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
2001-10-29
2004-08-17
Mulcahy, Peter D. (Department: 1713)
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...
C524S323000, C524S345000, C524S349000, C524S335000, C524S337000, C524S338000
Reexamination Certificate
active
06777473
ABSTRACT:
The present invention relates to stabilized compositions formed of functionalized polyolefins and in particular stabilized compositions formed of polyolefins functionalized by carboxylic acid groups, their esters, their anhydrides or their metal salts. It also relates to a process for their preparation and to their use.
Functionalized polyolefins are widely used, in particular as adhesive between a polyethylene (PE) layer and a layer of epoxy resin, for example for the coating of pipes. In practice, all plastics are subject to oxidation phenomena, commonly described using the terminology “ageing phenomenon”. The most widely used method for slowing down these phenomena is the addition of antioxidizing or stabilizing agents.
Phenolic antioxidants are used as stabilizing agents for polyethylenes. However, their combination with stabilizing agents of phosphite type is generally more effective; see U.S. Pat. No. 4,290,941. A frequently used combination is, for example, a blend of pentaerythrityl tetrakis(3,5-di-t-butyl-4-hydroxyphenylpropionate) and of tris(2,4-di-t-butylphenyl) phosphite.
The problem which is posed in the case of adhesives stabilized in this way, based on polyolefins functionalized by acid or anhydride groups, for example maleic-anhydride-functionalized polyethylene, is a long-term loss in adhesion. Furthermore, these compositions are subject to a loss in thermal stability and to an increase in the viscosity in the presence of moisture (loss in rheological stability), this phenomenon further being accelerated by an increase in the temperature.
The present invention is targeted at overcoming these disadvantages by novel compositions formed of functionalized polyolefins exhibiting better thermal stability and better rheological stability and giving better long-term adhesion.
One aspect of the present invention consequently relates to compositions comprising one or more olefin polymers functionalized by at least one functionalization agent chosen from carboxylic acids, their esters, their anhydrides and their metal salts and one or more stabilizing agents comprising one or more sterically hindered phenol groups and at most one ester functional group.
These functionalized compositions exhibit better rheological stability and give better long-term adhesion.
Furthermore, these compositions are no longer subject to a loss in thermal stability nor to an increase in the viscosity in the presence of moisture.
The stabilizing agents comprising one or more sterically hindered phenol groups and at most one ester functional group are chosen from stabilizing agents comprising one or more sterically hindered phenol groups which comprise an ester functional group and from stabilizing agents comprising one or more sterically hindered phenol groups which do not comprise an ester functional group.
The term “ester functional group” is understood to denote, for the purposes of the present invention, the ester functional group derived from the carboxylic acid functional group within the conventional meaning of organic chemistry (R—CO—O—R′).
Mention may be made, among stabilizing agents comprising one or more sterically hindered phenol groups which comprise an ester functional group, of, for example, stearyl &bgr;-(3,5-di-t-butyl-4-hydroxy-phenyl)propionate.
Mention may be made, among stabilizing agents comprising one or more sterically hindered phenol groups which do not comprise an ester group, of, for example, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 2,2′-isobutylidenebis(4,6-dimethylphenol), 2,2′-methylenebis(6-t-butyl-4-methylphenol), 2,6-bis(&agr;-methylbenzyl)-4-methylphenol, 4,4′-thiobis-(6-t-butyl-m-cresol), 2,2′-methylenebis(4-methyl-6-nonylphenol), diisobutylnonylphenol, tris (3, 5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris-(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-tri-azine-2,4,6-(lH,3H,5H)-trione, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene and their mixtures.
Preferably, at least one of the stabilizing agents does not comprise an ester functional group. In a particularly preferred way, at least one of the stabilizing agents is 1,3,5-trimethyl-2,4,6-tris-(3, 5-di-t-butyl-4-hydroxybenzyl)benzene (Irganox® 1330). In a very particularly preferred way, the compositions according to the invention comprise 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene as sole stabilizing agent.
The amounts of stabilizing agent employed in the compositions of the present invention depend on various factors, for example on the amount of radical initiator used, on the application intended for the compositions and on the nature of the functionalization agent. The amount of stabilizing agent is generally between 0.001 and 1% by weight.
Generally, the amount of stabilizing agent is greater than or equal to 0.001%, preferably greater than or equal to 0.01%, in a particularly preferred way greater than or equal to 0.1% by weight.
Generally, the amount of stabilizing agent is less than or equal to 1%, preferably less than or equal to 0.75%, in a particularly preferred way less than or equal to 0.5% by weight.
The olefin polymers functionalized by functionalization agents chosen from carboxylic acids, their esters, their anhydrides and their metal salts can be obtained by known techniques, for example by copolymerization or, preferably, by grafting. They are derivatives of polymers formed of linear olefins comprising from 2 to 8 carbon atoms, such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene and 1-octene.
The linear olefins preferably comprise from 2 to 6 carbon atoms, more particularly from 2 to 4 carbon atoms.
The olefin polymers (polyolefins) can be selected from homopolymers of the abovementioned olefins or from copolymers of these olefins, in particular copolymers of ethylene or of propylene with one or more comonomers. The constituent comonomers are advantageously chosen from the abovedescribed olefins and from diolefins comprising from 4 to 18 carbon atoms, such as 4-vinylcyclohexene, dicyclopentadiene, methylene- and ethylidenenorbornene, 1,3-butadiene, isoprene and 1,3-pentadiene.
The polyolefins are preferably chosen from propylene polymers and ethylene polymers, in particular ethylene homopolymer, propylene homopolymer, ethylene copolymers, propylene copolymers, copolymers of ethylene and of propylene, and their mixtures.
The propylene polymers are generally chosen from propylene homopolymers and copolymers with a melt flow index (MFI), measured at 230° C. under a load of 2.16 kg according to ASTM standard D 1238 (1986), of between 0.1 and 100 dg/min.
The ethylene polymers are generally chosen from ethylene homopolymers and copolymers exhibiting a standard density of between 915 and 960 kg/m
3
and a melt flow index (measured at 190° C. under a load of 5 kg) of between 0.1 and 200 dg/min.
Ethylene homopolymers and copolymers are particularly preferred. These advantageously exhibit a standard density of at least 915 kg/M
3
, in particular of at least 936 kg/m
3
. The standard density generally does not exceed 960 kg/m
3
, preferably does not exceed 953 kg/m
3
. The ethylene homopolymers and copolymers, in addition, usually exhibit a melt flow index (measured at 190° C. under a load of 5 kg) of at least 0.1 dg/min, preferably of at least 2 dg/min. The melt flow index generally does not exceed 200 dg/min, more particularly does not exceed 40 dg/min.
The functionalization agent is generally a compound comprising a vinyl unsaturation and optionally one or more aromatic nuclei and/or one or more carbonyl groups. The functionalization agent can be chosen, for example, from unsaturated mono- or dicarboxylic acids and their derivatives, unsaturated mono- or dicarboxylic acid anhydrides and their derivatives, unsaturated mono- or dicarboxylic acid esters and their derivatives or unsaturated mono- or dicarboxylic acid metal salts and their derivatives. The functionalization agents preferably comprise from 3 to 20 carbon atoms. Mention may be made, as typical examples, of acrylic acid, methacrylic ac
Collard Marie-Paule
Fassiau Eric
Vandevijver Eric
Wautier Henri
Mulcahy Peter D.
Solvay Polyolefins Europe--Belgium (Societe Anonyme)
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