MXPA97008673A - Water-based adhesive compositions sensitive to pressure derived from copolymers of superior vinyl esters - Google Patents

Abstract

The present invention relates to: The present invention is directed to water-based pressure sensitive adhesive emulsion polymers. The emulsion-based pressure sensitive adhesives consisting of polymerized units of acrylic esters and ethylenically unsaturated monomers, the copolymer has a Tg of -15 to -70 ° C. The improvement in pressure sensitive adhesives polymerized in water-based emulsion resides in the incorporation of a vinyl ester with 8 to 13 carbon atoms of a neo-acid in the copolymer present in the pressure sensitive adhesives. This vinyl ester is formed from a mixture of propylene oligomers and vinyl talistes represented by the following chemical formula: C8-13H17 / 27CO2CH = C

Description

WATER-BASED ADHESIVE COMPOSITIONS SENSITIVE TO PRESSURE DERIVED FROM COPOLYMERS OF SUPERIOR VINYL ESTERS DESCRIPTION OF THE INVENTION The invention relates to improved water-pressure sensitive adhesive emulsions, the improvement in the incorporation of poly-ester units of a vinyl ester of a neo-acid residing in the copolymer present in these emulsions. Pressure sensitive adhesives are widely used to make paper labels, laminate polymer films such as polyvinyl chloride lamination, polyester. etc., to form stickers and other related products. Most pressure sensitive adhesives have been solvent based, but in recent years government regulations have forced the industry to develop new water-based pressure sensitive adhesives. Water-based pressure sensitive adhesives consist of polymerized monomeric units of vinyl acetate, ethylene and / or acrylic esters, etc., which have been inferior to solvent-based pressure sensitive adhesives in that they do not have enough Adhesive power to low surface energy substrates neither have good water resistance etc.

The following patents describe a variety of emulsion polymers that incorporate pressure sensitive adhesives based on vinyl esters and / or emulsion. US Patent 5,461,103 discloses water based pressure adhesive emulsions which have the ability to coat low energy surfaces without retracting or cracking. The emulsion polymers are prepared by means of a two-step emulsion polymerization process, the first step results in the formation of an alkali-insoluble polymer system including acid functional groups and polymerized hydrophobic onomeric units, for example alkyl acrylates. with 4 to 12 carbon atoms and the second stage incorporates monomeric units suitable for the manufacture of pressure sensitive adhesives, for example acrylic and methacrylic esters, vinyl esters of sarboxylic acids with 2 to 5 carbon atoms, for example vinyl acetate and vinyl propionate and the like. U.S. Patent No. 4,923,919 discloses pressure-sensitive adhesive emulsions based on acrylic polymers which have a meri ^ A? * P? ? ßso from v * crils + O < ? * »< ? 1 tuilo v a support resin that is soluble in alkalis. The support resin contains polymerizable carboxylic acid anhydride groups having the resin polymerizes an average molecular weight of 1000 to 15000. Typically the support resins are based on vinyl monomers such as esters of acrylic and methacrylic acid, styrene and combinations thereof. The U.S. patent 4,322,516 discloses water-based pressure sensitive adhesives formed of ethylene units, acrylic ester units, vinyl acetate units, acrylamide units and other olefinically unsaturated monomers. Other adhesion agents are added to ethylene-based pressure sensitive adhesives. The patent US4, 39, 190 discloses emulsion pressure sensitive adhesives in which the emulsions are prepared in a stepwise process, the first step is to polymerize an ethylenically unsaturated monomer such as ethylene, acrylonitrile and / or [meta] acrylates in the presence of an adherent resin and a second step consisting of polymerizing alkyl acrylates having at least 4 carbon atoms in the presence of the polymer of the first stage. The U.S. patent No. 5,276,084 describes water-based pressure sensitive adhesives based on polymers comprising vinyl acetate, ethylene, alkyl acrylates, dialkyl maleates and fumarates, hydroalkyl acrylates, acrylamides and carboxylic acids unsaturated? you're eating < US Pat. No. 3,697,618 discloses pressure sensitive acrylic adhesives incorporating a vinyl ester of a carboxylic acid, for example vinyl acetate, a lower alkyl acrylate and an alpha dicarboxylic acid or anhydride. , beta-ethylenically unsaturated.

The U.S. patent 3,562,229 discloses copolymers polymerized with solvent of ethylene and vinyl esters in which the vinyl esters are derived from long chain carboxylic acids, for example versatile acid which are mixtures of carbsyl acids with 9 to 11 carbon atoms. The isotridecanonic and isononanoic acids are representative. Solvent-based polymers that incorporate vinyl esters of versatile acid are said to be superior to polymers that incorporate vinyl laurate having the same number of carbon atoms. The U.S. patent No. 3,294,727 describes vinyl esters polymerizing saturated monocarboxylic acids to form emulsions that are suitable for producing paints stable to freeze-thaw. Preferred saturated aliphatic monocarboxylic acids for forming vinyl esters are based on the compounds of the formula: R, O R3-C-C-OH. in] to which R, and R are alsuyl radicals of normal, branched or cyclic structure and R, represents hydrogen or a hydrocarbyl radical. The carboxylic acids have from about 9 to 19 carbon atoms. Representative copolymers consist of polymerized units of vinyl acetate and / or acrylic acid in the representative vinyl esters.

