers of the invention and desirably an isotactic polypropylene polymer, it is in the range of the whole polymer is 2.5 to 20.0, preferably in the range of 2.8 to 12.0, Even more desirably it comprises a reactor blend of two or more isotactic propylene homopolymers having different weight average molecular weights so as to have a molecular weight distribution within the range of 3.0 to 8.0.

Each isotactic propylene homopolymer desirably has a different melt flow rate. As such, polypropylene polymers were prepared in one or more isotactic propylene homopolymers with low melt flow rates, ie, low melt flow rate stages (0.15 dg / min to 4.0).
Low melt flow rate polymer species (within the range of dg / min), and one or more isotactic propylene homopolymers with high melt flow rate, i.e., prepared in the high melt flow rate stage (5 dg / min to 1000 dg High melt flow rate polymer species (in the range of 1 / min). Thus, the polypropylene polymer is desirably in the range of 0.2 dg / min to 30 dg / min,
It preferably has a melt flow rate in the range of 0.5 dg / min to 20.0 dg / min, and even more preferably in the range of 1.0 dg / min to 10.0 dg / min. The melting point of the polypropylene polymer is desirably above 145 ° C, more desirably above 150 ° C, and even more desirably above 155 ° C.
The upper limit of melting point will vary depending on the particular application and the metallocene used, but will typically be 170 ° C or lower. Polypropylene polymer (21 CFR 177.
The hexane extractable concentration (measured by 1520 (d) (3) (i)) is
Despite the broad MWD, it is desirably less than 2.0 wt%, more desirably less than 1.0 wt%.

The polypropylene polymer of the present invention is desirably 140,000 to 750.
It has a weight average molecular weight (MW) in the range of 1,000, more preferably in the range of 150,000 to 500,000, and most preferably in the range of 200,000 to 400,000.

Desirably, the polypropylene polymer comprises 40 wt% to 80 wt% low melt flow rate polymer species based on the total weight of the polypropylene polymer and 20 wt% to 60 wt% high based on the total weight of the polypropylene polymer. Melt flow rate polymer species, more preferably 55 wt% to 65 wt% low melt flow rate polymer species based on the total weight of polypropylene polymer and 35 wt% to 45 wt% based on the total weight of polypropylene polymer. Includes high melt flow rate polymer species.

The focus of the present invention is on homopolymers that have a unique combination of molecular weight distribution, good physical properties, and low extractables concentration, but likewise a combination of unique properties provides controlled concentrations. Of ethylene and comonomer (s) such as alpha-olefins such as 1-butene, 1-pentene, 1-hexene, and 1-octene are additionally used. There is
It will be apparent to those skilled in the art.

Polypropylene Polymer Polymerization Process The polypropylene polymer polymerization process involves the use of a metallocene catalyst system that includes a metallocene component and at least one activator. Desirably, these catalyst system components are supported on a support material.

The polypropylene polymers of the present invention are generally prepared in a multi-step process in which homopolymerization is carried out in each stage separately in parallel, or preferably in series. Individually, each stage has a gas phase, a slurry phase,
Alternatively, it can include any process including solution phase or high pressure autoclave processes. Desirably, the polypropylene polymer is prepared in a multi-stage, in-line, slurry loop reactor using propylene as the polymerization diluent. The polymerization is carried out at a temperature within the range of 50 ° C to 120 ° C from 200 kPa to 7,000 kP.
It is carried out using the pressure of a. In each stage, propylene can be homopolymerized, preferably using the same catalyst system containing a metallocene catalyst, but using different concentrations of chain terminator in at least two of the stages.

Examples of chain terminators include those commonly used to terminate chain growth in Ziegler-Natta polymerizations, a description of which is provided by Ziegler-Nat.
ta Catalyst and Polymerization Hydrogen
n; Can be found in Boor (Academic Press, 1979). Hydrogen and diethylzinc are examples of agents that are very effective in controlling the molecular weight of polymers in the polymerization of olefins. Hydrogen is a more desirable drug.

Preferably, the concentration of chain terminator in one stage is 0.15 dg / min to 4.0 dg / min, preferably 0.2 dg / min to 2.0 dg / min, and even more preferably 0.2 dg / min. Melt flow rate in the range of / min to 1.0 dg / min,
And 1.8 to 2.5, and preferably 1.8 to 2.3, is sufficient to produce a propylene homopolymer having a molecular weight distribution (Mw / Mn) in the range of 1.8 to 2.3. Preferably, the concentration of the chain terminator in a separate, earlier or later stage is from 5 dg / min to 1000 dg / min, preferably 20 dg / min to 200 dg / min.
Min, and more preferably a melt flow rate in the range of 30 dg / min to 100 dg / min, and a molecular weight distribution (Mw / Mn) in the range of 1.8 to 2.5 and preferably 1.8 to 2.3. ) Is sufficient to produce a propylene homopolymer having

