Brief Summary Of The Invention Technical Field

This invention relates to adhesives used in bonding laminates. In particular, aqueous dispersions of poly(vinyl alcohol) and certain poly(vinyl and/or vinylidene chloride) copolymers are especially suitable as adhesives for low energy, hard-to-adhere surfaces like plasticized poly(vinyl chloride) .

Background of the Invention

Aqueous polymer dispersions, i.e. latexes, made from vinyl monomers have been used as binders in various areas, such as in adhesives, pastes, paints and coatings. When used in adhesives for low energy, hard-to-adhere surfaces, such as plasticized poly(vinyl chloride), other specific polymeric substrates, glass and metal foil, the results obtained are often unsatisfactory. Among the low energy, hard-to-adhere substrates, plasticized poly(vinyl chloride) is particularly challenging. Flexible poly(vinyl chloride) films are used in a wide variety of industrial applications such as decorative wall paneling, furniture veneers, luggages and various laminates with different substrates. Large amounts of plasticizers are normally used to make poly(vinyl chloride) films flexible. The plasticizers, such as phthalate esters, are generally migratory materials which tend to exude out of the poly(vinyl chloride) and into the adhesive.

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especially with aging. This migration weakens and even destroys the adhesive causing the bond to fail.

Poly(vinyl acetate) homopolymer dispersions are often used as adhesives due to their rapid speed of set, polymer strength and the ability to adhere to hard-to-adhere surfaces. However, poly(vinyl acetate) is a hard polymer at ambient temperatures. The hardness of the polymer generally reduces the bond strength. Addition of plasticizer to the polymer is required to obtain good adhesion to these difficult surfaces. The plasticizers used in poly(vinyl acetate) have a tendency to migrate to the interface, thus weakening the adhesive bond and causing the bond to fail on aging.

To overcome the problems of the rigidity of poly(vinyl acetate) and weakening of the adhesive bond due to the plasticizer migration, copolymers of vinyl acetate with soft monomers such as acrylic esters, maleate and fumarate esters have been developed. The comonomers used in these polymer emulsions introduce pendant ester side groups into the polymer chain which increases the flexibility of the polymers by allowing intramolecular and intermolecular mobility. These copolymers are described as "internally" plasticized poly(vinyl acetate) . The soft comonomers which function as internal plasticizers are bound to the polymer chain and not subject to migration and its drawbacks. These permanently plasticized copolymers generally show greater adhesion to plastic surfaces than the homopolymers. This is probably related to the ability of the softer copolymers to deform and to wet

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the nonporous surface of a plastic film. However, in a lot of applications, plasticizer is used as one of the ingredients in the adhesive formulation. The adhesive bond of these copolymers weakens when in contact with plasticizer. For example, in addition to aqueous polymer dispersions, an adhesive formulation often contains other ingredients such as plasticizers, solvents, tackifiers, fillers and additives for specific end-use application properties. The plasticizer used in the adhesive formulation has a tendency to further soften poly(vinyl acetate) copolymers and to weaken the adhesive bond. Moreover, when these copolymer adhesives come into contact with plasticized poly(vinyl chloride) , the plasticizer in poly(vinyl chloride) has a tendency to migrate into the adhesive layer on aging and cause loss of adhesion.

The development of vinyl acetate-ethylene copolymers further improved the adhesive properties of the above-mentioned conventional poly(vinyl acetate) copolymers on low energy, hard-to-adhere surfaces. Ethylene functions as an efficient internal plasticizer as do other soft comonomers. The vinyl acetate-ethylene copolymers generally exhibit better adhesive strength than conventional poly(vinyl acetate) copolymers, presumably due to better polar interactions between vinyl acetate-ethylene copolymers and the low surface energy, hard-to-adhere substrates. Furthermore, addition of a reasonable amount of an external plasticizer into these latexes will not affect the peel strength of the laminate. When vinyl