The U.S. No. 3,669,942 discloses solvent-based polymers comprising a vinyl ester of a branched alpha saturated aliphatic monocarboxylic acid having from 5 to 20 carbon atoms and an alpha, beta-ethylenically unsaturated carboxylic acid having from 3 to 5 carbon atoms, a aromatic monovinyl compound and esters of acrylic acid including esters of hydroxyalkyl acrylate. The compositions are useful as water-thinner paint binders. The U.S. No. 3,654,213 discloses sticky pressure sensitive adhesives based on interpolymers of vinyl esters and alkyl acrylates, the interpsylimers are dissolved in organic solvents with a high solids content. Representative interpolymers are based on vinyl acetate, vinyl propionate, vinyl butyrate and vinyl valerate with vinyl acetate being preferred. Other monomers that can be incorporated into the polymer include acrylic acid esters such as methyl acrylate, ethyl acrylate, etc. The U.S. 4,322,516 discloses pressure sensitive adhesive emulsions whose copolymers consist of: a] 10-30% by weight of ethylene b] 26-29% by weight of acrylic acid esters of alcohols c] 20-55% by weight of ethyl acetate di 0.2-85 by weight of [meta] acrylamide, and] 0-12% by weight of olefinically unsaturated compounds The present invention is directed to improved water-based pressure sensitive adhesive emulsion polymers. The water-based pressure sensitive adhesives consist of a copolymer consisting of polymerized units of acrylic esters and ethylene-unsaturated monomers, the copolymer having a Tg of -15 to -70 ° C. the improvement of water-based emulsion polymerized pressure sensitive adhesives resides in the incorporation of a vinyl ester of a neo-acid with 8 to 13 carbon atoms in the copolymers present in the pressure sensitive adhesives, such copolymers incorporate a vinyl ester formed by a mixture of propylene oligomers and those vinyl esters are represented by the following chemical formula: There are important advantages associated with the above pressure-sensitive water-based adhesive emulsions and the process for producing those emulsions and these advantages include: the ability to provide improved properties to pressure sensitive adhesives by means of an ester mixture of vinyl rich in methyl groups having a lower solubility parameter compared to the corresponding linear alkyl vinyl esters; the ability to provide improved properties to pressure sensitive adhesives by means of the ability of the vinyl ester monomer to be subjected to emulsion polymerization with a variety of olefinically unsaturated comonomers; the ability to form an excellent bond and improve the resistance to migration of the plasticizer with pasty polyvinyl chloride. the ability to generate a class of pressure sensitive adhesives that have an excellent balance of release and cohesive strength; • the ability to provide improved thermal and hydrolytic stability to pressure-sensitive emulsion-based adhesives compared to its water-based vinyl acetate counterparts; and, the ability to provide improved properties to pressure sensitive adhesives by bonding to low low surface energy surfaces of low polarity, such as polyethylene, due to stronger bonding of the copolymers.

The polymerization of the emulsion of ethylenically unsaturated monomers such as lower alkyl acrylates and vinyl esters typically represented by vinyl acetate or vinyl propionate to produce water-based pressure sensitive adhesive emulsions containing vinyl copolymers. Improvements to pressure sensitive adhesives based on emulsions containing vinyl copolymers incorporating polymerized units of ethylenically unsaturated monomeric units reside in the incorporation of a vinyl ester of a neo-acid derived from a propylene oligomer base in the vinyl copolymer. The vinyl ester of a propylene oligomeric neo-acid or its mixture incorporated in the vinyl polymer consists of the vinyl ester of one or a mixture of tri- and tetramers of propylene which have been converted to neo-acid or the mixture of neo acids with 8 to 13 carbon atoms. These esters are typically prepared by first converting the tri- and tetramers of propylene to the corresponding acids and then converting those