Non-limiting examples of metallocenes suitable for use in homopolymer polymerization processes as well as copolymer polymerization processes include: Dimethylsilanediylbis (2-methyl-4-phenyl-1-indenyl) zirconium dimethyl Dimethylsilanediylbis (2-methyl-4,5-benzoindenyl) zirconium dimethyl; dimethylsilanediylbis (2-methyl-4,6-diisopropylindenyl)
Zirconium dimethyl; Dimethylsilanediylbis (2-ethyl-4-phenyl-1-indenyl) zirconium dimethyl; Dimethylsilanediylbis (2-ethyl-4-naphthyl-1-indenyl) zirconium dimethyl, phenyl (methyl) silanediylbis (2 -Methyl-4-phenyl-1-indenyl) zirconium dimethyl, dimethylsilanediylbis (2-methyl-4- (1-naphthyl) -1-indenyl) zirconium dimethyl, dimethylsilanediylbis (2-methyl-4- ( 2-naphthyl) -1-indenyl) zirconium dimethyl, dimethylsilanediylbis (2-methyl-indenyl) zirconium dimethyl,
Dimethylsilanediylbis (2-methyl-4,5-diisopropyl-1-indenyl) zirconium dimethyl, dimethylsilanediylbis (2,4,6-trimethyl-1-indenyl) zirconium dimethyl, phenyl (methyl) silanediylbis (2- Methyl-4,6-diisopropyl-
1-indenyl) zirconium dimethyl, 1,2-ethanediylbis (2-methyl-4,6-diisopropyl-1-indenyl) zirconium dimethyl, 1,2-butanediylbis (2-methyl-4,6-diisopropyl-1-indenyl) Zirconium dimethyl, dimethylsilanediylbis (2-methyl-4-ethyl-1-indenyl) zirconium dimethyl, dimethylsilanediylbis (2-methyl-4-isopropyl-1-indenyl)
Zirconium dimethyl, dimethylsilanediylbis (2-methyl-4-t-butyl-1-indenyl) zirconium dimethyl, phenyl (methyl) silanediylbis (2-methyl-4-isopropyl-1-indenyl) zirconium dimethyl, dimethylsilanediylbis (2-Ethyl-4-methyl-1-indenyl) zirconium dimethyl, dimethylsilanediylbis (2,4-dimethyl-1-indenyl) zirconium dimethyl, dimethylsilanediylbis (2-methyl-4-ethyl-1-indenyl) ) Zirconium dimethyl, dimethylsilanediylbis (2-methyl-α-acenaphtho-1-indenyl) zirconium dimethyl, phenyl (methyl) silanediylbis (2-methyl-4,5-benzo-1-indenyl) zirconium di Chill, phenyl (methyl) silanediylbis (2-methyl-4,5 (methylbenzo)
-1-Indenyl) zirconium dimethyl, phenyl (methyl) silanediylbis (2-methyl-4,5- (tetramethylbenzo) -1-indenyl) zirconium dimethyl, phenyl (methyl) silanediylbis (2-methyl-a-acenaphtho-1) -Indenyl) zirconium dimethyl, 1,2-ethanediylbis (2-methyl-4,5-benzo-1-indenyl) zirconium dimethyl, 1,2-butanediylbis (2-methyl-4,5-benzo-1-indenyl) zirconium Dimethyl, dimethylsilanediylbis (2-methyl-4,5-benzo-1-indenyl) zirconium dimethyl, 1,2-ethanediylbis (2,4,7-trimethyl-1-indenyl) zirconium dimethyl, dimethylsilanediylbis ( 2-methyl- 1-indenyl) zirconium dimethyl, 1,2-ethanediylbis (2-methyl-1-indenyl) zirconium dimethyl, phenyl (methyl) silanediylbis (2-methyl-1-indenyl) zirconium dimethyl, diphenylsilanediylbis (2-methyl-) 1-indenyl) zirconium dimethyl, 1,2-butanediylbis (2-methyl-1-indenyl) zirconium dimethyl, dimethylsilanediylbis (2-ethyl-1-indenyl) zirconium dimethyl, dimethylsilanediylbis (2-methyl-5) -Isobutyl-1-indenyl) zirconium dimethyl, phenyl (methyl) silanediylbis (2-methyl-5-isobutyl-1-indenyl) zirconium dimethyl, dimethylsilanediylbis (2-methyl) 5-t-butyl-1-indenyl) zirconium dimethyl, dimethylsilanediylbis (2,5,6-trimethyl-1-indenyl) zirconium dimethyl, dimethylsilanediylbis (2-methyl-4-phenyl-1-indenyl) Zirconium dichloride, dimethylsilanediylbis (2-methyl-4,5-benzoindenyl) Zirconium dichloride, dimethylsilanediylbis (2-methyl-4,6-diisopropylindenyl)
