SE362892B - - Google Patents

Description

10 50 40 FO 362892 pine compounds in a special ratio of polyvalent metal to carboxyl groups. Usually, but not necessarily, the medium is an aqueous medium, in which case it is believed that the polyvalent metal compound dissociates into polyvalent metal ions or polyvalent metal-containing ions which help to crosslink the carboxylate groups upon removal of the aqueous medium. It has surprisingly been found that the improved shear resistance is obtained without any appreciable reduction in tack. A valuable and unexpected property of the binder according to the invention is furthermore that it is resistant to removal with alkaline solutions, especially when the carboxylic acid monomer is used in lower contents. Thus, according to the invention, a composition is provided which, after the liquid component has been removed, forming a pressure sensitive adhesive, which composition comprises a dispersion or solution in a liquid medium of a polymer having a Tg value lower than 0 ° and derived from ethylenically unsaturated monomers and containing a proportion of free carboxyl groups, which dispersion or solution also contains one or more polyvalent metal compounds, which act as crosslinkers for the polymer. The characteristic of the invention is that A) the polymer is derived from a monomer batch which essentially consists of a) 0.5-3.5 parts by weight, per 100 parts by weight of the total monomer batch, of one or more monoethylenically unsaturated carboxyl acids, b) one or more monoethylenically unsaturated compounds of the formula R 1 CH 2 = C - COOR wherein R is hydrogen and B 1 is G 2 -C 12 alkyl or R is -CH 3 and R 1 is G 6 -C 14 alkyl, and optionally c) one or more monoethylenically unsaturated compounds of formula 1? CH 2 = C - COOR wherein R is H or C 1 -C 4 alkyl and R 2 is methyl or C 15 -C 20 alkyl when R is H or C 1 -C 5 alkyl or C 15 -C 20 alkyl when R is C 1 -C 4 alkyl, wherein the relative ratio of components b) and c), if 2 c) is present, is such that the polymer has a Tg value not exceeding 0 ° C, and the αden polyvalent metal compound is a compound of a Group IB, IIA metal, IIB, IIIA, IIIB, IVA, IVB, VA, VB, VIA, VIB, VIIB or VIII of the Periodic Table, which compound is at least partially soluble in the liquid medium and is present in an amount which gives an equivalence ratio of added value metal ion to carboxyl groups in the range 0.0l: l - 2.0: l.

Contact adhesive tape is in principle a layer structure and comprises 10 50 55 40 b! 362892 usually a backing sheet, which on one side is provided with a release layer or adhesive coating and on the other side with a primer, on which the pressure-sensitive adhesive is applied. from the above it appears that one of the monomers used in a substantial proportion for the preparation of the polymer base in the binder compositions according to the invention is a monomer which when homopolymerized gives a homopolymer with a Tg value not exceeding 0 ° C, which monomers are known as "sticky" or "soft" monomers. An optional component is a "hard" monomer, i.e. a monomer which, when homopolymerized, gives a homopolymer having a Tg value exceeding 0 ° C, the proportion of "hard" monomer not being such that the total Tg of the polymer value exceeds OOC. The total Tg of the polymer is preferably below -1500.

The "Tg value" of the polymer is a conventional criterion of the hardness of the polymer and is described by Flory, "Principles of Polymer Chemistry", pages 56 and 57, (1955), Cornell University Press. Although actual measurement of the Tg value is preferable, it can be calculated as described by Fox, Bull.Am.Physics Soc. 1, 5, p. 125 (1956). Examples of Tg values for homopolymers and the limit value for Tg that enable such calculations are as follows: Homopolymer of β-n-octylacrylate -8 ° C n-decyme-methacrylate r--60 ° C α-ethylhexyl-acrylate -70 ° c octyl methacrylate -2000 n-tetradecyl methacrylate - 900 methyl acrylate 900 n-tetraacyl acrylate in 20 ° C methyl methacrylate 10500 acrylic acid 10600 The "soft" monomers used in the preparation of the polymer base for the binder compositions of the invention can be represented by the following formula: EJJ-d-onl is alkyl of 2 -12 carbon atoms or R is methyl and B1 is alkyl of 6-14 carbon atoms. Examples of suitable alkyl groups are ethyl, propyl, n-butyl, 2-ethylhexyl, heptyl, hexyl, octyl, propyl, 2-methylbutyl, 1-methylbutyl, 2-methylpentyl, cyclohexyl, n-hexyl, isobutyl, n-octyl , 6-methylnonyl, decyl and dodeoyl. wherein R is H and H1 In addition to the tackifying monomer, the other essential monomer is an ethylenically unsaturated carboxylic acid, for example, 2,4-hexadienoic acid, cinnamic acid, vinyl-pyronucic acid, d-chloro-2,4-hexadienoic acid, p-vinylbenzoic acid, acrylic acid, methacrylic acid, maleic acid, fumaric acid, aconitic acid, atropic acid, crotonic acid and itaconic acid, or a mixture of two or more thereof, itaconic acid and the α, 6-unsaturated monocarboxylic acids, especially methacrylic and acrylic acid, being preferred. The acid monomer may also contain more than one carboxylic acid group, as shown in the concrete examples above.

