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
1997-03-28
2001-07-24
Yoon, Tae (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S191000, C525S215000, C525S219000, C528S205000, C528S219000
Reexamination Certificate
active
06265490
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to novolac resins obtained by condensation of an aromatic compound containing at least two hydroxyl groups and of an unconjugated diene, to the process for their preparation and to their use for improving the adherence between rubber and reinforcing materials. More particularly the invention relates to novolacs which exhibit substantially no smoke or hygroscopicity and which have good adherence properties when they are employed for vulcanizing rubber and reinforcing materials.
BACKGROUND OF THE INVENTION
With the aim of improving adherence, it is known to incorporate into rubber a formaldehyde acceptor such as a meta-substituted phenol (for example resorcinol or an m-aminophenol) and a formaldehyde donor capable of producing formaldehyde by heating in the rubber.
The abovementioned m-substituted phenols are very volatile. Also, when employed to improve the adherence of rubbers, they release noxious fumes at the vulcanization temperature (generally higher than 110° C.).
In addition, these formaldehyde acceptors are hygroscopic, and this leads to the formation of efflorescence in the rubber mixes during storage. Such efflorescence causes nonuniform adherence between the rubber and the reinforcing material, and this is detrimental to the quality of the vulcanized articles.
To solve these problems it has been proposed to employ a “resorcinol resin” as formaldehyde acceptor, which resin is obtained by condensation of resorcinol with formaldehyde (Industrial Engineering Chemistry, pp. 381-386 (1946)).
Although the resin makes it possible at the same time to obtain a high adherence and an improvement in the physical properties of the rubber (hardness and modulus), it exhibits such a state of deliquescence that it adheres packaging materials or forms a block. It is obvious that this presents many problems during storage or handling. In addition, the resin contains a large quantity of free resorcinol (≧15%), and this does not make it possible to solve the disadvantages linked with the presence of smoke and with lump formation.
In EP-A-419 741 and DE-A-4 001 606 it has been proposed to employ modified novolacs resulting from the cocondensation of a phenol (for example resorcinol), of an unsaturated hydrocarbon (for example styrene) and of an aldehyde (for example formaldehyde).
Ternary products of cocondensation of a phenol such as resorcinol, of an alkylphenol and of an aldehyde have also been proposed. For example, in FR 2 193 046, FR 2 223 391, FR 2 392 049 and EP-A-602 861 the said products are obtained by condensation of a resol (alkylphenol/formalin) with resorcinol in the presence of an acidic catalyst.
U.S. Pat. No. 5,030,692 describes the synthesis of a ternary compound by condensation of resorcinol with a resol obtained by reaction of an alkylphenol and of methylformcel or of furfural in acidic medium.
In the ternary products which have just been mentioned, while the free resorcinol content is undoubtedly low (<5%), it is sometimes accompanied by a loss in the reactivity towards the formaldehyde donor.
JP 62004720 describes novolak resins obtained by condensation of resorcinol in exces with dicyclopentadiene (resorcinol/dicyclopentadiene molar ratio=2.9), the exces of resorcinol at the end of the reaction being removed for example by reduced pressure distillation or fractional precipitation. These resins have enhanced heat resistance and flexibility that render them appreciated in the field of electronic materials.
Despite the disclosures of the prior art, there remains a need to obtain resins which do not produce smoke or lump formation and which are found to be as reactive as the resorcinol/formalin resins when rubber is vulcanized.
DESCRIPTION OF THE INVENTION
The subject-matter of the present invention is novolac resins obtained by condensation (A) of an aromatic compound containing at least two hydroxyl groups and (B) of an unconjugated diene, the said resins exhibiting a free aromatic compound content lower than 5% by weight.
Another subject-matter of the invention concerns a process for the preparation of the abovementioned resins, which consists in reacting the compound (A) and the diene (B) in an (A)/(B) molar ratio of between 0.7 and 1.75 in the presence of an acidic catalyst, and optionally in distilling.
