Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1997-11-24
1999-03-09
Buttner, David
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524425, 524426, 524447, 524451, 524522, 524 57, 524194, 525 57, 525194, 427392, 427393, 156327, 1563312, 156332, C08L 102, C08L 3104, C08L 2904, C09J13104
Patent
active
058801839
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to compositions which are especially suitable for use in the paper and woodworking and related fields. The present compositions find particular, but not exclusive use, as adhesives, binding, coating and sealing materials.
Many adhesives currently available, particularly for use in woodworking, contain polyvinyl alcohol (PVOH) or a dispersion of another polymer such as polyvinyl acetate in polyvinyl alcohol (PVAc) (PVOH). The adhesives operate by forming a physical bond with the wood substrate. In this respect the --OH groups in the adhesive composition and the --OH groups from cellulose in the wood substrate together form strong hydrogen bonds. Problems arise with such adhesives in that they exhibit poor water resistance. This limits the number of potential uses for such adhesives. The inherent moisture content of the wood substrate can also cause difficulties for such adhesives.
Also, many existing products in use in the woodworking field require metal salt catalysts in their crosslinking or curing reaction such as aluminium chloride and chromium nitrate, for example. Use of such metal salts has disadvantages in terms of safety for both manufacturing and handling of the adhesive. Also, many of the formulations presently available have a low pH value (approximately 3) which can give rise to discoloration of wood which contains tanin.
British patent GB 1423558 discloses a wood glue which uses a polyisocyanate crosslinker. These are, however, highly toxic and environmentally unfriendly chemicals. Aziridines have been used as crosslinkers for polymeric injection moulding compositions (GB 1424041) and in glues for amine-containing synthetics (JP 1026689).
The present invention seeks to alleviate at least some of the aforementioned problems.
With this aim in mind, in one aspect the present invention concerns a two part pack including components A and B, having hydroxyl groups; and polymer containing units having carboxyl groups; and being capable of crosslinking with at least one carboxyl group and at least one hydroxyl group.
In this aspect of the invention, suitably both components A and B are in liquid form. In preferred embodiments the pack includes a first openable compartment containing both components Ai) and Aii) and a second openable compartment containing component Bi).
In another aspect the present invention provides a composition obtainable by crosslinking Ai) a polymer containing hydroxyl units and Aii) a polymer derived from an optionally substituted styrene monomer, said polymer containing units having carboxyl groups, with Bi) a polyfunctional aziridine crosslinker which is capable of crosslinking with hydroxyl groups and with carboxyl groups.
In another aspect the present invention also relates to use of a composition obtainable by crosslinking Ai) a polymer containing hydroxyl units and Aii) a polymer derived from an optionally substituted styrene monomer, said polymer containing units having carboxyl groups, with Bi), a polyfunctional aziridine crosslinker as a protective coating, especially for products derived from or containing cellulose, including paper and wood products.
A yet further aspect of the present invention concerns use of a composition obtainable by crosslinking Ai) a polymer containing hydroxyl units; and Aii) a polymer derived from an optionally substituted styrene monomer, said polymer containing units having carboxyl groups; with Bi) a polyfunctional aziridine crosslinker as an adhesive, especially for wood products and other products derived from or containing cellulose.
Other aspects of the present invention concern methods of providing protective coatings especially for wood and paper products and methods for adhering surfaces of wood and paper products to other substrates. Preferably the methods of coating include applying the present compositions in the form of a spray. Suitably the method of adhering substrates involves applying the compositions to one substrate using brushes, rollers etc.
In some preferred embodiments Component Ai) is in
REFERENCES:
patent: 5059264 (1991-10-01), Sheets
Chemical Abstract 100:129814 (of JP57176063).
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