EP2318458A1

EP2318458A1 - Improvement of transparency of polypropylene using metalocene waxes

Info

Publication number: EP2318458A1
Application number: EP09777955A
Authority: EP
Inventors: Joachim Kohler
Original assignee: Clariant Finance BVI Ltd
Current assignee: Clariant International Ltd
Priority date: 2008-08-22
Filing date: 2009-08-19
Publication date: 2011-05-11
Also published as: DE102008039279A1; WO2010020399A1

Abstract

The invention relates to polypropylene homopolymers having a transparency of > 81%, and a method for the production thereof, comprising one or more metalocene polyolefin waxes at a concentration of 0.1 to 10% in weight, having a molecular weight Mn within the range of 500 to 15000 g/mol, and a viscosity within the range of 30 to 10000 mPa-s (at 170°C PP, or 140°C PE, respectively).

Description

Transparency improvement of polypropylene with metallocene waxes

This invention relates to improving the transparency of PP-H (polypropylene homopolymer) through the use of metallocene catalyzed polyolefin waxes, so-called metallocene waxes.

Due to its semi-crystalline character, PP-H is in and of itself an opaque polymer and therefore not suitable for full or semitransparent applications. It has been found that this disadvantage can be reduced by the addition of a minimum concentration of certain metallocene waxes.

PP (Polypropylene) is a versatile and globally available bulk polymer. In Germany alone, about 2 million tonnes are produced each year, of which around 25% flow into the PP-H-dominated packaging market. For some fields of application, such as packaging, containers or covers, there are often requirements for a minimum transparency. For example, to be able to read or recognize past markings or packaged goods, or not to minimize the light output of a light source (PlasticsEurope "Production and Consumption Data for Plastics in Germany including Utilization 2003", study by Consultic Marketing & Industrieberatung GmbH vom August 27, 2004, pages 26ff).

Examples of these applications are food packaging, wrapping films, bottles, containers, cups, lighthouses, etc. Regular PP-H is suitable for many applications in terms of mechanical requirements and barrier properties. For those with the o. G. Transparency requirements, however, is in most cases the opacity of PP-H an exclusion criterion.

Polypropylene homopolymer (PP-H) is known from the prior art, polymerized from only one, repeating monomer, the propylene: HH

H CH ₃

The spatial arrangement of the methyl group present on every other carbon atom may vary. One speaks in this case of tacticity. Three tactics for PP-H are known: isotactic, all methyl groups are on the same side; syndiotactic, the methyl groups are evenly alternating times on the one and the other side of the chain to find and atactic, with the methyl groups are randomly distributed and arranged arbitrarily.

Of these three possible modifications, only the isotactic variant is the most relevant and technically most useful. The uniform construction of isotactic PP favors the formation of crystalline domains, e.g. B. during cooling from the melt ("Hostalen PP" product data sheet HFKR 102 D-9020-022 Hoechst AG, February 1990 issue, page 2).

The crystalline portion of the PP depends on many other factors, which is why one assumes a degree of crystallinity of 50-70% for regular PP. In general, PP-H is therefore also referred to as semi-crystalline polymer with low transparency.

If, in addition to propylene, a second monomer, namely ethylene, is incorporated into the polymer chain, the so-called PP copolymer (PP-copo) is obtained. This can be different depending on the arrangement of the ethylene sequences in random copolymers (PP-R) or block copolymers (PP-B), which then also z. T. has significant effects on certain properties.

Thus, PP-B has a high toughness, especially at low temperatures. PP-R types, however, are predominantly used in highly transparent applications (Amemiya T, Kitade S, Kozai I, Minakami S, Takahashi K, Tayano T, Japan Polychem Corp., Application PRAI JP 2004-382168, 28.12.2004).

The arbitrary arrangement of the ethylene sequences in the PP-R polymer chain leads to a high amorphous content and thus to a very good transparency. Thus, the copolymerization of propylene with ethylene to PP-R is a way to obtain a polypropylene with good transparency.