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acetate-ethylene copolymers are used to laminate plasticized poly(vinyl chloride) with other substrates, the adhesion of the laminates does not change much on aging. Aqueous polymer dispersions of vinyl acetate-ethylene copolymers, such as AIRFLEX® 400 from Air Products and Chemicals, Inc., have replaced conventional poly(vinyl acetate) copolymers and are touted as the workhorse adhesive emulsions for laminating low surface energy and hard-to-adhere substrates. See I. Skeist, Ed., "Handbook of Adhesives", Second Edition, Van Nostrand Reinhold Company, New York, 1977, pages 484-494. These products are described in U.S. Patent No. 3,708,388 pertaining to the batch preparation and utilities of such vinyl acetate-ethylene copolymer emulsions. A continuous method of preparing vinyl acetate-ethylene copolymer emulsions is described in U.S. Patent No. 4,164,489. A higher solids version of vinyl acetate-ethylene copolymer emulsions is described in European Patent Application Publication No. 279,384.

Production of aqueous polymer dispersions of vinyl acetate-ethylene copolymers is limited in several ways. For example, ethylene is a gas at normal temperatures and pressures which requires cryogenic tank storage. The transfer of ethylene to the reactor normally requires a compressor and care must be taken to avoid critical conditions of high pressure and low temperatures, such as 9°C easily reached in winter, producing solid co-existing with gas at the critical zone which can damage the transferring equipment. Furthermore, ethylene will not co-react with vinyl acetate in emulsion

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polymerization except under high pressures. The reaction vessel must therefore have a considerable wall thickness to withstand the high operating pressure. Consequently, heat removal using jacket cooling of the reactor is much less efficient because of the substantial wall thickness. An expensive external circulating heat exchanger designed for full reactor pressure for maximum heat transfer is generally needed. Additionally, circulating pumps, seals, valves and piping should also withstand high pressure. Thus, a substantially higher capital investment is needed for such reactor systems. The operating and maintenance costs for such high pressure reactors are also considerably higher.

Copolymers of vinyl chloride and other monomers have been used in adhesives or other areas. For example, U.S. Patent No. 4,189,415 (Eck et al.) describes aqueous vinyl chloride/vinyl acetate/ethylene copolymer dispersions containing poly(vinyl alcohol) as protective colloid in certain adhesive applications. Also, European Patent Application Publication No. 0,206,295 (Iacoviello) describes ρoly(vinyl alcohol) stabilized, vinyl chloride/ethylene copolymer emulsions useful in coatings. These ethylene-based copolymers have production limitations similar to the vinyl acetate/ethylene copolymers noted previously in needing high operational pressures and high capital investment.

There is, however, a need for aqueous polymer dispersions which are easy to make and are effective adhesives for hard-to-adhere surfaces.

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Disclosure of the Invention

This invention pertains to adhesives, processes for laminating materials and laminates made with such adhesives. The adhesive composition comprises an aqueous dispersion containing water, poly(vinyl alcohol) and an effective adhering amount of a poly(vinyl and/or vinylidene chloride) copolymer. The copolymer consists essentially of repeating units made from: (a) about 5 to about 70 weight percent vinyl or vinylidene chloride; (b) about 30 to about 95 weight percent one or more ethylenically unsaturated carboxylate; and (c) up to about 5 weight percent other ethylenically unsaturated monomer. The laminate is made by applying the adhesive composition to the surface of one or more layer and/or substrate materials to be laminated together and then laminating the materials together.

Detailed Description It has been discovered that poly(vinyl alcohol) stabilized, poly(vinyl and/or vinylidene chloride) copolymer dispersions are excellent adhesives for a variety of substrates, including low surface energy and hard-to-adhere substrates such as glass, plywood, metal foils and plasticized poly(vinyl chloride) films. These adhesives exhibit excellent freeze-thaw stability, mechanical stability, fast speed of set, good open time and better wetting characteristics on various substrates. These adhesives also have good tolerance to compounding ingredients such as solvents and

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plasticizers in the adhesive formulation. The adhesive strength is generally maintained or enhanced with the addition of plasticizers. When these adhesives are used to adhere plasticized ρoly(vinyl chloride) to different materials, they develop unusually high adhesion at early stages of adhesion. Strong adhesion is maintained even after aging. Additionally, these adhesives can be prepared under relatively mild conditions and low pressure. The operating pressure during the reaction is only about one-tenth of that for vinyl acetate and ethylene polymerizations. Thus, the capital investment on the manufacturing equipment as well as operating and maintenance costs are significantly lower than that of vinyl acetate-ethylene copolymer dispersions.

