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
2000-04-27
2004-08-10
Short, Patricia A. (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...
C525S177000, C525S438000, C525S439000, C525S440030, C525S444000, C525S446000, C525S454000, C525S474000, C525S533000, C528S026000, C528S029000
Reexamination Certificate
active
06774183
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to novel copolyester compositions and novel methods employing such compositions. The copolyester compositions of the present invention contain a low polarity block segment in the polymer backbone. These copolyester compositions are particularly suitable for use as adhesive and coating materials and exhibit high initial adhesion and superior retained adhesion to various substrates.
BACKGROUND OF THE INVENTION
Many amorphous copolyester compositions are commonly used as adhesive and coating materials because of their useful properties, which include: strong cohesion when below their glass transition temperatures (“T
g
”), strong adhesion and good clarity. Such compositions are also generally inexpensive. However, amorphous compositions are not suitable in a variety of adhesive and coating applications. For example, such compositions do not adequately adhere to substrates such as polypropylene, polyethylene, thermoplastic polyolefins (“TPO's”) and various other low surface energy substrates. Additionally, the mechanical and adhesive properties of many amorphous adhesives and coatings are often inadequate for certain higher temperature applications above their T
g
's. They also possess limited tensile strength and hydrolytic stability above their T
g
. Still further, these materials are generally limited in solvent and chemical resistance.
Crystalline copolyesters are generally superior to amorphous materials, especially when the materials are above their glass transition temperatures, in that they possess many valuable properties, including rigidity, hardness, toughness, tensile strength, abrasion resistance, solvent resistance, chemical resistance, good elevated temperature performance up to their crystalline melt point, good balance of flexibility and toughness, and better hydrolytic stability. However, the adhesion of crystalline polymers to a variety of substrates, such as polyethyleneterephthalate (PET), decreases rapidly over time as these polymers shrink during crystallization and subsequently pull away from the substrate to which they were adhered. Amorphous polymers do not suffer this same fate since shrinkage of these polymers is not significant enough to result in loss of adhesion as they age.
It would, thus, be desirable to provide improved copolyester adhesives and coatings that possess both the properties of amorphous polymers, namely retained adhesion over time (“aged adhesion”), and the properties of crystalline polymers, namely toughness and tensile strength over a broad temperature range, and superior solvent resistance and hydrolytic stability.
Crystalline copolyester compositions containing a low polarity block in the polymer backbone have been described in various patents. However, these compositions have been developed and used specifically for applications in which their low or anti-adhesion properties are required. Namely, these crystalline copolyester compositions were developed and used to specifically provide slip, for example, in mold forming materials for use in processes wherein the molded articles must be readily released from the mold's surface.
U.S. Pat. Nos. 4,348,510 and 4,496,704 describe copolyester compositions formed from: hydroxyl terminated polyalkyleneoxide (A) and polydimethylsiloxane (B), in ABA triblock segments copolymerized with polyester forming components. Films, tapes, sheeting and other extruded or molded articles prepared from these polysiloxane block copolyesters are shown to exhibit improved slip or nonblocking tendencies, i.e. reduced tendency to adhere to other materials, as evidenced by their reduced static and kinetic coefficients of friction.
U.S. Pat. No. 4,382,131 and U.S. Pat. No. 4,686,262 describe a polyolefin block copolyester used in producing moldings exhibiting extremely low deformation and distortion even when processed into thin articles, and at the same time, retain their crystallinity despite the addition of the low polarity segment in the copolyester composition. U.S. Pat. Nos. 4,207,230 and 4,223,106 also describe block copolyesters containing a low polarity polyolefin block segment that are used as molding materials with properties being similar to those described in U.S. Pat. No. 4,382,131.
U.S. Pat. No. 3,935,154 describes solvent soluble block copolyester, containing low polarity polysiloxane block segments, suitable for uses which require good release properties. Specifically, the compositions described are particularly useful in the photographic field as release agents for photoconductive materials.
U.S. Pat. No. 4,659,786 describes a polyester-polysiloxane block copolymer suitable for use as dental impression materials, as well as mold materials for general uses with good release properties. Sealing materials are also claimed.
U.S. Pat. No. 4,927,895 describes a polysiloxane block copolyester that exhibits good resistance to impact shock and to hydrolysis without any loss of the inherent advantageous properties, such as mechanical strength, of the base polyester resin.
U.S. Pat. Nos. 4,845,158 and 4,994,526 describe compositions used to prepare block resins which are molded into gaskets, washers, flexible tubing and similar articles.
U.S. Pat. No. 5,773,517 describes thermoplastic polyolefin block copolyesters that are used as polymer compatibilizers and quality improving agents. These block copolyesters are blended with and are used to improve various properties of other polymers, such as impact strength, tensile strength; elongation, heat resistance, paintability, weather resistance, elasticity, resilience, flowability, dimensional stability and chemical resistance.
It would thus be desirable to provide improved copolyester adhesive and coating materials that possess both advantageous properties of amorphous polymers, specifically improved and/or retained adhesion over time, and advantageous properties of crystalline polymers, especially superior hydrolytic stability, solvent resistance, chemical resistance, tensile strength and toughness over a broad temperature range.
SUMMARY OF THE INVENTION
It has now been discovered that copolyesters containing low polarity segments in their backbone possess unexpected properties that make them particularly useful as adhesive and coating materials.
The present invention provides high performance block copolyester compositions that are particularly suitable for use as adhesives and coatings because these materials incorporate the advantages of crystalline polymers while possessing the quality of retained or aged adhesion of amorphous polymers.
The compositions of the present invention comprise a copolyester having a low polarity block segment incorporated into the copolyester backbone. These compositions are superior in initial adhesion and aged adhesion, and they retain toughness and resistance to solvents while possessing improved wettability and hydrolytic stability over a broad temperature range.
The copolyesters of the present invention may be prepared by any conventional method. Preferably, the copolyesters are prepared by standard polycondensation processes utilizing difunctional alcohols and dicarboxylic acids and optionally up to about 3% of a polyfunctional branching agent. This synthesis normally occurs in two stages, with the first stage being a direct esterification or transesterification (alcohololysis) stage and the second stage being a polyesterification stage. See, e.g. V. V. Korshak and S. V. Vinogradova,
Polyesters
, Chapter III, pp. 72-150, Pergamon Press, N.Y., N.Y., (1965).
The low polarity block is incorporated into the backbone of the copolyester, preferably by its addition at the beginning of the direct esterification 1
st
stage reaction along with the difunctional alcohols and dicarboxylic acids. The low polarity block may also be added at any time during the direct esterification stage, but preferably prior to the 2
nd
stage (polyesterification).
Some examples of difunctional alcohols useful in the practice of the present invention include: alkyl diols from C
2
t
Palumbo Jeffrey T.
Rossitto Francis C.
Sommerfeld Eugene Gary
Alexander John B.
Bostik, Inc.
Conlin David G.
Edwards & Angell LLP
Short Patricia A.
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