The "hard" monomers which may be used in combination with the above-mentioned soft monomers and acid monomers, provided that they do not adversely affect the desired properties of the binder (for example, cause too great an increase in the total Tg value) and do not seriously affect the crosslinking with the polyvalent metal, can be represented by the formula: In 2 g H 2 O = C - C - OR wherein R is H or C 1 -C 4 alkyl and R 2 is methyl or C 15 -C 20 alkyl when R is H or C 1 -C 5 alkyl or C 15 -C 4 alkyl C20 alkyl when R is C1-C4 alkyl. It can be seen from the above that in the case of alkyl acrylates and alkyl methacrylates the Tg value first decreases with increasing chain length for the alkyl group and then increases again, ie the alkyl acrylates and the alkyl methacrylates are "hard" or "soft" depending on the chain length. Examples of these hard monomers and other hard monomers include: methyl acrylate, acrylamide, vinyl acetate, tetradecyl acrylate, pentadeoylacrylate, methyl methacrylate, ethyl methacrylate, t-butyl acrylate, butyl methacrylate, styrene, pentadecyl methacrylamide, vinyl methacrylate and vinyl.

Polymers which are stated to consist essentially of unsaturated acid monomer and acrylic acid ester thus include such additive monomers which do not alter the basic properties of the binder material according to the invention. The specific contents of hard and soft monomer are not critical, provided that the product polymer has a Tg value not exceeding 0 ° C, preferably not exceeding -1500. In general, however, the levels of the monomers fall within the following ranges: Monomer Parts by weight / ï00 parts monomer Useful range Preferred range Soft monomer 10- - 99.5 70 - 99.5 Carboxylic acid monomer \ u- 0.5 - 3.5 Hard monomer 0 - 89.7 0 - 29.5 The preferred polymers used in the present invention are emulsion polymers having a molecular weight of between about 70,000 and 2,000,000 and preferably between about 250,000 and 1,000,000. Such polymers can be prepared by conventional emulsion polymerization techniques, as described, for example, in U.S. Patent Nos. 2,754,280 and 2,795,564. The monomers can thus be emulsified with an anionic, a cationic or a nonionic dispersant which normally used in an amount of 0.05 to 10% based on the total weight of the monomers. The acid monomer is usually soluble in water, so the dispersant has the function of emulsifying the other two monomers. A free radical polymerization initiator, such as ammonium or potassium persulfate, may be used alone or in combination with an accelerator, such as potassium metabisulfite or sodium thiosulfate. Organic peroxides, such as benzoyl peroxide and t-butyl hydroperoxide, are also useful initiators. The initiator and accelerator, commonly referred to as catalyst, can be used in an amount of 0.1-10% each based on the weight of the monomers to be copolymerized. The amount can be modified as indicated above to control the intrinsic viscosity of the polymer.

The temperature can be from room temperature to 6000 or higher according to conventional technology.

Suitable dispersants useful in emulsion polymerization include anionic types, such as sodium salts of higher fatty acid sulfates, such as that of lauryl alcohol, higher fatty acid salts, such as oleate or stearates or morpholine, 2-pyrrolidone, triethanolamine or mixed ethanolamines, or any of the nonanolamines. , such as ethylene oxide-modified alkylphenols, of which tert-octylphenol modified with 20 HO ethylene oxide units is representative, ethylene oxide-modified higher fatty alcohols, such as lauryl alcohol, containing -50 ethylene oxide units, similarly modified, long chain mercaptans or fatty acids, fatty acids. Mixtures of nonionic and anionic dispersants are also useful.