Aqueous dispersions useful as adhesives for this invention are generally made by polymerizing vinyl chloride, i.e. chloroethylene, or vinylidene chloride, i.e. 1,1-dichloroethylene, or both, with one or more other monomers, i.e. comonomers. Vinyl chloride is preferred. The kind of comonomer(s) copolymerized with the vinyl and/or vinylidene chloride monomer(s) is not narrowly critical but may be selected from any suitable ethylenically unsaturated carboxylate and, optionally, other addition monomers. Typical ethylenically unsaturated carboxylate comonomers include, but are not limited to, one or more of the following: vinyl carboxylates such as one or more vinyl acetate, vinyl propionat^, vinyl formate, vinyl n-butyrate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl pivalate, vinyl 2-ethyl-hexanoate, and the like; acrylates, maleates

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and fumarates such as one or more n-butyl acrylate, isobutyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, oleyl acrylate, dodecyl acrylate, stearyl acrylate, di-2-ethylhexyl maleate, di-2-ethylhexyl fumarate, dimethyl maleate, dimethyl fumarate, di-n-butyl maleate, di-n-butyl fumarate, diethyl maleate, diethyl fumarate and the like. Other addition monomers typically include, but are not limited to, one or more acrylic acid, methacrylic acid, sodium vinyl sulfonate, acrylamide, methacrylamide, sodium 2-acrylamido-2-methyl-propane sulfonate (AMPS®), diacetoneacrylamide, N-methylolacrylamide, N-methylolmethacrylarnide, maleic acid, fumaric acid, itaconic acid, crotonic acid, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, diallyl maleate, divinyl adipate, vinyl crotonate, pentaerythritol triacrylate, diallyl adipate, triallyl cyanurate, triallyl isocyanurate, hydroxyethyl acrylate, hydroxypropyl acrylate and the like. Preferred ethylenically unsaturated carboxylates include vinyl acetate, n-butyl acrylate, acrylic acid and other preferred comonomers include triallyl cyanurate, vinyl crotonate and N-methylolacrylamide.

The relative amount of vinyl and/or vinylidene chloride, ethylenically unsaturated carboxylates and other comonomer used is not narrowly critical. Generally, the amount of vinyl and/or vinylidene chloride ranges from about 5 to about 70, preferably from about 5 to 50, and most preferably from about 10 to about 35 weight percent, based on the weight of all monomers. Generally, the amount of

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ethylenically unsaturated carboxylate ranges from about 5 to about 95, preferably from about 50 to 95, and most preferably from about 65 to about 90 weight percent. When using more than one ethylenically unsaturated carboxylate, the amount of comonomer used can vary depending upon the kind of comonomer. For example, vinyl carboxylate when used generally ranges from about 10 to about 70, preferably from about 20 to about 50 weight percent. The amount of acrylic, maleate and fumarate ester comonomer, when used, generally ranges from about 10 to about 70, preferably from about 20 to about 60 weight percent. The amount of any other comonomer used is generally up to about 5, preferably less than about 5, and most preferably less than about 1 weight percent.

Any suitable method of polymerization, such as emulsion, may be used. The procedure may be semi-batch, staged adiabatic, full batch, continuous or any other suitable procedure. Any suitable polymerization conditions may be used. Generally, temperature may range from about 0° to about 100° and preferably from about 40° to about 90°C, while pressure may range from about 1 to about 10 and preferably from about 3 to about 8 atmospheres.

The polymerization may, and preferably is, conducted using polymerization initiators. Suitable polymerization initiators include, but are not limited to: water-soluble peroxides capable of generating free radicals such as ammonium persulfate, sodium persulfate, potassium persulfate, hydrogen peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, peracetic acid, perbenzoic acid, diacetyl peroxide.

