Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-08-27
2003-12-02
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C525S165000
Reexamination Certificate
active
06656981
ABSTRACT:
The present invention provides a method for reducing dust deposits on polyolefin films by incorporating therein a polyetherester amide or a composition containing a polyetherester amide. Further subjects of the invention are the use of a polyetherester amide based composition for reducing dust deposits on polyolefin films and coextruded multilayer polyolefin films containing a polyetherester amide at least in one outer layer.
Dust deposition on plastic foils is not only an esthetic but also a hygienic and safety problem. In packaging and subsequent storage of food, germs can be deposited together with the dust and may cause severe diseases. This must also be avoided in medical and pharmaceutical packaging.
In packaging of electronic parts, dust may cause malfunctions and consequently considerable damages may occur during use.
One of the major problems in agricultural applications such as in greenhouses, made from transparent polyolefin films, is dust deposition on the interior or exterior side of the film which sticks to the film and cannot easily be removed by simple rinsing with water. Already small amounts of dust reduce the light transmission of the film significantly which results in less plant growth. The effect of dust deposition on the light transmission of greenhouse foils is for example described by A. Jaffrin et al. in Plasticulture, No.101, 1994, page 33-44.
Several attempts have been made to reduce dust deposition on polyolefin films for packaging and particularly for agricultural applications, such as greenhous, mulch, silage or bale wrap. Typical antistatic agents such as alkylamine ethoxylates, polyethyleneglycol sorbitan monooleate or sorbitan stearate have been used with limited success.
It has now been found that dust deposition can be significantly reduced by incorporating polyetherester amides or compositions containing polyetherester amides into the films. The films remain essentially transparent. A further advantage is, that even if small amounts of dust are deposited, it can be easily washed away, since the dust particles adhere only loosely to the polymer film.
Alongside with dust deposition the formation of algae is observed on polyolefin films used in greenhouses. This is highly undesirable since it further decreases transmitted light and in addition can lead to plant diseases.
One subject of the present invention is a method for reducing dust deposition on polyolefin films, comprising, incorporating into the polyolefin film a polyetherester amide or a composition containing a polyetherester amide.
Examples for polyolefins from which films can be made are given below.
1. Polymers of monoolefins and diolefins, for example polypropylene, polyisobutylene, poly but-1-ene, poly-4-methylpent-1-ene, polyisoprene or polybutadiene, as well as polymers of cycloolefins, for instance of cyclopentene or norbornene, polyethylene (which optionally can be crosslinked), for example high density polyethylene (HDPE), high density and high molecular weight polyethylene (HDPE-HMW), high density and ultrahigh molecular weight polyethylene (HDPE-UHMW), medium density polyethylene (MDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), (VLDPE) and (ULDPE).
Polyolefins, i.e. the polymers of monoolefins exemplified in the preceding paragraph, preferably polyethylene and polypropylene, can be prepared by different, and especially by the following, methods:
a) radical polymerisation (normally under high pressure and at elevated temperature).
b) catalytic polymerisation using a catalyst that normally contains one or more than one metal of groups IVb, Vb, VIb or VIII of the Periodic Table. These metals usually have one or more than one ligand, typically oxides, halides, alcoholates, esters, ethers, amines, alkyls, alkenyls and/or aryls that may be either &pgr;- or &sgr;-coordinated. These metal complexes may be in the free form or fixed on substrates, typically on activated magnesium chloride, titanium(III) chloride, alumina or silicon oxide. These catalysts may be soluble or insoluble in the polymerisation medium. The catalysts can be used by themselves in the polymerisation or further activators may be used, typically metal alkyls, metal hydrides, metal alkyl halides, metal alkyl oxides or metal alkyloxanes, said metals being elements of groups Ia, IIa and/or IIIa of the Periodic Table. The activators may be modified conveniently with further ester, ether, amine or silyl ether groups. These catalyst systems are usually termed Phillips, Standard Oil Indiana, Ziegler (-Natta), TNZ (DuPont), metallocene or single site catalysts (SSC).
2. Mixtures of the polymers mentioned under 1), for example mixtures of polypropylene with polyisobutylene, polypropylene with polyethylene (for example PP/HDPE, PP/LDPE) and mixtures of different types of polyethylene (for example LDPE/HDPE).
3. Copolymers of monoolefins and diolefins with each other or with other vinyl monomers, for example ethylene/propylene copolymers, linear low density polyethylene (LLDPE) and mixtures thereof with low density polyethylene (LDPE), propylene/but-1-ene copolymers, propylene/isobutylene copolymers, ethylene/but-1-ene copolymers, ethylene/hexene copolymers, ethylene/methylpentene copolymers, ethylene/heptene copolymers, ethylene/octene copolymers, propylene/butadiene copolymers, isobutylene/isoprene copolymers, ethylene/alkyl acrylate copolymers, ethylene/alkyl methacrylate copolymers, ethylene/vinyl acetate copolymers and their copolymers with carbon monoxide or ethylene/acrylic acid copolymers and their salts (ionomers) as well as terpolymers of ethylene with propylene and a diene such as hexadiene, dicyclopentadiene or ethylidene-norbornene; and mixtures of such copolymers with one another and with polymers mentioned in 1) above, for example polypropylene/ethylene-propylene copolymers, LDPE/ethylene-vinyl acetate copolymers (EVA), LDPE/ethylene-acrylic acid copolymers (EAA), LLDPE/EVA, LLDPE/EAA and alternating or random polyalkylene/carbon monoxide copolymers and mixtures thereof with other polymers, for example polyamides.
Preferably the polyolefin is polyethylene (PE), a L- or LL-DPE, a L- or LL-DPE/ethylene-vinyl acetate copolymer (EVA) or a L-or LL-DPE/ethylene-butylacrylate copolymer (EBA).
The polyolefin film has typically a thickness from 10 to 300 micron, preferably 20-250 micron, most preferably 25-220 micron.
The polyolefin film may be of a single layer or be a multilayer construction, which has been manufactured by co-extrusion with up to 20 layers, preferably up to 7 layers, most preferably up to 5 layers.
A preferred embodiment of the present invention is a coextruded film with three to five layers wherein at least one outer layer contains a polyetherester amide or a composition containing a polyetherester amide.
More preferably only one outer layer contains a polyetherester amide or a composition containing a polyetherester amide.
The polyolefin films are particularly useful for agricultural applications (greenhouse, mulch, bale wrap, silage films), food packaging, electronic parts packaging, pharmaceutical packaging, hygienic films and medical equipment packaging.
When used in agricultural applications the films are preferably used for greenhouses. The films can form the cover of a greenhouse, protecting the plants from the influences of the surrounding or the films can be used in the inside of a greenhouse to cover or protect the plants or a part of the plants from influences originating from inside, such as artificial watering or spraying of herbicides and/or insecticides.
Consequently a preferred method is wherein the polyolefin film is used as a cover or protective film in a greenhouse.
The films can be coextruded by film extrusion such as blown film extrusion or by cast film extrusion or they can be laminated and they can include layers based on polymers such as polyamide (PA 6 or 6,6 or 11 or 12 or 6/6,6 copolymer including OPA), polyethylene terephtalate (PET including OPET), polyethylene naphtalate (PEN), ethylene vinyl alcohol (EvOH), polypropylene (including O
Ergenc Nadi
Lelli Nicola
Ciba Specialty Chemicals Corporation
Stevenson Tyler A.
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