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
2002-08-30
2004-04-06
Moore, Margaret G. (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...
Reexamination Certificate
active
06716920
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to high performance wire and cable resins and to hot melt adhesives containing a silyl grafted ethylene copolymer having particularly low levels of a glycidyl acrylate comonomer.
2. Description of the Related Art
U.S. Pat. Nos. 5,389,728 and 5,484,847 describe the preparation and use of moisture curable, melt processible, graft copolymers which are obtained by reacting certain ethylene copolymers having copolymerized therewith a glycidyl containing comonomer(s) which is then further reacted with a particular grafting agent selected from N-tert-butylaminopropyl trimethoxysilane. This particular class of grafted copolymers was described as sufficiently stable for co-extrudable hot melt adhesive use. Wire and cable applications were also mentioned for this particular class. The above patent disclosures also clearly described certain substituted aminopropyl trimethoxysilanes grafted ethylene copolymers (ethylene/alkyl acrylate/glycidyl methacrylate as the direct copolymer) which were particularly unsuitable for hot melt adhesive use because of their thermal instability under hot melt adhesive use conditions. Included among the list of particularly unsuitable silanes to be utilized as a grafting reagent was N-cyclohexylaminopropyl trimethoxysilane as well as numerous others. Comparative example 2 in U.S. Pat. No. 5,389,728 clearly shows the unsuitability of a copolymer having ethylene, an alkyl acrylate and a glycidyl termonomer grafted with N-cyclohexylaminopropyl trimethoxysilane. The only suitable N-alkylaminopropyl trimethoxysilane for hot melt adhesive use was the patented t-butyl derivative. Other comparative unsuitable examples were also described.
On the other hand, and with respect to vinyl acetate containing copolymers, U.S. Pat. No. 5,484,847 did not disclose any specific comparative examples showing other N-substituted aminopropyl trimethoxysilanes and only specifically disclosed an ethylene/vinyl acetate/glycidyl methacrylate copolymer containing 11.1 wt. % EVA and 7.4 wt. % glycidyl methacrylate with N-tert-butylaminopropyl trimethoxysilane grafted thereto. This patent disclosure did not teach anything about the use or potential use of other N-substituted aminopropyl trimethoxysilanes as grafting reagents with vinyl acetate containing ethylene copolymers. All comparative examples and/or teachings with respect to any reagent other than N-tert-butylaminopropyl trimethoxysilanes were directed to the alkyl acrylate containing copolymers.
Both patent disclosures discussed above expressly or implicitly teach away from the use or potential use of ethylene copolymers having an alkyl acrylate or a vinyl acetate as a comonomer along with a glycidyl containing comonomer which is subsequently grafted with an aminosilane other than the specific t-butylaminopropyl trimethoxysilane.
Furthermore, the above patent disclosures suggest that at lower percentages of glycidyl moiety in the disclosed compositions (equal to or less than 6 percent) grafting catalysts are required to speed up the grafting reaction.
In view of the above, there is a need to develop additional copolymers which provide good performance in hot melt adhesives as well as wire and cable applications which continue to demand reliable physical properties at extreme temperatures or wide temperature variations and which can be readily made in an extruder. In addition, prior art thermoset resins generally require continuous vulcanization (CV) tubes and/or radiation equipment to provide high performance thermoset properties and known vinyl silane moisture curable systems typically require peroxide, catalyst and high graft temperatures which can lead to undesired side crosslinking reactions and an increase in compound viscosity.
BRIEF SUMMARY OF THE INVENTION
The present inventors have discovered a thermally stable grafted terpolymer having a glycidyl moiety which contains an N-cyclohexyl-aminopropyl trimethoxysilane or other N-alkyl- or N-arylalkylaminopropyl trimethoxysilanes which were formerly thought to be unsuitable and which do not require a CV tube, peroxide, extruder catalyst addition or high graft temperatures. It has been discovered that because of a specific low range of glycidyl monomer in the present invention, thermal stability is achieved for hot melt adhesive compositions having the claimed grafted copolymers therein. It has also been surprisingly found that catalysts are unnecessary to effect the grafting reaction at these lower percentages of glycidyl monomer and that moisture-curing catalysts are also unnecessary.
