Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-11-28
2003-03-18
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C427S372200, C427S385500, C428S480000, C524S086000, C524S496000
Reexamination Certificate
active
06534585
ABSTRACT:
The invention relates to elastomer copolyetherester film having improved resistance to ageing under the influence of UV light. Elastomer copolyetherester film is increasingly being used as a moisture regulating top layer in roof coverings and other building applications. During the building phase the film is often exposed to direct sunlight for a longer period of time before the roof tiles are placed. Especially in mountainous regions the irradiation by UV light can be very intensive. UV irradiation causes the mechanical properties of the unprotected film to deteriorate very rapidly, and as a result the film may very easily be damaged, for example by falling tools. In more extreme cases it is no longer possible to tread on the roof covering without damaging it. In addition, the moisture regulating properties are adversely affected.
From Encyclopaedia of Polymer Science and Engineering Vol. 12, p. 102 (1988), John Wiley and Sons, Inc., it is known that copolyetheresters can effectively be protected against UV light in outdoor applications by the addition of 0.5-3 wt. % activated carbon. Vol. 15, pp. 563-564 (1989) of the same Encyclopaedia further discloses that good dispersion of the activated carbon is essential and the particle size should be between 15 and 25 nm. The claims of EP-0783016-A2 again repeat these findings, on account of which copolyetherester film would have a good UV stability and improved IR remission. The present inventors, however, have not been able to find any experimental basis in EP-0783016-A2 for said advantages or for any special effect. On the contrary, the UV resistance of carbon black containing copolyetherester film, in particular of the membranes disclosed in claim 14 of said patent, with a thickness of 5-30 &mgr;m, proves to differ only slightly from that of non-stabilized membranes.
The UV-stabilized copolyetherester films according to the state of the art appear to be wholly incapable of meeting the rigid conditions that are imposed on films in particular in the building world.
The aim of the invention is therefore a copolyetherester composition which, also when used in very thin film, has a considerably improved resistance to UV irradiation so as to enable application inter alia as a moisture regulating top layer in roof covering.
The inventors have achieved this aim with a copolyetherester composition containing a stabilizer combination of 0.1-10 wt. % activated carbon and 0.1-3 wt. % of a hindered amine light stabilizer (HALS). The use of HALS in a copolyetherester composition to improve the stability has been known for a long time, its use being disclosed inter alia in JP-52-044869-A. To improve its activity, it is known to apply combinations of HALS with other UW stabilizers. JP-60-015455-A, U.S. Pat. No. 4,524,165-A and JP-02-283754 describe the combination with a triazole and JP-04-337.349-A the combination with a thio-ether. The inventors have tested these combinations and some other combinations of UV stabilizers, but none of these yielded enough stability for the use in film.
It is highly surprising that the combination with activated carbon, conversely, yields a very substantial improvement of the resistance to UV radiation, to such an extent that even very thin polyetherester film can be exposed to direct UV light for a longer period of time.
The copolyetheresters of the composition comprise copolyetheresters derived from polyether glycols with an average molecular weight of 600-6000, glycols, preferably alkylene glycols, for example ethylene or butylene glycol, and dicarboxylic acids, for example aromatic dicarboxylic acids, preferably terephthalic acid and naphthalenic dicarboxylic acid, cycloaliphatic dicarboxylic acids, for example cyclohexane dicarboxylic acid and aliphatic dicarboxylic acids, for example adipic acid.
Examples and preparation of such copolyetheresters are described in, inter alia, Thermoplastic Elastomers, 2nd Ed., Chapter 8, Carl Hanser Verlag (1996) ISBN 1-56990-205-4, Handbook of Thermoplastics, ed. O. Otabisi, Chapter 17, Marcel Dekker Inc., New York 1997, ISBN 0-8247-9797-3 and the Encyclopaedia of Polymer Science and Engineering, Vol. 12, pp. 75-117 and the references cited therein. A large number of copolyetheresters are commercially available.
The ratio between the polyester units derived from the polyether glycol and those derived from the alkylene glycol, i.e. the ratio between the soft and hard segments of the copolyetherester may vary within a broad range and is determined mainly by the application of the polyetherester copolymer. In general this ratio will be chosen so that the Shore D hardness of the polymer is between 25 and 80.
The moisture-regulating capacity of the membranes obtained from the polyetherester copolymer is varied as needed through variation of the thickness of the membrane or by varying the C:O ratio in the polyalkylene oxide glycols in the polyetherester copolymer. In general the ratio is between 2 and 4.3, a low ratio generally leading to an increase in the water vapour permeability.
Activated carbon is in this context understood to be a specific form of carbon consisting of very fine primary particles combined into primary aggregates, which are not broken under normal dispersing conditions. These primary aggregates in turn generally combine in the form of agglomerates. Characteristic of this activated carbon is the large surface area that is optically available. This surface area is determined mainly by the size of the primary particles and their degree of packing in the primary aggregates. Activated carbon can be obtained in different manners and is commercially available in different forms and under various tradenames. Preferably, carbon black is used. It is preferred that under the conditions of preparation of the composition all agglomerates are broken down into primary aggregates, which should form a fine dispersion in the composition. The diameter of the primary particles may vary within a broad range, for example between 10 and 100 nm. Preferably, the average particle size is chosen to be between about 15 and 40 nm. When the particles are smaller, the radiation absorbing capacity decreases strongly as the radiation can bend around the particle. When the particles are bigger, the optically available surface area decreases too strongly, and the diameter of the primary aggregates may sometimes be too large as a result of which processing into thin films presents problems.
The activated carbon content of the composition may in principle vary within a broad range, for example between 0.1 and 10 wt. %. Preferably, the content is limited to between 0.5 and 5 wt. %, even more preferably between 0.5 and 3 wt. %, as lower concentrations have relatively little effect and at concentrations in excess of 3 wt. % only little more UV radiation is absorbed. The useful upper limit is A generally the content at which the surface layer of the composition just ceases to be transparent. For very thin film, therefore, a higher carbon content is desirable than for thicker film. Higher carbon contents, incidentally, generally have an adverse effect on the mechanical properties, such as elongation at break.
The hindered amine light stabilizer (HALS) of the composition according to the invention is a UV light stabilizer for copolyetherester compositions that in itself is often used by ones skilled in the art. Very well-known in the professional world is the HALS disclosed in the European patent EP-000389-B1, bis-(1,2,2,6,6-penta-methyl-piperidyl)-(3′,5′-di-tert-butyl-4′hydroxy-benzyl)-butyl-malonate, available under the tradename Tinuvin® 144 from Ciba-Geigy.
A hindered amine light stabilizer is understood to mean compounds of the following general formulas:
and combinations thereof.
In these formulas, R
1
up to and including R
5
are independent substituents. Examples of suitable substituents are hydrogen, ether groups, ester groups, amine groups, amide groups, alkyl groups, alkenyl groups, alkynyl groups, aralkyl groups, cycloalkyl groups and aryl groups, in which the subs
Dijkstra Krijn
Gijsman Pieter
DSM N.V.
Niland Patrick D.
Pillsbury & Winthrop LLP
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