corresponding neo-acids to the vinyl esters. Vinylation of these acids can be achieved either by transvinylation with vinyl acetate or by the catalytic addition of the neo-acids to acetylene. Some of the vinyl esters can be represented by a singular neo-acid, but generally the vinyl esters of the neo-acids are present as a mixture. Water-based pressure-sensitive adhesive emulsions are based on emulsions comprising a colloidal dispersion of the vinyl copolymer in water. The copolymers present in the pressure sensitive adhesives are typically derived from the following monomers and within the following percentages: a] 5-40% by weight of a vinyl ester of a neo-acid with from 8 to 13 carbon atoms, preferably 15 to 30% by weight; b] 30-80% by weight of an alkyl ester with 1 to 12 carbon atoms of acrylic or methacrylic acid, preferably 40 to 70% by weight, c] 0-20% by weight of an acid vinyl ester saturated aliphatics, preferably 0 to 10%; d] 0-30% by weight of ethylene, styrene or butadiene, preferably 0 to 20% by weight, e] 0-20% by weight of di-alkyl maleate fumarate with 1 to 13 carbon atoms, preferably 0 to 105 in weight; f] 0-55% by weight of a hydroxyalkyl [meta] acrylate; g] 0-55% by weight of [meta] acrylamide; and h] 0-10% by weight of alpha, beta-ethylene-unsaturated monocarboxylic acid. A variety of other comonomers, for example other ethylenically unsaturated monomers sometimes used in the formation of water-based pressure sensitive emulsions can be copolymerized with the vinyl ester of a neo-acid to form adhesives. For example vinylalkyl ethers with 1 to 8 carbon atoms, vinyl chloride, vinylidene chloride, nitrile, carboxylic amides such as N-vinylformamide and N-vinylacetamide, acrylonitrile and methacrylonitrile to produce a variety of polymers, examples of ethers Useful vinyl alkyl are methyl vinyl ether, ethyl vinyl ether, isopropyl vinyl ether, n-propyl vinyl ether, tert-butyl vinyl ether and isobutyl vinyl ether. The components [a] have been defined, which are the vinyl esters of neo-acids with 8 to 13 carbon atoms and are used to produce the improved pressure sensitive adhesives. The components fb] are monomers used for the production of the pressure-sensitive adhesives containing the vinyl esters of neo-acids with 8 to 13 carbon atoms are alkyl esters of acrylic or raetacrylic acid. These are esters of acrylic or methacrylic acid and an alcohol with 1 to 12 carbon atoms. Examples of alcohols suitable for the preparation of these esters are methanol, ethanol, propanol, isopropanol, n-, iso-, and tert-butyl alcohol, neopentyl alcohol, 2-ethylhexanol, n-octanol, dodecanol, palmityl alcohol and stearyl alcohol. Specific examples of unsaturated alkyl acrylate monomers include methyl methacrylate, ethyl acrylate, butyl acrylate, hexyl acrylate 2-ethylhexyl acrylate, isooctyl acrylate, isododecyl acrylate, and the like. The monomers of the component [c] that can be used to form emulsion polymers for pressure sensitive adhesives can include other vinyl esters different from the vinyl esters of neo-acids. Some of the most common vinyl esters used in the synthesis of polymers include alkanoic acids with 3 to 18 carbon atoms, such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl laurate and the like. These esters and particularly the lower alkyl esters can be lowered from the general properties of the pressure sensitive emulsion imparted by the vinyl ester of the neo-acids with 8 to 13 carbon atoms. The monomers of component (d) used as a fraction of the polymers used to form the emulsion polymers for pressure sensitive adhesives may include hydrocarbon monomers such as ethylene, styrene, butadiene. The monomers of component (e) used to form many of the pressure sensitive adhesives include an alkyl marateate or fumarate, for the purpose of providing improved adhesion, etc. Suitably the diesters of maleic acid or fumaric acid can be used, the diester is formed by the reaction of the acid with an alcohol with 1 to 13 carbon atoms such as n-octyl alcohol, isooctyl alcohol, butyl alcohol, isobutyl alcohol , methyl alcohol, amyl alcohol and the like, preferably an alcohol with 4 to 8 carbon atoms is used.

