Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-12-14
2003-05-20
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C556S436000, C528S029000, C528S025000, C528S196000, C528S204000, C528S391000, C568S028000, C568S723000
Reexamination Certificate
active
06566458
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to polycarbonate block copolymers and especially to flame retardant polycarbonate block copolymers.
Polycarbonate resins are useful in high temperature applications because they exhibit excellent high heat performance. It is therefore important for these resins and/or resin compositions to be flame resistant. Previously, flame resistance has been achieved with the addition of flame retardants, generally halogenated flame retardants or halogenated blocks within the polycarbonate polymer chain. The addition of flame retardants increases the cost of the materials, and plastics employing halogenated materials may release toxic gas when heated to elevated temperatures. As a result, non-halogenated fire resistant materials, especially those that are transparent, are in demand for a wide range of applications.
Copolymers having organopolysiloxane blocks and polycarbonate blocks are known. U.S. Pat. No. 3,419,635 to Vaughn, incorporated by reference herein, discloses room temperature vulcanizing organopolysiloxane-polycarbonate block copolymers and methods of making them. The organopolysiloxane-polycarbonate block copolymers are useful in elastomeric applications. U.S. Pat. No. 6,072,011 to Hoover also discloses block copolymers useful as molding resins comprising polycarbonate blocks and polysiloxane blocks. In contrast to the compositions disclosed in Vaughn, the compositions as taught by Hoover are thermoplastic. Neither composition is disclosed to be transparent, and the compositions of Hoover as taught in the examples employ a halogenated fire retardant.
Accordingly, there is a need in the art for non-halogenated, highly fire resistant polycarbonate resins, especially polycarbonate resins that are transparent and exhibit excellent high heat performance.
BRIEF SUMMARY OF THE INVENTION
The above described drawbacks and deficiencies are overcome or alleviated by a block copolymer comprising structural units of the formula (I):
wherein R
1
comprises polysulfone groups, and structural units of the formula (II):
wherein R
2
comprises polysiloxane groups.
DETAILED DESCRIPTION OF THE INVENTION
A block copolymer comprises structural units of the formula (I):
in which R
1
comprises polysulfone groups, and structural units of the formula (II):
wherein R
2
comprises polysiloxane groups. The block copolymer may further comprise structural units of the formula (III):
wherein R
3
comprises aromatic and/or aliphatic groups. The structural units of formula (I) are hereinafter referred to as the polysulfone structural units. The structural units of formula (II) are hereinafter referred to as the polysiloxane structural units. The structural units of formula (III) are hereinafter referred to as the aromatic/aliphatic structural units. The polysulfone structural units and polysiloxane structural units and, when present, the aromatic/aliphatic structural units may be arranged in a random sequence or in a non-random repeating sequence. Typically the polysulfone structural units comprise about 80 weight percent to about 99.9 weight percent of the block copolymer. The polysiloxane structural units typically comprise about 0.1 weight percent to about 20 weight percent of the block copolymer. When it is desired for the block copolymer to be transparent, the polysiloxane structural unit content is preferably less than about 4.6 weight percent of the block copolymer. The aromatic/aliphatic structural units, when present, comprise about 0.1 weight percent to about 98 weight percent of the block copolymer. The block copolymer may have an average molecular weight, Mw, in the range of about 10,000 to about 100,000, with a range of about 25,000 to about 35,000 preferred.
The block copolymer is preferably made by the reaction of a carbonate precursor, such as phosgene, dihydroxy polysulfone oligomer(s) and dihydroxy polysiloxane oligomer(s). When the block copolymer comprises aromatic or aliphatic, structural units as well as polysulfone structural units and polysiloxane structural units it is preferably made by the reaction of a carbonate precursor, such as phosgene, dihydroxy polysulfone oligomer(s), dihydroxy polysiloxane oligomers and dihydroxy aromatic and/or dihydroxy aliphatic compound(s). It is also possible that the block copolymer may be made by other methods known in the art for making polycarbonates such as transesterification as disclosed in U.S. Pat. No. 3,154,008.
