DE3740322C2 - - Google Patents

Description

The invention relates to salt-like crosslinkers for the solution and / or block polymerization of ethylenically unsaturated Monomers with at least two unsaturated anionic Groups and a multivalent cation, procedure for Vernet of ethylenically unsaturated monomers baren and produced polymers with a crosslinker and the use of the crosslinker.

It is often desirable to have polymers with good cohesion to get, especially with adhesives, such as adhesive Besides good cohesion, adhesives are also useful Adhesion and sufficient thermal stability are desired. This is u. a. for the production of glue the coatings on labels, moldings and. Like. Not agile. A particular problem with such adhesives is the processing, because during the dosing or opening the glue does not carry too high a viscosity of the mate rials is desired, which increases with increasing cohesion increases, on the other hand in the finished product, a pressure-sensitive adhesive material, such as an adhesive tape, adhesive labels, Trims or the like - so the "gluing" - a good Ko adhesion of the adhesive to produce a good adhesive connection is essential.

So far, attempts have been made by solvent polymerization first to copolymerize or homopolymerize the monomers and then after evaporation of the solvent, at elevated post-crosslinking the solid concentration to improve cohesion. With that, the above problems described during processing the. Furthermore, there was already pressure sensitive adhesives on acrylate basis tries to use polyfunctional acrylates.  

However, their use is due to the high viscosity resulting PSAs and because of the risk of gelling highly limited.

In addition, solvent polymerizations are not very environmentally friendly friendly and require a lot of effort in solving disposal of funds.

The use of metal (meth) acrylates for crosslinking in the polymerization of ethylenically unsaturated monomers is already known, some of which are ionic mechanisms must be taken and given specific objectives are. The results in the pressure sensitive adhesive sector cannot be described as satisfactory on all sides.

It is therefore an object of the invention, one under Beibe attitude of other desired properties pronounced ko adhesive thermally stable homo- or copolymer create.

The object is achieved by a salt-like Crosslinker for the radical polymerization of ethyl niche unsaturated monomers, with at least two unsaturated saturated anionic groups and a multivalent cat ion solved, which has the following general formula:

where R₁ and R₂ are the same or different and H or Cl, F, Br, J; R₃ and R₄ the same or different and a methyl group, a hydrogen, a halogen atom or  Can be CN, m is an integer between 2 and 4 and K is a polyvalent central group with a polyvalent metal atom from the group of the periodic table IIa, IIIa, IVa, Va, VIa, Ib, IIb, IVb, Vb, VIb, VIIb, VIIIb with the valency m + x, where x is an integer between 0 and 4 and the valences of Central atom partially saturated by other atoms A. can be solved.

The central group preferably has a polyvalent metal cation that, for example, Ca, Ba, Sr, Mg, Zn, Al, Sn, Cu, Zr, Fe, Cr, Mo, Mn, Co, Ni, Cd, Bi, Ti, Hf, V or Pb.

The central group can also be a metal oxycation, such as ZrO ²⁺ or TiO ²⁺ .

Preferred examples of such compounds are aluminum β-carboxyethyl acrylate, zirconium β-carboxyethyl acrylate or iron β-carboxyethyl acrylate.

A method according to the invention for the radical crosslinking of Polymers that can be produced from ethylenically unsaturated monomers with a crosslinker is characterized by mixing the monomers with 0.01 to 30 wt .-% of one or more of those described above Crosslinker (s) and subsequent homo / co-polymerization.

In a preferred variant of the invention Process crosslinking after homo / copolymerization of the ethylenic unsaturated monomers take place, preferably in one separate process step, possibly even at a different location, see above that z. B. a polymerized precursor only on a desired Location is networked.

Suitable monomers are ethylenically unsaturated, such as styrene, Acrylates, vinyl acetate and the like. Like., In which polymers with improved cohesion are desired.  

The crosslinking reaction can be seen by UV irradiation bare light, electrons, highly accelerated ions, neutrons, Deuterons or alpha particles triggered and in solution or in Mass to be performed.

The polymer / crosslinker mixture can be applied to a carrier and then crosslinked thereon by radiation. These Process variant is for example for the production of Adhesive tapes very cheap, since the pressure sensitive adhesive is initially used in workable viscosity applied to the carrier material and thereafter while maintaining the necessary adhesion by radiation be equipped with the desired improved cohesion can.

The crosslinker content is preferably 0.05 to 25% by weight and very particularly preferably 0.1 to 15% by weight of the monomer content.