Although emulsion polymers prepared in water are preferred, polymers prepared in organic solutions, for example in xylene, methylcellosolve and the like, in a well known manner, such as free radical initiation with benzoyl peroxide or the like, are also useful. Solution polymers useful in the invention preferably have a molecular weight of between about 10,000 and 10,000,000.

The polyvalent metal compound used in the composition of the invention may be a simple ionic compound or a metal complex or a metal chelate which is at least partially ionizable or soluble in the system. The polyvalent metals are selected from groups IB, II-A, II-B, III-B, IV-B, VB, VI-B, VII-B, VIII, III-A, IV-A, VA and VI -A in the periodic table. Preferably, the polyvalent metal is selected from the group II-B or IV-B. Suitable polyvalent metals include: Copper, gallium, tin, cerium, titanium, vanadium, chromium, molybdenum, manganese, iron, cobalt, nickel, beryllium, cadmium, calcium, magnesium, zinc, zirconium, barium, strontium , aluminum, bismuth, antimony, lead and cobalt which are added to the composition in the form of an oxide, hydroxide or basic, acidic or neutral salt or other compound or complex having substantially solubility in the liquid medium, for example at least about 1% by weight therein. Zinc, cadmium and zirconium compounds are preferred. The choice of polyvalent metal and the anion is determined by the solubility of the metal complex or compound formed in the liquid medium used.

Examples of organic and inorganic metal salts and compounds include carboxylic acid salts and chelates, such as zinc acetate, zinc benzoate, tin tartrate, lead acetate, chromium acetate, manganese tartrate, manganese benzoate, magnesium nitrate, ferroacetate, iron lactate, cobalt acetate, nickel cobalt acetate, nickel cobalt acetate chelates or complexes, which involve coordination bonding and may be partially ionizable, such as the zinc chelate of alanine or glycine, calcium chloride, aluminum diacetate, magnesium acetate, calcium carbonate, zinconium acetate, calcium acetate, potassium hydroxide, barium acetate, manganese sulfate, magnesium sulfate, magnesium sulfate , zinc carbonate or zinc sulphate.

Any salt or chelate which has both ionic bonding and coordination bonding in which the metal is sufficiently available or dissociable to bond the carboxyl groups in the polymer is useful.

Ammonia and amine complexes (especially those coordinated with NH5) of these metals are particularly useful. Amines that can form complexes include morpholine, monoethanolamine, diethylaminoethanol and ethylenediamine. Polyvalent metal complexes (salts) of organic acids __; ¿Which can cause solubilization within the alkaline pH range, 'å-can also be used. Anions such as acetate, glutamate, formate, carbonate, salicylate, glycolate, octoate, benzoate, gluconate, oxalate and lactate are satisfactory. Polyvalent metal chelates in which the ligand is a bifunctional amino acid, such as glycine or alanine, are especially preferred. The polyvalent metal compound must be such that the metal is available to exert its crosslinking action, i.e. dissociable to some extent to form polyvalent, metal-containing ions, or can be attracted to the carboxyl groups by any equivalent mechanism. It is not intended that the invention be limited to these or other theories or hypotheses regarding the mechanism that occurs in the interaction between the metal compound and the carboxyl groups of the polymer. The term "crosslinking" as used herein is intended to cover any conceivable phenomenon or mechanism by which the polyvalent metal modifies the binder of the invention.

Preferred polyvalent metal compounds, complexes and chelates include zinc acetate, cadmium acetate, zinc glycinate, cadmium glycinate, zirconium carbonate, zinc carbonate, cadmium carbonate, zinc benzoate, zinc salicylate, zinc glycolate and cadmium. Although the polyvalent metal compound can be added to the binder composition in dry form such as in the form of a powder, it is preferable to first solubilize the polyvalent metal compound using a volatile ligand, such as ammonia or a volatile amine. For the purpose of the present invention, a ligand is considered volatile if at least a portion of said ligand tends to volatilize under the prevailing film-forming conditions. Since ammonia can be complex with the polyvalent metal compound, a compound such as zinc glycinate, when solubilized in dilute aqueous solution of ammonia, may be termed zinc amine glycinate or zinc ammonium glycinate.

