Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
1999-11-17
2001-11-13
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S516000, C428S041400, C525S09200D, C525S100000, C525S106000, C528S041000
Reexamination Certificate
active
06316112
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to anionically polymerized fluoro-functional polyethylene/cyclic siloxane block copolymers for use in release coatings.
BACKGROUND OF THE INVENTION
Linear block copolymers of polystyrene and polydimethylsiloxane have been synthesized, both by graft and block copolymerization. In block copolymerization of such linear polymers, polystyrene is produced by anionic polymerization with an organo lithium initiator and the living polymer (PS
−
Li
+
) created thereby is reacted with hexamethylcyclotrisiloxane, (Me
2
SiO)
3
, in the presence of a polar promoter wherein a block of polydimethylsiloxane (PDMS) grows on the end of the living polystyrene block. These polymers are useful for impact modification of engineering thermoplastics and forming coatings with low energy surfaces. PDMS exhibits superior heat resistance, low-temperature flexibility, weather resistance, chemical inertness.
U.S. Pat. No. 5,618,903 describes an anionically polymerized polyethylene(PE)-PDMS block copolymer with increased molecular weight, strength, service temperature stability and purity. The PE blocks exhibit the high level of crystallinity and high melting point of high density polyethylene and thus give higher strength and service temperature capability to the block copolymers.
U.S. Pat. No. 5,300,609 describes a fluorosilicone block copolymer useful in silicone/fluorosilicone rubber mixtures. These fluorinated siloxane polymers have two major advantages over a non-fluorinated siloxane. One is their lower surface tension property and the other is their more chemical resistant nature. In
Makromol. Chem
., 194(5), 1403-10, Kobayashi describes a polydimethylsiloxane-poly(methyl-3,3,3-trifluoropropyl-siloxane) copolymer blend having improved fuel and oil resistance over PDMS polymers. These fluorosilicone elastomers are prepared as both random and block copolymers using anionic living polymerization techniques. They do not, however, have a polyolefin block that exhibits the high level of crystallinity and high melting point of high density polyethylene necessary to give the polymer higher strength and service temperature capability.
Thus it can be seen that it would be advantageous to be able to produce a block copolymer with the characteristics of the PE-PDMS described in the '903 patent in addition to heat, weather and chemical resistance, and low temperature flexibility. PE-PDMS copolymers when coextruded with polyethylene and other polyolefins quickly migrate to the surface, leaving in effect, a surface coated with the low-surface energy PDMS block. However, in some cases PE-PDMS polymers are not sufficiently efficient in migration rates to the surface in the time frame of residence time in the extruder. This leads to unacceptable utilization levels of these high value materials. The present invention describes a copolymer that meets these needs and is highly useful in release coatings. The fluoro-containing PE-PDMS polymers of this invention impart both a stronger driving force to the surface and faster migration (more efficient use).
SUMMARY OF THE INVENTION
The present invention is a living fluoro-functionalized anionically polymerized block copolymer comprising at least one anionically polymerized block of polyethylene (PE) and at least one anionically polymerized block of a cyclic siloxane monomer. In one embodiment, the cyclic siloxane monomer contains at least one functional group containing a fluorocarbon substituent. The siloxane polymer block may also be a random copolymer of a cyclic siloxane monomer without a fluorocarbon substituent along with the siloxane monomer that has such a substituent. In another embodiment, the fluoro-functionality is provided by end-capping (terminating) the polymer with a small polymer block derived from a cyclic siloxane monomer containing at least one functional group containing a fluorocarbon substituent.
In a preferred embodiment, the cyclic siloxane monomers have the formula:
(R
1
R
2
SiO)
n
wherein n is from 3-10 and R
1
and R
2
are, independently, alkyl having 20 or less carbon atoms alkenyl having 20 or less carbon atoms, hydrogen, benzyl, phenyl, alkyl substituted aromatics. In the case of the fluoro-functionalized monomer, at least one R
1
or R
2
group contains a fluorocarbon substituent.
The present invention also encompasses a release coating prepared by extruding a release film comprising a blend of a film grade polymer and a polyethylene-fluoro-functionalized siloxane block copolymer, as described above.
