Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2001-08-01
2003-09-23
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S049000, C528S053000, C528S058000, C528S905000, C525S131000, C152S209500, C428S423100, C524S873000, C524S874000
Reexamination Certificate
active
06624283
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an adhesive usable at ambient temperature to bond together two cross-linked rubber compositions, to a process for preparing the adhesive, to a tread of a tire cover and to such a cover comprising this adhesive, and to an article comprising two parts securely bonded together by means of this adhesive. The invention applies in particular to the tire retreading industry, wherein a cross-linked tread is bonded to a cross-linked tire casing (known as “cold” retreading).
Known adhesives for bonding together two cured elastomeric articles, such as the casing of a tire cover to be retreaded and a cross-linked tread, are often based on polyurethane or polyurea type polymers.
A polymeric adhesive which is produced by reacting a polyurea prepolymer, which may comprise urethane groups and which ends with isocyanate groups, with a binary blend consisting of a particular polyether amine (polyoxytetramethylene bis(p-aminobenzoate)) and of a chain extender consisting of an aromatic diamine, is disclosed in U.S. Pat. No. 5,183,877. The polyurea prepolymer is obtained in gel form by reacting a polyisocyanate, such as a methylene diisocyanate modified with a carboimide (abbreviated as CD-MDI), with a polyether amine such as the one described. A major drawback of the adhesive described in U.S. Pat. No. 5,183,877 lies in the use of the prepolymer for its preparation. Specifically, the high viscosity of the prepolymer inevitably involves using the aromatic diamine chain extender and bringing the prepolymer to a temperature of 40° C. in order to go from its gel state at ambient temperature, to the liquid state in order to use as an adhesive.
SUMMARY OF INVENTION
The Inventors have unexpectedly found that a copolymer comprising isocyanurate groups combined with urea or urethane groups, which is a reaction product of:
1) a polyisocyanate comprising isocyanurate rings, having a functionality equal to or greater than three,
2) a functional polymer comprising an amine or alcohol group at each of its chain ends, the polymer being selected from the group consisting of polyether diamines, polyether diols, polyester diols and (ether-ester) diol copolymers, and
3) at least one trimerization catalyst capable of forming isocyanurate rings from isocyanate groups;
wherein the molar ratio of the total number of moles of isocyanate groups to the total number of moles of amine in the copolymer is between 1.5 and 2.2,
may be used as an adhesive for the satisfactory bonding together at ambient temperature of two cross-linked rubber compositions, because the copolymer exhibits reduced viscosity at ambient temperature.
DETAILED DESCRIPTION OF THE INVENTION
The presence of the isocyanurate rings in the copolymer thus provide the adhesive thermal stability at temperatures above 100° C., which may be reached, for example, by a tire cover under driving conditions.
In addition, the adhesive of the invention has a relatively long “open time” (time limit for use, also known as the “pot life”). As a guide, this “open time” ranges from 5 min to 15 min.
Polyisocyanates with a low viscosity at ambient temperature, preferably those having a viscosity, measured according to the Brookfield technique, of between 8 and 16 Poises, are used for the present invention. The polyisocyanates may be aliphatic or aromatic and may be dimers or trimers. In accordance with a preferred embodiment of the invention, a trimer derived from hexamethylene diisocyanate having a functionality of equal to or greater than three is used as polyisocyanate.
A polyether diamine, which is intended to react with the polyisocyanate to obtain the urea groups may be used as the functional polymer. Examples include a polyoxypropylene diamine, a polyoxyethylene diamine and, preferably, a polyoxytetramethylene diamine, such as polyoxytetramethylene bis(p-aminobenzoate).
Additionally, the polyether diamine may be a polyether comprising an aliphatic amine group at each chain end, such as a polypropylene glycol diamine or a polytetrahydrofuran diamine (obtained by reacting anthranilic acid with polytetrahydrofuran, whose molecular mass can range from 650 to 2000 g/mol).