The monomers of component (f) are frequently incorporated into the pressure-sensitive adhesive polymer, representative monomers include hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylates, hydroxypropyl methacrylate, hydrosypropyl acrylates, hydroxypropyl methacrylates, hydroxybutyl acrylates and hydroxybutyl methacrylates. The monomers of the component (g) are frequently incorporated into the copolymers at some levels, examples of the amides include acrylamide, methacrylamide and N-methylol acrylamide. The monomers of component (h) include carboxylic acids with 3 to 6 carbon atoms alpha, beta-ethylenically unsaturated which can be incorporated in the polymer can be methacrylic acid, crotonic acid, acrylic acid and the like. The * total of the monomers used to form the pressure sensitive copolymers is 100 percent. The emulsion copolymers have a Tg less than -15 * C, preferably -15 to -70 * C and typically -20 to -50'C. Aqueous emulsions contain about 40 to 70% solids. The emulsion polymerization process typically includes an initial homogenization in which the monomers including the vinyl esters of neo-acids and the other monomers that are employed to form the vinyl copolymer such as alkyl acrylates or methacrylates with from 1 to 12 carbon atoms, vinyl acetate, diallyl maleate / fumarate, ethylene, acrylamide and other monomers are vigorously stirred. If ethylene is added to the reactor to form a copolymer, the reactor is pressurized to the working pressure to obtain the ethylene solution in the monomers. Then, the reaction medium is gradually heated to the polymerization temperature. The period of hopogenization is followed by a period of polymerization during which the source of free radicals is gradually added. Various catalysts formed from free radicals such as peroxide compounds can be made by performing the emulsion polymerization of the monomers. Catalysts of the combined type that employ both reducing agents and oxidants can also be used. The use of this type of combined catalysts is generally referred to in the art as "redox polymerization" or "redox system". The reduced agent is also frequently called the activator and the oxidizing agent as the initiator. Suitable reducing or activating agents include bisulfites, sulfoxylates or other compounds having reducing properties such as iron salts and tertiary aromatic amines, for example N, N-dimethylaniline. Oxidizing agents or initiators include hydrogen peroxide, organic peroxides such as benzoyl peroxide, t-butyl hydroperoxide and the like, persulfates such as ammonium or potassium persulfate, t-butyl hydroperoxide and the like, persulfates such as ammonium persulfate. or potassium, perborates and the like. A specific catalyst of the combined type or redox system that can be used in hydrogen peroxide and sodium formaldehyde sulfoxylate. The initiator is used in an amount of 0.1 to 2%, preferably 0.25 to 0.75% based on the total weight of the monomers introduced into the reactor. The activator is generally added in the form of an aqueous solution and the amount of activator is generally 0.25 to 1 times the amount of initiator. A wide variety of nonionic, anionic and cationic surfactants can be used to stabilize the emulsion in emulsion polymerization processes. Suitable nonionic emulsifying agents include polyoxyethylene condensates. The polyoxyethylene condensates can be represented by the general formula: R (CH2-CH, -0) PH in which R is the residue of a fatty alcohol containing from 10 to 18 carbon atoms, an alkylphenol, a fatty acid containing from 10 to 18 carbon atoms, an alkylphenol, a degree acid containing from 10 to 18 carbon atoms, an amide, an amine, or a mercaptan or in which n is an equal integer. Some specific examples of the polyoxyethylene condensates can be used to include polyoxyethylene aliphatic ethers such as polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene hydroabythyl ether and the like, polyoxyethylene alkaryl ethers such as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether and similar; polyoxyethylene esters of higher fatty acids such as polyoxyethylene laurate, polyoxyethylene oleate and the like as well as condensates of ethylene oxide with resinous acids and sebasic fatty acids; polyoxyethylene amide and amine condensates such as N-polyoxyethylene lauramide and N-lauryl-N-polyoxyethylene amine and the like; and polyoxyethylene thioethers such as n-dodecyl polyoxyethylene thioether. Other suitable nonionic surfactants are alkylarylethoxylate alcohols, alkyl ethoxylate alcohol, ethoxyproxylate, ethylene oxide alcohols and / or propylene oxide and the like. Other classes of nonionic surfactants are sold under the Igepal trademark. An example within this class is a nonylphenyl polyoxyethylene ether and a point of nebulization of between 52.2 and 56.1 ° C and marketed under the maca "Igepal CO-630", another is polyoxyethylene nonylphenyl ether having a point of nebulization by above 44.5 * C and marketed under the trademark "Ingepal CO-887". Examples of anionic surfactants include metal or ammonium salts of long chain alkyl sulfates and the like; metal or ammonium salts of alkylarylethoxylated sulphates or sulphonates, paraffin sulphonates, alkyl sulfosuccinates, alkylaryl sulphonates, alkyl phosphates, etc. A protective colloid can also be used in the polymerization mixture as a stabilizing agent. Various colloids and amounts conventionally used in the polymerization by polymerization can be incorporated into the latexes as desired and in combination with the surfactants. Representative colloids that can be used include polyvinyl alcohol, partially acetylated polyvinyl alcohol, for example 50% acetylated antibacterial, casein, hydroxyethyl starch, carboxymethylcellulose, gum arabic, and the like. The concentration range of the total amount of emulsifying agents used in the emulsion polymerization is 0.1 to 10% based on the aqueous phase of the latex regardless of the solids content. The stabilizers used in part are governed by the use for which the copolymer latex was used. By using the appropriate levels of surfactant and / or protective colloid, particular latex polymers having a variety of ranges and distributions of average particle size can be obtained. To maintain the pH of the system at the desired value, a buffering agent of any convenient type is suitably added. Any alkaline material that is compatible with the stabilizing agent can be used as a buffer, the amount of buffer that is sufficient to adjust the ph of the system within the desired range, for example 2.5 to 10 and preferably 3.5 to 8.5. The amount of buffer is generally about 0.1 to 0.5% by weight based on the monomers. The reaction temperatures for the emulsion polymerization of the vinyl esters of neo-acids together with other monomers are conventional. The reaction temperature can be controlled by the speed of the addition of the catalyst and by the rate of heat dissipation. It is generally advantageous to maintain a temperature of about 50 to 90 * C. While temperatures as low as 0 * C can be used, economically, the lower temperature limit is approximately 40 * C. The reaction time will also vary depending on other variables such as temperature, catalyst, and the desired degree of polymerization. It is generally desirable to continue the reaction until less than 0.1% vinyl ester remains unreacted. Under those circumstances, a reaction time of about 4 hours has been found to be generally sufficient to complete the polymerization, but reaction times in the range of 2 to 1 hours have been used and other reaction times may be employed if you want The following examples are provided to illustrate different embodiments of the invention and are not intended to limit its scope.

