DE3936890A1 - ADHESIVE COATINGS AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Abstract

Permanently adhesive and reversibly usable adhesive compositions are produced on substrate materials by monomer mixtures which on polymerization yield permanently adhesive, film-forming acrylic ester polymerizates. In a first process step the monomer mixtures are polymerized up to the onset of gelation, and in a second process step the gelled reaction mixture is size-reduced mechanically and applied to the substrate material. A coherent film layer is then formed on the substrate by heat treatment. If necessary, in the second process step the reaction mixture is diluted with solvent and subjected to a shearing stress in order to spread the gel. The subsequent heat treatment should be carried out at temperatures of 90 to 170 DEG C.

Description

The present invention relates to a method for the manufacture provision of frequently used PSA coatings with a relatively low tack over other materials, but one high cohesion and good anchoring on the carrier material. Be the pressure-sensitive adhesive coating is preferably applied to paper.

Self-adhesive fabrics with permanent adhesion from a substrate made up of microspheres on at least one side normally sticky elastomeric copolymers of a certain Composition exists and in which between the substrate and the Microspheres there is a binder in which the microspheres have already been embedded from the German patent specification 24 17 312 known. The mentioned patent specification goes further Development of the teaching given in US Patent 36 91 140 for the production of self-adhesive fabrics, in which also described acrylate copolymers in the form of microspheres are. Only if the Mi crocodiles suspended in a non-solvent and then coated with a cross-linked acrylic polymer are so that the microspheres partially out of the binder protrude, the desired long-term adhesion is achieved.

The object of the present invention was therefore to provide a method for Coating of surfaces to be found in which without separate  Procedural measures directly applied a pressure sensitive adhesive coating can be, which on the one hand adheres firmly to the base, the other on the other hand, frequent loosening with a relatively small tack and reuniting with other areas allowed.

The solution to the problem is now achieved by mixing monomers cues that become permanently sticky and film during the polymerization lead the acrylic ester polymers, in a first process step polymerized until the onset of the gel effect and in egg nem further process step under the gelled reaction mixture crushed mechanical influence and on the carrier material brings and then together by thermal treatment hanging film layer produced on the carrier.

It must be regarded as surprising that the above specified procedure coatings or polymer films he that have a sufficiently low adhesion and a have sufficiently strong film cohesion, even after frequent ab separate to allow re-gluing. That this with the specially obtained reimbursed polymers would be possible could not be expected at all, and it must be surprising can be seen that no special primer or an anchor Binding agent is necessary to the with a relatively low Tack equipped polymer film to bind firmly to the base.

To carry out the method according to the invention, one takes advantage moderately first the polymerization in solution using fol gender components before:

• a) 75 to 98 wt .-% of a monomer or monomer mixture of the formula I CH₂ = C (R₁) -COOR₂ (I) in the mean
  R₁ = H or CH₃ and
  R₂ = an alkyl radical with 2 to 18 carbon atoms or an alkyl terminated (oligo) alkyl ether radical with up to 18 carbon atoms
• b) 2 to 25 wt .-% of a monomer or monomer mixture of formula II CH₂ = C (R₁) -COO-R₃-OOC-C (R₁) = CH₂ (II) in which R₁ = H and / or CH₃ and R₃ is a residue of a di- or polyfunctional hydroxy compound, its molecular weight does not exceed 3500, and if necessary additionally
• c) up to 20% by weight of a monomer with pronounced polarity, where the weight percentages are based on the sum of the ver obtain bonds according to a) and b).

The polymerization itself is carried out under normal conditions means exclusion of air at temperatures of around 60 to 120 ° C made for half an hour to a few hours. It is generally not required that the viscosity of the Solution is measured. The expert can namely the Observe a sudden increase in the viscosity of the stirred systems ten.

Particularly suitable solvents are those with a pronounced Solvation capacity for the polymers formed, such as Es ethyl acetate or methyl ester, toluene, xylene, chloroform, Perchlorethylene and 1,1,1-trichloroethane, optionally under Mit use of minor amounts of methylene chloride, butanone, Acetone or low boiling aliphatic hydrocarbons.