An ether and/or ester diol polymer, which is intended to react with the polyisocyanate to obtain the urethane groups, may also be used as functional polymer. Exemplary polyether diol include a polypropylene glycol, an (ethylene oxide-propylene oxide) diol copolymer or a polytetrahydrofuran diol.
A polyester diol, such as a polyadipate diol, a poly(&egr;-caprolactone diol), a polyphthalate diol or a polycarbonate diol, may also be used as the functional polymer.
The functional polymer may also be an (ether-ester) diol copolymer, preferably comprising a central polyester moiety, for example a poly(&egr;-caprolactone), and two adjacent polyether moieties, for example a polytetrahydrofuran.
Trimerization catalysts according to the invention include tertiary amines which allow the catalysis of the reactions for forming isocyanurates and also the reactions between hydroxyl and isocyanate groups or water and isocyanate groups. Such catalysts include DMEA (dimethylethanolamine), TMBDA (tetramethylbutanediamine), alkylamino ethers (for example bis(dimethylaminoethyl) ether), piperazines such as piperidine, tertiary alkylamines such as 3dialkylaminopropionamides, TEA (triethylamine), N,N-dialkyl-3-(dialkylamino)propylamine, substituted morpholines such as N-acetamidopropylmorpholine, tris(dimethylamino)phenol and tris(dimethylaminomethyl)phenol, or metal salts such as dibutyltin dilaurate. Advantageously, tris(dimethylaminomethyl)phenol or dibutyltin dilaurate is used.
According to a further embodiment of the invention, the copolymer according to the invention containing isocyanurate groups combined with urea or urethane groups is the reaction product of the polyisocyanate with the functional polymer, with the trimerization catalyst and also with a chain extender comprising an aromatic diamine.
A mixture of monoamine and diamine which is of low viscosity at 20° C., one or more of which are grafted onto a polyether block with a molecular mass of between 250 and 5,000 g/mol, and one or more diamines of low molecular weight may be used as a chain extender according to the invention.
The extender may be a mixture of 2,4 and 2,6 isomers of DETDA (diethyltoluenediamine), piperazine or DEDA (diethylenediamine), MEA (monoethanolamine), methylenebis(N,N-dibutyldianiline), IPDA (isophoronediamine), or a mixture of 3,5-dimethylthio-2,4-toluenediamine and -2,6-toluenediamine isomers.
Additional useful extenders include triols such as glycerol or trimethylol propane, polyesters or polyethers such as polyethylene adipate (PEA) or any other polyadipate, polypropylene glycol, polypropylene glycol diamine, polytetramethylene ether glycol (PTMEG) or polytetramethylene ether glycol diamine.
According to a further embodiment of the invention, the adhesive also comprises a hydrophobic or hydrophilic silica, in a mass fraction ranging from 0.01% to 1%.
In addition, the adhesive of the invention may comprise a diene elastomer, at least partly derived from butadiene, and/or a polyether comprising a silane group at each of its chain ends, in a mass fraction ranging from 1% to 50%. The diene elastomer, for example, a butadiene homopolymer or a butadiene-acrylonitrile copolymer, and the polyether containing a silane group are each used in liquid form (they are also known as “reactive liquid rubbers”) to impart flexibility or a given suppleness to the adhesive according to the invention.
An example of a butadiene homopolymer which may be used is a polybutadiene containing hydroxyl end functional groups.
A butadiene-acrylonitrile copolymer may be used is an example of a copolymer containing amine end groups.
An example of a polyether containing silane groups which may be used is a polyoxypropylene containing silane end groups.
The process for preparing the adhesive comprises reacting polyisocyanate, functional polymer, trimerization catalyst and chain extender to obtain the copolymer
Isnard Roger
Viegas Nathalie
Baker & Botts L.L.P.
Gorr Rachel
Michelin & Recherche et Technique S.A.
LandOfFree
Adhesive for rubber compositions, process for its... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Adhesive for rubber compositions, process for its..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Adhesive for rubber compositions, process for its... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3066964