A group of polyvalent metal complexes used in the binder formulations of the present invention contain a polyvalent metal moiety, an organic, bifunctional amino acid ligand moiety and usually an alkaline moiety if the chelate is to be added to the formulation in solubilized form. The polyvalent metal ions may be those mentioned above, such as beryllium, cadmium, copper, calcium, magnesium, zinc, zirconium, barium, strontium, aluminum, bismuth, antimony, lead, cobalt, iron, nickel or any other polyvalent metal which may be added to the composition in the form of an oxide, hydroxide or basic, acidic or neutral salt chelate or complex with substantial solubility in water, such as at least about 1% by weight therein. The alkaline moiety can be provided in the form of ammonia or an amine. The bifunctional amino acid ligand is preferably an aliphatic amino acid but may also be a heterocyclic amino acid. The bifunctional amino acid ligands can be represented by the formula BRN-R -ßß H2 / 3 \ <> H wherein R1 and RE are independently hydrogen, alkyl, phenyl or benzyl, and EB represents a straight or branched alkylene, alkylidene or aralkylidene radical with 1:12 carbon atoms, preferably 1-6 carbon atoms, with the proviso that 1-3 carbon atoms are in the straight chain attached to the nitrogen atom and the carbonyl carbon atom, or "" wherein R 2 is hydrogen and B 1 and H 5 may form a 5- or 6-membered heterocyclic ring with the attached nitrogen atom. Although R 1 and R 2 are preferably hydrogen, suitable B 1 and R 2 alkyl radicals may contain 1-6 carbon atoms, such as methyl, ethyl, propyl, isopropyl and butyl. H3 propylene, ethylidene, n-propylidene, isopropylidene, butylidene and phenylethylidene. is preferably methylene but may also be ethylene. Representative amino acid ligands of the above type include glycine (aminoacetic acid), alanine (α-aminopropionic acid), β-alanine (β-aminopropionic acid), valine (α-isopropylaminoacetic acid), norvaline (an- propylaminoacetic acid), α-aminobutyric acid, leucine (2-amino-4-methylpentanoic acid), norleucine (2-aminohexanoic acid), N-methylaminoacetic acid, N-ethylaminoacetic acid, dimethylaminoacetic acid, diethylaminoacetic acid, Nino amino acid -isopropylaminoacetic acid, N-butylaminoacetic acid, phenylalanine, N-phenylaminoacetic acid, N-benzylaminoacetic acid, proline, nicotinic acid and tetrahydronicotic acid.

Preferred polyvalent metal complexes include cadmium glycinate, nickel glycinate, zinc glycinate, zirconium glycinate, cobalt talaninate, copper paralaninate, zinc alaninate, copper B-alaninate, zinc-B-alaninate, nickenquinvalinate acamate and zinc norvaline acinate.

The polyvalent metal complexes used in the composition of the invention must be stable in alkaline solution. However, a complex that is too stable is undesirable because dissociation. of the metal ions would be inhibited during film formation of the coating.

The polyvalent metal compound used is used in such an amount that the ratio of polyvalent metal to carboxyl groups in the d, β-ethylenically unsaturated acid or other polymerizable carbonic acid in the addition polymer ranges from about 0.01-2.0 and preferably from about 0.05-1. , 5. This is expressed on an equivalent basis as the ratio of metal, such as Zn ++, to -COOH or -COONH4 groups, a ratio of 0.5 being stoichiometric. When the polymer is a dispersion or emulsion and the metal is calcium and / or magnesium, it can also be added in whole or in part by using hard water in contrast to the usual process in the preparation of emulsion polymers by using deionized or distilled water. It is preferred at the higher carbonic acid levels to use proportionally less amount of polyvalent metal. The proportions are chosen so that the adhesive remains tacky but still has good cohesive ability. In some cases, excess metal compound has no harmful effect.