Another subject-matter of the invention further concerns rubber-based compositions containing the abovementioned resins.
Another subject-matter of the invention concerns, lastly, the use of these resins as adhesion-promoter agent improving the adherence of the rubber to the reinforcing materials.
Other subject-matters and advantages of the invention will appear in the light of the following description.
The novolac resins according to the invention are obtained by condensation (A) of an aromatic compound containing at least two hydroxyl groups and (B) of an unconjugated diene in an (A)/(B) molar ratio of between 0.7 and 1.75 in the presence of an acidic catalyst.
The aromatic compound is generally chosen from monoaromatic compounds such as resorcinol, pyrocatechol, hydroquinone, pyrogallol and phloroglucinol, and the compounds of formula:
in which R denotes an alkylene or arylalkylene radical containing 1 to 12 carbon atoms.
The aromatic compound may consist of only one or of a number of the abovementioned compounds. Resorcinol is preferably employed.
The aromatic compound may additionally contain up to 25 mol % of at least one other phenol, substituted or otherwise, chosen, for example, from alkylphenols in which the alkyl radical contains from 1 to 14 carbon atoms and catechu oil.
The unconjugated diene according to the invention is generally chosen from the adducts obtained by a Diels-Alder reaction from at least two conjugated dienes such as butadiene, isoprene, piperylene, cyclopentadiene and methylcyclopentadiene. Examples of such compounds which may be mentioned are dicyclopentadiene, dimethyldicyclopentadiene, dipentene, norbornadiene, the oligomers and cooligomers of the abovementioned conjugated dienes and mixtures of these compounds.
Unconjugated dienes containing from 8 to 25 carbon atoms are preferably employed.
Advantageously, a diene containing from 75 to 100% by weight of at least one dimer such as dicyclopentadiene and 0 to 25% by weight of at least one other dimer, codimer, trimer and/or cotrimer is employed.
Better still, the diene includes 75% by weight of dicyclopentadiene and 25% by weight of at least one codimer chosen from cyclopentadiene-piperylene, cyclopentadiene-isoprene and cyclopentadiene-methylcyclopentadiene.
The unconjugated diene may additionally contain up to 25 mol % of at least one compound chosen from aliphatic olefins, for example diisobutylene, isobutylene or amylene or branched olefins containing a C
6
-C
14
alkyl, aryl or alkylaryl radical, for example tyrene, alpha-methylstyrene or vinyltoluene.
The acidic catalyst is generally chosen from acids of Lewis type, such as alkylsulphonic, arylsulphonic, alkylarylsulphonic, phenolsulphonic, alkylphenolsulphonic and aryldisulphonic acids and the mixtures of these acids, and BF
3
, gaseous or in the form of complexes with a phenol, an alcohol or an acid, especially acetic.
An acidic catalyst chosen from Friedel and Crafts acids, such as sulphuric acid, can also be employed.
The quantity of acid used is generally between 0.5 and 5% by weight, relative to the weight of the reactants (A) and (B).
The molar ratio of the compound (A) to the compound (B) is preferably between 0.75 and 1.25. When the molar ratio is lower than 0.7 gelling of the resin is generally observed.
The condensation of the compounds (A) and (B) in the presence of the catalyst is carried out at a temperature which can vary from 50 to 130° C. To control the reaction exotherm it is preferred to operate at the reflux of the volatile compounds and optionally in the presence of a solvent, especially an aromatic hydrocarbon such as toluene or xylene, or an aliphatic one such as hexane.
In a preferred alternative form the compound (B) is introduced continuously
Bekhiekh Messaoud
Dreyfus Thierry
Morel-Fourrier Christophe
Stuck Bonnie L.
CECA S.A.
Smith , Gambrell & Russell, LLP
Yoon Tae
LandOfFree
Phenol/diene novolac resins, process of preparation and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Phenol/diene novolac resins, process of preparation and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Phenol/diene novolac resins, process of preparation and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2559239