CS259825B1 - Ultimate acrylate contact adhesives - Google Patents

Abstract

The subject of the solution are solvent-type acrylate contact adhesives, suitable for the preparation of pressure-adhesive and at the same time easily removable adhesive layers. The essence is the composition of the adhesives, which consist of 20 to 60 parts by weight of specified copolymers of acrylic acid esters, α,β-ethylenically unsaturated aliphatic carboxylic acids, monomers containing an oxirane group and optionally monomers from the group including alkyl esters of methacrylate, styrene and vinyl acetate, 30 to 80 parts by weight of organic solvents, 2 to 40 parts by weight of specified plasticizers and optionally up to 5 parts by weight of catalysts of the substituted amino compound type and up to 60 parts by weight of other additives.

Description

The invention relates to solvent-type removable acrylate contact adhesives suitable for the preparation of pressure-sensitive, yet readily removable adhesive layers on bonded articles or on suitable substrates.

Self-adhesive labels, tapes and foils of various materials (paper, plastics, metal foils, etc.) have a surface with a thin adhesive layer with an adhesive character. This layer is obtained by applying a solution of the adhesive in organic solvents or an aqueous dispersion of the adhesive to the material by crayfish, a slit, by means of rollers or other coating technique and subsequently evaporating the volatile solvents or water. The adhesives may also be applied to a removable backing from which the adhesive layer is transferred to the top of the second substrate. In order to create a perfect bond by means of an adhesive layer with an adhesive character, it is essential that the adhesive layer have the following important properties in balance: adhesion, cohesion, strength and elasticity.

However, some self-adhesive applications require that, after a period of time, the article, label or film to be bonded can be easily separated from the article on which it was. glued without damaging the surface of the article or leaving part or all of the adhesive layer on the surface of the other article. Adhesives that meet this requirement are removable and are used, for example, for labeling self-adhesive price labels or inscriptions with important warnings, cautions or instructions, as well as for multi-color coatings of objects to mask areas to be unpainted, for temporary surface protection various objects from mechanical and other damage and in many other applications.

Most commonly, removable contact adhesives are prepared from raw natural or synthetic rubbers to which some organic plasticizers are added to reduce surface adhesion of the adhesive layer. Modifying resin materials are not added to these compositions at all or are present in very limited amounts (Dunning H. R., Pressure Sensitive Adhesives, Formulations and Technology, Noves Data Corp., Park Ridge, USA, 1977). A disadvantage of these rubber adhesive layers is the fact that the remaining double bonds undergo further chemical processes, which substantially change the properties of the adhesive layer. The elasticity of the layer decreases and the concentration of the nodes in the three-dimensional mesh increases, causing increased excretion of organic plasticizers on the surface of the adhesive layer. The deposited plasticizers either penetrate and degrade to some extent the porous substrates or articles, or cause complete loss of adhesion of the adhesive layer and the sticking of the self-adhesive material from the article. Other adhesives are also known, the most important of which are acrylic. These adhesives are more stable, more uniform and of higher quality than rubber-based adhesives, but are predominantly permanent in nature and are difficult to remove from the surface of the adhesive. Adhesion reduction for acrylate-type adhesives has been achieved to some extent by increasing the acrylic and / or methacrylic acid content of the starting monomer blend for radical polymerization (U.S. Pat. No. 2,607,711), but at the expense of significantly deteriorating the elasticity of the adhesive layer. Other authors have achieved removability using aqueous dispersions of acrylic copolymers prepared from special, hardly available monomers.