The preferred aqueous dispersion, when finally formulated into a binder composition, should have a pH of 2.0-0.0.0 or more. Its pH is especially from 6.5 to about 9.5. Suitable alkaline substances or buffers, such as borax, sodium hydroxide, ammonia, or amines, such as diethylamine, triethylamine, morpholine or triethanolamine, may be added to adjust the pH to the desired value. At least a portion of the alkaline material should be such that it volatiles upon curing of the binder coating so that the polyvalent metal ions can exert their ionic crosslinking or comparable function of linking or bonding the carboxyl groups.

Conventional additives for contact adhesive are also useful, for example fillers or pigments, tackifying resins such as wood rosin, polyesters and the like, plasticizers such as alkyl esters of adipic acid or phthalic acid, antioxidants, solvents such as alkanols having 1 to 12 carbon atoms, for example isopropanol, antifoam funds and so on. Many types of fillers or pigments can be used. One of the best is titanium dioxide in the form of rutile. Others, such as titanium dioxide in the form of anastase, lithopone, magnesium silicate, clay, vollastinite, zinc oxide, potassium carbonate, clays including kaolin and bentonite, walnut shells, etc., are useful. To some extent, fiber fillers, such as cellulose fibers or nylon staple fibers, can be used.

These additives are incorporated into the anhydrous or aqueous dispersion or solution prior to coating the substrate therewith.

Any substrate or carrier is useful including rigid, flexible, unstretchable or extensible materials, such as textile fabric, plastic film, nonwoven fibrous sheets, including water-coated and air-coated products, sheet metal or foil, rubber or synthetic rubber, decorative sheets, plywood edge strips, plywood sheets, decals, etc. If the tape is in a roll, it is usually coated with a release liner, an adhesive layer or an adhesive coating. Double-sided adhesive objects are also useful. If the product is not in the form of a roll, peelable paper or other protective device is provided. Usually, the surface of the substrate to which the pressure-sensitive adhesive is applied is prepared to improve the adhesion between the substrate and the adhesive.

The binder of the present invention has been found to provide exceptionally good compounds with a myriad of materials, including wood, paper, Formica R) I chloride, Saran resins, urea-formaldehyde resins and other thermosetting materials, other plastic materials such as methyl methacrylate, polyvinyl , polyethylene glycol terephthalate, nylon, phenol-formaldehyde- such as melamine-formaldehyde resins3 rayon, cotton, silk, wool, fibers of the above polymeric materials, leather, linoleum, asphalt tiles, vinyl tiles, ceramic tiles, various silicates, such as glass, mineral wool, asbestos, concrete, asbestos elements, plaster, metals, such as aluminum, steel, iron, copper, zinc, chromium, nickel, as well as painted or enamelled surfaces, such as painted automobile bodies, wooden details, walls, ceilings or floors.

Pre-glued objects, such as tapes, wallpaper or tiles for decorating walls, floors or ceilings, can be made, the part to be finally applied to a surface for decoration, such as a tape, wallpaper or tile, being provided on the back with a layer of the composition according to the present invention and a protective layer applied to the adhesive layer and can be torn off when the part is to be applied to the surface for which it is finally intended. The protective layer may consist of a thin film of polyethylene or other material, which may be peeled off more or less easily from the adhesive layer. In addition to tape, wallpaper and tile, this technology can be used in connection with plastic films, wood veneer layers or thin sheets of resin or plastic material, such as sheets of Formica plastic or vinyl resin. Such films or sheets can be of any size and can be cut to final size when coated on tables, counters or other furniture.

The pressure-sensitive adhesive composition is applied to the support or substrate by conventional coating techniques, after which it is dried and heated to provide crosslinking of the polymer.

In the following examples which illustrate the invention, parts and percentages are by weight unless otherwise indicated.

Example 1 A glass bottle is charged with 100 g of distilled water and a tetrafluoroethylene-coated magnetic stirrer. The container is placed on a magnetic stirrer plate and the stirring speed is set so that the tip of the vortex reaches close to the bottom of the liquid. Zinc oxide (22 g) is sieved into the water and stirring is carried out until a well-mixed slurry is obtained. Then 40 ml of 28% ammonium hydroxide are added and then 42 g of glycine and stirring is continued until a clear solution is obtained. A second container is charged with 100 g of an aqueous dispersion containing 55% by weight of a sticky acrylic emulsion copolymer prepared in a conventional manner of butyl acrylate and methacrylic acid. a weight ratio of 98/2. The emulsion is stirred using a magnetic stirrer, and zinc ammonium glycinate solution * prepared as described above is added in an amount corresponding to about 0.25 equivalents of zinc per carboxyl. After mixing for several minutes, an aqueous solution of 7% ammonium hydroxide is added to the emulsion until the pH rises to 9.5, which is checked with a pH meter of the type Leeds and Northrup model 7400-A-2.