Zirconium dichloride, dimethylsilanediylbis (2-ethyl-4-phenyl-1-indenyl) zirconium dichloride, dimethylsilanediylbis (2-ethyl-4-naphthyl-1-indenyl) zirconium dichloride, phenyl (methyl) silanediylbis (2 -Methyl-4-phenyl-1-indenyl) zirconium dichloride, dimethylsilanediylbis (2-methyl-4- (1-naphthyl) -1-indenyl) zirconium dichloride, dimethylsilanediylbis (2-methyl-4- ( 2-naphthyl) -1-indenyl) zirconium dichloride, dimethylsilanediylbis (2-methyl-indenyl) zirconium dichloride, dimethylsilanediylbis (2-methyl-4,5-diisopropyl-1-indenyl) Zirconium dichloride, dimethylsilanediylbis (2,4,6-trimethyl-1-indenyl) zirconium dichloride, phenyl (methyl) silanediylbis (2-methyl-4,6-diisopropyl-
1-indenyl) zirconium dichloride, 1,2-ethanediylbis (2-methyl-4,6-diisopropyl-1-indenyl) zirconium dichloride, 1,2-butanediylbis (2-methyl-4,6-diisopropyl-1-indenyl) Zirconium dichloride, dimethylsilanediylbis (2-methyl-4-ethyl-1-indenyl) Zirconium dichloride, dimethylsilanediylbis (2-methyl-4-isopropyl-1-indenyl)
Zirconium dichloride, dimethylsilanediylbis (2-methyl-4-t-butyl-1-indenyl) zirconium dichloride, phenyl (methyl) silanediylbis (2-methyl-4-isopropyl-1-indenyl) zirconium dichloride, dimethylsilanediylbis (2-Ethyl-4-methyl-1-indenyl) zirconium dichloride, dimethylsilanediylbis (2,4-dimethyl-1-indenyl) zirconium dichloride, dimethylsilanediylbis (2-methyl-4-ethyl-1-indenyl) ) Zirconium dichloride, dimethylsilanediylbis (2-methyl-α-acenaphtho-1-indenyl) zirconium dichloride, phenyl (methyl) silanediylbis (2-methyl-4,5-benzo-1-indenyl) Benzalkonium dichloride, phenyl (methyl) silanediylbis (2-methyl-4,5 (methylbenzo)
-1-Indenyl) zirconium dichloride, phenyl (methyl) silanediylbis (2-methyl-4,5- (tetramethylbenzo) -1-indenyl) zirconium dichloride, phenyl (methyl) silanediylbis (2-methyl-a-acenaphtho-1) -Indenyl) zirconium dichloride, 1,2-ethanediylbis (2-methyl-4,5-benzo-1-indenyl) zirconium dichloride, 1,2-butanediylbis (2-methyl-4,5-benzo-1-indenyl) zirconium Dichloride, dimethylsilanediylbis (2-methyl-4,5-benzo-1-indenyl) zirconium dichloride, 1,2-ethanediylbis (2,4,7-trimethyl-1-indenyl) zirconium dichloride, dimethylsilanediylbis (2-Methyl-1-indenyl) zirconium dichloride, 1,2-ethanediylbis (2-methyl-1-indenyl) zirconium dichloride, phenyl (methyl) silanediylbis (2-methyl-1-indenyl) zirconium dichloride, diphenylsilanediylbis (2-Methyl-1-indenyl) zirconium dichloride, 1,2-butanediylbis (2-methyl-1-indenyl) zirconium dichloride, dimethylsilanediylbis (2-ethyl-1-indenyl) zirconium dichloride, dimethylsilanediylbis ( 2-Methyl-5-isobutyl-1-indenyl) zirconium dichloride, phenyl (methyl) silanediylbis (2-methyl-5-isobutyl-1-indenyl) zirconium dichloride, dimethy Silanediylbis (2-methyl -5-t-butyl-1-indenyl) zirconium dichloride, dimethylsilanediylbis (2,5,6-trimethyl-1-indenyl) zirconium dichloride, and the like.