DETAILED DESCRIPTION OF THE INVENTION
In general, when solution anionic techniques are used, polymers of anionically polymerizable monomers are prepared by contacting the monomer to be polymerized simultaneously or sequentially with an anionic polymerization initiator such as Group IA metals, their alkyls, amides, silanolates, naphthalides, biphenyls and anthracenyl derivatives. It is preferable to use an organo alkali metal (such as sodium or potassium) compound in a suitable solvent at a temperature within the range from −150° C. to 300° C. preferably at a temperature within the range from 0° C. to 100° C. Particularly effective anionic polymerization initiators are organo lithium compounds having the general formula:
RLi
n
wherein R is an aliphatic, cycloaliphatic, aromatic or alkyl-substituted aromatic hydrocarbon radical having from 1 to 20 carbon atoms; and n is an integer of 1-4.
In general, any of the solvents known in the prior art to be useful in the preparation of such polymers may be used. Suitable solvents, then, include straight- and branched-chain hydrocarbons such as pentane, hexane, heptane, octane and the like, as well as, alkyl-substituted derivatives thereof; cycloaliphatic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane and the like, as well as, alkyl-substituted derivatives thereof; aromatic and alkyl-substituted derivatives thereof; aromatic and alkyl-substituted aromatic hydrocarbons such as benzene, naphthalene, toluene, xylene and the like; hydrogenated aromatic hydrocarbons such as tetralin, decalin and the like; linear and cyclic ethers such as methyl ether, methyl ethyl ether, diethyl ether, tetrahydrofuran and the like.
Ethylene may be polymerized as described above with the addition that it is usually best to include a promoter, such as a diamine, to facilitate the reaction. Examples of these amines which include but are not limited to follow: N,N,N′,N′-tetramethylmethylenediamine (TMMDA), N,N,N′,N′-tetramethylethylenediamine (TMEDA), N,N,N′,N′-tetraethylethylenediamine (TEEDA), N,N,N′,N′-tetramethyl-1,3-propanediamine (TMPDA), N,N,N′,N′tetramethyl-1,4-butanediamine (TMBDA), dipiperidinomethane (DIPIM), 1,2-dipiperidinoethane (DIPIE), 1,8-bis(dimethylamino)-naphthalene, N,N,N′,N′tetramethyl-o-phenylenediamine (TMOPDA), 1,2-dipyrolidinoethane (DIPIP), 1,3-dipiperidino-propane (DIPIP), 1,2-bis(2.6-dimethylpiperidino)cyclohexane (BDMPC), sparteine, and the like.
The ethylene polymerization reaction can be carried out at 0° C. to 100° C. preferably 25° C. to 60° C. The ethylene pressure can be from 10 psig to 1000 psig, preferably 100 to 500 psig. The polymerization time can run from 10 minutes to 2 hours, preferably 30 minutes to 1 hour.
When the polymerization of the ethylene is complete, living polyethylene blocks are present in the polymerization mixture. These are perfectly linear polyethylene-alkyllithiums. These living polyethylenes can then be reacted with cyclic siloxane monomers such as those of the formula (R
1
R
2
SiO)
n
, where n is from 3-10, R
1
and R
2
are, independently, alkyl having 20 or less carbon atoms alkenyl having 20 or less carbon atoms, hydrogen, benzyl, phenyl, alkyl substituted aromatics. Specific siloxane monomers include (Me
2
SiO)
3
, (MeHSiO)
3
, (Me
2
SiO)
4
, (Me
2
SiO)
5
, (MeHSiO)
4
, (MeHSiO)
5
, (Ph
2
SiO)
3
, (Ph
2
SiO)
4
, (Ph
2
SiO)
5
, (PhHSiO)
4
, (PhHSiO)
5
, (PhHSiO)
3
, (vinylmethylSiO)
4
, (vinylmethylSiO)
5
, (vinylHSi
Allen John
DuBois Donn Anthony
Hoxmeier Ronald James
Southwick Jeffrey George
Dawson Robert
Kraton Polymers US LLC
Zimmer Marc S.
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