Resorcinolic derivative for rubber compounds

Details Resorcinolic derivative for rubber compounds Resorcinolic derivative for rubber compounds

2000-12-21

2003-04-01

Mulcahy, Peter D. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

Reexamination Certificate

active

06541551

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to resorcinolic compounds for rubber reinforcement. More particularly, the invention relates to resorcinolic derivatives that can be substituted for resorcinol during rubber manufacture; use of the present resorcinolic compounds results in enhanced cure and mechanical properties of the cured rubber compound as compared with resorcinol, while maintaining the favorable properties of uncured rubber compounds achieved when resorcinol is used.
BACKGROUND OF THE INVENTION
Resorcinol, resorcinolic derivatives and resorcinol-formaldehyde resins have been used in the rubber industry as rubber compounds and adhesives. These resorcinolic compounds are unique materials in rubber compounding, since they act as thermosetting and vulcanizing plasticizers. They are very efficient plasticizers for rubber during the processing operations. The use of these compounds allows easier processing, higher loading and excellent extrusions of the rubber compounds.
Resorcinol and resorcinol based derivatives and resins, which act as methylene acceptors, have thermosetting properties that, upon curing, form a resin network within the rubbery polymer by reacting with various methylene donors. This results in increased hardness, abrasion resistance, aging resistance, solvent and oil resistance, and stiffness, and also gives a much improved finish to the cured rubber stock. This combination of plasticizing and reinforcing action is rare for a single material used in rubber compound formulations. In addition, resorcinolic compounds may act as antioxidants when used in natural rubber.
The network formation during rubber curing is more effective with phenolic methylene acceptor compounds having meta-substitution capability than with other compounds due to their high reactivity towards methylene donors. Examples of such phenolic compounds include resorcinol, phloroglucinol and m-aminophenol. The use of phloroglucinol and m-aminophenol in rubber compounding formulations is limited due to their high cost and melting points. Therefore, the most commonly employed methylene acceptor is resorcinol, due to its comparatively low cost and high reactivity. Resorcinol has three reactive sites, namely at C2, C4 and C6, indicated in formula 1 by the *:
The high reactivity of resorcinol towards conventional methylene donors such as formaldehyde, hexamethylenetetraamine (HMTA) and hexamethoxymethylmelamine (HMMM), etc., is due to the presence of three reactive sites, meta with respect to each other, on the resorcinol molecule. The presence of two hydroxyl groups, meta with respect to each other, on the molecule further enhances the reactivity of the molecule towards methylene donors.
Though resorcinol provides enhanced physical, mechanical and adhesion properties in the cured rubber compounds, fuming associated with this material can be a problem to the tire industry. To overcome this problem, the tire industry needs compounds such as modified resorcinolic derivatives and resins that do not produce volatiles, such as those produced by resorcinol at mixing temperatures above 110° C. In addition to low volatility, the new resorcinolic compounds should have a reactivity similar to resorcinol in the rubber compound.
When the resorcinol is derivatized by attaching functional groups to either the benzene ring or hydroxyl groups, the reactivity of the resulting resorcinolic derivatives towards the methylene donor compounds is greatly reduced or altered. For example, substitutions at the 2, 4 or 6 positions of the benzene ring reduce the number of reactive sites for methylene donor interaction. Also, monoether or monoester derivatives have reduced reactivity towards methylene donor compounds as compared to resorcinol.
Resorcinol monobenzoate and derivatives of resorcinol such as resorcinol monorosinate, resorcinol diphenyl ether, resorcinol monomethyl ether, resorcinol monoacetate, phloroglucinol and derivatives used in the rubber composition are disclosed in U.S. Pat. No. 4,605,696. For example, to overcome the fuming of resorcinol, monoester derivatives of resorcinol, such as resorcinol monobenzoate, were used in the rubber compound. While improved dynamic mechanical properties were observed for the cured rubber, the monoester derivatives were less reactive than resorcinol due to the presence of an ester group substituent.
U.S. Pat. No. 4,892,908 discloses a keto derivative of resorcinol, namely benzoylresorcinol, which can be used as a low-fuming reinforcing material in the rubber compound. But, benzoylresorcinol has two reactive sites and a high melting point as compared to resorcinol.
U.S. Pat. No. 5,049,618 discloses a vulcanizable rubber composition, which comprises rubber, a filler and N-(3-hydroxyphenyl)maleimide. N-(3-hydroxyphenyl)maleimide has three active sites for methylene donor compounds but is believed to have a higher melting point than resorcinol.
Thus, while modifications to the resorcinol molecule are expected to lower the fuming characteristics of resorcinol, they also affect the networking efficiency during curing. Therefore, it is important to develop resorcinolic compounds/derivatives that can at least maintain the reactivity of resorcinol, if not impart higher reactivities towards the methylene donor compounds. Increased reactivity of resorcinolic derivatives is expected to speed up the network formation during rubber vulcanization, which ultimately enhances the physical and mechanical properties of the cured rubber.
SUMMARY OF THE INVENTION
The present invention provides for the use of 3-hydroxydiphenylamine (“3-HDPA”) in place of resorcinol to enhance the physical and mechanical properties of both uncured and cured rubber compounds. Several advantages are realized by using 3-HDPA as a methylene acceptor. For example, 3-HDPA has a lower melting point than resorcinol; this means the compound has better dispersibility or mixing with rubber compounds at a lower temperature. Because of its high molecular weight, 3-HDPA has a lower volatility than resorcinol. While 3-HDPA has the same number of reactive sites as resorcinol, it has a higher reactivity, due to its being an m-aminophenol-type derivative.
The 3-hydroxydiphenylamines used in the present invention have been described. U.S. Pat. No. 2,376,112 discloses the synthesis of 3-hydroxydiphenylamine from resorcinol and aniline using 85% phosphoric acid. U.S. Pat. No. 4,265,833 outlines the preparation of various 3-hydroxyphenylamines from resorcinol and aniline using a PTSA catalyst. Neither of these patents teach or suggest the use of 3-hydroxydiphenylamine as a rubber-reinforcing compound, however.
One aspect of the present invention to provide rubber compounds having enhanced physical and mechanical properties in both their cured and uncured forms.
It is a further aspect of the invention to provide a method for making rubber compounds having improved physical and mechanical properties.
These and other aspects of the invention will be apparent based upon the following detailed description of the invention and appended claims.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to vulcanizable rubber compositions having improved physical and mechanical properties in both the cured and uncured forms. More specifically, the vulcanizable rubber compositions of the present invention comprise: (a) a rubber component selected from natural rubber, synthetic rubber or combinations thereof; (b) a methylene donor; and (c) a methylene acceptor that is substituted or unsubstituted 3-hydroxydiphenylamine (“3-HDPA”). If substituted, the 3-HDPA contains one or more C1-6 alkyl substituents, which can be straight chain or branched, and/or can contain an additional OH group on the phenyl ring.
“Rubber” as used herein refers to both natural and synthetic rubber. Representative synthetic rubber polymers include the butadiene polymers. Butadiene polymers include those polymers having rubber-like properties, prepared by polymerizing butadiene alone or with one or more other polymerizable ethylenically unsatur

Affiliated with

Also associated with

Rating

Resorcinolic derivative for rubber compounds does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Resorcinolic derivative for rubber compounds, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Resorcinolic derivative for rubber compounds will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3067902