Example 1 Preparation of water-based pressure sensitive adhesives of vinyl neo-esters with 8 to 13 carbon atoms, 2-EHA, methyl methacrylate and acrylic acid Loa neo-vinyl esters with 8 to 13 atoms of carbon used to form the pressure sensitive adhesive emulsions are formed from a propylene oligomer base consisting predominantly of propylene thimeros and tetramers. To a 2 liter resin reactor is added the following initial reaction mixture consisting of 200 g of deionized water, 1.28 h of sodium citrate and 133 g of a monomeric pre-eulsion mixture of the following composition:% Pgs? > Deionized water 288.00 g Abex EP-120 [30% active] * 8.23 g Igepal CO-887 [70% active] 8.23 g Aerosol MA-80 [80% active] 7.20 g Monomer of neo-vinyl ester C3.a 144.00 g 25.0 % * Methyl methacrylate 74.90 g 13.0% * 2-ethylhexyl acrylate 345.60 g 60.0% * Acrylic acid 11.52 g 2.0% * * abex EP-120 is the ammonium salt of an ethoxylated alkylene sulfate, * the percentage of each monomer in the list is expressed as the weight of the total monomers used to form the copolymer in the pressure-sensitive adhesive emulsion. The initial reaction mixture is heated to 80 ° C under nitrogen with stirring at 150-200 rpm. A portion of 4.5 g of a 5% aqueous solution of sodium persulfate is added in a period of 15 minutes to initiate the polymerization reaction. After the initiation, the additions of the pre-emulsion feed of delayed feed begin [ 6.2 g / min] and the delayed feed of persulphate initiator [0.3 g / rain], respectively. 755 g of the pre-emulsion mixture and 36 g of initiator solution are consumed within 150 minutes. An additional portion of 5 g of the 5% solution of sodium persulfate is added to complete the polymerization reaction at a residual monomer value less than 1000 ppm. The copolymerization temperature is maintained at 81-83 'C. The resulting copolymer latex has 55% solids, a vicosity of 2350 cps at 20 rpm [RVT # 3 spindle] and a pH of 2.6, a Tg = -42 * C, and numerical values of particle size D == 145 nm and weight values of the particle size D. ^ 163 nm. Example 2 Preparation of water-based pressure sensitive adhesives blended with vinyl neo-esters with 8 to 13 carbon atoms, butyl acrylate, methyl methacrylate and acrylic acid The procedure of example 1 was repeated except for the substitution of butyl acrylate by the 2-ethylehexyl acrylate in the polymerization formulation. The resulting latex had 55% solids a viscosity of 725 cps at 20 rpm (spindle # 3), a pH of 3.1 and a Tg of -28 * C. EXAMPLE 3 Preparation of water-based pressure sensitive adhesives of vinyl versa ato 2-EHA, methyl methacrylate and acrylic acid The procedure of example 1 was repeated except for the substitution of vinyl versatate by the monomer of vinyl neoester with 8 to 13 carbon atoms mixed in the polymerization formulation. The resulting VeoVa ester-based copolymer latex 10 had 54.4% solids, a viscosity of 1250 cps at 20 rpm (RVT # 3 screw), a pH of 2.8 and a Tg of -34 * C. Example 4 Preparation of water-based pressure sensitive adhesives of vinyl versatate, methyl butyl acrylate methacrylate and acrylic acid The procedure of Example 3 was repeated except for the substitution of butyl acrylate by 2-ethylehexyl acrylate in the polymerization recipe. The resulting latex had 55% solids a viscosity of 2350 cps at 20 rpm (spindle # 3), a pH of 2.6 and a Tg of -24 * C. EXAMPLE 5 Preparation of water-based pressure sensitive adhesives of vinyl 2-ethylhexanoate 2-EHA, methyl methacrylate and acrylic acid The procedure of example 1 was repeated except for the substitution of vinyl 2-ethylhexanoate for the monomer of Vinyl neoesters are from 8 to 13 carbon atoms mixed in the polymerization recipe. The purpose was to determine the influence of the more linear ester on the resulting product versus the monomer of neo-ester mixed with 8 to 13 carbon atoms. The resulting VeoVa ester-based copolymer latex 10 had 51% solids at a viscosity of 475 cps at 20 rpm (RVT spindle # 3), a pH of 2.8 and a Tg of -39 * C. Example 6 Preparation of water-based pressure sensitive adhesives of vinyl neo-esters with 8 to 13 carbon atoms, 2-EHA, ethylene, 2-hydroxypropyl acrylate and acrylic acid To a high pressure reactor with capacity from a Gaul n is added a pre-mix of the following ingredients: Deionized water 720.1 g Versulf S-1333 * [40% active] 21.3 g Versulf NOS-25 [35% active] 41.4 g Sodium vinyl sulphonate [25% active] ] 9.5 g acrylic acid 14.2 g ferrous ammonium sulphate [1% active] 1.7 g * Versulf S-1333 is from the sodium sulfosuccinate family. * Versulf NOS-25 is a sodium salt of a nonylphenol ethoxylate sulfate. The pH of the pre-mixture is adjusted to 3.5 with 2.6 g of 14% aqueous ammonium hydroxide. A monomer mixture of: 580.3 g of monomer of vinyl neo-ester with 8 to 13 carbon atoms and 177.7 g of 