Stock material or miscellaneous articles – Composite – Of polyester
Reexamination Certificate
1999-08-27
2001-11-06
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of polyester
C525S419000, C525S437000, C525S441000, C525S09200D, C525S442000, C428S474400, C428S475200, C428S480000, C428S475500, C428S483000, C428S506000, C428S524000, C428S412000, C428S421000, C428S422000, C428S423700, C428S458000, C156S157000, C156S242000, C156S244110
Reexamination Certificate
active
06312824
ABSTRACT:
This invention relates to copolyester elastomer compositions, in particular copolyether ester compositions which provide an improved adhesion to polyamide and other materials when compared to the direct adhesion of copolyester elastomer to these materials, the use of these compositions and articles made thereof. As a wide range of viscosity is covered by these blend compositions, they are suitable for co-extrusion applications and for injection-molding methods like co-injection and multiple-shot molding.
BACKGROUND OF THE INVENTION
It is known that compatibility and adhesion between copolyether ester (TEEE) and polyamide (PA) is low.
Good adhesion between TEEE and PA would be desirable for co-extrusion, over-moulding and assembly by welding methods.
As a first example, plastic tubings prepared from polyamide resin are known and are used for various applications. However, single-layer polyamide tubings are not always capable of meeting all the requirements of chemical compatibility with the material flowing in them and resistance to the range of end-use temperatures and mechanical stresses. In particular, during transportation of aliphatic or aromatic solvents or fuels, they exhibit several problems, such as a lack of barrier action against the medium, dimensional instability and insufficient resistance to mechanical stresses.
Attempts have been made to solve these problems by the use of multilayer pipes comprising inner layers and/or barrier layers made of fluoropolymer (U.S. Pat. No. 5,743,304; WO 9744186; WO9409303), polyolefin (DE 3,715,251; DE 3,821,723), polyvinylalcohol (DE 3,510,395; DE 3,827,092) or combinations of these (DE 4,001,125; DE 4,001,126). Although these methods are useful for some applications, there is a need for alternatives providing a different combination of chemical resistance, temperature range, gas permeability and cost. For such co-extrusion applications, it is a further advantage to have a close match of the viscosity of the materials at processing temperature.
As a second example, both polyamides and copolyether esters have, for many years, been commonly used to form articles of all sizes and shapes. Each group of materials has its own advantages and drawbacks. More specifically, polyamides generally yield products having high rigidity and good resistance to many corrosive chemicals. In contrast, copolyester elastomers are renowned for their flexibility, resistance to fatigue, resistance to oils and hydrocarbons and soft touch characteristics. Since there are many mechanical and electrical components which comprise pluralities of functional parts, it is not surprising to note that in many cases, a combination of flexible and rigid materials is required.
Mechanical assembly methods (screw connections, snap-fitting) and adhesive joining are possible for dissimilar and incompatible materials, but they are not always acceptable for cost or performance reasons. Possible alternatives are the direct welding of separately molded parts and the special injection-molding methods like co-injection or multiple-shot molding. These methods require that the materials have a good adhesion to each other, otherwise the joining interfaces are not tight to either liquids or gases and can be separated with little force.
U.S. Pat. No. 5,149,589 recognises the problems of fusion bonding of synthetic resins such as polyamide to thermoplastic elastomers, particulary those having high rubber elasticity, namely the strength and sealing at the bond are unsatisfactory. It proposes therefore a composition of the thermoplastic elastomer with a thermoplastic polyester elastomer (TEEE) in given proportions, fusion bonded to the synthetic resin. However, such compositions have properties which are not suitable for all applications. In particular, the compositions including thermoplastic polyurethane (TPU) should not be processed at temperatures above 230° C. because of the risk of decomposition to isocyanates, which limits their use in coextrusion applications. Also, these compositions have a high fraction of thermoplastic elastomer, so that they are too soft and rubbery for some mechanical requirements.
U.S. Pat. No. 4,268,570 recognises the problems of adhering polyester block copolymers to metal and discloses a metal-coated plastic product which comprises a molded mixture of a polyester block copolymer with a copolymer comprising an acrylic monomer, butadiene and styrene, and a metallic coating, optionally with an adhesive therebetween.
SUMMARY OF THE INVENTION
The invention overcomes the aforementioned limitations of the prior art by providing a composition comprising 60 to 99 weight percent of a copolyester elastomer, and 1 to 40 weight percent of a novolac resin, said weight percents based on the total weight of the copolymer elastomer and the novolac resin only, wherein the composition comprises greater than 50 weight percent copolyester elastomer based on the total weight of the composition.
The compositions according to the invention exhibit good adhesion to polyamide material and other materials, with a range of viscosity that makes them suitable for applications in coextrusion and in various injection molding methods. Moreover, they exhibit good adhesion to polyamide material and other materials, and can be processed in a wide range of conditions in particular at temperatures above 230° C. These compositions furthermore exhibit superior adhesion to polyamide material and other materials compared to known copolyester elastomer compositions, over a wide range of processing conditions and composition ranges.
The copolyester elastomer is advantageously a copolyetherester consisting essentially of a multiplicity of recurring long chain ester units and short chain ester units joined head-to-tail through ester linkages. The long chain ester units are represented by the formula
and the short-chain ester units are represented by the formula:
where G is a divalent radical remaining after removal of terminal hydroxyl groups from a poly(alkylene oxide) glycol having a molecular weight of about 400-6000 and a carbon-to-oxygen ratio of about 2.0-4.3; R is a divalent radical remaining after removal of carboxyl groups from a dicarboxylic acid having a molecular weight less than about 300 and D is a divalent radical remaining after removal of hydroxyl groups from a diol having a molecular weight less than about 250; provided said short chain ester units amount to about 15-95% by weight of the copolyetherester.
Alternatively, the copolyester elastomer is a copolyester ester.
Copolyetherester elastomers and copolyester ester elastomers are described or example in U.S. Pat. Nos. 4,981,908; 5,824,421 and 5,731,380, the descriptions hereof are incorporated herein by way of reference.
Polyetherester block copolymers and their preparation are also described in Encyclopedia of Polymer Science and Engineering, Volume 12, pages 76-177 (1985) and the references reported therein.
Various polyetherester block copolymers are commercially available from a number of companies under various tradenames, for example IIYTREL of E.I. du Pont de Nemours, RITEFLEX of Ticona and ARNITEL of DSM.
Varying the ratio hard/soft segment and using different alkylene oxides and molar weights of the soft segments makes it possible to obtain block copolyesters having different hardnesses, for example between Shore D 30 and 80.
Depending on the desired pattern of characteristics, persons skilled in the art will be able to select the polyetherester block copolymer for the compositions according to the invention.
The polyetherester block copolymer may contain the usual additives, for example stabilizers, dyes or pigments, fillers, flame retardants, processing aids, for example release agents, etc.
The novolac resin used in the compositions according to the invention is a condensation product of phenol and formaldehyde with an average molecular weight between 400 and 5000. Novolac resins are described in the Encyclopaedia of Polymer Science and Engineering, Volume 11, pages 45-95 (1985).
Thermoplastic novolac resins are p
Flexman, Jr. Edmund Arthur
Philippoz Jean-Michel
Dawson Robert
E. I. Du Pont de Nemours and Company
Peng Kuo-Liang
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