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t-butyl peracetate, t-butyl perbenzoate, and the like, and azo initiators, such as 2,2'-azobisisobutyronitrile, and the like. The amount of such free radical initiators used generally ranges from about 0.05 to about 6 weight percent, based on the weight of monomers. Alternatively, redox initiators may be used, especially when polymerization is carried out at lower temperatures. For example, reducing agents may be used in addition to the peroxide initiators mentioned above. Typical reducing agents include, but are not limited to: alkali metal salts of hydrosulfites, sulfoxylates, thiosulfates, sulfites, bisulfites, reducing sugar such as glucose, sorbose, ascorbic acid, erythorbic acid, and the like. In general, the reducing agents are used at levels from about 0.01 to about 6 weight percent, based on the weight of monomers.

The polymerization is conducted in the presence of stabilizer, i.e. protective colloid, for aqueous polymer dispersions. Although poly(vinyl alcohol) is generally preferred, any suitable stabilizer or protective colloid may be used, such as poly(vinyl alcohol)s named ELVANOL® by E.I. DuPont de Nemours & Company, Inc. The stabilizer imparts aqueous polymer dispersions with desirable adhesive properties such as wet tack and fast setting speed. Poly(vinyl alcohol)s which are suitable for use in this invention are generally partially hydrolyzed from about 70 to about 90, and preferably from about 84 to about 89, mole percent; and have a degree of polymerization ranging from about 100 to about 4000. Fully hydrolyzed poly(vinyl alcohol)s can also be

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used. Stabilizers can be added to the aqueous polymer dispersions after polymerization, however, it is preferable to add the stabilizer during the polymerization for better polymer dispersion stability.

Various additives can be added before, during or after polymerization. These include surfactants, buffer, neutralizing agents, defoamers, chain-transfer agents, and plasticizers. Suitable surfactants which may be used include one or more: alkyl and/or aryl sulfates, sulfonates, or carboxylates such as sodium lauryl sulfate, sodium salt of alkylaryl polyether sulfates and the like; oxyalkylated fatty amines, fatty acid amides and/or monoalkylphenols such as oxyethylated lauryl alcohol, oxyethylated oleyl alcohol, oxyethylated stearyl alcohol, oxyethylated stearamide, oxyethylated oleylamide, oxyethylated p-iso-octylphenol, oxyethylated p-n-nonylphenol, oxyethylated p-n-dodecylphenol, and the like. Preferred surfactants include 15 mole ethoxylate of nonylphenol, such as TERGITOL® NP-15 from Union Carbide Chemicals and Plastics Company Inc., and sodium dodecyl diphenyloxide, such as DOWFAX® 2A1 from Dow Chemical Company. The amount of surfactant may range from 0 to about 15 weight percent and preferably from about 0.5 to about 8 weight percent, based on the weight of the monomers.

The adhesives of this invention are compatible with plasticizers. In most cases, adhesion on the low energy, hard-to-adhere surfaces is enhanced upon addition of plasticizers. Typical

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plasticizers include one or more: butoxyethoxyethyl acetate; acetyl ricinoleic acid butyl ester; diesters of oxalic acid, succinic acid, adipic acid, phthalic acid with aliphatic, branched or unbranched alkanols such as oxalic acid, dibutyl ester, succinic acid dibutyl ester, diisobutyl phthalate, dioctyl phthalate, diisotridecyl phthalate; dipropylene glycol dibenzoate; diethylene glycol dibenzoate; ethylene glycol; propylene glycol; hexamethylene glycol; diphenyl phosphate; triphenyl phosphate; tricresyl phosphate; cresyl diphenyl phosphate; and the like. Preferred plasticizers include dipropylene glycol dibenzoate, such as BENZOFLEX® 9-88 from Velsicol Chemical Corporation. The plasticizers can be added to the adhesive before, during or after the polymerization. The amount of plasticizers used is generally from 0 to less than about 40 weight percent and preferably from 0 to less than about 30 weight percent, based on the weight of total adhesive composition.

A typical emulsion polymerization recipe for making the adhesive composition contains water, monomers, free radical initiator, protective colloid, emulsifier, buffer, other specialty agents such as neutralizing agent and defoamer, and any other suitable materials. Water is typically present in an amount sufficient to provide the adhesive composition with a solids content of from about 40 to about 70, preferably from about 50 to about 65, weight percent.