2-ethylhexyl acrylate is subsequently added to the reactor followed by a purge of nitrogen and ethylene. The reactor is then blocked and stirred at 200 rpra. When the reaction temperature reaches 50 * C, the ethylene is charged in and equilibrated at 58.8 kg / cm2 for 5 minutes and turned off. The agitator speed increases to 800 rpm. A separate feed of the initiator and activator solution is added at 0.4 ml / min. to start the polymerization reaction. The composition of the delayed charges are the following: Initiating solution: Amount Such ammonium persulfate 15.0 OT OH [28%] 9.0 Deionised water 190.0 Activating solution; Sodium sulfoxylate formaldehyde 7.5 Deionized water 200.0 Monomeric mixture: 2-ethylhexyl acrylate 656.1 Acrylic acid 22.5 2-hydroxypropyl acrylate 77.0 Surface charge / emulsifier Versulf NOS-25 [35% active] 360 deionized water 110 After start, start delayed charges of the monomer and surfactant at a rate of 3.2 ml / min and 0.8 ml / min respectively. After 2.5 hours, the delayed monomer charge is reduced to 2.4 ml / min and the surfactant charge is reduced to 0.6 ml / rain. After four hours, a total of 755 g of monomer and 175 ml of surfaker are added. The initiating and activating retardant solutions continue to be added until the residual monomer value is equal to or less than 1000 ppm. At the end of the initiation and activation delay, the reaction mixture is cooled to 30 ° C and then transferred to a degasifier to release the excess ethylene pressure. The resulting latex has 50% solids, a pH of 4.2, a viscosity of 94 cps at 2 rpm, a Tg of -49 * C and particle size values of Da = 176 nm and D "= 287 nm. Example 7 Preparation of water-based pressure sensitive adhesives of vinyl neo-esters with 8 to 13 carbon atoms, butyl acrylate, ethylene, 2-hydroxypropyl acrylate and acrylic acid The procedure of Example 6 was repeated except for the substitution of butyl acrylate for 2-ethylhexyl acrylate in the polymerization recipe. The resulting copolymer latex has 46% solids, a viscosity of 114 cps at 20 rpm [spindle RVT # 3], a pH of 4.4 and a Tg of -43 * C. Example 8 Preparation of water-based pressure sensitive adhesives of vinyl neo-esters with 8 to 13 carbon atoms, 2-EHA. ethylene, vinyl acetate, methyl methacrylate and acrylic acid To a 2-liter resin reactor equipped with a stirrer, condenser and external thermal controls is added the following initial reaction mixture comprising 320 g of deionized water, 1.6 g of sodium citrate and 166.4 g of a pre-emulsion mixture of the following composition: Deionized water 360.00 g Abex EP-120 [30% active] * 10.29 g Igepal CO-887 [70% active] 10.29 g Aerosol MA-80 [80 % active] 9.00 g Vinyl acetate 36.00 g 5% Monomer of vinyl neoester C3_i3 144.00 g 20% Methyl methacrylate 93.60 g 13% 2-ethylhexyl acrylate 432.00 g 60.0% Acrylic acid 14.40 g 2.0% The initial reaction mixture is heated to 80 * C under a nitrogen atmosphere with stirring at 150-200 rpm. The polymerization reaction is initiated by the addition of 3.4 g of a 5% solution of sodium persulfate over a period of 14 minutes. After the start, both the delay charge of pre = emulsion [6.2 g] and the delayed feed of persulphate initiator [0.3 g / min], respectively. A total of 926 g of the pre-erase mixture and 45 g of sodium persulfate solution are consumed within 150 minutes. An additional 3 g portion of the sodium persulfate solution is added to reduce the residual monomer to a value less than 1000 ppm as determined by GC. The polymerization temperature is maintained at 80-83 * C. The resulting copolymer latex has 49% solids, a vicosity of 160 cps at 20 rpm [spindle RVT # 2] and a pH of 3.5, a Tg = -37 ° C, and numerical values of the particle size Da = 157 nm and weight values of the particle size D? = 169 nra. Example 9 Performance Evaluation of a Pressure Sensitive Adhesive on Polyester The emulsions of Examples 1-8, when coated on 50 μm polyester film [Mylar] with a dry weight of 22-24 g / m2, after dry for 5 minutes at 110 ° C, give the pressure sensitive adhesive properties [detachment, adhesion and tear] measured by the following methods of the Council on Pressure Sensitive Tape [PSTC]: The results are reported in Table 1. Council Methods on TPSTC Pressure Sensitive Tape] • Adhesion is measured at a peel angle of 180 * after a residence time of 20 minutes, for a 25.4 mm wide tape on stainless steel at 23 * C u a relative humidity condition of 50% at a release rate of 30.48 cm / min [PSTC-1]. The adhesion of a spiral is measured by means of the instantaneous contact of a spiral of 25.4 mm of width perpendicular to a plane of a test panel of stainless steel of 6.45 cm2 of area. The tear is measured in terms of the time required to detach a standard belt area from a stainless steel test panel under a standard load [PSTC-7].