The schematic structure of a PP-R from the propyl (P) and ethyl (E) groups may be as follows:

, ... [- P-P-P-E-P-E-E-P-E-P-P-P-P-E-P]

Understandably, this polymerization technique is not possible with a PP-H for lack of co-monomers. For this reason, to improve the transparency of PP-H, other technologies are commonly used, such as:

a) PP-H types with specifically adjusted crystallite form (eg γ-form) or optimized spherulite size and spherulite distribution. Such settings are z. B. with special cooling or specific catalyst technology reached (Saechtling, plastic paperback, 28th edition, p 422 Chapter 4.1.5.2). However, these PP-H grades are bound to specific processing or manufacturing processes and are not available to the broad masses of processors, or only at a certain expense.

b) Perhaps the most widely used technique is the addition of nucleating agents. With this technology, it must be ensured that only PP-H with an α- or ß-crystallite form can be nucleated appropriately. Of the large number of investigated nucleating agents, such as metal stearates, benzoates, carbonates, phosphates, etc., have in particular those from the Class of sorbitol esters has proven to be most effective, particularly with regard to mechanical and optical properties ("Plastics Additive Handbook", 5 ^m edition, Chapter 18 "Nucleating Agents for Semi-crystalline Polymers", pages 960 ff).

c) Disadvantages of sorbitol esters are primarily the very high prices. But also organoleptic impairments in the form of odor and relatively narrow processing windows, ie temperature limitations, represent constant problems.

c) Biaxial, ie two-dimensional, stretching of PP is used primarily in films for food packaging. In these so-called BOPP (biaxially oriented PP) films, on the one hand, the crystallinity is increased by aligning the polymer chains and, on the other hand, the refractive index in the different planes is made uniform. But as noted in example a), BOPP is also bound to this one processing method.

Based on the above-described prior art and the problems encountered here, it is the object of the present invention

Transparency of polypropylene waxes so far that they are also suitable for applications that could not be served until now.

In order to achieve the suitability of PP-H for applications with a minimum requirement for transparency, an economically acceptable, technically easy-to-use procedure is necessary, which must take into account the following parameters:

- Odor and color of the PP must not be affected by the transparency improvement measure. Especially in the field of

Food packaging does not accept deterioration of organoleptic properties and is an exclusionary criterion. A "smelly" PP sachet as a bread package is unthinkable and unacceptable; - The mechanical properties of the PP-H end article must not be impaired, as otherwise certain applications can no longer be operated, or only to a limited extent. Examples include packaging such as canisters, bottles and beakers, which among other things also exert a protective function against external, mechanical effects;

- Food law approvals must be maintained. Since a significant proportion of transparent PP films may flow or flow into the area of food packaging, no authorization should be removed by a transparency improvement measure. So it is u. a. Aim to expand, not limit, the range of applications for PP-H;

The processing conditions of a pure PP-H, z. As temperature ranges, should ideally be able to be taken over unchanged. Machine designs and machine settings do not need to be changed. This would greatly simplify manageability, it would help avoid processing errors and increase flexibility.

- The transparency improvement measure must be applicable by all parties involved in PP processing, such as polymer manufacturers, compounders, masterbatchers and processors. Only then is wide acceptance achievable.

Surprisingly, it has now been found that by adding metallocene waxes, such as. As Licocene PP 1302, PP 6102, PP 2602, PE 4201 or PPSI 3262, the transparency of PP-H increased to over 81% and thus a significant improvement to the PP-H produced by known methods can be achieved. This positive effect is achieved without changing the color or mechanical properties of the articles equipped with them. It is irrelevant whether the metallocene waxes are incorporated in a compound or added as a masterbatch or pure substance in polymer processing. The metered addition can be carried out gravimetrically, or else by means of a physical premix, or as a preparation or in pure form by side metering on the extruder. A change in the PP-H processing conditions, such as temperature profile, residence times, shear rate in the extruder, etc. is not necessary.

Metallocene compounds of the formula (I) are used for the preparation of the metallocene polyolefin waxes used according to the invention.

