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AN F V O N (M Ny // | VN 5C N I Ya 5 Loool \ - H F N O V\ | // T VV I M 5OO W - 1 July 16, 1968 G. H. POTTER ETA 3,393,174 HOT MELT ADHESIVE COMPOSITION Filed Sept. 17, 1965 LAP SHEAR AND PEEL STRENGTH WS. PER CENT MgO INETHYLENE/WINYLACETATE (72.28) - -T M 2OOOH- |- - / N 2O O tap SAAAA S7APAWG7A/ I A. AEA/ 57 AAWG7A/ 5OO |- H ea | 5 / | V AN f V o N (m Ny // | VN 5C N I Ya 5 loool \ - H f N O V\ | // t VV I M 5OO w - 1. - - |- 5 -----1 : \/ O O 2O 3O 4O so 68 % BY WT. MgO NVENTORS GEOAPGA. A1 AO77 Ap CA1ADA M/A/7M/OAP7Ay VA By6.waufMA7HAW L. ZV77 ATTORNEY 3,393,174 United States Patent Office Patented July 16, 1968 1. 2 3,393,74 The a-olefin content of the olefin polymers is at least HOT MELT ADHESIVE COMPOSITION 60% of the total copolymer. Where vinyl esters are utilized George H. Potter, St. Albans, and Clyde J. Whitworth, as comonomers with a-olefins they constitute at least Jr., Charleston, W. Va., and Nathan L. Zutty, West 10% by weight of the total copolymer and preferably field, N.J., assignors to Union Carbide Corporation, a about 18% to 40% by weight. Where acrylic acids or corporation of New York alkyl esters are utilized as the comonomers with ox-olefins Filed Sept. 17, 1965, Ser. No. 488,086 they are preferably present in an amount constituting at 8 Claims. (CI. 260-41) least about 5% by weight and preferably about 10% to 30% by weight of the total copolymer. ABSTRACT OF THE DISCLOSURE 10 Among the fillers that are useful in these hot melt The lap shear and peel strengths of the vinyl polymers, adhesive compositions can be mentioned zinc oxide, such as, polyvinyl acetate, ethylene/vinyl acetate copoly barium oxide, magnesium oxide, calcium oxide, lead mers, ethylene/acrylic acid copolymers and ethylene/ethyl Oxide (PbO4), ferric oxide, carbon black, hydrated silica, acrylate copolymers were enhanced by blending these hydrated magnesium aluminum silicate and the like. It vinyl polymers with 30 to 50% by weight of iron oxide 15 is preferred to use oxides in these adhesive compositions or oxides of elements of Group II-A of the Deming and of these magnesium oxide, MgO, and ferric oxide, Periodic Table. The resultant compositions can be used Fe2O3, are particularly preferred in an amount con stituting between about 30 and 50% by weight of the for bead-sealing, metal joining, laminating and the like. total composition. 20 Any conventional mixing equipment such as Banbury This invention relates to hot melt adhesive compositions mixers or 2 roll mills can serve to blend the vinyl poly comprising a vinyl polymer and an oxide filler. mer and fillers to the desired composition. For this oper Various vinyl polymers exhibit satisfactory adhesive ation temperature and pressure are not critical although properties but suffer in competition with glues and other Standard temperature and pressure are preferred for con natural adhesives because of their higher cost. Attempts venience. to lower the cost of vinyl polymer adhesives by addition All commercially available metals commonly used for of cheaper fillers usually results in sacrifice of the original laminating can be bonded with the hot melt adhesive com adhesive strength as demonstrated by lower lap shear and positions of this invention. Aluminum and steel are pre peel strengths. ferred metals because of the frequency of their use in the It has now been unexpectedly discovered that hot melt 30 fabrication of laminates although other metals such as adhesive compositions comprising vinyl polymers, such brass, copper, tin, lead, zinc and the like are also amen as olefin polymers or polyvinyl esters and from about 30 able to bonding with these adhesive compositions. The to about 50 percent by weight of oxides of iron or mem bonded Substrate need not be metallic but may instead be bers of Group II-A of the Deming Periodic Table, have thermoplastic polymers as for example, polyethylene, higher lap shear and peel strengths than compositions con 35 polypropylene, polymethyl methacrylate, or thermoset taining only the olefin polymers or polyvinyl esters with polymers Such as epoxy resins, polyurethanes, phenol out an oxide filler. aldehyde condensation products, melamine resins and the This observation is quite unexpected from the teachings like. of the prior art and would not be apparent to a researcher The invention is further described by the examples skilled in the art conducting methodical screening tests of 40 which follow in which all parts and percentages are by fillers because as shown in the figure, where the effect on weight unless otherwise specified. lap shear and peel strength of an ethylene/vinyl acetate (72:28) copolymer is plotted against weight percent of EXAMPLES 1-5 MgO in the adhesive composition, additions of up to An ethylene/vinyl acetate (72/28) copolymer was about 20% of MgO cause a progressive drop in both of 45 blended