Among the monomers used for the polymerization mixtures are of particular interest within Group I se: butyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, n-  Octyl acrylate, n-decyl acrylate, isodecyl acrylate, lauryl methacrylate, Decyl methacrylate, methoxyethyl methacrylate. Within group II: Hexanediol acrylate, hexanediol methacrylate, trimethylolpropane trimeth acrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, Polybutadiene diacrylate, tetradecyl diol diacrylate, tetraglycol dimeth acrylate.

Within the optional monomers with pronounced Polarity are particularly noteworthy acrylic acid, methacrylic acid, Hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, Hydroxypropyl methacrylate, vinyl pyrrolidone, vinyl acetate and meth aryloyloxypropyltrimethoxysilane.

The polymerization is carried out in a known manner by radical formers, especially peroxides. For practical reasons dibenzoyl peroxide is preferred here, albeit others, ins special radical images soluble in organic solvents, e.g. B. azobutyric acid dinitrile can be used.

After the polymerization recognizable by the steep viscosity increased gel formation, sudden increase in visco is finished, it is expediently diluted with further solution means from the group described above and subjects resulting product of a strong shear stress in strong Agitators or other comminution devices such as dispersing agents, Dissolver mixer etc.

The viscosity is expediently reduced to values below 5000, preferably pressed down below 1000 mPa · s. On in this way, between 100 and 1000 mPa · s is obtained portable masses, which according to known techniques to be layered documents are applied. The so applied Lyogel is then in by heating and vacuuming the solvent  a Xerogel is transferred, which due to the still existing niedermo immediately and with the lecular and per se soluble components Is connected underground. This enables film formation light, whereby the gel particles are also firmly integrated. At Appropriate selection of the monomers covers surfaces with structure structures that have a low tack overall.

Simultaneously or immediately after the evaporation of the Solvent, associated with film formation, becomes another ther mixed treatment made, which takes about half an hour to lasts two minutes, and at which the polymers reach temperatures brought between about 90 and 170 ° C. Here at this ther mixing treatment then occurs the final formation of the ge wanted a relatively low tack surface. The thermal treatment is expediently known Dry or heated plants made, which in general work continuously. The heating can be done using steam or done electrically with infrared radiation.

As a base comes primarily paper for the invention Procedure in question. Of course, others can porous underlays such as non-woven fabrics or suitable fabrics made of natural or synthetic fibers.

The present invention thus relates to removable Pressure sensitive adhesives with such permanent pressure sensitive are equipped, so that a very frequent gluing and separating the gluing points is made possible. Claimed and explained also permanently sticky and reversibly usable coated Surfaces, especially paper-based, which after the Processes according to the invention have been produced. You can with appropriate management of the manufacturing process also others  flat fabrics are coated, provided that they have the thermal loading survive the process virtually unchanged. Come to this Fabrics or foils made of plastics or metals in question. Everything dings must in this case for a reliable permanent Ver anchoring of the pressure-sensitive adhesives by using known per se Measures are taken.

Examples

The coating compositions required to produce the coating were prepared by polymerizing the monomers in 625 g of ethyl acetate. For this purpose, the monomers were added to the solvent and, after the addition of benzoyl peroxide, with stirring in a laboratory apparatus with the exclusion of air, ie in a dry N ₂ atmosphere with stirring in a reflux condenser, kept at an internal temperature of 70.degree. It is held at this temperature until the gel point is reached, as can be seen from the sudden increase in viscosity. After about a further 5 minutes, 350 ml of dry toluene are added to the mixture and the mixture is cooled to about 25 ° C.

After cooling, the reaction amount is treated in a dissolver until the viscosity is between 100-300 mPa · s (25 ° C). Paper (70-85 g / m ² ) is coated with this product and heated to 150 ° C. in a drying tunnel for 3 minutes. The coating was then 7 µm.

In the following tables 1a and 1b are dependent on the serial number of the example shows the monomer in g. The Polymerizations were initiated with 0.7 g benzoyl peroxide in the Examples 5 and 8, however, with 1.8 g and 0.9 g, respectively.  