The present invention is directed to removable acrylic contact adhesives based on solutions of acrylic copolymers in organic solvents and additives. The invention is based on the fact that these adhesives consist of 20 to 60 wt. % of acrylic copolymers prepared by free-radical polymerization of a mixture of monomers containing 37 to 99.3 percent by weight of acrylic copolymers; acrylic acid esters derived from aliphatic primary or secondary alcohols having a carbon number of 1 to 14, wherein the weight average alkyl group of these esters is 4 to 12 carbon atoms, 0.5 to 15 wt. % α, β-ethylenic unsaturated aliphatic carboxylic acids having a carbon number of 3 to 5, in particular acrylic or methacrylic acid, 0.2 to 8 wt. % of unsaturated epoxy compounds selected from the group consisting of glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether, and optionally up to 40 wt. monoethylenically unsaturated monomers selected from the group consisting of alkyl esters of methacrylic acid having a carbon number of 1 to 14, styrene and its alkyl derivatives having a carbon number of 1 to 4, and vinyl acetate. In addition to the acrylic copolymers mentioned, the adhesives also contain 30 to 80 wt. 2 parts to 40 wt. parts of plasticizers and optionally up to 5 wt. parts of the catalyst based on substituted amino compounds up to 40 wt. parts of other additives, in particular natural and synthetic resins, dyes, pigments or fillers. Plasticizers used are carboxylic acid esters of 4 to 12 carbon atoms derived from hydroxyl compounds of the aliphatic type of primary or secondary alcohols having 1 to 12 carbon atoms, mono-, di- and triglycols and their monoethers, polyols and aryl alcohols and / or liquid oligomeric compounds. average mol. 200 to 3,000, in particular polyethylene glycols, polypropylene glycols, liquid polyesters and low molecular weight polymers and copolymers of esters of acrylic and / or methacrylic acid derived from aliphatic primary or secondary alcohols having 1 to 12 carbon atoms, optionally with n-methylstyrene, butadiene, isobutylene or % of other unsaturated monomers, optionally in admixture with 35 wt. other plasticizers.

The removable acrylate contact adhesives of the present invention have the advantage that they contain a copolymer which, in addition to acrylic acid esters and possibly other vinylic monomers, has acrylic and / or methacrylic segments in its molecule, and oxyran group monomer segments which together after evaporation the solvents react to form a three-dimensional network. Curing takes place at normal or elevated temperature and is accelerated by catalysts based on substituted amino compounds. The three-dimensional network of acrylic copolymer carries elasticity, high cohesion, and sufficient adhesion of the adhesive layer to provide the necessary bond strength. Due to the osmotic action of the network, the organic plasticizers present are slightly deposited on the surface of the adhesive layer and are a source of removable properties of the adhesive. The formation of the three-dimensional mesh is complete when the entire number of reactive functional groups have reacted and since then the properties of the adhesive layer have practically not changed. Organic plasticizers are no longer eliminated from the network and therefore cannot migrate to porous substrates. The self-adhesive materials prepared from the removable acrylic adhesive of the present invention are characterized by long-term stability of their mechanical and adhesive properties.

An acrylic copolymer prepared by the free-radical polymerization of a monomer mixture in which acrylic esters of aliphatic alcohols, with the exception of tertiary alcohols having 1 to 14 carbon atoms, such as methanol, ethanol, n-propanol, is used to prepare the removable acrylate contact adhesives. , isopropanol, n-butanol, isobutanol, π-pentanol, isopentanol, pentanol-3,1-methylbutanol, 2-methylbutanol, n-hexanol, 1-methylpentanoJ, 2-methylpentanol, 3-methylpentanol, 2-ethylbutanol, n -heptanol. 1-methylhexanol, 2-methylhexanol, 3-methylhexanol, heptanol-3,2-ethylpentanol, n-octanol, isooctanol, 2-ethylhexanol, 3,5,5-trimethylhexanol, n-decanol or dodecanol. The average length of the alkyls in the acrylic acid ester mixture must be 3 to 12 carbon atoms in order to create the prerequisites for high adhesion of the adhesive layer to the various materials. The other components of the basic acrylic copolymer comprise from 0.5 to 15 wt. % of acrylic and / or methacrylic acid, optionally other α, β-ethylenically unsaturated aliphatic acids, such as vinylacetic acid, crotonic acid, allylacetic acid and maleic acid or its anhydride, and 0.2 to 8 wt. unsaturated epoxy compounds selected from the group consisting of glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether. For special purposes, the copolymer may contain up to 40 wt. modifying other monoethylenically unsaturated monomers such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, nheptyl methacrylate, 2-ethylhexylacrylate, 3,5,5-trimethylhexyl methacrylate - methylstyrene, vinyltoluene, tert-butylstyrene, vinyl acetate and the like.