The present inventors have also found that the relative composition of the direct copolymer, wherein one of the monomers is vinyl acetate, affects the suitability of a grafted copolymer based thereon for wire and cable applications. It has also been found that an ethylene vinyl acetate copolymer having a narrow, specific range of glycidyl comonomer which is subsequently grafted in an extruder with an N-substituted aminopropyl trimethoxysilane (excluding N-t-butyl) and subsequently formed into a coating for a wire or cable (or material suitable for forming a coating for a wire and cable) provides a particularly effective wire and cable coating with good moisture curing thermoset properties, thus, further providing effective wire and cable products.
Thus the present invention provides a thermally-stable, grafted copolymer E/X/Y-(G) composition comprising monomers E, X, and Y in random order and grafting reagent G, wherein:
E is ethylene;
X comprises from 8 to 70 weight percent relative to the total weight of E/X/Y and is selected from the group consisting of a C
1
to C
8
alkyl acrylate, a C
1
to C
8
alkyl methacrylate, and vinyl acetate;
Y comprises about 1 to 4 weight percent relative to the total weight of E/X/Y of a glycidyl containing monomer selected from the group consisting of glycidyl acrylate, glycidyl methacrylate and glycidyl vinyl ether; and
G comprises from 15 to 150 percent of a stoichiometric amount with respect to the weight of the glycidyl moiety, of a secondary aminosilane compound of the formula
R—N(H)—R′—Si(OR″)
3
wherein R′ is a C
1
to C
6
alkylene group, R″ is a C
1
to C
6
alkyl group, and R is selected from
a) a secondary radical of the formula —CHR
1
R
2
wherein R
1
and R
2
are independently selected from C
1
to C
6
alkyl or C
1
-C
6
arylalkyl and wherein R
1
and R
2
may be joined to form a C
5
to C
9
cycloaliphatic ring; or
b) a primary radical of the formula —CH
2
R
3
wherein R
3
is selected from (i) a C
3
to C
12
alkyl group, wherein, in the case of a C
3
to C
6
alkyl group, said alkyl moiety is branched, or (ii) a (C
1
to C
12
alkyl)-aryl group, wherein R
1
, R
2
, and R
3
may be unsubstituted or substituted with substituents selected from C
1
-C
4
alkyl.
Preferably the X comprises about 8 to 50 weight percent and most preferably about 8 to 46 weight percent of the E/X/Y copolymer and the Y can be from about 0.5 to 9 weight percent, and preferably about 1 to 4 weight percent of the E/X/Y copolymer.
The present invention also comprises a grafted copolymer having zero mole percent X corresponding to the formula E/Y-(G) as illustrated in Example 5 (grafted ethylene/GMA). As such the present invention provides a thermally-stable, grafted copolymer E/X/Y-(G) composition comprising monomers E, X, and Y in random order and grafting reagent G, wherein:
E is ethylene;
X comprises from 0 to 70 weight percent relative to the total weight of E/X/Y and is selected from the group consisting of a C
1
to C
8
alkyl acrylate, a C
1
to C
8
alkyl methacrylate, and vinyl acetate;
Y comprises about 1 to 4 weight percent relative to the total weight of E/X/Y of a glycidyl containing monomer selected from the group consisting of glycidyl acrylate, glycidyl methacrylate and glycidyl vinyl ether; and
G comprises from 15 to 150 percent of a stoichiometric amount with respect to the weight of the glycidyl moiety, of a secondary aminosilane compound of the for
Arhart Richard James
Prejean George Wyatt
E. I. du Pont de Nemours and Company
Moore Margaret G.
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