Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2003-06-23
2004-11-30
Moore, Margaret G. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S500000, C528S024000, C528S025000, C528S031000, C525S100000, C525S106000
Reexamination Certificate
active
06824881
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to thermoplastic silicone block copolymers, their preparation and use.
2. Description of the Related Art
To produce abhesive coatings curable polyorganosiloxanes are applied to substrate materials and then cured with supply of thermal energy or by radiation. Curing of the coating material is frequently the rate-determining step in the production of abhesive substrate materials. An additional necessity is that of installing drying ovens or UV or IR lamps. Their operation, moreover, is energy-intensive. Accordingly, more recent developments have been aimed at providing coating materials which allow this curing step to be omitted.
EP-A 168 624 and the corresponding U.S. Pat. No. 4,673,611 describe the coextrusion of PP backing films with an antiadhesive layer comprising polydimethylsiloxane.
EP-A 541 103 describes laminated PET films by application of emulsions of polysiloxane-polyvinyl graft polymers.
EP-A 254 050 describes the production of a release liner by extruded application of a mixture of polymer and silicone resin.
U.S. Pat. No. 5,700,571 describes release films produced by coextrusion with organic release materials.
U.S. Pat. No. 5,086,141 describes a crosslinked polysiloxanestyrene/butadiene copolymer.
WO 96/39459 describes-block copolymers of ethylene and cyclic siloxane monomers which can be used in coextrusion for release liners. In a blend with HDPE, release liners having good abhesive properties are obtainable.
WO 95/00578 describes coextrusion-prepared copolymers of monofunctional silicones and polyolefins, which can be used as release material.
WO 91/15538 describes release films comprising a base polymer and a silicone copolymer. This copolymer is added to the base polymer as an additive.
The products employed to date, however, frequently exhibit unsatisfactory abhesive properties, migration from the release layer or low substrate adhesion, or are difficult to obtain by synthesis.
An object was therefore to provide thermoplastic silicone block copolymers which are suitable for producing abhesive coatings and with which the abovementioned drawbacks are avoided.
The invention provides thermoplastic silicone block copolymers comprising:
(A) a hard segment polymer component comprising a polymer prepared from monomers selected from the group consisting of styrene, methyl methacrylate, butyl acrylate, acrylonitrile, vinyl monomers, and mixtures thereof, and
(B) a soft segment polymer component of the general formula
G—[(SiR
2
O)
m
SiR
2
—X—]
n
(SiR
2
O)
m
SiR
2
-G (I)
where each R can be identical or different and is a monovalent, optionally halogenated hydrocarbon radical having 1 to 18 carbon atoms per radical, X is a divalent radical selected from the group consisting of the radicals of the formula
each G can be identical or different and is a radical (A)-Z-(Si) or Z′-(Si), where Z is a divalent radical selected from the group consisting of radicals of the formula
where (A)- is a bond to the hard segment polymer component (A) and (Si)— is a bond to the silicon atom in (B),
with the proviso that in the formula (I) not more than one radical G can be a radical Z′-,
m is an integer from 1 to 1000, preferably from 1 to 500, and
n is 0 or an integer from 1 to 20,
with the proviso that if n is not 0 then for the product of n and m it is the case that 4≦n·m≦1000.
The two components of the silicone block copolymer of the invention are a nonpolar soft segment (B) and a polar hard segment (A). The nonpolar soft block is a silicone segmented by organic groups which has a low free surface energy, while the hard segment is characterized by the ability to adhere to the surface of the substrate. In addition the hard segment gives the silicone block copolymer physical properties such that the silicone block copolymer is not liquid at 25° C. and can be extruded.
The expression “segmented” refers to a relatively short length of a repeating unit.
The silicone block copolymers of the invention are preferably of the formula A-B-A. The silicone block copolymers may have a number of different configurations depending on the number of polymer blocks suspended from the soft segment, a silicone segmented by organic groups. In their simplest form the copolymers can have the configuration A-B. The silicone block copolymers may also be of the type B-A-B or A-B-A-B, etc., depending on the coupling methods or formation methods for the blocks. The silicone block copolymers of the invention may vary in their composition and structure. They can be grafted, branched or linear block copolymers; as block copolymers they contain repeating segments or blocks of the same monomeric unit. The average block length of one polymerized comonomer component may differ, however, from the average block length of a second polymerized comonomer component, and it is the relative average block lengths which largely determine the properties of the silicone block copolymers.
The silicone block copolymers of the invention possess a molecular weight (M
w
) of preferably from 3,000 to 2,000,000 g/mol, more preferably from 5,000 to 1,000,000 g/mol, very preferably from 10,000 to 500,000 g/mol.
The silicone block copolymers of the invention contain the soft segment polymer component (B) in amounts of preferably from 1 to 75% by weight, more preferably from 1 to 50% by weight, most preferably from 5 to 40% by weight, based in each case on the overall weight of the silicone block copolymer.
A preferred hard segment polymer component (A) is polystyrene.
Examples of radicals R are alkyl radicals, such as the methyl, ethyl, n-propyl, iso-propyl, 1-n-butyl, 2-n-butyl, iso-butyl, tert-butyl, n-pentyl, iso-pentyl, neo-pentyl, tert-pentyl radical, hexyl radicals, such as the n-hexyl radical, heptyl radicals, such as the n-heptyl radical, octyl radicals, such as the n-octyl radical and iso-octyl radicals, such as the 2,2,4-trimethylpentyl radical, nonyl radicals, such as the n-nonyl radical, decyl radicals, such as the n-decyl radical, dodecyl radicals, such as the n-dodecyl radical, and octadecyl radicals, such as the n-octadecyl radical; cycloalkyl radicals, such as cyclopentyl, cyclohexyl, cycloheptyl, and methylcyclohexyl radicals; aryl radicals, such as the phenyl, naphthyl, anthryl, and phenanthryl radical; alkaryl radicals, such as o-, m-, p-tolyl radicals, xylyl radicals, and ethylphenyl radicals; and aralkyl radicals, such as the benzyl radical, the &agr;- and the &bgr;-phenylethyl radical.
Examples of halogenated radicals R are haloalkyl radicals, such as the 3,3,3-trifluoro-n-propyl radical, the 2,2,2,2′,2′,2′-hexafluoroisopropyl radical, the heptafluoroisopropyl radical, and haloaryl radicals, such as the o-, m-, and p-chlorophenyl radical.
One example of a silicone block copolymer of the invention with n=0 is one of the following formula: (PS=polystyrene, R=methyl radical, m=1-1000)
One example of a silicone block copolymer of the invention with n=1 is one of the following formula: (PS=polystyrene, Me=methyl radical)
Segmented block copolymers can be prepared by a number of procedures, which differ in the extent to which the structure of the resulting product can be defined, as is described in U.S. Pat. No. 4,675,361.
One procedure includes the coupling of at least two preformed blocks or segments prepared prior to the coupling reaction in separate reactions. This approach produces a well-defined structure if the coupling reaction prevents identical blocks or segments from reacting with themselves and allows only unlike blocks or segments to couple to one another.
Other coupling reactions may occur, resulting in a less defined structure, if the two preformed blocks or segments possess the ability (by way of the coupling reaction) as well to react with themselves, in the same way as the unlike blocks or segments.
In one preferred coupling reaction at least one preformed block or preformed, segment is coupled during a coupling reaction wit
Dauth Jochen
Keller Wolfgang
Lautenschlager Hans
Mayer Theo
Stark Kurt
Brooks & Kushman P.C.
Moore Margaret G.
Wacker-Chemie GmbH
Zimmer Marc S.
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