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
2001-11-06
2003-08-12
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S331900, C525S332600, C525S149000, C524S394000, C524S432000, C524S492000, C524S495000, C524S494000, C546S291000, C540S485000, C548S578000, C548S577000
Reexamination Certificate
active
06605670
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to improved methylene acceptors having a low molecular weight, a low free resorcinol content, and a low softening point. The derivatives of the present invention provide low fuming and low viscosity in the uncured rubber compound, good adhesion for steel cord, high dynamic storage modulus in the cured rubber product and ease of processing. In addition, they are non-hazardous to produce.
BACKGROUND INFORMATION
Resorcinol (molecular weight 110; melting point 110° C.) has long been used in the rubber industry as a reinforcing and bonding agent to promote adhesion between steel wire and rubber compounds. Resorcinol is referred to as a methylene acceptor because it reacts with a methylene donor, a compound that generates methylene or methylol groups capable of crosslinking with the methylene acceptor. The methylene donor and methylene acceptor crosslink during rubber processing to form in situ a resin that promotes adhesion of the rubber to reinforcing materials such as metal wire, glass, organic filaments, fibers, cords and fabrics.
Because it is a small molecule, resorcinol can become uniformly distributed among the rubber molecules during compounding with rubber, resulting in an uncured rubber mixture that exhibits very low viscosity. This is a desirable property, as it results in greater ease of processing and extrusion of the uncured rubber. However, even though resorcinol provides excellent physical, mechanical and steel adhesion properties in the uncured and cured rubber products, fuming associated with resorcinol at rubber processing temperatures causes problems, particularly with loss of product. For example, slight variations in the processing temperature can result in variations in the amount of resorcinol in, and properties of, the end product.
To overcome the resorcinol fuming problem, derivatives of resorcinol have been used as methylene acceptors in rubber processing. Various resorcinol-formaldehyde resins which can act as suitable methylene acceptors have also been developed, reducing the free resorcinol content and the associated resorcinol fuming. See, for example, the following related patents:
U.S. Pat. No. 4,476,262 discloses a water dilutable resinous product prepared by reacting together a resin, an aldehyde and a sulfurous or organic acid.
U.S. Pat. No. 4,605,696 discloses use of monoesters of resorcinol, including resorcinol monobenzoate and resorcinol monorosinate, in rubber compositions.
U.S. Pat. No. 4,731,430 discloses phenol resins modified with compounds possessing amide and/or imide groups that are useful as crosslinking agents and in the preparation of adhesives and rubber assistants.
U.S. Pat. No. 4,889,891 discloses alkyl substituted resorcinolic novolak resins as suitable methylene acceptors for vulcanizable rubber compositions.
U.S. Pat. No. 4,892,908 discloses the use of keto derivatives of resorcinol, such as benzoyl resorcinol, as methylene acceptors in vulcanizable rubber compositions.
U.S. Pat. No. 5,021,522 discloses aralkyl substituted resorcinolic novolak resins including a styrene substituted resorcinol-formaldehyde resin.
U.S. Pat. No. 5,030,692 discloses alkylphenol modified resorcinolic novolak resins.
U.S. Pat. No. 5,244,725 discloses a vulcanizable rubber composition that includes a rubber compound, a methylene donor and a methylene acceptor.
One problem with resorcinol-formaldehyde resins is diminished rubber compounding properties because the formaldehyde molecule contains two sites of reactivity. Formaldehyde will crosslink two resorcinol molecules, resulting in a higher molecular weight resin. Resorcinol resins of higher molecular weight have less reactive sites with which to crosslink the methylene donor, do not disperse as well in the rubber, and increase the viscosity of the uncured rubber.
Other methods of producing resorcinolic resins, such as by adding styrene to resorcinol before reaction with formaldehyde, or by using an epoxy reaction followed by styrenation, have been attempted. The methylene acceptors produced by these methods are of relatively high molecular weight, and have the problems mentioned above. None have achieved the desired product or processing properties in combination with low molecular weight, low fuming and low free resorcinol content.
SUMMARY OF THE INVENTION
The present invention solves the above need by providing a method of making a low molecular weight methylene acceptor having physical and mechanical properties similar to resorcinol, but without the fuming problems, for use in rubber processing. The methylene acceptor is prepared by reacting a polyhydric phenol with an aromatic olefinic compound in the presence of an acid catalyst to produce a first reaction product, and then further reacting the first reaction product with a monofunctional compound which is an N-methylol lactam derivative, such as propiolactam, butyrolactam, valerolactam, caprolactam, and heptalactam. The resulting methylene acceptor has a low molecular weight, low softening point, and a low free resorcinol content. Additional advantages include the formation of water as a by-product, as compared with by-products such as alcohol or other organic compounds produced in prior art methods, and the absence of a need for a co-solvent such as xylene or toluene. The method of the present invention can use existing plant conditions, without the need for re-engineering. Derivatives produced by the above-described method are also provided in the present invention.
The present invention further provides a rubber composition comprising: (a) a rubber compound; (b) a methylene donor; and (c) a methylene acceptor; the methylene acceptor is prepared by reacting a polyhydric phenol with an aromatic olefinic compound in the presence of an acid catalyst to produce a first reaction product, and then further reacting the first reaction product with an N-methylol lactam derivative, such as propiolactam, butyrolactam, valerolactam, caprolactam, and heptalactam, to produce a second reaction product which is the methylene acceptor. Rubber compositions further comprising a reinforcing material are also provided by the present invention.
It is an object of the present invention, therefore, to provide a low molecular weight methylene acceptor.
It is an additional object of the present invention to provide styrenated (polyhydroxy N-benzyl) lactam derivatives.
It is an additional object of the present invention to provide a methylene acceptor with low free resorcinol content to reduce fuming during rubber processing.
It is a further object of the present invention to provide a methylene acceptor which is a low melting solid, to improve ease of processing and handling.
It is another object of the present invention to provide a methylene acceptor with bulkier substituents to provide high dynamic storage modulus in the cured rubber compound.
It is an additional object of the present invention to provide a methylene acceptor made by a simple and nonhazardous process.
These and other objects of the invention will be more fully understood from the following description of the invention and the claims appended hereto.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention provides a method of making a low molecular weight methylene acceptor comprising reacting about 1.0 mole of a polyhydric phenol with about 0.1-1.2 moles of an aromatic olefinic compound in the presence of an acid catalyst to produce a first reaction product, and further reacting this first reaction product with about 0.1-1.2 moles of an N-methylol lactam derivative, such as propiolactam, butyrolactam, valerolactam, caprolactam, and heptalactam, to produce a second reaction product which is the methylene acceptor of the present invention. Thus, the molar ratio of polyhydric phenol:aromatic olefin:N-methylol lactam derivative is about 1:0.1-1.2:0.1-1.2.
As used herein, the term “low molecular weight methylene acceptor” refers to the second reaction product, made as described above, which includes derivatives of the polyhydric phenol which
Durairaj Raj B.
Lawrence Mark A.
Anderson Debra Z.
Eckert Seamans Cherin & Mellott , LLC
Indspec Chemical Corporation
Lee Rip A
Wu David W.
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