The adhesive composition consists essentially of water, poly(vinyl alcohol) and an effective adhering amount of the poly(vinyl and/or

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vinylidene chloride) copolymer. An effective adhering amount of poly(vinyl and/or vinylidene chloride) copolymer is an amount of copolymer sufficient to adhere one or more layer and/or substrate materials together. Generally, the amount of copolymer is not narrowly critical but may range from about 5 to about 70, preferably from about 10 to about 65, and most preferably from about 40 to about 60, weight percent, based on the total weight of the adhesive composition. The amount of stabilizer, e.g. poly(vinyl alcohol), is also not narrowly critical and may range from about 0.1 to about 15, preferably from about 0.5 to about 10, and most preferably from about 1 to about 7 weight percent, based on the weight of all monomers. The adhesive composition may contain other suitable ingredients, such as other than those used in polymerization, selected from ingredients known in the art, such as listed in the Handbook of Adhesive Raw Materials, by Ernest W. Flick, published by Noyes, second edition (1989), which is incorporated herein by reference. Other ingredients may be provided in any suitable amounts. The materials to which the adhesive can be applied are one or more suitable layer and/or substrate materials, including but not limited to: wood and wood products such as plywood, board wood, kraft paper, and masonite; textiles such as cloth, canvas, and synthetic fibers; metals, such as aluminum and steel; glass; leather; and plastics such as poly(vinyl chloride), polyester, polystyrene, polyethylene, polypropylene, poly(methyl methacrylate) , and so on. One or more of the

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materials may be made of low or high surface energy and hard-to-adhere substance. Such materials include plasticized poly(vinyl chloride), glass, metal foil and the like. Preferably, at least one of the materials to be adhered is a low energy, hard-to-adhere substance, especially plasticized poly(vinyl chloride) or similarly hard-to-adhere materials. Low energy, hard-to-adhere substances are those which are generally more difficult to adhere than average materials and generally have a surface energy of less than about 40 millijoules per square meter, mJ/M ² .

The way in which the adhesive is applied to the layer and/or substrate material is not critical and includes any suitable procedure, such as those known in the art.

It is observed that the poly(vinyl and/or vinylidene) chloride copolymers develop unusually high initial adhesion when used as the adhesives for low energy, hard-to-adhere surfaces, especially for plasticized poly(vinyl chloride) . This high initial adhesion may be due to stronger physico-chemical attractions between the adhesives and adherends. In other words, these copolymers may have better compatibility with the low energy and the hard-to-adhere surfaces.

The following examples present illustrative embodiments of this invention and are not intended to limit its scope. All of the parts, percentages and proportions referred to herein, including the claims, are by weight unless otherwise indicated.

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Example 1 This example shows the preparation of an aqueous polymer dispersion, i.e. latex, as the adhesive for plasticized PVC with various substrates. The relative amounts of ingredients used are given in Table I. A steel reaction kettle was equipped with a pressure gauge, an agitator, a thermocouple, nitrogen inlet, water jacket, and suitable addition ports. The kettle was charged, in amounts given under step A in Table I, with deionized water and ELVANOL® 50-42 which was fully dissolved into the water. TERGITOL® NP-15, DOWFAX® 2A1, sodium acetate, NALCO® 2343 (defoamer), potassium persulfate, vinyl acetate, vinyl chloride, n-butyl acrylate, and acrylic acid, in amounts given under step A in Table I, were charged to the kettle. The kettle was purged with nitrogen and heated to 67°C. with continued agitation. Vinyl acetate, vinyl chloride, butyl acrylate, acrylic acid, and NALCO® 2343, in amounts given under step B in Table I, were added to the reaction kettle over a 4-hour period. The temperature of the kettle was raised and maintained at 75°C. The pressure of the kettle was monitored to ensure that it was below 100 psig. Thirty minutes later, potassium persulfate in deionized water, in amounts given under step B in Table I, was added to the kettle over a 3.5-hour period. The temperature of the kettle was maintained at 75°C. for 30 minutes more after all additions. Optionally, small amounts of t-butyl hydroperoxide and sodium metabisulfite post catalysts were added to reduce the residual vinyl chloride below 10 ppm. The

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- 16 -

latex was then cooled to room temperature. The latex produced had a 54.9 weight percent solid content, and a 3700 cps viscosity (Brookfield Model LVT, No. 4 Spindle, 60 rpm at 25°C).