Many of these desirable transition metal compound components are found in US Pat. No. 5,145,81.
9, No. 5,243,001, No. 5,239,022, No. 5,239,03
3, No. 5,296,434, No. 5,276,208, No. 5,672,66
8, 5,304,614, and 5,374,752, and European Patents 549 900 and 576 970, all of which are incorporated herein by reference. Fully incorporated into.

Further, US Pat. No. 5,510,502, US Pat. No. 4,931,417, US Pat. No. 5,532,396, US Pat. No. 5,543,373, WO9
8/014585, European Patent No. P611 773 and WO98 / 22486 (
Metallocenes, such as those described in US Pat.

The above polymers and polymerization processes are further described in US patent application Ser. No. 09 / 293,656 (98B030) filed Apr. 16, 1999, which is incorporated herein by reference. Fully incorporated into.

Activators Metallocenes are commonly used in combination with some form of activator to make an active catalyst system. The term "active agent" is used herein to refer to
Defined as a compound or component or combination of compounds or components that can enhance the ability of one or more metallocenes to polymerize an olefin into a polyolefin. Alkylalumoxanes such as methylalumoxane (MAO) are commonly used as metallocene activators. Generally, the alkyl alumoxane comprises from 5 to 40 repeating units: R (AlRO) x AlR _{2 for} linear species and (AlRO) x for cyclic species, where R is a mixed alkyl. Including C ₁ -C ₈ alkyl. Particularly desirable is the presently marketed "modified alumoxane" by AKZO,
Compounds where R is methyl or other lower alkyl such as C ₃ -C ₈ .
Alumoxane solutions, especially methylalumoxane solutions, are available from commercial vendors as solutions with varying concentrations. There are various methods for making alumoxanes, non-limiting examples of which are described in US Pat. Nos. 4,665,208, 4,952,540, 5,091,352, 5 , 206, 199, 5,204, 419, 4,874, 734, 4,924, 018, 4,908, 463, 4, 968, 827, 5, 308. No. 815, No. 5,329,032, No. 5,248,801, No. 5,235,081, No. 5,103,031, and European Patent Publication No. 0 561 476, European Patent Publication. No. 0 279 586, and European Patent Publication No. 0 594 218, and WO 94/10180, each of which is fully incorporated herein by reference. (As used herein, unless otherwise stated, "solution" means all liquids, including mixtures, including suspensions.)

A separate ionizing activator can also be used to activate the metallocene. These activators are compounds that are neutral or ionic, or ionize neutral metallocene compounds, such as tri (n-butyl) ammonium tetrakis (pentafluorophenyl) borate. Such ionized compounds can include active protons or certain other cations that are associated but not coordinated or only loosely coordinated with the remaining ions of the ionized compound.
Combinations of activators can also be used, such as, for example, combined alumoxane and ionizing activators. See, for example, WO94 / 07928.

A description of ionic catalysts for coordination polymerization consisting of metallocene cations activated by non-coordinating anions can be found in EP 0 277 003 (incorporated herein by reference), European Patent Publication No. 0 277 004,
And US Pat. No. 5,198,401, and during earlier work in WO-A-92 / 00333. These are protonated so that the metallocene (bis Cp or mono Cp) is anionic precursor, the alkyl / hydride group is abstracted from the transition metal to become cationic and the non-coordinating anion balances the charge. Teaching the preferred method of preparation. Suitable ionic salts include tetrakis-substituted borates or ammonium salts with fluorinated aryl moieties such as phenyl, biphenyl, and naphthyl.

The term “non-coordinating anion” (NCA) is sufficient to be either an anion that does not coordinate to said cation or only weakly to said cation and thereby displaced by a neutral Lewis base. Means an anion that maintains its instability. "
A "compatible" non-coordinating anion is one that does not degrade to neutrality when the initially formed complex decomposes. Also, such anions do not transfer anionic substituents or fragments to the cations to form neutral four-coordinate metallocene compounds and neutral byproducts from the anions. Non-coordinating anions useful in accordance with the present invention are compatible and stabilize the metallocene cation in the sense of balancing the ionic charge of the +1 state of the metallocene cation, and further ethylenically or acetylenically unsaturated during polymerization. It retains sufficient instability to allow substitution by the monomer.

The use of ionizable ionic compounds that are free of active protons but are capable of producing both active metallocene cations and non-coordinating anions is also known.
See, for example, EP 0 426 637 and EP 0 573 403 (incorporated herein by reference).
Another method of making ionic catalysts uses an ionized anion precursor that is initially a neutral Lewis acid but forms an anion with a cation during the ionization reaction with a metallocene compound. For example, tris (pentafluorophenyl) borane is used. European Patent Publication No. 05 (incorporated herein by reference)
See 20732. Ionic catalysts for addition polymerization can also be prepared by oxidation of the metal center of the transition metal compound with an anionic precursor containing a metal oxidizing group in addition to the anionic group. See European Patent Publication No. 0 495 375 (incorporated herein by reference).

Where the metal ligand contains a halogen moiety which is not capable of ionizing abstraction under standard conditions (eg biscyclopentadienyl zirconium dichloride), a hydride of lithium or aluminum or an alkyllithium or alkylaluminum, It can be converted via known alkylation reactions with organometallic compounds such as alkyl alumoxanes, Grignard reagents, etc. Regarding in-situ methods illustrating the reaction of an alkylaluminum compound with a dihalo-substituted metallocene compound prior to or simultaneously with the addition of an activated anionic compound, European Patent Publication No. See 0 500 944 and EP 0 570 982.

A preferred method for supporting ionic catalysts containing metallocene cations and NCA is US Pat. No. 5,643,847, US patent application Ser. No. 09184358, filed Nov. 2, 1998, and 1998. No. 09184389, filed November 2, which is fully incorporated herein by reference in its entirety.

When the activator for the metallocene supported catalyst composition is NCA, it is preferably NCA.
Are added to the support composition first, followed by the metallocene catalyst. When the activator is MAO, desirably the MAO and metallocene catalyst are co-dissolved in solution. The support is then contacted with the MAO / metallocene catalyst solution. Other methods and order of addition will be apparent to those skilled in the art.

Support Material The catalyst system used in the method of the present invention is desirably a porous particulate material such as, for example, talc, inorganic oxides, inorganic chlorides, and resinous materials such as polyolefins or polymeric compounds. It is supported using a substance.