Table 1 PSA properties of examples 1-8 The results show that the higher Tg material of Example 2 vs the lower tg material of Example 1 resulted in values of similar shear strength but greater cohesive strength [tear] than the material with the smaller Tg. Spiral adhesion was lower than expected from adhesives that have greater tear. The vinyl vesatate system of Example 3 had the best resistance to peeling and good tearing. Again the higher Tg of Example 4 had a greater tear than the product of Example 3. The detachment was noticeably affected but remained well in relation to the commercial systems. Example 5 shows a detrimental effect on the cohesive force when a higher vinyl ester is replaced by vinyl neo-esters with 8 to 13 carbon atoms. Pressure sensitive adhesives including ethylene had a significantly lower tear than expected due to the softness imparted by ethylene. However, in relation to comparable ethylene-based pressure sensitive adhesives, those values are good, example 8 shows that replacing up to 5% of the vinyl neo-esters with 8 to 13 carbon atoms with an ester of aliphatic vinyl less, versus vinyl acetate can adversely affect the release and spiral adhesion. Although the tear is somewhat better in the adhesive that contains vinyl acetate. Example 10 Evaluation of the performance of pressure sensitive adhesive on plasticized PVC The construction of pressure sensitive adhesives is prepared by coating the liquid dispersions on a siliconized, dried and laminated base in the plasticized flexible PVC film with a coating weight of 27-29 g / m2. The pressure-sensitive performance properties for the initial and thermally aged samples [70 * C for 7 days on a siliconized base] are presented in Table 2: Table 2 * Flexbond 1625 emulsion is a water-based commercial pressure sensitive adhesive. The results show excellent detachment and cohesive strength on plasticized PVC. An important feature is the 180 * release, thermally aged emulsions that have vinyl polymers that incorporate vinyl esters of neo-acids with 8 to 13 carbon atoms with the formula Ci., 3H1? .a7CO, CH = CH2 resulted in substantially better adhesion and resistance to migration of the plasticizer in the PVC compared to the commercial adhesive. Example 11 Performance of comparable PSA vs. commercial products on plasticized flexible polyvinyl chloride film In a similar manner to example 10, pressure sensitive adhesive constructions were prepared by coating the liquid dispersion on a silified basis, drying and laminating on the chloride film of flexible plasticized polyvinyl [vinyl film F 400] with a coating weight of 27 g / m2. The pressure-sensitive properties and thermal aging [70 * C for 7 days in a siliconised base] for the adhesives of examples 1 and 4, two commercial water-based acrylic emulsions and a pressure-sensitive adhesive based on Acrylic commercial solvent were determined and the results are presented in table 3.

Table 3 The results show superior thermal detachment and aging properties for emulsion-based pressure sensitive adhesives in PVC films incorporating vinyl neo-esters with 8 to 13 carbon atoms of the formula Cs_liH17.2? CO, CH = CH, compared to commercial water-based pressure sensitive adhesive emulsions and commercial solvent-based pressure sensitive adhesive.

Claims (21)

1. CLAIMS 1. In a pressure sensitive adhesive based on aqueous emulsion consisting of a copolymer having polymerized units of alkyl acrylates with 1 to 12 carbon atoms or alkyl methacrylates with 1 to 12 carbon atoms, the improvement consists of the incorporation of a vinyl ester of neo-acid with 8 to 13 carbon atoms obtained from a base of propylene oligomers.
2. 2. The emulsion according to claim 1 wherein the copolymer has a tg of -15 to -70 * C.