This formula also includes compounds of the formula (Ia)

(Ia)

of the formula (Ib)

and the formula (Ic)

In formulas (I), (Ia) and (Ib), M ^{1 is} a Group IVb, Vb or VIb metal of the Periodic Table, for example, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, preferably titanium , Zirconium, hafnium. R ¹ and R ² are identical or different and represent a hydrogen atom, a C1-C1 _0, preferably Ci-C ₃ alkyl, in particular methyl, a C1-C1 ₀ -, preferably Ci-C ₃ alkoxy group, a C ₆ - Ci ₀ , preferably C ₆ -C ₈ -aryl, a C ₆ -C ₀ -, preferably C ₆ -C ₈ -aryloxy, a C ₂ -C _{1 0} , preferably C ₂ -C ₄ -alkenyl, a C ₇ -C ₄₀ -, preferably C ₇ -Cio-arylalkyl group, a C ₇ -C ₄ O-, preferably C ₇ -C ₂ alkylaryl group, a C ₈ -C ₄ O-. preferably C 8 -C 12 arylalkenyl group or a halogen, preferably chlorine atom.

R ³ and R ⁴ are identical or different and denote a mononuclear or polynuclear hydrocarbon radical which can form a sandwich structure with the central atom M ¹ . R ³ and R ⁴ are preferably cyclopentadienyl, indenyl, tetrahydroindenyl, benzoindenyl or fluorenyl, it being possible for the basic units to carry additional substituents or to bridge them with one another. In addition, one of the radicals R ³ and R ^{4 may be} a substituted nitrogen atom, wherein R ^{24 has} the meaning of R ¹⁷ and is preferably methyl, tert-butyl or cyclohexyl.

R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ are identical or different and denote a hydrogen atom, a halogen atom, preferably a fluorine, chlorine or bromine atom, a C 1 -C 10, preferably C 1 -C 4, alkyl group, a C ₆ -C _O -, preferably C ₆ -C ₈ -aryl group, a C1-C1 ₀ -, preferably Ci-C ₃ alkoxy group, a -NR ¹ V, -SR ¹⁶ -, -OSiR ¹ V, -SiR ¹ V or -PR ¹⁶ ₂ radical, where R ¹⁶ is a C1-C10-, preferably -C ₃ alkyl group or C ₆ -C ₀ -, preferably C ₆ -C ₈ - aryl group, or in the case of Si- or P-containing radicals is also a halogen atom, preferably chlorine atom, or each two adjacent radicals R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ or R ¹⁰ form a ring with the C atoms which connect them. Particularly preferred ligands are the substituted compounds of the parent compounds cyclopentadienyl, indenyl, tetrahydroindenyl, benzoindenyl or fluorenyl.

R is ¹³ R ¹⁷ ? 17 R ¹⁷ R ¹⁷ R ¹⁷

IVP- - O-

= BR ¹⁷ , = AIR ¹⁷ , -Ge, -Sn, -O-, -S-, = SO, = SO ₂ , = NR ¹⁷ , = CO, = PR ¹⁷ or = P (O) R ¹⁷ , where R ¹⁷ , R ¹⁸ and R ^{19 are} identical or different and are a hydrogen atom, a halogen atom, preferably a fluorine, chlorine or bromine atom, a C 1 -C ₃₀ , preferably C 1 -C ₄ -alkyl, in particular methyl, group, a CiC-io-fluoroalkyl, preferably CF ₃ group, a C ₆ -C | ₀ -Fluoraryl-, preferably pentafluorophenyl, a C _δ -Cio-, preferably C ₆ -C ₈ - aryl group, a CIC-IO, preferably Ci-C ₄ -Aikoxy-, especially methoxy group, a C ₂ -Ci ₀ , preferably C ₂ -C ₄ alkenyl group, a C ₇ -C ₄₀ -, preferably C ₇ -C ₀ aralkyl group, a C ₈ -C ₄₀ -, preferably C ₈ -C ₂ - arylalkenyl or C ₇ -C _40, preferably C ₇ -C ₂ denote alkylaryl group, or R ¹⁷ and R ¹⁸ or R ¹⁷ and R ¹⁹ each form a ring together with the atoms connecting them.