Desirably, the support materials are porous inorganic oxide materials, including those from metal oxides of Groups 2, 3, 4, 5, 13, or 14 of the Periodic Table of the Elements. . Silica, alumina, silica-alumina, and mixtures thereof are especially desirable. Other inorganic oxides that can be used alone or in combination with silica, alumina, or silica-alumina are magnesia, titania, zirconia, and the like.

Desirably, the support material has a surface area within the range of 10 to 700 m ² / g, 0.
Total pore volume in the range of 1 to 4.0 cc / g
e), and porous silica having an average particle size in the range of 10 to 500 μm. More preferably, the surface area is in the range of 50 to 500 m ² / g, the pore volume is in the range of 0.5 to 3.5 cc / g, and the average particle size is 20 to 200 μm.
It is within the range of m. Most desirably, the surface area is in the range of 100 to 400 m ² / g, the pore volume is in the range of 0.8 to 3.0 cc / g, and the average particle size is in the range of 30 to 100 μm. The average pore size of typical porous support materials is in the range of 10 to 1000 Angstroms. It is desirable to use a support material having an average pore diameter of 50 to 500 Angstroms, 75
Most preferably, a support material having an average pore diameter of ˜350 Å is used. It may be particularly desirable to dehydrate the silica at a temperature of 100 ° C to 800 ° C for 3 to 24 hours.

The metallocenes, activator, and support material can be combined in many ways. Suitable loading techniques are described in US Pat. Nos. 4,808,561 and 4,701,
No. 432, each of which is fully incorporated herein by reference. US Pat. No. 5,240,894, WO94 / 28034, WO9
6/00243, and WO 96/00245, each of which is fully incorporated herein by reference, wherein the metallocene and the activator are combined and their reaction product is porous. It is preferably supported on a quality support material. Alternatively, the multiple metallocenes can be separately preactivated and then separately or combined with the support material. If the metallocenes are separately supported, they are preferably dried and then combined as a powder prior to use in the polymerization.

Whether the metallocene and the activator are pre-contacted separately or the metallocene and the activator are combined at once, the total volume of reaction solution applied to the porous support is desirably Is less than 4 times the total pore volume of the porous support, more preferably less than 3 times the total pore volume of the porous support, and even more preferably the total pore volume of the porous support. Is more than 1 time and less than 2.5 times. Methods for measuring the total pore volume of porous supports are well known in the art. One such method is Volume 1, Experimenta.
l Methods in Catalyst Research, Academ
ic Press, 1968, pp. 67-96.

Methods for supporting an ionic catalyst containing a metallocene cation and a non-coordinating anion are described in WO 91/09882, WO 94/03506, US Pat. No. 5,072,8.
23, WO96 / 04319, and WO95 / 06343,
All of these are incorporated herein by reference. These methods generally involve either physical adsorption on a conventional polymer or inorganic support that has been significantly dehydrated or dehydroxylated, or the Lewis acid becomes covalent and the hydrogen of the hydroxyl group is protonated to the metallocene compound. Including the use of a neutral anion precursor that is a Lewis acid strong enough to activate the retained hydroxyl groups in the silica-containing inorganic oxide support so that it can be utilized for conversion.

The supported catalyst system can be used directly in the polymerization, or the catalyst system can be prepolymerized using methods known in the art. For more information on prepolymerization, see US Pat. Nos. 4,923,833 and 4,921,8.
25, EP 0 279 863 and EP 0 354 893. Each of these is fully incorporated herein by reference.

Additives Additives may be included in the polypropylene polymer of the present invention. Such additives and their use are generally well known in the art. These are conventional amounts of heat stabilizers or antioxidants, plasticizers, neutralizers, slip agents, anti-blocking agents, pigments, anti-fog agents, anti-static agents, transparency agents, nucleating agents, UV absorbers. Or include those commonly used with plastics such as light stabilizers, fillers and other additives. Effective concentrations are known in the art and will depend on the details of the base polymer, the mode of fabrication, and end use.

Blowing Agent Blowing agents or additives can be generally divided into two classes: physical blowing agents and chemical blowing agents.

Physical foaming or blowing agents are generally gases such as carbon dioxide or nitrogen. Hydrocarbon gases such as butane or pentane and fluorocarbon gases such as trichlorofluoromethane and dichlorodifluoromethane are effective as physical blowing agents to produce good quality foams. The use of hydrocarbon and fluorocarbon gases is generally not the most desirable, as they have been seen as indicating certain health and environmental concerns. The more desirable physical blowing agents are carbon dioxide, nitrogen, and argon. Physical foaming agents are used when low foam density (0.5 g / cm ³ or less) is required.

Chemical blowing agents generally allow the production of foamed products with densities of greater than 0.5 g / cm ³ . Examples of chemical blowing agents are bicarbonate of soda (typically used in combination with citric acid), azodicarbonamide (azodicar).
Bonamide), sulfonyl hydrazide (sulfonyl hydraz)
ide), sulfonyl semicarbazide
zide) is included. Soda bicarbonate (an endothermic agent) and azodicarbonamide (an exothermic agent) are probably the most widely used chemical blowing agents.