The latex was used as the adhesive to laminate poly(vinyl chloride), i.e. PVC, films to plywood, medium density board and masonite substrates. Generally, the latex adhesive was coated on plasticized PVC film from Goodyear Tire & Rubber Company, with a No. 20 Wire-Wound Applicator. The coated PVC films were placed immediately on top of plywood, medium density board or masonite blocks, and a 4.5 pound roller was passed over the film once. The laminates were allowed to air dry overnight or heat aged in an oven at 60°C. for two weeks. The laminates were then checked on an Instron for an 180° angle peel strength on a one-inch strip. The Instron was set on a 10-pound scale with a crosshead speed at 2 inches per minute. The results, reported in pounds per linear inch (pli), are given in Table II. The latex showed good adhesion as the adhesive for plasticized poly(vinyl chloride) to plywood, medium density board and masonite. The adhesion was largely maintained after heat aging.

Example 2 This example shows the preparation of a latex with addition of a plasticizer during polymerization. The equipment and procedure described in Example 1 were used. The kettle was charged, in amounts given under step A in Table I, initially with deionized water, ELVANOL® 52-22,

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ELVANOL® 51-05, BENZOFLEX® 9-88, TERGITOL® NP-15, DOWFAX® 2A1, sodium acetate, NALCO® 2343, potassium persulfate, triallyl cyanurate, vinyl acetate, vinyl chloride, butyl acrylate, and acrylic acid. When the kettle was heated to 67°C, vinyl acetate, vinyl chloride, butyl acrylate, acrylic acid, triallyl cyanurate, and NALCO® 2343, in amounts given under step B in Table I, were added to the reaction kettle over a 4-hour period. The amount of fed potassium persulfate and reaction procedures were the same as described in Example 1. The latex produced had a 56.0 weight percent solids content, and a 2740 cps viscosity (Brookfield Model LVT, No. 4 Spindle, 60 rpm at 25°C.) .

The latex was used to laminate PVC films to plywood, medium density board, and cotton poplin cloth. The general test procedures and conditions described in Example 1 were used except that 0.1 part of AEROSOL® OT-75 was added to the latex, and a No. 40 Wire-Wound Applicator was used to coat latex on PVC Films for laminating cotton poplin cloth. The results, in pounds per linear inch (pli), are given in Table II. The latex showed better adhesion for plasticized PVC films to various substrates tested. The adhesion was largely maintained or even improved after heat aging.

Example 3 This example shows the preparation of a latex with post addition of plasticizer. Its performance as a laminating adhesive was compared with a representative, high performance, commercial

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vinyl acetate-ethylene copolymer, i.e. VAE, named AIRFLEX® 400 from Air Products and Chemicals, Inc. The equipment described in Example 1 was used. The procedure and the levels of ingredients described in Example 2 were used, except that slightly higher amounts of deionized water and sodium acetate were used in the initial charge; and triallyl cyanurate during the feed, as given in Table I. The BENZOFLEX® 9-88 in the initial charge in Example 2 was eliminated. Instead, 5.0 parts of BENZOFLEX® 9-88 was post added to the latex in this example. The latex produced before plasticizer addition had a 53.8 weight percent solids content, and a 1460 cps viscosity (Brookfield Model LVT, No. 4 Spindle, 60 rpm at 25°C.) .

This latex, with 5 parts of BENZOFLEX® 9-88, was used to laminate PVC films to plywood, medium density board, and cotton poplin cloth. The general test procedures and conditions described in Example 2 were used except that no wetting agent was added to latex in this example. The performance of the latex was compared with commercial VAE. The results, reported in pounds per linear inch (pli), are given in Table II. The results indicate that this latex exhibits excellent adhesion as a laminating adhesive for plasticized PVC to adhere to plywood, medium density board and cotton poplin cloth. The excellent adhesion was maintained even after heat aging. In most of the cases, the adhesion was better than the commercial vinyl acetate-ethylene adhesive emulsion. This latex was also coated on a Kraft paper with a No. 20 Wire-Wound Applicator. An aluminum

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foil was immediately placed on the coated Kraft paper, and a 4.5 pound roller was passed over the aluminum foil once. The laminates were separated to examine the strength of adhesion to aluminum foil and failure pattern after the laminates were allowed to dry at various lengths of time. The failure pattern with fiber tear on Kraft paper was considered to have excellent adhesion with aluminum foil. The results, given as follows, indicate that this latex has strong adhesion to aluminum foil.