M ² is silicon, germanium or tin, preferably silicon and germanium. R ¹³ is preferably = CR ¹⁷ R ¹⁸ , = SiR ¹⁷ R ¹⁸ , = GeR ¹⁷ R ¹⁸ , -O-, -S-, = SO, = PR ¹⁷ or = P (O) R ¹⁷ .

R ¹¹ and R ¹² are the same or different and have the meaning given for R ¹⁷ , m and n are the same or different and are zero, 1 or 2, preferably zero or 1, where m plus n is zero, 1 or 2, preferably zero or 1. R ¹⁴ and R ¹⁵ have the meaning of R ¹⁷ and R ¹⁸ .

Examples of suitable metallocenes are:

Bis (1 ^, S-trimethylcyclopentadienyzirconium dichloride,

Bis (1, 2,4-trimethylcyclopentadienyl) zirconium dichloride,

Bis (1, 2-dimethylcyclopentadienyl) zirconium dichloride,

Bis (1,3-dimethylcyclopentadienyl) zirconium dichloride,

Bis (1-methylindenyl) zirconium dichloride, bis (1-n-butyl-3-methylcyclopentadienyl) zirconium dichloride,

Bis (2-methyl-4,6-di-i.propyl-indenyl) zirconium dichloride,

Bis (2-methylindenyl) zirconium dichloride _J

Bis (4-methylindenyl) zirconium dichloride,

Bis (5-methylindenyl) zirconium dichloride, bis (alkylcyclopentadienyl) zirconium dichloride,

Bis (alkylindenyl) zirconium,

Bis (cyclopentadienyl) zirconium,

(Indenyl) zirconium,

Bis (methylcyclopentadienyl) zirconium dichloride, bis (n-butylcyclopentadienyl) zirconium dichloride,

To (octadecylcyclopentadienyl) zirconium,

Bis (pentamethylcyclopentadienyl) zirconium,

Bisftrimethylsilylcyclopentadienyljzirkoniumdichlorid,

Biscyclopentadienylzirconiumdibenzyl, biscyclopentadienylzirconiumdimethyl,

Bistetrahydroindenylzirkoniumdichlorid,

Dimethylsilyl-θ-fluorenylcyclopentadienylzirkoniumdichlorid,

Dimethylsilyl-bis-I ^ .S.S-trimethylcyclopentadienylJzirkoniumdichlorid,

Dimethylsilyl-bis-1- (2,4-dimethyl-cyclopentadienyl) zirconium dichloride, dimethylsilyl-bis-1- (2-methyl-4,5-benzoindenyl) zirconium ammonium chloride,

Dimethylsilyl-bis-1- (2-methyl-4-ethylindenyl) zirconium dichloride,

Dimethylsilyl-bis-1- (2-methyl-4-i-propylindenyl) zirconium dichloride,

Dimethylsilylbis-1- (2-methyl-4-phenylindenyl) zirconium dichloride, (2-methyl-indenyl) zirconium dichloride dimethylsilyl-bis-1,

Dimethylsilyl-bis-1- (2-methyltetrahydroindenyl) zirconium dichloride,

Dimethylsilyl-bis-1-indenylzirkoniumdichlorid,

Dimethylsilylbis-1-indenylzirconiumdimethyl, dimethylsilylbis-1-tetrahydroindenylzirconium dichloride,

Diphenylmethylene-θ-fluorenylcyclopentadienylzirkoniumdichlorid,

Diphenylsilyl-bis-1-indenylzirkoniumdichlorid,

Ethylene-bis-1- zirconium dichloride (2-methyl-4,5-benzoindenyl)

Ethylene-bis-1- (2-methyl-4-phenyl-indenyl) zirconium dichloride, ethylene-bis-1- (2-methyltetrahydroindenyl) zirconium dichloride,

Ethylene-bis-1- (4,7-dimethyl-indenyl) zirconium dichloride,

Ethylene-bis-1-indenylzirkoniumdichlorid,

Ethylene-bis-1-tetrahydroindenylzirkoniumdichlorid,

Indenyl-cyclopentadienyl-zirconium dichloride isopropylidene (1-indenyl) (cyclopentadienyl) zirconium dichloride, isopropylidene (9-fluorenyl) (cyclopentadienyl) zirconium dichloride,

Phenylmethylsilyl-bis-1- (2-methyl-indenyl) zirconium dichloride, and in each case the alkyl or aryl derivatives of these metallocene dichlorides.