in five examples with 10, 20, 30, 50 and 60 parts these physical properties. But surprisingly, at about 30% respectively, of magnesium oxide, MgO. Steel specimen of MgO this trend is reversed and these properties are pairs 1' x 6' x 0.26' were then bonded at 180° C. and enhanced over the values of the unfilled polymer. It was 500 p.s.i.g. with these ethylene/vinyl acetate copolymers then further discovered that although the lap shear and MgO blends and their lap shear and peel strengths meas peel strengths increase upon further additions of MgO 50 ured. These data are presented in Table I together with beyond this 30% level, there is a maximum reached be that of a Control consisting of steel specimens bonded yond which these physical properties again begin to de with unfilled ethylene/vinyl acetate copolymer, that is, crease. For practical purposes an upper limit of about containing no MgO. A continuous plot of these data, 50% of MgO is set at which point a cheaper hot melt percent MgO vs. lap shear and peel strength, indicates a adhesive composition is afforded with satisfactory physical useful range from about 30-50% and an optimum filler properties. content between 35 and 45%. The olefin polymers used in this invention are copoly A description of the tests for lap shear and peel strength mers of an ox-olefin with a vinyl comonomer. The preferred follows. vinyl comonomers are vinyl esters such as vinyl acetate, (I) Lap shear strength vinyl propionate and the like and acrylic acids or alkyl 60 (a) Preparation of samples.-A portion of either a esters such as acrylic acid, CH2=CHCO2H, methacrylic pressed polished or milled plastic sheet was placed between acid, one inch precleaned steel (cross-sectional area=0.026 Sq. in.) or aluminum (cross-sectional area=0.044 sq. in.) CII--C OH paint panels which in turn were placed between two CH3 65 chrome plates. The chrome plates were shimmed so as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl to give uniform coatings of plastic on the metal. These methacrylate and the like. plates were then placed in a press and allowed to come The preferred ca-olefin is ethylene although others such to the desired temperature. The desired pressure was then as propylene and butene-1 and the like can also be used if applied for 1 min. followed by cooling. desired. Homopolymers of the vinyl esters referred to 70 (b) Measurement.- The values for lap shear were above can also be employed as the vinyl polymer of the measured by determining, on an Instron, the force re instant hot melt adhesive compositions. quired to break the bond. The rate of extension was 10 3,393,174 3 4 percent per minute. The force divided by the area of the EXAMPLES 6-13 bond gives the lap shear in pounds per square inch. The effect of varying bond pressures on bonding steel (II) Peal strength panels 1’ x 6' x 0.026' at 150° C. with ethylene/vinyl (a) Preparation of samples-A strip of either a pressed acetate (72:28) copolymer and vinyl acetate homopoly or milled sheet of plastic was placed on a 1 x 5 inch strip 5 mer filled with a series of fillers was evaluated by meas of precleaned steel or aluminum and placed between Tef uring their relative lap shear strengths at 23° C. The fol lon coated glass. This in turn was placed between shimmed lowing controls were also included in this evaluation: plates and placed in a press. The desired pressure was Control. 2, unfilled ethylene/vinyl acetate (72:28) co applied for one minute after the temperature had reached polymer; Control 3, unfilled vinyl acetate homopolymer, the desired level. O and Control 4, unfilled ethylene/vinyl acetate (82:18) co (b) Measurement.-The peel strength was measured polymer. The data obtained are presented in Table II. TABLE II.-STEEL, LAP SEEAR STRENGTH OF FILLED WINYLACETATE POLYMERS Lap Shear, p.s. i. 23. C., Bond Example No. Resin Filler, percent Preparation Pressure 150° C. 80 p.S.i.g. 500 p.s.i.g. 1,000 p.s.i.g. ZnO (50)---- 533 490 625 Fe2O3 (50) 940 900 820 BaO (50).--- 640 590 585 Eas 86 SO 1,070 900 (EEi-Si 233 9984 ( } 50 730 80 MgO (50).----- 1,140 1,280 1,070 Pb3O4 (50)---- 65 345 445 Hi-Sil 233 (50)------------------------------------ 1,030 --------------- Carbon black (30) - - - - - - - - - - - - - - - - - - - - - - - 144 --------------- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - { 6498605 } 505 --------------- 14a-------------------- B Hi-Sil283 (40)------------------------------------- 90 } - - - - - - - - a re & 8250 14b------------------- B MgO (10)----------------------------------------- 1,380 --------------- Control 3------------- B ---------------------------------------------------- 57,310 1,220 } - - - - - - - - - - - - Control 4------------- C ---------------------------------------------------- 750 --------------- 1 All measurements for a one-inch overlap unless otherwise designated.
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