Aluminum Foil to Kraft Paper Adhesion ³

b - With 5 parts BENZOFLEX® 9-88. c - AIRFLEX® 400 vinyl acetate/ethylene copolymer, with 0.2 part dioctyl sodium sulfosuccinate (AEROSOL® OT-75 from American Cyanamid Company) to wet the aluminum foil.

* - Fiber tearing observed.

Example 4 This example shows the preparation of a latex and its surprising capability of building excellent adhesion at early stages of the drying process. The equipment and procedure described in Example 1 were used. The kettle was charged initially with deionized water, ELVANOL® 52-22, ELVANOL® 51-05, TERGITOL® NP-15, DOWFAX® 2A1, sodium

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acetate, NALCO® 2343, potassium persulfate, triallyl cyanurate, vinyl acetate, vinyl chloride, butyl acrylate, and acrylic acid, in amounts given under step A in Table I. When the kettle was heated to 67°C, vinyl acetate, vinyl chloride, butyl acrylate, acrylic acid, triallyl cyanurate, and NALCO® 2343 were added to the reaction kettle over a 4-hour period, in amounts given under step B in Table I. The amount of fed potassium persulfate and reaction procedures were the same as described in Example 1. The latex produced had a 55.0 weight percent solids content, and a 4140 cps viscosity (Brookfield Model LVT, No. 4 Spindle, 60 rpm at 25°C) .

The latex was used to laminate plasticized PVC films to plywood, medium density board and cotton poplin cloth and the peel adhesion was examined. The general test procedures and conditions described in Example 3 were used. The results, reported in pounds per linear inch (pli), are given in Table II.

The freeze/thaw stability is an important property for aqueous polymer dispersions. The latex lacking freeze/thaw stability will coagulate upon freezing and remain coagulated after thawing. The latexes in this example were frozen for 16 hours at -10°C and thawed at room temperature for 8 hours. The stability of the latexes under this kind of repeated cycles was examined. The VAE latex coagulated in one cycle. The latex of this example passed through five cycles without difficulty.

The results in Table II showed that surprisingly excellent adhesion was obtained at early stages of the drying process for the aqueous polymer

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dispersion in this invention on the low energy and hard-to-adhere surfaces. This exceptionally strong early adhesion exhibited by the aqueous polymer dispersion in this invention implies that the dimensional stability of the laminates made with the adhesives in this invention can be maintained shortly after lamination, thus facilitating handling of the laminates and speeding up their production. The results also indicate that, in general, adhesion increased with the time of aging, and with increasing amounts of plasticizer, post added to the latex in this example. The freeze/thaw stability for this latex was excellent.

Example 5

This example shows the preparation of a latex dispersion with two poly(vinyl alcohols), used at different levels. The adhesion of this latex to a clear, float glass was compared with a commercial vinyl acetate/ethylene copolymer. Equipment as described in Example 1 was used. Procedures and relative amounts of ingredients as described in Example 3 were used, except for the amounts of ELVANOL® 52-22, ELVANOL® 51-05 and deionized water, as shown in step A in Table I.

The resulting latex had a 52.6 weight percent solids content, and a 1360 cps viscosity (Brookfield Model LVT, No. 4 Spindle, 60 rpm at 22°C).

The latex was coated on a cotton poplin cloth with a No. 20 Wire-Wound Applicator. A clear, float glass plate was immediately placed on the coated cloth. This laminate was allowed to dry

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overnight at 22°C. The laminate was then checked on an Instron for a 180° angle peel strength on a one-inch strip. The Instron was set on a 50-pound scale with a crosshead speed at 12 inches per minute. The results, reported in pounds per linear inch (pli), were as follows:

Cloth to Glass Adhesion Latex Adhesion (pli)

Example 5 2.1

Example 5 ^a 2.3

AIRFLEX® 400 0.63

AIRFLEX® 400 ^a 0.56 a - with 6.3 parts BENZOFLEX® 9-88 plasticizer.

