Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-02-07
2001-12-25
Mullis, Jeffrey (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S098000, C525S099000
Reexamination Certificate
active
06333382
ABSTRACT:
This invention relates to a polymeric composition and more particularly to a polymeric composition based on a random copolymer of propylene. It also relates to the use of said composition for the manufacture of objects and to the objects so obtained.
Random copolymers of propylene are propylene copolymers containing a small amount of ethylene, generally from about 0.5 to about 6 weight %. They are used for applications that require improved clarity over homopolymers polypropylene.
For example, their properties make them attractive for use in the manufacture of food containers. However, like propylene homopolymer, they have a low impact strength, which leads to whitening under minor impact events, a phenomenon commonly known as blushing or hazing. The tendency towards blushing makes the random copolymers of propylene unattractive for certain uses, such as food containers.
In U.S. Pat. No. 4,904,731, it was found that a hydrogenated elastomeric block copolymer comprising at least two polymeric blocks containing predominantly monoalkenyl aromatic hydrocarbon monomer units and at least one block containing a predominantly hydrogenated, conjugated diene unit and a linear low density polyethylene (LLDPE) can be combined with the random copolymers of propylene to improve impact resistance and clarity. However, impact related hazing problems are still seen in this polymer when it is used at low temperature. Therefore, even greater impact resistance and clarity, particularly at low temperatures, was desirable.
In GB-A-2,323,363, it was found that blending a hydrogenated elastomeric block copolymer and an elastic metallocene based polyolefin with random copolymer of propylene provided improved impact strength, particularly low temperature impact strength, and also an excellent clarity. According to the description, the concentration of the clastomeric block copolymer is up to 25 weight %, e.g. 15 weight %, and the concentration of the metallocene based polyolefin is up to 25 weight %; the weight ratio of block copolymer to metallocene based polyolefin being in the range from about 25:75 to 75:25, most preferably 50:50. The drawback of such composition is, beside its relatively high cost, the high concentration of the elastomeric block copolymer that makes the composition unsuitable for packaging applications where FDA “cooking in the bag” compliance is required. Moreover, at very high concentration of clastomeric block copolymer, the composition becomes unacceptable even for simple food contact application. It was therefore desirable to obtain a better balance between mechanical properties and FDA compliance.
New compositions have now been found containing a random copolymer of propylene, an elastomeric block copolymer and LLDPE that meet these objectives.
For this purpose, the present invention relates to a polymeric composition containing:
a) 100 parts by weight of a random copolymer of propylene and ethylene containing less than 6 weight % of ethylene,
b) 0.1 to 4 parts by weight of an elastomeric block copolymer having at least one polymeric block containing predominantly polymerized monovinyl aromatic compound and at least one polymeric block containing predominantly polymerized conjugated diene, and
c) 12 to 20 parts by weight of an elastic metallocene polyolefin.
The random copolymers of propylene involved in the composition of the invention most often contain from 0.5 to 4 weight % of ethylene. The ethylene content is preferably of at least I weight %; ethylene content of at most 3 weight % giving good results. Random copolymers containing from I to 3 weight % of ethylene are particularly suitable.
The random copolymers of propylene usable in the present invention advantageously contain monomer units derived only from propylene and ethylene.
Such random copolymers of propylene are known by the man of ordinary skill in the art and are generally obtained by any polymerization process of blends of suitable contents of propylene and ethylene.
The ethylene content in the random copolymers is measured by infrared spectrography and estimated from the bands measured 732 and 720 cm
−1
. The random copolymer usable according to the present invention most often have a melt index (MFI), measured at 230° C. under a 2.16 load according to ASTM Standard D 1238 (1986), of 0.1 to 50 g/10 min, in particular from 1 to 50, values from 1 to 10 being the most common because they provide with adequate Theological behavior during the process of blow moulding.
Any block copolymer containing at least one polymeric block containing predominantly polymerized monovinyl aromatic compound and at least one polymeric block containing predominantly polymerized conjugated diene, herein after designated as elastomeric block copolymer, may be used in the compositions of the invention.
According to the present invention, the term predominantly defines an amount of at least 85% by weight. The other portion of monomer may be any monomer copolymerizable with the indicated monomers. Examples of said monomers are &agr;-olefins such as, preferably, ethylene.
Suitable monovinyl aromatic compounds have 8 to 20 carbon atoms such as stryrene and styrene homologues. Styrene is specially preferred.
In most cases, the conjugated diene have 4 to 8 carbon atoms such as for examples 1,3 butadiene (butadiene), 2-methyl-1,3-butadiene and 2-methyl-1,3-pentadiene. Preferred dienes are butadiene and isoprene, butadiene giving the best results.
Copolymers of conjugated diene with a-olefin give good results.
Amongst them copolymers of butadiene and ethylene are specifically preferred.
Moreover, mixture of elastomeric block copolymers may be used such as, for example, mixtures of a diblock copolymer containing one block of polymerized monovinyl aromatic compound and one block of polymerized conjugated diene with a triblock copolymer containing two endblocks of polymerized monovinyl aromatic compound and one midblock of polymerized conjugated diene.
The elastomeric block copolymer for use in this invention is preferably formed from blocks hereabove described and is generally not grafted with functionalized monomers such as for example carboxylic and/or anhydride or sulphonate.
Typically, the elastomeric block copolymer is a styrene/ethylene-butadiene/styrene triblock copolymer or a mixture thereof with styrene/ethylene-butadiene diblock copolymers, these latter being specifically preferred.
Said copolymers are known in the art and may be prepared by sequential anionic polymerization of the monomers using known initiators such as alkyl lithium initiators.
The elastomeric block copolymer used in the composition according to the invention are preferably hydrogenated in order to provide weatherability to the polypropylene composition. The hydrogenation may be carried out by using any known hydrogenation method. In general, the conditions used to said hydrogenation are selected to insure that at least 50%, preferably at least 80% and most preferably at least 95% of the ethylene unsaturations remaining in the conjugated block copolymer are saturated. Usually these conditions are such that less than 20%, most often less than 10% and more particularly less than 5% of the aromatic unsaturations in the monoalkenyl aromatic hydrocarbon polymer blocks are hydrogenated.
The content of elastomeric block copolymer is usually of at least 0.5 and more particularly of at most 3 parts by weight per 100 parts of random copolymer of propylene.
Contents of from 0.5 to 2 parts by weight per 100 parts of random copolymer of propylene makes it possible to reach particularly advantageous properties at reasonable costs.
Beside the random copolymer of propylene and the elastomeric block copolymer, the composition of the invention contains from 12 to 20 parts of an elastic metallocene polyolefin per 100 parts of random copolymer of propylene.
Any random copolymer of ethylene containing less than 20% by weight of an &agr;-olefin having 3 to 10 carbon atoms made using a metallocene catalyst may be used as elastic metallocene polyolefin. Copolymers of ethylene cont
Scott Swanzy
Sherwood Kelley
Mullis Jeffrey
Schneller Marina V.
Solvay Polyolefins Europe-Belgium
Venable
LandOfFree
Polymeric composition, its use for the manufacture of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polymeric composition, its use for the manufacture of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polymeric composition, its use for the manufacture of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2562189