A film of the resulting emulsion is applied to a polyethylene terephthalate sheet using an adjustable Gardner knife set at a gap of 0.2 mm. After standing for 2 hours at 25 DEG C., the film is baked for 15 minutes at 120 DEG C. to evaporate ammonia and create ionic crosslinking. After 48 hours of conditioning at 2500 and 50% relative humidity, the coated sheet is cut into strips of tape measuring 2.5 x cm. The shear resistance is measured using method no. 7 according to the Pressure Sensitive Tape Council, according to which it is determined how long a tape section was x 25 mm carries a 100 g weight under standard conditions. Stickiness is determined with a 5-fold sample plate using qualitative comparison with touch or thumb. The results are shown in Table I.

Example 2 An acrylic emulsion copolymer based on 98% by weight of butyl acrylate and 2% by weight of methacrylic acid is treated with half the amount of zinc glycinate as the product described in Example 1, and the pH is raised to 9.5. The mixing is carried out in the same manner as described above.

Test samples are prepared and evaluated using the same methods as those used in the examination of the product of Example 1. The data obtained are shown in Table I.

Table I Sample 'Equivalent Shear- Adhesive zinc per resistance 2 -COOH Product from ex. l 0.25 7 hrs' Excellent Product from ex. 2 0.125 6 hours Excellent unmodified 98 BA / a MAsX 'copolymer None 0.9 hours Excellent x BA = butyl acrylate MAS = methacrylic acid Example Repetition of examples 1-2 but use of zinc alkaninate and zirconium alaninate as metal compound gives similar results. Any of the soluble or solubilized metal compounds disclosed above are also useful.

Claims (1)

A composition according to which the liquid component has been removed to form a pressure-sensitive binder, which composition comprises a dispersion or solution in a liquid medium of a polymer having a Tg value lower than 0 ° and derived from ethylenically unsaturated monomers and containing a proportion of free carboxyl groups, which dispersion or solution also contains one or more polyvalent metal compounds which act as crosslinkers for the polymer, characterized in that A) the polymer is derived from a monomer batch consisting essentially of a) 0.5-5.5 parts by weight, per 100 parts by weight of the total monomer charge, of one or more monoethylenically unsaturated carboxyl lighthouses, b) one or more monoethylenically unsaturated compounds of the formula R CH 2 = α - COOR wherein R ooh nl is ca-012 -alkyl or R is -CHB ooh R1 is 06-014-alkyl, 1 and optionally c) one or more monoethylenically unsaturated compounds of formula I cH2 = c - coong wherein R is H or C1-C6 alkyl and RQ is methyl or O13-C20 R is H or C1-C5-alkyl or C15-C20-alkyl when R is C1-C6-alkyl, wherein the relative ratio of components b) and c), if c) is present, is such that the polymer has a Tg value not exceeding 0OC, and B) the polyvalent metal compound is a compound of a Group IB, IIA, IIB metal , IIIA, IIIB, IVA, IVB, VA, VB, VIA, VIB, VIIB or VIII of the Periodic Table, which compound is at least partially soluble in the liquid medium and is present in an amount which gives an equivalence ratio of polyvalent metal ion to carboxyl groups in the range 0.0l: 1 - 2.0: l. -alkyl near 2. Composition according to claim 1, characterized in that the polymer is derived from a monomer batch containing 0.5 - 5.5% by weight of component a), 70 - 99.5% by weight of component b) and 0 - 29.5% by weight of component c). 5. A composition according to claim 1 or 2, characterized in that component a) is acrylic acid, methacrylic acid or itaconic acid. 4. A composition according to any one of the preceding claims, characterized in that the polymer has a Tg value below 15 ° C. 5. A composition according to any one of the preceding claims, characterized in that the liquid medium is water.