3. 3. The emulsion according to claim 2 in which the vinyl ester is represented by the chemical formula: Ca., 3H,? _ 27C02CH = CH2
4. 4. The emulsion according to claim 2 in which the copolymer consists of the monomers [a] to [h] in the percentages by weight of the following total copolymer: a] 5-40% by weight of a vinyl ester of a neo-acid b] 30-80% by weight of an alkyl ester with 1 to 12 carbon atoms of acrylic or methacrylic acid, c] 0-20% by weight of a vinyl ester of saturated aliphatic acids, d] 0-30% by weight of ethylene, styrene or butadiene, e] 0 20% by weight of maleate / di-alkyl fumarate with 1 to 13 carbon atoms, f] 0-5% by weight of a hydroxyalkeyl [meta] acrylate; g] 0-5% by weight of [meta] acrylamide; and h] 0-10% by weight of unsaturated alpha, beta-ethylene-unsaturated monocarboxylic acid.
5. 5. The emulsion according to claim 4 wherein the alkyl ester of acrylic or methacrylic acid present in an amount of from 40 to 70% by weight of the vinyl polymer particle.
6. 6. The emulsion according to claim 5 in which the vinyl ester represented by the component [a] is present in an amount of about 15 to 30% by weight of the copolymer.
7. 7. The emulsion according to claim 6, wherein the copolymer has a Tg of -20 to -50 ° C.
8. 8. The emulsion according to claim 6 wherein the alkyl acrylate represented by the component [b] is selected from the group consisting of methyl methacrylate, butyl acrylate and 2-ethylhexyl acrylate.
9. 9. The emulsion according to claim 7 in which the vinyl ester is vinyl versatate.
10. 10. The emulsion according to claim 6, wherein the copolymer incorporates acrylic or methacrylic acid units.
11. 11. The emulsion according to claim 10, wherein the acrylate portion of the copolymer consists essentially of polymerized units of methyl methacrylate, an acrylate consisting of 2-ethylhexyl acrylate and butyl acrylate, vinyl versatate.
12. 12. In a process for producing a pressure sensitive adhesive based on aqueous emulsion consisting of a copolymer having polymerized units of alkyl acrylate with 1 to 12 carbon atoms or alkyl methacrylate with 1 to 12 carbon atoms and an ethylenically unsaturated monomer consisting of forming a system stabilized with a surfactant and then polymerizing the alkyl acrylate with 1 to 12 carbon atoms or alkyl methacrylate with 1 to 12 carbon atoms and ethylene-unsaturated monomer under conditions for forming the copolymer, the improvement consists in incorporating a vinyl neo-ester with 8 to 13 carbon atoms obtained from a propylene oligomer base in the form of an ethylenically unsaturated monomer.
13. The process for producing the pressure sensitive adhesive emulsion based aqueous emulsion of claim 12 wherein the copolymer has a Tg of -15 to -70 ° C.
14. The process for producing the pressure sensitive adhesive emulsion based aqueous emulsion of claim 12 wherein the vinyl ester is represented by the chemical formula:
15. 15. The process for producing the pressure sensitive adhesives at base of aqueous emulsions according to claim 14 in the lime the copolymer consists of the monomers [a] to [h] in the following percentages of the following total copolymer: a] 5-40% by weight of a vinyl ester of a neo-acid b] 30-80% by weight of an alkyl ester having from 1 to 12 carbon atoms of acrylic or methacrylic acid, c] 0-20% by weight of a vinyl ester of saturated aliphatic acids, d] 0-30% by weight of ethylene, styrene or butadiene, e] 0-20% by weight of maleate / di-alkyl fumarate with 1 to 13 carbon atoms, f] 0-5% by weight of a hydroxyalkyl [meta] acrylate; g] 0-5% by weight of [meta] acrylamide; and h] 0-10% by weight of alpha, beta-ethylenically unsaturated monocarboxylic acid.
16. 16. The process for producing pressure sensitive adhesives based on aqueous emulsions according to claim 15 in which the alkyl ester of acrylic or methacrylic acid present in an amount of from 40 to 70% by weight of the vinyl polymer.
17. 17. The process for producing pressure sensitive adhesives based on aqueous emulsions according to claim 15 in which the vinyl ester is present in an amount of about 15 to 30% by weight of the copolymer.
18. 18. The process for producing pressure sensitive adhesives based on aqueous emulsions according to claim 15 wherein the copolymer has a Tg of -20 to -50 * C.
19. 19. The process for producing pressure sensitive adhesives based on aqueous emulsions according to claim 18 wherein the alkyl acrylate is selected from the group consisting of methyl memtacrylate, butyl acrylate and 2-ethylhexyl acrylate.
20. 20. The process for producing pressure sensitive adhesives based on aqueous emulsions according to claim 18 in which the vinyl ester is vinyl versatate.
21. 21. The process for producing pressure sensitive adhesives based on aqueous emulsions according to claim 20 in which the copolymer incorporates the polymerized units of acrylic or methacrylic acid.