Useful dihydroxy polysulfone oligomers include dihydroxy aromatic polysulfone oligomers. An aromatic polysulfone oligomer is defined as a polyarylene compound in which an arylene unit, an ether unit, and a sulfone bond are essential constitutional units and in which the arylene units are disorderly or orderly arranged together with the ether and sulfone bonds. Suitable arylene units include substituted and unsubstituted phenylene, napthylene, and other multi-cyclic aromatic compounds as well as divalent aromatic moieties of the formula:
—A
1
—Y
1
—A
2
—
wherein A
1
, Y
1
, and A
2
are described below.
It is preferred that the hydroxyl functionalities be located terminally although it is within the scope of the invention for one or both hydroxyl functionalities to have a non-terminal location. Non-terminal is herein defined as being located in a position other than at the end of the oligomer chain. Useful molecular weights of dihydroxyl aromatic polysulfone oligomers are about 500 to about 10,000. Dihydroxyl aromatic polysulfone oligomers with a molecular weight of about 2,000 to about 3,500 are preferred.
A preferred aromatic polysulfone oligomer comprises repeating units characterized by the general formula:
wherein useful values for n are in the range from 1 to about 10.
An especially preferred hydroxyl terminated aromatic polysulfone oligomer has the formula
wherein n is equal to approximately 5. The especially preferred hydroxyl terminated aromatic polysulfone oligomer is well known and can be made by the reaction of dichlorodiphenylsulfone and bisphenol A wherein bisphenol A is present in slight excess.
Useful dihydroxy polysiloxane oligomers include, but are not limited to hydroxyl terminated poly(dialkylsiloxane)oligomers comprising repeating units of the general formula:
wherein R
4
and R
5
are selected independently from saturated and unsaturated hydrocarbons having 1 to about 15 carbons, including alkyl groups, alkylene groups, and aryl groups. Preferably, R
4
and R
5
are methyl or phenyl. The number of repeating units can range from 0 to about 120. Preferred dihydroxy polysiloxane oligomers are terminated by a substituted or unsubstituted hydroxy aromatic group, wherein the substituents may be halo, aryl, alkyl, alkylene, alkoxy or aryloxy groups having from 1 to about 15 carbons. Especially preferred dihydroxy polysiloxane oligomers are phenol or eugenol terminated. A preferred eugenol terminated polysiloxane oligomer has the formula:
with m=0-47 and R
6-11
selected independently from saturated and unsaturated hydrocarbons having 1 to about 15 carbons, including alkyl groups, alkylene groups, and aryl groups. Preferably, R
6-11
are methyl or phenyl.
Useful dihydroxy aromatic or aliphatic compounds comprise from 2 to about 50 carbons. Preferably the dihydroxy compound is an aromatic dihydroxy compound with the formula
HO—A
1
—Y
1
—A
2
—OH
wherein each of A
1
and A
2
is a monocyclic aryl group and Y
1
is a bridging group having one or two atoms which separate A
1
from A
2
. In an exemplary embodiment, one atom separates A
1
from A
2
. Illustrative non-limiting examples of groups of this type are —O—, —S—, —S(O)—, —S(O)
2
—, —C(O)—, methylene, cyclohexyl-methylene, 2-[2.2.1]-bicycloheptylidene, ethylidene, isopropylidene, neopentylidene, cyclohexylidene, cyclopentadecylidene, cyclododecylidene, and adamantylidene. The bridging group Y
1
can be a hydrocarbon group or a saturated hydrocarbon group such as methylene, cyclohexylidene or isopropylidene.
Especially preferred are bisphenol compounds having general formula (VIII) as follows:
Duncan Miles A.
Kloppenburg Lioba M.
Likibi Parfait Jean Marie
Dawson Robert
General Electric Company
Peng Kuo-Liang
LandOfFree
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