Table 1a

Table 1b

The coatings prepared as described above were subjected to the following tests:

Peel strength

Five 375 mm × 25 mm adhesive strips are glued to paper and at 23 ° C at an angle of 180 ° at a speed of 300 mm / min separated from each other. The value in g / 25 mm is a measure for cohesion and adhesion of the adhesive. The adhesive layer would be not destroyed in the peel test and completely detaches from the sub strat (broken adhesive).

Tensile shear strength of paper bonds

Five adhesive strips of 125 mm × 25 mm are glued to paper with an area of 625 mm ² and torn in a pulling / stretching machine at a speed of 50 mm / min feed. The value g-force / mm ² is a measure of the cohesion and adhesion of the adhesive. No transmission or destruction (adhesion breakage) takes place here either.

These tests were carried out once a day after the coating had been produced and after 30 days of storage at 20-25 ° C. and 50-60% relative atmospheric humidity. In the following table 2a and 2b the averaged measured values in g / 25 mm for peel strength and g / mm ² for shear strength after 1 day (1d) and 30 days (30d) are given under the serial numbers of the examples.

Table 2a

Table 2b

Claims (7)

1. A process for the preparation of permanently tacky and reversibly usable PSA coatings on carrier materials, characterized in that monomer mixtures which lead to permanently tacky and film-forming acrylic esters during the polymerization are polymerized in a first process step until the gel effect occurs and in one a further step of the process, comminuted the gelled reaction mixture under mechanical influence and applied it to the support material and then produced a coherent film layer on the support by thermal treatment. 2. The method according to claim 1, characterized in that in second process step, the reaction mixture if necessary after dilution with solvent a shear stress for the purpose of dividing the gel formed and the be traded mixture of a thermi applied on a carrier after-treatment at temperatures from 90 to 170 ° C undergoes. 3. Process according to claims 1 and 2, characterized in that one carries out the polymerization using the following components:

• a) 75 to 98 wt .-% of a monomer or monomer mixture of the formula I CH₂ = C (R₁) -COOR₂ (I) in the mean
  R₁ = H or CH₃ and
  R₂ = an alkyl radical with 2 to 18 carbon atoms
  or an alkyl end-capped (oligo) alkyl ether radical having up to 18 carbon atoms
• b) 2.0 to 25 wt .-% of a monomer or monomer mixture of the formula II CH₂ = C (R₁) -COO-R₃-OOC-C (R₁) = CH₂ (II) in which R₁ = H and / or CH₃ means and R₃ = a residue of a di- or polyfunctional hydroxy compound, the molecular weight of which does not exceed 3500, and optionally additionally
• c) up to 20% by weight of a monomer with pronounced polarity, the percentages by weight relating to the sum of the compounds according to a) and b).

4. The method according to claims 1 to 3, characterized in that the monomers according to formula I from the group of butyl acrylate, octyl acrylate, decyl acrylate, lauryl methacrylate, decyl methacrylate, Methoxyalkyl methacrylate and the formula II from the group Hexanediol diacrylate, hexanediol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, pentaerytrite tetraacrylate, polybutadiene diacrylate, tetradecyl diacrylate, tetra glycol dimethacrylate, tetraethylene glycol diacrylate, triethylene glycol dimethacrylate as well as those with pronounced polarity the group acrylic acid, methacrylic acid, hydroxyethyl acrylate, Hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, methacryloyloxypropyltrimethoxysilane, N-vinyl pyrrolidone and vinyl acetate have been selected. 5. The method according to claims 1 to 4, characterized in that the radical-initiated polymerization in solvents (such as ethyl acetate, toluene, xylene, chloroform, perchlorethylene or 1,1,1-trichloroethane) with pronounced solvation capacity for the polymers formed.   6. Removable pressure sensitive adhesives, producible according to the first existing claims 1 to 5. 7. Permanently sticky and reversibly usable coated Ma materials, in particular papers, can be produced according to one of the preceding claims 1 to 5.