Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-12-18
2003-07-15
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S065000, C526S113000, C526S114000, C526S115000, C526S116000, C526S117000, C526S118000, C526S119000, C526S348000, C526S351000, C526S905000, C525S191000, C525S240000, C525S053000, C428S910000, C264S435000, C264S901000
Reexamination Certificate
active
06593442
ABSTRACT:
The present invention relates to semicrystalline propylene polymer compositions which are particularly suitable for producing biaxially oriented films. The invention further relates to the use of the semicrystalline propylene polymer compositions for producing films, fibers or moldings, and also to the films, fibers and moldings made from these compositions.
The term polypropylene is generally understood to denote a wide variety of different polymers, a common feature of which is that they have been built up to a substantial extent from the monomer propylene. The various polypropylenes are generally obtained by coordinative polymerization on catalysts made from transition metals, which give predominantly ordered incorporation of the monomers into a growing polymer chain.
The polymer chains obtained during the polymerization of propylene with the usual coordination catalysts have a methyl side group on each second carbon atom. The polymerization therefore proceeds in a regioselective manner. Depending on the orientation of the monomers during incorporation into the chain, various stereochemical configurations are obtained. If the monomers all have the same arrangement when they are incorporated, the methyl side groups in the polymer chain are then all on the same side of the principal chain. The term used is isotactic polypropylene. If all of the monomers alternate in their spatial orientation when incorporated into the chain, the resultant polypropylene is termed syndiotactic. Both of these varieties with their stereoregular structures are semicrystalline and therefore have a melting point.
However, since the incorporation of the propylene monomers when coordination catalysts are used is not absolutely consistent, but some of the monomers are introduced in a way which differs from that of the majority, the polymer chains formed always have “defects” in the prevailing arrangement, and the number of these defects can vary considerably.
The longer the defect-free structure sequences in the polymer chains, the more readily the chains crystallize and therefore the higher are the crystallinity and the melting point of the polypropylene.
If the methyl side groups have an irregular stereochemical arrangement the polypropylenes are termed atactic. These are completely amorphous and therefore have no melting point.
The industrial preparation of polypropylene nowadays mostly uses heterogeneous catalysts based on titanium, and the resultant product is a predominantly isotactic polymer. These catalysts, for which the term Ziegler-Natta catalysts has become established, have a number of different centers active for polymerization. These centers differ both in their stereospecificity, i.e. in the number of “defects” which the resultant chains have, and also in the average molar mass of the chains formed. The predominant defects observed in all cases are stereo-defects, meaning that individual propylene monomers were incorporated syndiospecifically instead of isospecifically. The result of polymerization with heterogeneous catalysts of this type is therefore a mixture of various polymer chains which differ both in their stereochemistry and in their molar mass.
A substantial application sector for polypropylenes is that of films, particularly biaxially stretched films, frequently also termed BOPP (biaxially oriented polypropylene) films.
A general aim of almost all developments in the polypropylenes sector is to reduce the soluble fractions of the polymers used. This is frequently possible via the use of optimized conventional Ziegler-Natta catalysts. The result is firstly an improvement in organoleptic properties, advantageous for applications in the medical and food sectors, and secondly a favorable effect on mechanical properties, in particular stiffness. However, polypropylenes of this type with reduced soluble fractions cannot be used for producing biaxially stretched polypropylene films, since they have low capability, or no capability, for processing to give these films. Many efforts have therefore been made to use variations in the composition in order to find polypropylenes suitable for producing biaxially stretched polypropylene films.
EP-A 339 804 describes a mixture of a homopolypropylene and a random propylene copolymer, where the comonomer has been incorporated within the upper range of the molecular-weight distribution of the mixture. Mixtures of this type have good optical and mechanical properties, but have limited processibility.
EP-A 115 940 discloses propylene-ethylene copolymers suitable for producing biaxially stretched films and having from 0.1 to 2.0 mol % of ethylene and high isotacticity. These polymers have good extensibility, stiffness, transparency, impact strength and stability in relation to heat-shrinkage. However, they frequently do not meet the requirements of BOPP film producers with respect to mechanical, rheological and optical properties.
EP-A 657 476 describes an &agr;-olefin polymer obtained by polymerizing an a-olefin having 3 or more carbon atoms and whose composition has been defined via the proportions by weight of fractions soluble in xylene at 20° C. and insoluble in xylene at 105° C.
JP-A 10 053 675 describes a polypropylene composition composed of a high-molecular-weight crystalline polypropylene with a soluble fraction of less than 5% and a low-molecular-weight polyolefin composition with a soluble fraction of more than 30%.
Although the propylene polymer compositions known from the prior art permit the production of biaxially oriented polypropylene films, they do not combine this property with ideal processibility and very good mechanical properties of the films. This means that it has hitherto not been possible to decouple the inverse correlation between processibility and mechanical properties of the films.
It is an object of the present invention, therefore, to develop propylene polymer compositions which have excellent processibility to give biaxially stretched films and from which, at the same time, films with very good mechanical and optical properties can be produced. It should also be possible to obtain these by a very uncomplicated process, and the films should have good barrier action, for example with respect to oxygen and water vapor.
We have found that this object is achieved by a semicrystalline propylene polymer composition with good suitability for producing biaxially oriented films and prepared by polymerizing propylene, ethylene and/or C
4
-C
18
-1-alkenes, where at least 50 mol % of the monomer units present arise from the polymerization of propylene,
and with a melting point T
M
of from 65 to 170° C., where the melting point T
M
is determined by differential scanning calorimetry (DSC) to ISO 3146 by heating a previously melted specimen at a heating rate of 20° C./min, and is measured in ° C. and is the maximum of the resultant curve,
and where the semicrystalline propylene polymer composition can be broken down into
from 40 to 85% by weight of a principal component A,
from 0 to 55% by weight of an ancillary component B, and
from 0 to 55% by weight of an ancillary component C,
where the proportions of components A, B and C are determined by carrying out TREF (temperature rising elution fractionation) in which the polymers are firstly dissolved in boiling xylene and the solution is then cooled at a cooling rate of 10° C./h to 25° C., and then, as the temperature rises, that fraction of the propylene polymer composition which is soluble in xylene at (T
M
/2)+7.5° C. is then dissolved and separated off from the remaining solid, and then, as the temperature rises, at all of the higher temperatures 70° C., 75° C., 80° C., 85° C., 90° C., 94° C., 98° C., 102° C., 107° C., 112° C., 117° C., 122° C. and 125° C. the fractions soluble within the temperature range between this elution temperature and the preceding elution temperature are eluted, and the fractions taken into consideration during the evaluation which follows are those whose proportion by weight is at least 1% by weight of the initial weight of the propylene polyme
Bidell Wolfgang
Hingmann Roland
Langhauser Franz
Lilge Dieter
Rauschenberger Volker
Basell Polypropylen GmbH
Keil & Weinkauf
Rabago R.
Wu David W.
LandOfFree
Semicrystalline propylene polymer compositions with good... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semicrystalline propylene polymer compositions with good..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semicrystalline propylene polymer compositions with good... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3087664