An important component of the adhesives of the present invention are organic plasticizers added in an amount of 2 to 40 wt. 20 parts to 60 parts by weight of the base acrylic copolymer. These agents both soften the adhesive layer and, on the other hand, due to the osmotic action of the polymer network and thermodynamic interactions with the polymer, precipitate on the surface of the adhesive layer and thus contribute to the removable nature of the adhesive materials. Plasticizers based on mono-, di-, tri-, tetraa-higher esters of organic acids having 4 to 22 carbon atoms (butyric, caprylic, lauric, palmitic, myristic, stearic, oleic, hydrostearic, ricinine acids) can be advantageously used for this purpose. , acetylricinooleate, violet, and the like) with aliphatic primary or secondary alcohols having 1 to 12 carbon atoms, mono-, di- and triglycols and their monoethers, polyols and aryl alcohols (such as methanol, ethanol, n-butanol, i-butanol, n). hexanol, 2-ethylbutanol, 1,3-dimethylbutanol, n-octanol, iso-octanol, 2-ethylhexanol, n-decyl alcohol, cyclohexanol, benzyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, ), organic phosphates such as tri-n-butyl phosphate, tricresyl phosphate, octyldiphenyl phosphate and the like and liquid oligomeric substances average molecular weights of 200 to 3,000, such as polyethylene glycols, polypropylene glycols, liquid polyesters, low molecular weight oligomers of acrylic and / or methacrylic esters with aliphatic alcohols (except tertiary) having carbon numbers of 1 to 12, α-methylstyrene, butadiene, isobutylene and other vinyl monomers.

The formation of the three-dimensional network of the removable acrylate contact adhesives according to the invention can be favorably influenced by the addition of up to 5% by weight. parts of catalysts based on substituted amino compounds. In principle, all known amino-hardeners of epoxy resins can be used, in particular diethylenetriamine, triethylenetetramine, triethylenediamine, dipropylenetriamine, tetraethylenepentamine, trimethylenehexamethylenediamine, cyclohexylaminopropylamine, 4,4'-diaminodifluoroethane, 4,4'-diaminodiphane, 4,4'-diaminodiphenyl, 4,4'-diaminodiphenyl, 4,4'-diaminodiphenyl, , dimethylaminoethanol, 1,3-bis (dimethylamino) -2-hydroxypropane, various types of resanils and the like.

Some properties of the adhesives of the present invention can be further modified and improved by adding up to 60 wt. parts of organic and / or inorganic additives. Adhesive and cohesive properties are generally modified by the addition of unmodified or modified natural and / or synthetic resins, such as rosin, modified rosin-based resins (rosin-glycol resin resins, polyols, phenol-formaldehyde condensation products, and fatty acid, fumaric, fatty acids , including mixed fatty acids of natural origin and their dimers and trimers, etc.], as well as copal resins, shellacs and balsams, phenol-formaldehyde resins, epoxy, epoxyester, polyester resins, etc. To enhance the adhesive layer, the adhesive can be colored with soluble organic dyes, preferably monoazo such as resinol yellow, resinol orange, resinol red and the like, or treated with inorganic pigments and / or fillers such as titanium white, zinc white, limestone, talc, talc, slate meal, blanc-f ixe, chalk, precipitated calcium carbonate, feldspar dust, iron oxide, ocher, bauxite, chrome pigments, etc.

30 to 80 wt. parts of organic solvents, the list of which is not limited thereto. Preferably, hydrocarbon solvents of petrochemical origin can be used, but also esters, alcohols, ketones and others, generally boiling up to 200 [deg.] C., can be rapidly evaporated during film formation.

The adhesives of the present invention are suitable for the preparation of pressure-sensitive adhesive layers on paper and textile materials, either by direct application of skates, slots, rollers or other coating techniques, or by applying onto a suitable substrate from which the adhesive layer is transferred to the surface. other material.

Example 1

Removable contact adhesive especially suitable for the preparation of self-adhesive labels, labels and protective films.

wt. parts of a copolymer prepared from:

- 62 wt. 2-ethylhexyl acrylate - 34 wt. % butyl methacrylate - 1 wt. % acrylic acid - 3 wt. glycidyl methacrylate wt. parts of a solvent mixture comprising:

- 33 wt. % ethyl acetate - 31 wt. isopropyl alcohol - 29 wt. toluene - 7 wt. % n-hexane wt. parts of dibutyl phthalate as plasticizer

0.3 wt. % of triethanolamine.

The prepared adhesive is a clear, colorless liquid with a viscosity of 1.4 to 4 Pa. s, so it is particularly suitable for application of skates.

Example 2

Removable contact adhesive especially suitable for preparing textile self-adhesive tapes.

wt. parts of a copolymer prepared from:

- 28 wt. % ethyl acrylate - 60 wt. 2-ethylhexyl acrylate - 7.7 wt. % acrylic acid - 0.3 wt. glycidyl methacrylate - 4 wt. vinyl acetate wt. parts of a solvent mixture comprising:

- 28 wt. toluene - 19 wt. isopropanol - 51 wt. % naphtha with a distillation range of 80 to 110 ° C - 2 wt. % ethylene glycol monoethylene ether acetate wt. parts of a plasticizer mixture consisting of:

- 30 wt. % of tricresyl phosphate - 70 wt. di-isooctyl phthalate wt. parts of an additive mixture comprising:

- 65 wt. % mixed glycerin ester and rosin with a softening point of 90 ° C - 13% by weight; Anatase type titanium dioxide - 22 wt. finely ground limestone.

