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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. 2 Trademark of a hydrated magne sium aluminum silicate. 3 Trademark of a hydrated silica (87%. SiO2, 0.5% CaO, 0.2% Fe2O3, 0.6% AsO3; 1% NaCl). 4 Trademark of dibenzoate esters of glycols in parts per hundred of resin. 5% inch overlap. 680A=Ethylenefvinyl C. 7 120° C. acetate (72:28) copolymer; B=Polyvinyl acetate; C=Ethylene/vinyl acetate (82:18) copolymer. at 180° bend by use of a Hunter spring gage which reads 35 EXAMPLES 15-36 in pounds. The values obtained are an average of at least six measurements on the same sample and are reported The effects of varying amounts of MgO and FeO3 as in lbs. per inch of sample width. fillers in ethylene/vinyl acetate (72:28) copolymer bonded TABLE I-LAP S.HEAR AND PEEL STRENGTH OF MgO 2024-T3 aluminum panels 1' x 6' x 0.044' were measured FILLED ETHYLENEIVINYL ACETATE (72:28). COPOLY MER ON STEEL 40 in terms of lap shear and peel strength, as shown in Table Example No. Percent MgO Lap Shear Peel Strength, III. Steel panels 1' x 6' x 0.026' were also bonded with Strength, p.S.i. lbs./in. ethylene/vinyl acetate (72:28) copolymer filled with vary Controll------O i 498 146.1 0 1440 2 11.2 ing amounts of Attagel 30 (trademark for a hydrated 20 405 3.0 45 magnesium aluminum silicate) and Hi-Sil 233 (trademark 30 650 3.1 50 31,870 11.4 for a hydrated silica). Comparative data for these exam 60 31,340 10.4 ples are also contained in Table III. 11' overlap. 2150° C. 36" overlap. TABLE III.-LAP SEIEAR AND PEEL STRENGTH OF FILLED ETHYLENEIVINYL ACETATE (72:28). COPOLYMER Peel Strength Lap Shear, p.s. i. 23° C.I. Lbs.I In. of Width Example No. Metal Filler, Percent --m- Bond Preparation Temperature 500 p.s.i.g., C. 120° C. 50° C. 180° C. 150° C. 180° C. 15.------Steel------Fe2O3 (10)------Fe2O3 (20) Fe2O3 (30) Fe2O3 (50)

Fe2O3 (20)--- - Fe2O3 (30).--- Fe2O3 (50)-- Fe2O3 (60)-- Attage 30 (10). Attage 30 (30)-

---- i-Sil 233 (20)-- ---. Hi-Sil 233 (30) 36------do------Bi-Sil 233 (50).------21,030 21,030 1 All measurements are for a one-inch overlap unless otherwise designated. 2% inch overlap. a Pressure used for bond preparation was 80 p.s.i.g 3,393,174 5 6 EXAMPLES 37-50 The hot melt adhesive compositions of this invention The effects of MgO and Fe2O3 as fillers in the bonding are particularly useful for the preparation of metal to of steel and aluminum panels 1’ x 6' x 0.044' with metal or metal to olefin polymer laminates, bead-sealing, ethylene/vinyl acetate, ethylene/acrylic acid and ethyl metal joining and the like. ene/ethyl acrylate copolymers were also evaluated by lap Although the invention has been described in its pre shear strength measurements at 23° C. and 50 C. and ferred forms with a certain degree of particularity, it is peel strength measurements at room temperature. The understood that the present disclosure has been made only data obtained are shown in Table IV. by Way of example, and that numerous changes can be TABLE IV.-LAP S.HEAR AND PEEL STRENGTHIS OF FILLED ETHYLENE-ACRYLIC COPOLYMERS Lap Shear, p.S.i.1 Example Metal Resin Filler, 23°C., Bond Prepara- Peel Strength, No. (Percent) tion Pressure 180° C. lbs.iln. of 50° C., Width 80 P.S.i.g. 500 P.S.i.g. 500 P.s.i.g. Control 7- E ---- 2, 650 21,340 216.7 Control 8 E ---- 21,860 21,240 226.3 D Fe2O3 (50)-- 1,500 390 22.4 D Fe2O3 ------s 25.2 E MgO (30) ------72 E MgO (40)------05 E Fe2O3 (30). 29.8 E. Fe2O3 (40).---- 2.5 F MgO (30).------8,3 F MgO (40)------16.6 F Fe2O3 (30) 320 3. F Fe2O3 (40). 380 6.9 E MgO (30).------860 500 .7 E MgO (40)-- 140 ... 2 E Fe2O3 (30) 1,630 15.2 E Fe2O3 (40). 1,900 Stuck