When used at low concentrations, generally less than 1% by weight, and preferably about 0.25% by weight, based on the weight of the polymer being expanded, the chemical blowing agent, when used, is a foam nucleating agent. It can function and promote the formation of more uniform size bubbles. This function is often utilized even when the primary blowing medium is a physical blowing agent such as carbon dioxide gas. Talc can also be used for bubble nucleation.

The resulting foamed products produced from these multi-stage processes have a more uniform foam cell morphology and good extrudate skin surface. More specifically, the expandable polypropylene polymers of the present invention are useful in applications such as sheet extrusion and molded articles, such as molded automobile parts. In the case where the application is sheet extrusion, the foamed sheet can then be thermoformed into packaging containers. When the application is for a molded article, the molded article can be a variety of molded parts, especially
Examples include molded parts associated with or used in the automotive industry such as bumpers, side panels, floor mats, dashboards, and instrument panels. Examples of other applications where foamed plastics, such as expanded polypropylene, are useful are Encyclopedia of Che by Kirk-Othmer.
Mal Technology, 4th Edition, Vol. 11, pages 730-783, which are incorporated herein by reference.

Examples The following examples are provided to illustrate the above discussion. The examples may relate to particular aspects of the invention, but should not be seen as limiting the invention in any particular sense. The equipment used and the experimental procedures used to obtain the data in the table below are outlined below.

Various foaming tests / tests on polypropylene polymers have been carried out by the New Jersey Institute of Technology, Newark, NJ, New Jersey Institute of Technology.
Polymer Processing Institute (Polymer Proc)
essing Institute). 40L with high pressure gas inlet located 19L / D length and equipped with 1/8 inch rod die
1.25-inch diameter killion-segment (K / D) (length / diameter)
An extruded foam was made with a physical blowing agent using an illion-segmented) single screw extruder. Carbon dioxide gas, typically about 2
Used as a blowing agent at various pressures ranging from 50 psi (172.75 kPa) to over 1000 psi (6895 kPa). The polymeric material tested was plasticized within the first 19 diameters of the screw. The remaining extruder length past the gas inlet was used for gas mixing, compression of the gas-containing polymer and cooling. The temperature at the die exit was about 150 ° C to 160 ° C. An auger feeder was used to control the flow of resin into the line. The extrusion line was typically operated in a near-underfeed manner to optimize residence time and maximize foam formation. Under steady-state conditions, the extrudate exiting the die expanded to a diameter greater than 1/8 inch, which reflected the formation of gas bubbles as the gas exited the solution from the extruded polymer melt. ing. Controllable line parameters include temperature profile settings (feed section to die), extruder speed and auger screw feed rate, blowing agent gas flow rate and gas pressure and die pressure.

Sample 1 (Comparative) Sample 1 is a Montel Polyolefins (Mont) having an MFR of about 4.
is a commercially available Ziegler-Natta catalyst-produced isotactic homopolypropylene polymer product (Product No. PP 6523) available from Dell Polyolefins). Some of its physical properties are shown in Table 1 (see Figure 1).

Sample 2 (Invention) Sample 2 data was taken on an isotactic polypropylene homopolymer. This homopolymer was prepared in a manner similar to the homopolymer polymerization process described above.

Dimethylsilylbis (2-methyl-4-phenyl-indenyl) zirconium dichloride metallocene, methylalumoxane (in toluene) as activator,
Styrene as modifier and Davison X as support material
PO 2407 Silica (WR Grace, Baltimore, MD, Duvision Chemical Division (Dav)
A catalyst system was prepared containing ion Chemical Division)).
The procedure for preparing the catalyst is described in USSN 09 / 293,656, which is incorporated herein by reference. Specific catalyst formulation details for the prepared catalyst system are as follows: Zr loading (mmol / g SiO ₂ ) 0.028 Al loading (mmol / g SiO ₂ ) 2.9 Styrene / Zr loading. Quantity 5.7

Several batches of catalyst system were combined to provide the charge for the polymerization experiments. The catalyst system was oil slurried with Drakeol ^™ white mineral oil (Witco Chemical) to facilitate addition to the reactor.

The polymerization was conducted in a pilot scale, two reactor, continuous, stirred tank bulk liquid phase process. The reactor was equipped with a jacket for removing the heat of polymerization. The reactor temperature was 70 ° C in the first reactor and 64.5 ° C in the second reactor. The catalyst was fed at a rate of 5.2 g / h. TE
AL (2.0 wt% in hexane) was used as a scavenger and was added at a rate of 17.3 wppm. Feeding the catalyst system prepared above as a 20% slurry in mineral oil,
The first reactor was flushed with propylene. The total propylene monomer feed to the first reactor was 80 Kg / hr. Propylene monomer feed to the second reactor is 3
It was 0 Kg / hour. 530mppm hydrogen to the first reactor for molecular weight control
And at a rate of 8450 mppm to the second reactor. The reactor residence time is 2.5 hours in the first reactor and 1.
It was 8 hours. Polymer production rate was 20 Kg / hr from the first reactor and 11 Kg / hr from the second reactor. 65% of the final polymer product was obtained from the first reactor and 35% was obtained from the second reactor. The polymer was discharged from the reactor as a granular product with an MFR of 3.6 dl / g. The product produced in the first reactor was estimated to be of 1 MFR and the product produced in the second reactor was estimated to be of 78 MFR. After pelletizing the product with stabilizer, the MFR of the pellet is 1.8
Met.