To activate the single-center catalyst systems are suitable

Cocatalysts used. Suitable cocatalysts for metallocenes of the formula (I) are organoaluminum compounds, in particular alumoxanes or else aluminum-free systems such as R ²⁰ _x NH ₄ . _x BR ²¹ ₄ , R ²⁰ _x PH _4- χBR ²¹ ₄ , R ²⁰ 3CBR ²¹ 4 or BR ²¹ ₃ . In these formulas, x is a number from 1 to 4, the radicals R ²⁰ are identical or different, preferably identical, and are C ₁ -C ₁₀ -alkyl or C ₆ -C ₈ -aryl or two radicals R ²⁰ form together with the they combine a ring and the radicals R ²¹ are the same or different, preferably the same, and are C ₆ -C ₈ -aryl which may be substituted by alkyl, haloalkyl or fluorine. In particular, R ^{20 is} ethyl, propyl, butyl or phenyl and R ^{21 is} phenyl, pentafluorophenyl, 3,5-bis-trifluoromethylphenyl, mesityl, xylyl or ToIyI. In addition, a third component is often required to provide protection against catalyst poisons. For this purpose, organoaluminum compound such. As triethylaluminum, tributylaluminum and others and mixtures suitable.

Depending on the process, supported single-center catalysts can also be used. Preference is given to catalyst systems in which the residual contents of support material and cocatalyst do not exceed a concentration of 100 ppm in the product.

To improve the transparency of PP-H, metallocene catalyzed, unmodified but also grafted polyolefin waxes can be used. For reasons of compatibility in polypropylene, unmodified polyolefin metallocene waxes are to be preferred, and within this product range, the PP metallocene waxes have been found to be particularly suitable.

Metallocene waxes which can be used according to the invention have a molecular weight Mn in the range from 500 to 15,000 g / mol, preferably in the range from 1,000 to 13,000 and / or a viscosity in the range from 30 to 10,000 mPa.s, preferably from 50 to 8,000 (measured at 170 ° ^C C for PP waxes and 140 ^° C for PE (polyethylene) waxes). The metallocene waxes are used in concentrations in the range from 0.1 to 10% by weight, preferably from 1 to 5% by weight, based on the total weight of the mixture.

When adding the metallocene waxes shown in the diagram 1, such as. As Licocene ^® PP 1302, PP 6102, PP 2602, PE 4201 or PPSI 3262, it is irrelevant whether it is an isotactic, syndiotactic or atactic PP-H. Also, the effect is not limited to a certain viscosity range of the PP-H, so that a transparency improvement in an MFI (MeIt Flow Index) range of 0.2-50 g / 10min, but especially in the range of 0.3-40 g / 10min (at 230 ⁰ C / 2.16 kg) is achieved. The present invention also relates to a process for the preparation of the polypropylene homopolymer waxes according to the invention having a transparency ≥ 81% by blending polypropylene homopolymer waxes with 0.1 to 10 wt.% Of one or more metallocene waxes having a molecular weight Mn in the range of 500 to 15000 g / mol and a viscosity in the range of 30 to 10,000 mPa.s (at 170 ⁰ C or 140 ⁰ C), melting and then extruding and granulating the mixture.

The premixing of the individual components can be advantageous and can be carried out at room temperature in a suitable mixing apparatus.

When mixing, the heat energy can be introduced via friction, via separate heating of the mixing trough or in both ways. A pre-tempering to about 25 ⁰ C is considered advantageous. Higher starting temperatures in the hot mix lead to clumping of the carrier and formation of bottom deposits. Cooling of the mixing trough after the last mixing phase to the pre-treatment temperature is also advantageous.