The results show that the latex of this example, with or without plasticizer, has excellent adhesion to a clear, float glass plate. The adhesion was much better than that of the commercial VAE latex.

Example 6

This example shows the preparation of a latex with a small amount of vinyl crotonate and N-methylolacrylamide. Its performance as a laminating adhesive was compared with a commercial vinyl acetate-ethylene copolymer, i.e., AIRFLEX® 400. The equipment described in Example 1 was used. Procedures and relative amounts of ingredients as described in Example 3 were used, except that vinyl crotonate was charged under step A in Table I and added under step B in Table I and N-methylolacryl¬ amide was added under step B in Table I.

The latex produced had a 54.0 weight percent solids content, and a 4655 cps viscosity (Brookfield Model LVT, No. 4 Spindle, 60 rpm at 25°C) .

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The latex was used to laminate plasticized PVC films to medium density board and cotton poplin cloth and the peel adhesion was examined. The general test procedures and conditions described in Example 3 were used. The results, reported in pounds per linear inch (pli), are given in Table II.

The results indicate that this latex exhibits excellent adhesion as a laminating adhesive for plasticized PVC to adhere to medium density board and cotton poplin cloth. The adhesion was significantly increased after heat aging. Both initial and aged adhesion were better than the commercial vinyl acetate-ethylene adhesive emulsion.

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Table I: Latex Preparation

Example 1, Example 2. Le_&

c

D

21 c

CO x m m H

BENZOFLEX® 9-88 ^e 2.43 5

Solids content 54.9 56 53.8 55 52.6 54.0 a - from E.I. DuPont de Nemours & Company, Inc. b - from Union Carbide Chemicals and Plastics Company Inc. c - from Dow Chemical Company. d - from Nalco Chemical Company. e - from Velsicol Chemical Corporation.

Table II: Poly(Vinyl Chloride) Film Adhesion Aging Comparative* Peel Strengths (in pli) from: ≥ L (days ) Plywood Board cioth ⁽ or other ⁾

1 1 3.25 6.61 1.65(masonite) 14 ^a 2.04 1.32 2.86(masonite)

2 1 3.03 5.37 2.0 14 ^a 5.70 3.63 1.05

3 ^b 1 6.39 v 3.51* 4.84 v 3.74* 3.93 v 1.67*

3.94* ^b ' 4.65* ^b ' 1.78* ^b ' 14 ^c 5.34 v 4.02* 4.83 v 5.89* 4.17 v 2.77*

5.78* ^b ' 4.93* ^b ' 4.08* ^b ' 14 ^a 5.38 v 6.34* 4.46 v 4.37* 4.48* ^b ' 4.42* ^b* 4 1 5.29 v 2.37* 4.96 v 3.74* 2.42 v 1.71* 3 4.74 v 3.52* 3.36 v 4.21* 2.92 v 2.88* 7 6.50 v 3.52* 5.18 v 3.88* 3.45 v 3.82* 4 ^d 1 6.69 v 3.33* 3.66 v 3.72* 4.41 v 2.34* 3 5.89 v 4.02* 4.68 v 4.35* 3.87 v 2.97* 7 7.58 v 3.03* 5.12 v 3.36* 3.95 v 2.17* 4 ^b 1 6.67 v 4.52* 5.76 v 4.02* 4.67 v 1.85* 3 6.58 v 4.04* 5.51 v 3.77* 5.29 v 3.45* 7 5.51 v 4.32* 4.36 v 3.52* 8.32 v 9.14* 6 ^e 1 5.72 v 4.79* 2.93 v 2.74*

14 ^a 9.96 v 5.55* 6.76 v 6.41*

* - compared with ethylene/vinyl acetate copolymer (AIRFLEX® 400), with AEROSOL® OT-75 to wet PVC film, a - at 60°C. b - including 5 parts BENZOFLEX® 9-88 plasticizer. b*- excluding 5 parts BENZOFLEX® 9-88 plasticizer. c - at 50°C. d - including 2.5 parts BENZOFLEX® 9-88 plasticizer e including 3.5 parts BENZOFLEX® 9-88 plasticizer

SUBSTITUTESHEET