Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1997-01-21
2003-07-01
Reddick, Judy M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S319000, C524S019000, C524S025000, C524S026000, C524S430000, C524S432000, C524S704000
Reexamination Certificate
active
06586505
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to aqueous resin dispersions comprising water, resin, a surfactant, and a caseinate. This invention also relates to the process for producing the aqueous resin dispersion and to adhesives formulated with the aqueous resin dispersion.
BACKGROUND OF THE INVENTION
Resin dispersions can be produced through a variety of mechanisms and equipment configurations. They may range from total solvent systems to solvent-assisted systems to solvent-less systems (100% water-based). In a total solvent system, resin is dissolved in a hydrocarbon solvent and used in a solvent medium. In a solvent-assisted system, resin is cut in a hydrocarbon solvent at a minimum level required to assist the emulsification and is subsequently added to water.
Contact adhesives typically require both high temperature strength and good contactability. This can be achieved through the use of resin dispersions based upon relatively high softening point resins in combination with either a lower softening point resin to improve contactability, or an even higher softening point resin to improve high temperature strength. However, production of such resin dispersions is difficult without use of a hydrocarbon solvent and requires pressurized dispersing systems which are relatively expensive. If the softening point of the base resin exceeds 85° C., the resin dispersion must be produced under elevated pressure to prevent the aqueous phase of the dispersion from boiling. This equipment is both expensive and complex in nature.
Furthermore, emulsification of resins with small particle size and distribution requires selection of proper emulsifier system and equipment. This becomes more complex as softening point of the resin increases. Consequently, many high softening point resin dispersions, such as terpene phenolics, are larger in particle size and often contain a bimodal particle size distribution with a significant level of very large particles. This bimodal character with larger particle size contributes to instability in these resin dispersions often manifesting as decreased shelf-life. Also, these resin dispersions can develop grit and coagulation problems.
Until now, water-based contact adhesive formulators have been forced to either (1) use solvent-assisted resin dispersions, however use of these materials are becoming undesirable due to increased regulation due to their solvent content; (2) use complex blends of high and low softening point resin dispersions to achieve the required contactability without destroying the high temperature strength performance; or (3) produce adhesive formulations which exhibit inferior performance as compared to total solvent systems-and solvent-assisted systems.
In the past, casein has been used in solvent-less systems as an emulsifier. Casein emulsified resin dispersions were good tackifiers for polymers typically used in water-based contact adhesives, such as polychloroprene. However, due to biological attack and/or natural degradation of casein, casein-emulsified products are less desirable as compared to those resin dispersions produced with synthetic emulsifiers which are relatively resistant to. microbial degradation.
Casein solutions have been used in water-based resin dispersions to disperse resin in the water phase. In this role, the casein solution serves as the only or primary emulsifier and is integral in establishment of particle size and distribution. A side benefit of casein's presence in these resin dispersions is an improvement in high temperature strength seen in products used in water-based contact adhesives.
In those resin dispersions where casein is used to form a dispersion of resin in an aqueous phase, degradation of the casein leads to partial or complete dispersion failure. When used as a primary surfactant, once the casein is destroyed the resin dispersion is destroyed. When used as a primary surfactant the amount of casein used in dispersions is limited by the amount required to disperse the resin phase.
The invention differs from the traditional role of casein in resin dispersions, in that casein in the form of a caseinate solution functions solely as a performance additive. Since the caseinate solution does not contribute to the dispersement of the resin or participate in the creation of particle size of the resin in the dispersion, the caseinate solution does not significantly effect stability of the resin dispersion to which it is added.
The invention is particularly useful in water-based contact adhesives, which require both high temperature performance and good contactability or combinability. Those skilled in the art of water-based contact adhesive formulations have in the past used multiple resin dispersions to achieve adhesive formulations with contactability and high temperature strength. This approach requires a complex balance of low and high softening point resin dispersions. A further complication, aside from logistical concerns of handling multiple resin dispersions, is interaction of various included surfactants contained in the resin dispersion and their effect on adhesives containing these dispersions.
The invention provides both the desired contactability and combinability typical of lower softening point resin dispersions and the high temperature performance often associated with higher softening point resin dispersions in a solvent-less system.
SUMMARY OF THE INVENTION
The invention relates to a process for producing an aqueous resin dispersion comprising the steps of forming a mixture of resin and water and surfactant to form an aqueous resin dispersion precursor; and adding a caseinate solution to the aqueous resin dispersion precursor. Additional surfactant(s), thickener(s), performance additive(s), biocide/preservative(s), and antioxidant(s) may be blended with the resin dispersion precursor.
The process of the invention may be a process using either a direct method or an invert method. Also the process may be batch, semi-continuous or continuous in nature.
At any time after the resin dispersion precursor has been formed, a caseinate solution is added to the dispersion through any known mechanism, including simple mixing.
Additionally, the invention relates to a resin dispersion comprising a resin, water, a surfactant; and a caseinate solution.
The resin dispersion of the invention is combined with a polymer latex to produce an adhesive. Additional surfactant(s), thickener(s), performance additive(s), biocide/preservative(s) and antioxidant(s) may be blended with the resin dispersion precursor.
The resins may be aliphatic, aromatic, aliphatic-aromatic, or any combination thereof. Resins suitable for the aqueous resin dispersions of the invention include rosins and resins derived from wood, gum, and tall oil sources and blends thereof. These rosins and resins can be polymerized, disproportionated, hydrogenated, esters of aromatic and aliphatic alcohols, modified with phenolic compounds or other suitable polar compounds. The resins used may range in softening point from 10-190° C. and have molecular weights from 300-10,000 Mw. The most effective resins range in softening point from 60-120° C. and have molecular weights from 300-2,000 Mw.
Among the plasticizers of utility in resin dispersions of the invention include liquid or low softening point tackifying resins, petroleum-derived oils, aromatic hydrocarbon oils, paraffinic oils, napthenic oils, olefin oligomers, low molecular weight polymers, vegetable and animal oils and their derivatives.
Among the surfactants of utility in the resin dispersions of the invention include alkali metal soaps of carboxylates such as wood rosins, gum rosins, tall oil rosins, disproportionated rosins, polymerized rosins, hydrogenated rosins, esters thereof, and/or blends thereof. Surfactants may also be alkali metal salts, ammonium salts, or amine salts of alkyl sulphates, alkyl sulphonates, alkyl aryl sulphates, alkyl aryl sulphonates, ethoxylated alkylphenol sulfates, ethoxylated alkylphenol sulfonates, and sulfates and sulfonates of fatty acids.
Amon
Cronin Michael J.
Dunckley Peter M.
Kutsek George J.
Boshears B. J.
Eastman Chemical Resins Inc.
Gwinnell Harry J.
LandOfFree
Aqueous resin dispersion does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Aqueous resin dispersion, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aqueous resin dispersion will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3054923