1 -3-inch lap. 2 50° C. (Bond preparation temperatures). 3 Albroke. 4 The Imaterial could not be peeled off without breaking. Peel strength would be >30 lbs.fin. of width. D=An ethylene-vinyl acetate copolymer containing 28 wit. percent vinyl acetate. E=Ethylene-acrylic acid copolymer containing 13 wt. percent acrylic acid. F=Ethylene-ethyl acrylate copolymer containing 13 wt. percent ethyl acrylate. EXAMPLES 51-52 made without departing from the spirit and scope of the

s invention. The peel strength of ethylene/vinyl acetate (72:28) s We claim: compositions containing 50% by weight of Fe2O3 or MgO 1. Hot melt adhesive composition comprising: bonded to low density polyethylene was also measured (a) vinyl polymers selected from the group consisting and compared with Control 8 containing no filler. These of polyvinyl acetate, ethylene/vinyl acetate copoly data are presented in Table V. mer, ethylene/acrylic acid copolymer, and ethylene/ TABLE v.-PEEL STRENGTH OF FILLED COPOLYMER 40 alkyl acrylate copolymer; and COMPOSITIONS ON POLYETHYLENE 1 (b) from about 30 to 50% by weight of magnesium Filler Wt., Peel Strength, Example Copolymer percent lbs.finch oxide. of Widt 2. The composition claimed in claim 1 wherein the Control 8------(2) 6. 45 vinyl polymer is polyvinyl acetate. 50----- (2) 15.0 3. The composition claimed in claim 1 wherein the 51------(2) 50% MgO---- 2.2 vinyl polymer is an ethylene/vinyl acetate copolymer. i Bond prepared at 180 C. and 500 p.s.i.g. 2 Copolymer of ethylene and vinyl acetate containing 28 wit, percent 4. The composition claimed in claim 1 wherein the vinyl acetate. vinyl polymer is an ethylene/acrylic acid copolymer. 5. The composition claimed in claim 1 wherein the EXAMPLES 53-54 50 vinyl polymer is an ethylene/alkyl acrylate copolymer. The lap shear strengths of 2024-T3 aluminum panels 6. Laminate consisting essentially of metal substrates bonded with a low density polyethylene layer sandwiched bonded with the composition claimed in claim 1. in between by means of ethylene/vinyl acetate (72:28) 7. Laminate claimed in claim 6 wherein the metal is copolymer containing 50 weight percent of MgO or FeO3 55 steel. were measured. These data and Controls containing no 8. Laminate claimed in claim 6 wherein the metal is filler are presented in Table VI. aluminum. References Cited TABLE W-LAP S.HEAR STRENGTH OF ALUMNUM BONDEED WITH LOW DENSITY POLYETYLENE UNITED STATES PATENTS SANDWICHED BETWEEN FILLED COPOLYMER 60 COMPOSITIONS 2,388,169 8/1945 McAlevy et al. 260-41 Example No. Copolymer Filler Wt., Lap Shear Strength, 2,628,214 2/1953 Pinkney et al. ------260-41. percent lbs./sq.inch 3,310,522 3/1967 Takahash et al. ------260-41. Control 9 (2) 775 52. (2) 1,300 65 OTHER REFERENCES 53- (2) 1,330 Skeist, Handbook of Adhesives, Reinhold Publishing Control O- (3) 2,100 Corp., New York, 1964, page 484 relied on. Bond prepared at 180 C. and 500 p.s.i.g. 2 Copolymer of ethylene and vinyl acetate containing 28 wt. percent vinyl acetate. MORRISLIEBMAN, Primary Examiner. 3 Copolymer of ethylene and acrylic acid containing 13 wt. percent acrylic acid. S. L. FOX, Assistant Examiner.