Homogenization of the mixture of the above ingredients results in a fast-drying, filled contact adhesive suitable for application to the skate. The viscosity is up to 40 Pa. with.

Example 3

Removable contact adhesive with high cohesion and temperature stability of the adhesive layer.

parts by weight of copolymer prepared from:

- 17 wt. % ethyl acrylate - 33.5 wt. % butyl acrylate — 43 wt. 3,5,5-trimethylhexyl acrylate - 0.5 wt. % methacrylic acid - 6 wt. glycidylacrylate wt. parts of the solvent mixture containing

5 9 8.2 5 - 30% wt. toluene - 70 wt. techn. 80-110 ° C wt. parts of an oligomeric butyl acrylate type plasticizer having a molecular weight of 600 to 800 wt. parts of palm type epoxy resin of average molecular weight. 1 200 wt. parts of diethylenetriamine.

Homogenization of the mixture of components yields a reactive contact adhesive having a viscosity of 3 to 8 Pa. It is suitable for roll coating, the catalyst being added immediately prior to processing.

Example 4

Removable contact adhesive crosslinkable at normal temperature within 7 days after the adhesive layer has dried.

wt. parts of a copolymer prepared from:

- 12 wt. % ethyl acrylate — 36 wt. 2-ethylhexyl acrylate - 6.4 wt. % acrylic acid - 6.4 wt. maleic anhydride - 0.2 wt. allylglycidyl ether - 27 wt. % of vinyl acetate - 11 wt. styrene mass. parts of a solvent mixture comprising:

- 20 wt. % toluene - 36 wt. acetone - 28 wt. isopropanol - 16 wt. of ethanol anhydrous mass. parts of polyethylene glycol having a molecular weight of 300 as a plasticizer of mass. parts resinol yellow

0.4 wt. % of 1,3-bis-dimethylamino] -2-hydroxypropane

The adhesive is a clear, golden yellow liquid with a viscosity of 6 to 8 Pa. It is suitable for application of rollers or rollers.

Claims (2)

Subject 1. Removable acrylate contact adhesives based on solutions of acrylic copolymers in organic solvents and additives, characterized in that they consist of: 20 to 60 parts by weight of acrylic copolymers prepared by the free-radical polymerization of a monomer mixture comprising 37 to 99.3% by weight of acrylic acid esters of derived primary or secondary alcohols having a carbon number of 1 to 14, wherein the weight average alkyl group of these esters is 4 to 12 carbon atoms, 0.5 to 15% by weight of α, β-ethylenically unsaturated aliphatic carboxylic acids having a carbon number of 3 to 5, in particular acrylic or methacrylic acid, 0.2 to 8% by weight of unsaturated epoxy compounds selected from the group consisting of glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether, and optionally up to 40% by weight of monoethylenically unsaturated monomers selected from the group consisting of alkyl esters of methacrylic acid having 1 to 14 carbon atoms; the number of carbon atoms in the alkyl substituent 1-4 and vinyl acetate, VYNALEZU 30 to 80 parts by weight of organic solvents, 2 to 40 parts by weight of a plasticizer, and optionally up to 5 parts by weight of substituted amino compound catalysts and up to 60 parts by weight of other additives, in particular natural and synthetic resins, dyes, pigments or fillers. 2. Removable acrylate contact adhesives according to claim 1, characterized in that they contain, as plasticizers, carboxylic acid esters of 4 to 12 carbon atoms derived from hydroxyl compounds of the type of aliphatic primary or secondary alcohols having 1 to 12 carbon atoms, mono-, dia-triglycols and their monoethers, polyols and aryl alcohols and / or liquid oligomeric compounds having an average mol. 200 to 3,000, in particular polyethylene glycols, polypropylene glycols, liquid polyesters and low molecular weight polymers and copolymers of esters of acrylic and / or methacrylic acid derived from aliphatic primary or secondary alcohols having 1 to 12 carbon atoms, optionally with α-methylstyrene, butadiene, isobutylene or % of other unsaturated monomers, optionally in admixture with 35 wt. organic phosphates, based on the content of other plasticizers.