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
1995-07-06
2002-04-02
Gallagher, John J. (Department: 1733)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C156S332000, C428S002000, C528S361000
Reexamination Certificate
active
06365680
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to biodegradable/compostable adhesive compositions that are useful in a variety of applications. The adhesives can take virtually any form, but preferably are used as hot melt adhesives. Such adhesives can be used in applications including case and carton sealing, book binding, bottle labeling, film laminating, etc. More particularly, the adhesives can be formulated to produce hot melt pressure sensitive properties and can be applied in the construction of disposable articles including infant diapers, incontinent pads and sanitary applications.
BACKGROUND OF THE INVENTION
Adhesive compositions are commonly manufactured by combining thermoplastic resins or similar polymeric materials with available plasticizers, tackifiers and other additives to produce a wide range of adhesive properties. Common tackifiers or plasticizers are petroleum based or are derived from naturally occurring feedstocks, such as wood, tall oil rosin and terpenes. Synthetic resin materials used in these adhesives include vinyl resins such as polyethylene or polypropylene; a variety of polyester resins; polycarbonate materials; block copolymers such as styrene isoprene styrene, styrene butadiene styrene, and similar resins. Synthetic resin technology has become very advanced. Typically, these polymeric resins are usually made from petroleum sources, have attractive fiber and structural properties, are low in cost and are easily processed. Formulation technology for the manufacture of a variety of blended useful products is well advanced. Many synthetic resin materials can be biodegradable/compostable and can be recycled. However, the chemical nature of the materials used in the formulation HMAs is such that no currently available blend of the resin or polymer material with other components is fully subject to degradation by microbial populations in the biodegradable/compostable context. (A substantial need has arisen for adhesives and, in particular, hot melt adhesives that are biodegradable/compostable in the appropriate environment including municipal composting facilities.)
One effort to manufacture partially biodegradable/compostable adhesives is disclosed in Kauffmann et al., U.S. Pat. No. 5,169,889, which discloses a hot melt adhesive composition made by combining a linear polyester comprising 3-hydroxy butyric acid and 3-hydroxy pentanoic acid (3-hydroxy valeric acid) (PHBV). These PHBV materials known under the tradename BIOPOL® are sold by Zeneca. The PHBV polymers are versatile polymers that are environmentally degradable. The PHBV polymer containing adhesive compositions, disclosed in Kauffmann et al., are not fully biodegradable/compostable because of other materials in the polymer blend. Both non-biodegradable tackifiers and plasticizers are used. These adhesive formulations can still resist substantial biodegradation because of the presence of non-degradable components. (Edgington, G. J., Ryan, L. L., Biodegradable Hot Melt Adhesives. Paper Presented at the INDEX 93 International Congress for the Nonwovens Industries, Geneva, Switzerland, 1993.) Accordingly, a substantial need exists to develop (biodegradable/compostable adhesive compositions, particularly hot melt adhesive compositions comprising a thermoplastic resin, a tackifier and a plasticizer (each fully biodegradable/compostable) that can be blended to form a hot melt product to obtain adhesive, preferably pressure sensitive adhesive properties.
BRIEF DESCRIPTION OF THE INVENTION
We have found a biodegradable/compostable (tackifying resin,) having a molecular weight less than 30,000, preferably less than 20,000 based on (2-hydroxy propanoic acid (lactic acid)) that can be combined with biodegradable/compostable polymers or resins to form fully formulated biodegradable/compostable hot melt adhesives and hot melt pressure sensitive adhesives. We have further found classes of (biodegradable/compostable thermoplastic resins having a molecular weight greater than 30,000, that can be used with the tackifier of the invention. Such resins include but are not limited to a high molecular weight polylactic acid polymer, a polyester urethane or a high molecular weight PHBV polymer.) Further, we have identified compatible small molecule compostable plasticizers that can be combined with the compostable thermoplastic resins and the tackifying resins of the invention.
In the broadest aspect of the invention, we have found that the (polylactic acid (PLA) material can be useful as an) (adhesive (used on a 100 wt-% basis) or as a resin or tackifier component in adhesive compositions) and can provide a variety of useful properties. If combined with other degradable or compostable materials, the fully formulated adhesive can be biodegradable/compostable in appropriate environments.
A first aspect of the invention resides in the biodegradable/compostable tackifying resin, based on a PLA. Preferred materials have a molecular weight of less than or equal to 30,000, preferably less than 20,000 grams per mole comprising 2-hydroxy propanoic acid. Further, the tackifying resins can be modified to improve their tackifying utility in adhesive compositions. (Lactic acid can act directly as a food source for microbial populations. The tackifying resins containing substantial amounts of lactic acid are directly degradable/compostable.)
A second aspect of the invention provides a thermoplastic resin used in the formulation of biodegradable/compostable hot melt adhesive. Such thermoplastic resins include, but are not limited to: (1) a thermoplastic polylactic acid polymer resin, (2) a resin grade or high molecular weight thermoplastic polyester such as a polyester urethane, or (3) a thermoplastic PHBV polymer with the tackifying resin of the invention. Such adhesive compositions can also be manufactured using fully biodegradable/compostable 2-hydroxy-propanoic acid based tackifiers which we have identified as fully degradable. (Edgington, G. J., M. Mulligan, Compostable Hot Melt Adhesives: An Update, Paper presented at the Insight 93 International conferences, Toronto Canada 1993. ) The fully formulated biodegradable/compostable adhesive compositions can comprise from 10-90 wt-% of the 2-hydroxy propanoic acid based tackifying resins of the invention; 10-50% of a thermoplastic polyester urethane, a polylactic acid resin (Mn greater than 20,000 grams per mole) or a PHBV thermoplastic resin containing 5-35 wt-% of the hydroxy valerate component; 0-45 wt-% of degradable compostable ester plasticizer; and 0-5 wt-% of a stabilizer or stabilizer package. (The term “tackifying agent” typically refers to a relatively low molecular weight material that when added to a thermoplastic resin results in a composition having substantial and measurable tack.)
DETAILED DESCRIPTION OF THE INVENTION
The tackifying resin materials of the invention can be biodegradable/compostable amorphous resins made from at least 5 mole-%,. preferably 10 mole-% or most preferably 50 mole-% of either a d-2-hydroxy propanoic acid, or a 1-2-hydroxy propanoic acid or mixtures thereof.
Useful tackifier resins of the invention can contain as little as 5 mole-% 2-hydroxy-propanoic acid in a polymer with other reactive polymer forming materials. Either the d-isomer or the 1-isomer or mixtures of isomers can be used. Preferred tackifier grade materials are polymers made using 2-hydroxy propanoic acid (having) at least 0-100 mole-%, preferably 50-95 mole-%, most preferably 50-85 mole-% of 1-2-hydroxy propanoic acid in the polyester, the balance comprising d-2-hydroxy propanoic acid or other polymerizable reactive monomer compounds. These materials can be made in combination with other biodegradable/compostable monomers including hydroxy substituted carboxylic acid, amine substituted carboxylic acid; mono-, di- or tricarboxylic acid materials; mono- di, tri- or other polyol materials. The polyesters of the invention can be homopolyesters comprising repeating units derived solely from either d- or 1-2-hydroxy propanoic acid monomer or mixtures thereof or a copolyester m
Edgington Garry J.
Ryan Christopher M.
Binsu
Gallagher John J.
H. B. Fuller Licensing & Financing Inc.
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