In the production of the highly transparent PP homopolymers, it is also expedient to work with an initial mixing process. First, a mixture of the individual components is produced. The mixture is done with appropriate mixing technique. The preparation of mixtures can be omitted, however, by feeding the individual components of a recipe directly to the extrusion plant. The said mixture is then fed by means of a suitable metering device to an extrusion plant. As a rule, these are single or twin-screw extruders, but it is also possible to use continuous and discontinuous kneaders or compactors. The subsequent granulation takes place via strand and Kopfgranulierung, but also spraying is possible.

The high-transparency polypropylene homopolymers according to the invention are particularly suitable for the production of polypropylene articles by injection molding, Extrusion, thermoforming, extrusion blow molding, sintering, rotomolding, pressing or calendering.

An improved transparency of PP homopolymer plays a role mainly in PP films in layer thicknesses of 25-1000 μm and PP thick-wall articles in the thickness ranges above 1 mm. Applications are films such. As cover films, protective films, packaging films, etc. which are produced by a blow molding or calendering, or containers such as canisters, bottles, cups, etc. which z. B. in the deep drawing, injection molding or blow molding.

For plates, the application interests are mainly limited to those which are produced by extrusion or injection molding and z. B. for covers, construction purposes or as support plates use.

Examples:

The results of the study presented in Diagram 1 were generated using a regular PP-H extrusion type (Moplen HF 500 N), MFI 12 (23072.16 kg). For this purpose, the additives were mechanically mixed with the polymer powder and then extruded once with a standard twin-screw extruder (Leistritz) and granulated. These granules were then sprayed into 1 mm thick test plates on an Arburg injection molding machine. The processing conditions corresponded to the usual practice for this polymer in all steps.

Diagram 1

For a more detailed differentiation of the graphically displayed results in Diagram 1, the recipes are summarized in tabular form in the overview below.

Table 1

The addition of Licocene waxes does not affect other finishing processes or their effects on PP-H. For example, coloring with pigments, stabilizing with additives, such as antioxidants or light stabilizers, equipping with antistatic agents, etc.

Claims

claims

A polypropylene homopolymer having a transparency> 81%, containing one or more metallocene polyolefin waxes in a concentration of 0.1 to 10 wt.%, With a molecular weight Mn in the range of 500 to 15,000 g / mol and a viscosity in the range from 30 to 10,000 mPa.s (at 170 ^° C. PP or 140 ^° C. PE).

2. Metallocene wax-containing polypropylene homopolymer according to claim 1, characterized in that its melt index (MFI) in the range of

0.2 - 50 g / 10 min. (at 230 ⁰ C / 2.16 kg).

3. Polypropylene homopolymer according to claim 1, characterized in that the molecular weight Mn of the metallocene waxes contained in the range of 1000 to 13000 g / mol.

4. Polypropylene homopolymer according to at least one of the preceding claims, characterized in that the viscosity of the metallocene waxes contained, measured in the melt at 170 ⁰ C (PP) or 140 ⁰ C (PE), in the range of 50 to 8000 mPa- s is.

5. polypropylene homopolymer according to at least one of the preceding claims, characterized in that the metallocene wax contained therein by direct polymerization of the monomers, for. As propylene and / or ethylene, were prepared using metallocene catalysts.

6. A process for the preparation of polypropylene homopolymer waxes having a transparency> 81% by blending polypropylene homopolymer waxes with 0.1 to 10 wt .-% of one or more metallocene waxes having a molecular weight Mn in the range of 500 to

15,000 g / mol and a viscosity in the range of 30 to 10,000 mPa-s (at 170 ⁰ C and 140 ⁰ C), melting and then extruding and granulating the mixture.

7. Use of polypropylene homopolymers according to at least one of claims 1 to 5 for the production of polypropylene articles by injection molding, extrusion, thermoforming, extrusion blow molding, sintering, Rotomoulding, pressing or calendering.