in general , this invention comprises materials and methods for improving the adhesive strength of adhesives , coatings and composites to biological substrates . the terms &# 34 ; adhesives , coatings and composites &# 34 ; are taken to mean any composition that can be stored in either a single or multi - component form , is used to adhere , cover , adorn , replace , or otherwise protect a surface , and can be polymerized by one or more of a variety of free radical - type initiation processes . examples of such materials are ( 1 ) two - component ( powder and liquid ) artificial fingernail prosthesis formulations , which polymerize through a peroxide / tertiary amine type initiation ; ( 2 ) one component , glass / resin dental compositions , which are polymerized by actinic ( visible and / or ultraviolet ) light activation of a photoinitiator , together with an optional tertiary amine ; and ( 3 ) ultraviolet and visible light cured , unfilled or filled , coatings and adhesives used to attach and / or cover natural or artificial fingernails ; similar compositions are utilized for the reparation of livestock hooves that have become split or cracked . although not limited to the above types of adhesives , coatings and composites , the three categories listed are those compositions that show marked improvement in adhesive strength through the practice of the present invention . the most preferred inventive method for pretreating the surfaces to be adhered to comprises contacting the surface with a non - aqueous solution of a methacryloyloxyethyl maleate ( herein referred to as mahema ), and allowing the non - aqueous solvent to completely evaporate . then , the adhesive , coating or composite is allowed to contact the treated surface and polymerized through free radical mechanisms . the preferred concentration of mahema in the non - aqueous solvent is from about one percent to about 30 percent , and the most preferred concentration is about 5 to 20 percent . differences in the porosity and surface free energy of the substrate will have a bearing on the optimal mahema concentration for each individual surface to be &# 34 ; primed &# 34 ;. in general , following the complete evaporation of the carrier solvent , the treated substrate should appear relatively dry . treated surfaces that appear shiny and wet tend to have a thick layer of residual mahema , which can act as a boundary layer and lead to decreased adhesive strength . mahema was prepared by heating together 1 mole of maleic anhydride and in slight excess of 1 mole of 2 - hydroxyethyl methacrylate together with about 200 ppm of the monomethyl ether of hydroquinone as a stabilizer against premature polymerization . in addition 500 ppm of triethylamine was included in the reaction mixture as a catalyst for the addition reaction . upon cooling , a slightly yellow , moderately viscous liquid is obtained , having a refractive index of 1 . 484 ( at 20 degrees c .) and a brookfield viscosity ( at 23 degrees c .) of 470 cps . this liquid was stored in amber glass bottles until further use . the structure of mahema is as follows : ## str3 ## care must be taken during the heating process above to keep the reaction process at or below about 80 - 90 degrees c . to avoid premature polymerization due to the methacrylate group . alternatively , mahema may be synthesized in the solvent carrier to be used in the practice of this invention . for example , the properly calculated amounts of maleic anhydride and 2 - hydroxyethyl methacrylate may be added to ethyl acetate to provide the desired final concentration of mahema in situ . attention must be paid to this method of synthesizing mahema , in that certain solvents , such as isopropyl alcohol , can compete with the 2 - hydroxyethyl methacrylate for addition to the anhydride group of maleic anhydride . proteinaceous substrates were tested to demonstrate the adhesive strength improvement caused by the adhesion promoting compositions of this invention . the differences in the adhesive strength provided by pretreating the substrate with the present invention relative to prior art systems are shown . solutions ranging from one to 30 percent mahema in anhydrous ethyl acetate were prepared and packaged in amber glass bottles with a polyethylene brush cap for application to the surfaces to be tested . in order to test the extent of adhesion improvement by the mahema solutions on keratinaceous substrates , cattle hooves were chosen due to their availability and ease of handling during tensile adhesive strength testing . flat sections of cattle hooves were prepared with the hoof fibers running parallel to the surface to be tested . the hoof surface was then abraded with a fine grit sandpaper and subsequently rinsed with water and allowed to dry thoroughly . the abraded and rinsed hoof surface was then treated with the mahema solution , being brushed on and allowing the ethyl acetate to evaporate completely . the surface of the hoof at this point appeared dry and slightly glossy . a stainless steel cylinder with a tapered bore and an access port was then contacted to the treated hoof surface perpendicularly . the following formulation was mixed , poured into the testing cylinder through the access port , and allowed to polymerize . this assembly was allowed to age at room temperature for 24 hours and subsequently tested for tensile adhesive strength in an instron tensile strength tester model 1011 ( instron corp , quincy , ma ) at a crosshead speed of 0 . 1 mm / minute . ratio of liquid a : powder b is approximately 1 : 3 in the final mixture . ______________________________________ no . mahema % avg . adh . * adh . range ** measurements______________________________________0 240 110 - 330 51 570 400 - 670 52 720 460 - 790 53 780 600 - 840 54 800 690 - 880 55 870 810 - 910 58 080 940 - 1170 510 1410 1250 - 1500 513 1840 1610 - 1990 516 2320 1980 - 2500 520 2450 2020 - 2610 525 2030 1880 - 2150 530 1490 1200 - 1780 5______________________________________ * average adhesion in psi ( lbs per sq . inch ) ** adhesion range in psi ( lbs per sq . inch ) the adhesion promoting capabilities of the maleic anhydride addition reaction products of this invention were compared to those of other known and / or potential adhesion promoters . all compounds tested had at least one carboxylic group and at least one unsaturated group capable of participating in free radical type polymerizations . each promoter is listed below , together with it &# 39 ; s concentration , solvent ( if any ), substrate appearance , and tensile adhesive strength as described in example 1 . ______________________________________adhesion promoter conc . solvent avg . adh . sup . 3______________________________________methacrylic acid 20 % ethyl acetate 680methacrylic acid 100 % none 1250acrylic acid 20 % ethyl acetate 820acrylic acid 100 % none 1500mahema . sup . 4 20 % ethyl acetate 2510pmdm . sup . 1 5 % acetone 1110pmdm . sup . 1 20 % acetone 730maleic acid 20 % ethyl acetate 300mahpma . sup . 2 , 4 20 % ethyl acetate 2480______________________________________ . sup . 1 pyromellitic dianhydride / 2hydroxyethyl methacrylate adduct ( ref . patent no . 4 , 521 , 550 ) . sup . 2 maleic anhydride / 2hydroxypropyl methacrylate adduct . sup . 3 average adhesion in psi ( lbs per sq . inch ) . sup . 4 invented compositions it is anticipated that just about any substrate comprised entirely or in part of protein will be adhered to better by pretreatment of the substrate surface with the compositions of this invention . the preceding disclosure has demonstrated the improved adhesion of a free - radical initiated composition to keratin substrates treated with mahema and other cyclic anhydride addition reaction products as previously described . it is believed that substrates such as fingernails , hooves , bone , ivory , leather , dentin , enamel , and other partially or wholly proteinaceous materials will show the adhesion - promoted benefits of the present inventive compositions .
an invented composition for promoting the adhesion of adhesives , coatings and / or composites to proteinsceous substrates is disclosed comprising a water - miscible solvent ; and an unsaturated caboxylic acid of the general formula : ## str1 ## where r 1 is selected from ch ═ ch , c ═ c , c ═ ch , ch 2 ch 2 , or ch 2 ch 2 ch 2 ; and r 2 is selected from a terminally mono -, di -, tri -, or multi - unsaturated group . methods of making the compound and methods of its use are also disclosed .