[0049]

[Table 1] Note to Table 1 : Molecular weights are according to standard GPC method-Tensile properties of polypropylene polymers are according to Instron test at room temperature 2 inches / minute (A
Equivalent to STM method D-524) -Tm, Tc, and heat of fusion are from the standard DSC method using heating and cooling rates of 10 ° C / min.

Results Experiments on two samples revealed a clear and significant advantage in favor of Sample 1. These advantages mainly exist in the field of foam production and in the quality of the final foamed product.

In more detail, it was observed that foam formation by the above method was much easier during foaming of sample 2 compared to sample 1 at all gas pressures generally given. Was done. For example, during foaming of sample 1, 250 to 7
Excessive bubble collapse was observed in the gas pressure range of 50 psi (1723.75 to 5171.25 kPa). In addition, the final foamed Sample 1 product had undesirably large foam and poor texture, as shown in FIG. The presence of large bubbles is generally the structural integrity of the final foamed product.
And the lack of foam uniformity generally results in an end product with a rough or rough surface. Reduced structural integrity and rough surfaces are undesirable properties in foam products. In the case of Sample 1, it was also observed that the extrudate became excessively helical and rounded at the exit of the die due to foam bursting. This indicates poor / undesirable processability and foam control. The density of the foamed product of Sample 1 (see Table 1) was somewhat higher than that of Sample 2 of the invention under similar foaming conditions.

In contrast to Sample 1 shown in FIG. 1, Sample 2 exhibited a wider foam processing window. Figure 2
The texture of the final foamed product is smoother, as shown in Figure 1, which reflects the desired more uniform size of the foam. The cell structure showed only a few cell bursts, if any, as they exit the extruder die. 0.3 g /
A wider density range of foam down to cm ³ (see Table 1) could be produced using Sample 2.

[0053]   It should be noted that the final value of foam density depends on the commonly used equipment.
I have to. Low level (0.5g / cm^ThreeTo achieve a foam density of less than)
A physical blowing agent is usually used for. Very low foam density (0.1 g / cm^Three Of less than) is generally achieved by multiple extruders (tandems) arranged in series.
on the line using the extruders, where in the second extruder
The focus is mainly on the optimal mixing of the gases before the formation of bubbles as the extrudate exits the die.
And melting and effective cooling of the polymer / gas mixture. Sample 2 of the present invention
However, under the same foam fabrication configuration and conditions, standard Ziegler-Natta
The fact that it provided a lower foam density than sample 1 of homopolypropylene
, With the advantage that the above mentioned products can be customized. Furthermore, the port of the present invention
Tandem extrusion of the limmer is 0.1 g / cm
^ThreeFoamed products with low densities such as can be possible. Other areas
Among the benefits provided by the polymers of the present invention are improved gas solubility and
Thought to be diffusion, these are desirable for producing high quality foam products
It is a parameter.

Carbon dioxide was used as blowing agent in the present case, but with heptane, nitrogen,
Other gases such as helium, butane, isobutane, and isopentane can also be used to foam the polymers of this invention.

Although the present invention has been described and illustrated above with reference to particular embodiments, it is understood that the present invention is directed to many different variants not illustrated herein. The vendor will understand. For these reasons, reference should be made solely to the appended claims for purposes of determining the true scope of the present invention.

Although the appended claims are single dependent according to US patent practice, each of the features in any dependent claim may be combined with any of the other dependent or main features.

[Brief description of drawings]

[Figure 1]   FIG. 1 is a photomicrograph of the expanded homopolymer described in Example 1.

FIG. 2 is a photomicrograph of the expanded homopolymer of the present invention as described in Example 2.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 23:10 B65D 1/00 A (81) Designated country EP (AT, BE, CH, CY, DE, DK) , ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE), CA, JP, MX (72) Inventor Meita, Aspie Kay, USA 77346, Ha Mumble, Atakosita Point Drive 21210 F Term (Reference) 3E033 BA16 BB01 CA03 FA02 4F074 AA24 AA98 AB01 AB03 AB05 BA01 BA31 BA32 CA22 DA02 DA33 DA34 DA35 DA45 DA59 4J011 AA05 AC03 BA01 BB05 DA02 FA03 FA05 NB13 FB13 FB13 FB13 FB13 FB13 FB13

Claims (19)

