Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-12-21
2002-10-29
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S432000, C524S492000, C525S134000, C525S135000, C525S139000, C525S140000, C528S219000
Reexamination Certificate
active
06472457
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to nonformaldehyde, nonfuming resorcinolic resins, and methods of making and using the same. These resins are particularly useful when combined with curing agents in rubber, imparting improved physical and mechanical properties such as low volatility, reduced fuming in rubber compounding, and improved adhesion properties of vulcanized rubber and rubber composites.
BACKGROUND INFORMATION
Resorcinol and resorcinol-formaldehyde resins have been used in the rubber industry as reinforcing and bonding agents in rubber compounds. These resins are unique materials for rubber compounding, since they act as thermosetting and vulcanizing plasticizers. They are very efficient plasticizers for rubber during the processing operations. Use of these resins allows easier processing, higher loading and excellent extrusions for the rubber compounds.
The thermosetting properties of resorcinol upon curing provide the vulcanizate with increased hardness, abrasion resistance, aging resistance, solvent and oil resistance, and stiffness as compared with vulcanizates made without resorcinol or its derivatives; resorcinol also gives much improved finishes to the cured rubber stock. This combination of plasticizing and reinforcing action is rare for a single material in rubber compounds.
Although resorcinol imparts good mechanical and adhesion properties to rubber, fuming of resorcinol during compounding at a temperature in excess of 110° C. can occur. To overcome the fuming problems of resorcinol, tire manufacturers are seeking modified resorcinolic derivatives and resins that do not produce volatiles at Banbury temperatures. In order to reduce fuming completely, the compounds used should not contain any free resorcinol, or should have levels of free resorcinol of about 1.0 wt. % or less.
One of the ways to reduce the fuming of resorcinol in the rubber compound is to use resorcinol-formaldehyde resins (RF resins) in place of resorcinol. Generally, RF resins are produced by the reaction of resorcinol with formaldehyde in the presence of an acid catalyst. The free resorcinol content of RF resins can be reduced by increasing the formaldehyde level. When the formaldehyde content is increased in the RF novolak synthesis, however, the softening point of the final material is also increased due to an increase in its molecular weight. If the formaldehyde level is increased beyond a certain level, the final resin will become a gel. Due to these limitations, it is very difficult to develop an RF type resin containing less than 1.0 wt. % free resorcinol with a softening point less than 105° C. For example, U.S. Pat. Nos. 2,746,898 and 3,596,696 disclose the preparation of RF resins, but the free resorcinol content in these resins is well above 1 wt. %, and, hence, the fuming problems exist with these resins. In addition, RF resins tend to absorb moisture upon exposure to humidity, and therefore soften and coalesce during storage.
Another approach developed to address the problem of resorcinol fuming is the use of derivatives of resorcinol such as alkyl, aralkyl, monoester and monoether compounds. Simple alkyl substituted resorcinol, such as methylresorcinol, is difficult to synthesize. Aralkyl substituted resorcinols often have low melting points, and are paste-like and difficult to handle by the tire industry. Synthesis of these derivatives often requires extensive processing steps that involve different organic solvents and isolation procedures. In addition, if organic solvents are used, their handling and disposal often bring more problems and cost.
U.S. Pat. No. 4,605,696 discloses the synthesis of resorcinol monobenzoate and resorcinol monorosinate and their use in the rubber compound formulation. The synthesis of monorosinate involves the use of a xylene solvent, requiring distillation and disposal of solvent waste. Resorcinol monobenzoate has a higher melting point than resorcinol and, therefore, a processing problem exists in the rubber compound application.
U.S. Pat. No. 4,892,908 discloses a keto derivative of resorcinol, namely 4-benzoylresorcinol, which can be used as a low-fuming resorcinolic derivative replacing resorcinol in rubber compounds. The preparation of benzoylresorcinol, however, requires the use of toxic chemicals, such as benzotrichloride, and highly volatile organic solvents. Therefore, the cost of benzoylresorcinol is about 3-4 times higher than that of resorcinol. In addition, benzoylresorcinol has a higher melting point than resorcinol and also exhibits processing difficulties.
Yet another approach to eliminate or minimize the resorcinol fuming is to alkylate or aralkylate part of the resorcinol and then react the product with formaldehyde to develop an alkyl or aralkyl substituted resorcinol-formaldehyde type resin. U.S. Pat. No. 4,889,891 discloses such resins formed by reacting an alkylsubstituted resorcinol, prepared from the reaction of resorcinol with dicyclopentadiene, dipentene, piperylene, or another composition, with formaldehyde. While the softening points of these resins are acceptable for rubber compounding, the resins still contain free resorcinol in amounts greater than 1 wt. %. U.S. Pat. Nos. 5,021,522 and 5,049,641 disclose resorcinolic resins prepared by reacting an aralkyl substituted resorcinol, prepared from the reaction of styrene and resorcinol, with an aqueous formaldehyde solution. Though the softening points of these resins are acceptable for the rubber compounds, the free resorcinol content is typically greater than 2.5 wt. %.
Several other attempts have been made to develop low-fuming or non-funming resorcinol modified resins for the tire industry. For example, resorcinol was used with phenol or alkylphenol and formaldehyde to develop phenol-resorcinol-formaldehyde (PRF) and alkylphenol-resorcinol-formaldehyde type resins. Problems with these compounds arise due to the handling of formaldehyde and solvents to effect the synthesis. Moreover, to achieve a modified resorcinolic resin containing less than 1.0 wt. % free resorcinol and having a softening point less than 105° C., the final distillation to remove unreacted monomers must be done at temperatures in excess of 180-190° C. and vacuum conditions of 5-6 mm of Hg. Without hot oil heating of the reactor and an efficient high vacuum pump, which require higher capital expenses, low free resorcinol levels in these resins are difficult to achieve.
U.S. Pat. No. 5,244,725 discloses the synthesis of a nonformaldehyde type resorcinolic resin from the reaction of resorcinol with bisphenol-A epoxy. Although the resin of this patent shows good dynamic mechanical properties compared to resorcinol, fuming associated with a 10.0 wt. % free resorcinol content of this resin restricts its use in the rubber compound formulations.
EP 798 324 (abstract) reports preparation of resins by reacting aromatic compounds with nonconjugated dienes in the presence of an acid catalyst. Free resorcinol content of the product, however, is still at least about two.
SUMMARY OF THE INVENTION
The present invention provides resorcinolic resins that have a wide variety of desirable properties. The resins have about 1 or less than 1 wt. % free resorcinol, and have softening points between about 75 and 1 10° C. The resins are non-fuming and are less hygroscopic as compared to other resorcinol derivatized resins, such as RF resins. The present resins are capable of undergoing cross-linking with curing agents during rubber vulcanization to give improved physical, mechanical and adhesion properties to the rubber.
Another embodiment of the present invention provides a method for making such resins, by reacting resorcinol with dicyclopentadiene, and then further reacting that product with an olefinic compound. Significantly, the methods can be carried out at processing temperatures below 180-190° C. Moreover, the process is carried out in the absence of both solvents and formaldehyde, thus eliminating handling hazards of waste solvents and distillates.
Yet another embodiment of this invention prov
Durairaj Raj B.
Peterson, Jr. Alex
Anderson Debra Z.
Eckert Seamans Cherin & Mellott , LLC
Indspec Chemical Corporation
Sanders Kriellion A.
LandOfFree
Nonformaldehyde, nonfuming resorcinolic resins and methods... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Nonformaldehyde, nonfuming resorcinolic resins and methods..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nonformaldehyde, nonfuming resorcinolic resins and methods... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2967353