Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Reexamination Certificate
1995-05-08
2002-03-26
McDowell, Suzanne E. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
C264S259000, C264S266000, C264S319000, C264S331130, C264S331180, C264S331190
Reexamination Certificate
active
06361730
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to composite shaped articles comprising a vulcanized elastomer directly or autogenously bonded, i.e., essentially in the absence of adhesive, to a thermoplastic elastomer comprising recurring polyamide-6 and polyether structural units, for example to thermoplastic polyetheresteramide elastomers.
2. Description of the Prior Art
EP-0,550,346 describes composite materials formed from a vulcanized elastomer in adhesive-free combination with a thermoplastic elastomer comprising polyamide sequences. These materials can exist in the form of a vulcanized elastomer sheet adhering to a sheet of the thermoplastic elastomer. By “adhesive-free combination” is intended that the two elastomers adhere by themselves to one another and that, if an attempt is made to separate them, failure of one of the two elastomers occurs.
This is cohesive failure, in contrast to adhesive failure when the separation takes place at the interface of the two elastomers.
The composite material of the prior art can be produced by vulcanization of the elastomer in a mold, a part of which is occupied by the thermoplastic elastomer comprising polyamide sequences.
To date, it is necessary to carry out the vulcanization over a temperature range having a magnitude of at most 5° C.
If this range is not observed, the risk exists of obtaining poor adhesion (adhesive failure), or difficulties in removing the composite material from the mold.
This prior art technique is useful for producing shoe soles, but it is difficult, in an industrial plant having many molds which are opened and closed frequently, to avoid temperature variations with a magnitude greater than 5° C.
SUMMARY OF THE INVENTION
It has now unexpectedly been determined that composite shaped articles can be prepared from a thermoplastic elastomer comprising sequences based on polyamide-6 and polyether sequences, at vulcanization temperature varying over a temperature range, the magnitude of which can be as high as several tens of degrees and often more than 40° C.
The composite materials thus produced are subject to cohesive failure, rather than adhesive failure, whatever the vulcanization temperature selected within this wide range. Thus, they are less subject to delamination.
Briefly, the present invention features a composite material comprising a vulcanized elastomer which is adhered, essentially without adhesive or autogenously bonded, to a thermoplastic elastomer comprising recurring structural units based on polyamide-6 and polyether sequences.
The present invention also features a process for the preparation of such composite material.
DETAILED DESCRIPTION OF BEST MODE AND PREFERRED EMBODIMENTS OF THE INVENTION
More particularly according to the present invention, the vulcanizable synthetic or natural elastomers which are suitable for the subject composites are well known to this art; the term “elastomer” also includes mixtures of a number of elastomers.
These elastomers or elastomer mixtures exhibit a compression set (C.S.) at 100° C. of less than 50%, generally ranging from 5% to 40% and preferably of less than 30%.
Exemplary of these are natural rubber, polyisoprene having a high degree of double bonds in the cis-orientation, a polymerized emulsion based on styrene/butadiene copolymer, a polybutadiene having a high degree of double bonds in the cis-orientation prepared via catalysis with nickel, cobalt, titanium or neodymium, a halogenated ethylene/propylene/diene terpolymer, a halogenated butyl rubber, a styrene/butadiene block copolymer, a styrene/isoprene block copolymer, the halogenated products of the above polymers, an acrylonitrile/butadiene copolymer, an acrylic elastomer, a fluorinated elastomer and chloroprene. Epichlorohydrin rubbers are also included.
In the event that the elastomers indicated above do not contain carboxylic acid functional groups or anhydrides thereof (which is the case in the majority of such instances), said functional groups will be introduced by grafting, in known manner, the elastomers indicated above or any mixtures of elastomers, for example with acrylic elastomers.
The selection will advantageously be made from among the elastomers indicated above, of the following: carboxylated nitrile elastomers, acrylic elastomers, carboxylated polybutadienes, grafted ethylene/propylene/diene terpolymers or mixtures of these polymers with the same elastomers, but ungrafted, such as nitrile rubbers, polybutadienes or ethylene/propylene/diene terpolymers, whether alone or in admixture.
The aforesaid vulcanizable elastomers preferably contain a degree by weight of carboxylic acid functional groups or dicarboxylic acid anhydride functional groups ranging from 0.3% to 10% with respect of said elastomers.
The vulcanization systems or initiators which are suitable for the present invention are well known to this art and the invention is consequently not limited to a specific type of system.
When the elastomer is based on an unsaturated monomer (butadiene, isoprene, vinylidene
orbornene, and the like), four types of vulcanization systems are exemplary:
(1) Sulfur systems comprising sulfur in combination with the usual accelerators such as metal salts of dithiocarbamates (zinc or tellurium dimethyldithiocarbamate, and the like), sulfuramides, and the like.
These systems can also contain zinc oxide in combination with stearic acid.
(2) Sulfur donor systems in which the majority of the sulfur employed for the bridgings emanates from sulfur-containing molecules such as the organosulfur compounds indicated above.
(3) Phenol resin systems comprising difunctional phenol/formaldehyde resins, which may be halogenated, in combination with accelerators such as stannous chloride or zinc oxide.
(4) Peroxide systems; all of the free radical donors can be used (dicumyl peroxides, and the like) in combination with zinc oxide and stearic acid.
When the elastomer is acrylic (poly(butyl acrylate) with acid or epoxy functional groups or any other reactive functional group which enables crosslinking), conventional crosslinking agents based on diamines ((ortho-tolyl)guanidine, diphenylguanidine, and the like), or on blocked diamines (hexamethylenediamine carbamate, and the like), are used.
The elastomeric compositions can be modified for certain specific properties (improvement in the mechanical properties, for example) by the addition of fillers such as carbon black, silica, kaolin, aluminum, clay, talc, chalk, and the like. These fillers can be surface-treated with silanes, poly(ethylene glycol)s or any other coupling molecule. In general, the amount of filler material in parts by weight ranges from 5 to 100 per 100 parts of elastomers.
In addition, the compositions can be rendered flexible by plasticizers such as mineral oils derived from petroleum, phthalic acid or sebacic acid esters, liquid polymer plasticizers such as optionally carboxylated low molecular polybutadiene and other plasticizers well known to this art.
The combinations of vulcanization agents used for carrying out the subject process are such that they must permit complete crosslinking of the elastomer according to kinetics providing good properties of resistance to separation, as indicated above, and in general to good rubber properties (measured by a compression set at 100° C., tensile-test properties, and the like).
As regards the thermoplastic elastomers which comprise polyether sequences and recurring structural units based on polyamide-6, these can be distributed in a statistical or regular fashion. The polyamide units can be isolated or grouped in oligomers emanating from the condensation of caprolactam.
By “based on polyamide-6” are intended that the polymers are homopolymers of caprolactam or copolymers with C6 diamines and diacids or lauryllacitam or any other structural unit, the polyamide units being comprised essentially of caprolactam residues.
The most typical elastomers are those comprising polyamide blocks and polyether blocks. The polyamide blocks can emanate from the condens
Alex Patrick
Cerf Martine
Dousson Christian
Tron Loic
Elf Atochem S.A.
McDowell Suzanne E.
Pennie & Edmonds LLP
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