[Claims] 1. A method for forming a foamed isotactic polypropylene polymer comprising: (a) propylene, metallocene and a melt flow rate in the range of 0.15 dg / min to 4.0 dg / min and 1.8. Homopolymerizing in the presence of a first concentration of chain transfer agent sufficient to produce a first propylene homopolymer having a molecular weight distribution in the range of 1, a propylene homopolymer and a metallocene in the presence of a molecular weight distribution in the range of 1.8 to 2.5 and 5 dg / min to 1000 dg /
Homopolymerizing in the presence of a second concentration of chain transfer agent sufficient to produce a second propylene homopolymer having a melt flow rate in the range of minutes, wherein the isotactic polypropylene polymer is And the isotactic polypropylene polymer is a blend of first and second homopolymers having a molecular weight distribution in the range of 2.5 to 20, wherein the first homopolymer is isotactic polypropylene. 40% to 80% of the isotactic polypropylene polymer, and the second homopolymer comprises 20% to 60% of the isotactic polypropylene polymer, (c) the isotactic formed by steps (a) and (b). A foamed isotactic polypropylene polymer is formed with a tic polypropylene polymer blowing agent So as to make contact. 2. The method of claim 1, wherein the chain transfer agent in at least one of steps (a) and (b) is hydrogen. 3. The method of claim 1, wherein the isotactic polypropylene polymer comprises 55% to 65% by weight of the first propylene homopolymer, based on the total weight of the isotactic polypropylene polymer. 4. The molecular weight distribution of the first and second propylene homopolymers is 1.
The method of claim 1, which is in the range of 8 to 2.3. 5. The melt flow rate of the first propylene homopolymer is less than 0.
The method of claim 1, wherein the melt flow rate of the second propylene homopolymer is in the range of 2 dg / min to 2.0 dg / min and the second propylene homopolymer is in the range of 30 dg / min to 100 dg / min. 6. The isotactic polypropylene polymer further comprises 1.
Less than 0 wt% hexane extractables, melting point above 145 ° C, and 0.2 dg /
The method of claim 1 defined as having a melt flow rate in the range of 3 to 30.0 dg / min. 7. The method of claim 1, wherein the blowing agent is a physical blowing agent. 8. The method of claim 1, wherein the blowing agent is a chemical blowing agent. 9. The method of claim 1, wherein the isotactic polypropylene polymer comprises 35% to 55% by weight of the second propylene homopolymer, based on the total weight of the isotactic polypropylene polymer. 10. The melt flow rate of the first propylene homopolymer is 0.
． The method of claim 1, wherein the melt flow rate of the second propylene homopolymer is in the range of 2 dg / min to 2.0 dg / min and the second propylene homopolymer is in the range of 30 dg / min to 100 dg / min. 11. The expanded isotactic polypropylene polymer is 0
． The method of claim 1, having a density in the range of ^{3 to} 1.0 g / cm ³ . 12. A molecular weight distribution within the range of 2.5 to 20.0, 1.0% by weight.
A product comprising a polypropylene polymer foam comprising less than hexane extractables, an isotactic propylene homopolymer having a melt flow rate in the range of 0.2 dg / min to 30.0 dg / min, the polypropylene polymer foam comprising: An article having a density in the range of 0.3 to 1.0 g / cm ³ . 13. The article of claim 12 selected from the group comprising bumpers, side panels, floor mats, dashboards, instrument panels, and containers. 14. A molecular weight distribution within the range of 2.5 to 20.0, 1.0% by weight.
A product comprising a polypropylene polymer foam comprising less than hexane extractables, an isotactic propylene homopolymer having a melt flow rate in the range of 0.2 dg / min to 30.0 dg / min, the polypropylene polymer foam comprising: Has a density in the range of 0.3 to 1.0 g / cm ^{3 and} the isotactic propylene homopolymer comprises a blend of first and second propylene homopolymers, wherein the first propylene Homopolymer is 0.1
Melt flow rate in the range of 5 dg / min to 4.0 dg / min and 1.8 to 2
． The second propylene homopolymer has a molecular weight distribution in the range of 5 and the second propylene homopolymer is 5 dg /
A product having a melt flow rate in the range of minutes to 1000 dg / min and a molecular weight distribution in the range of 1.8 to 2.5. 15. The article of claim 14, wherein the isotactic propylene homopolymer comprises 40% to 80% by weight of the first propylene homopolymer, based on the total weight of polypropylene polymer. 16. The article of claim 14, wherein the isotactic propylene homopolymer further comprises 55% to 65% by weight of the first propylene homopolymer, based on the total weight of polypropylene polymer. 17. The molecular weight distribution of the first and second propylene homopolymers is 1.
． The product of claim 14, which is in the range of 8 to 2.3. 18. The melt flow rate of the first propylene homopolymer is 0.
． 15. The article of claim 14, wherein the melt flow rate of the second propylene homopolymer is in the range of 2 dg / min to 2.0 dg / min and the second propylene homopolymer is in the range of 30 dg / min to 100 dg / min. 19. The article of claim 14 selected from the group comprising bumpers, side panels, floor mats, dashboards, instrument panels, and containers.