In polymerization media in which the crosslinker is heavy or is hardly soluble, the crosslinker is used as a complex (s) with a Compound from the group of 1,2,3-triols and / or glycerol mono ether and / or thioether with at least 6 carbon atoms and / or used a vicinal diol with at least 6 carbon atoms, such as for example from DE-OS 27 39 312 or DE-OS 28 38 473 are known.

This embodiment can in particular be problem-free Regulation of the viscosity of the uncrosslinked mass of adhesive that they are at relatively low temperatures (such as 65 Apply grade C) in the form of a thin film on a substrate lets be achieved.

An acrylate-based pressure sensitive adhesive is preferred as the polymer.

Acrylate-based pressure sensitive adhesive systems produced according to the invention with crosslinkers have the following advantageous properties:  

• - good stickiness with high cohesion;
• - Excellent thermal stability, so upright maintaining cohesion even at elevated temperatures;
• - easy control of the degree of networking;
• - easy handling during the polymerization and Application because of the viscosity caused by the crosslinking Increase in crime does not occur during the application of the detention adhesive, but only occurs after irradiation.

The method according to the invention is particularly simple add, because the PSA only on the carrier, such as one Adhesive tape backing material, a label or the like is provided.

Salt-like crosslinking agents according to the invention were used as reaction pro products between the ethylenically unsaturated carboxylic acids and corresponding metal chelates.

In the following, the invention is illustrated by examples refines, but do not limit the inventive idea should.  

example 1

In a mixture of 190 g of ethyl acetate and 10 g of n-hexane 2 g of aluminum β-carboxyethyl acrylate and 2 g of benzophenone sus oscillates and with stirring until the boiling point is reached heated. After the dropwise addition of a monomer mixture of 142 g 2-ethylhexyl acrylate, 20 g methyl acrylate, 20 g butyl acrylate, 12 g acrylic acid, 2 g diacetone acrylamide and 1.2 g AIBN becomes the Polymerization then continued for a further 4 hours. The Polymerization product is applied to a polyester film dried and irradiated with a UV lamp.

Example 2

8 g of zirconium β-carboxyethyl acrylate and 80 g of 1,2-octanediol in Ratio 1:10 are stirred until a homogeneous Mixture arises. Mixture obtained in this way becomes un The solution was dissolved in 200 g of ethyl acetate and stirred until it was reached of the boiling point heated. After dropping (approx. 2 h) one Monomer mixture of 138 g of 2-ethylhexyl acrylate, 36 g of methyl acrylate, 6 g maleic anhydride, 3 g diacetone acrylamide, 1 g Acrylamide, 8 g Michler's ketone and 0.8 g AIBN will this reak tion mass stirred for a further 4 hours, on a polyester film applied, dried in a drying tunnel and using a UV lamp irradiated.

Examples 3 to 7

After the polymerization described in Examples 1 and 2 Further radiation-crosslinked materials according to the invention are used Adhesive systems manufactured. The together in Table 1 contained monomer mixtures are polymerized in solution, wherein the polyfunctional metal salt pure or as a mixture with mentioned complex-forming compounds presented in the solvent or is added dropwise with starting monomers.  

Table 1

Example 8

In a 1 liter flask with a thermometer, a reflux condenser and a mechanical stirrer is, a monomer mixture of 150 g of 2-ethylhexyl acrylate, 30 g Lauryl acrylate, 12 g acrylic acid, 4 g photo initiator benzophenone, 1 g AIBN and one with tert. Dodecylglycerol thioether in the ratio nis 1:12 mixed aluminum β-carboxyethyl acrylate before Polymerization submitted. The monomer mixture is mixed stirred vigorously and heated to 70 ° C. After about 1 hour there will be a quick Reaction and the increase in the viscosity of the reaction mixture observed. The temperature has risen to 150 ° C, but it does dropped back to 70 ° C after 30 minutes.

Example 9

A solvent-free, radiation-crosslinked pressure-sensitive adhesive system is - as in Example 8 - from a monomer mixture of 160 g Lauryl acrylate, 20 g butyl acrylate, 8 g trimethylolpropane triacrylate, 5 g acrylic acid, 1 g acrylamide, 5 g photo initiator benzophenone and 1 g of aluminum β-carboxyethyl acrylate. It is in in this case no very strong temperature rise was observed.

The test results (according to AFERA 4001, 4015) were summarized in Table 2. The following conditions were met:
Irradiation lamp: UVRC 500 (500 W)
Irradiation time: 2 to 10 sec
Distance lamp / adhesive layer: 40 mm
Load: 10 N, 30 N

Table 2

Continuation of table 2

Production of aluminum β-carboxyethyl acrylate

144 g of β-carboxyethyl acrylate was measured with a stoichiometry amount of aluminum acetylacetonate (456 g) in 1000 g of solution medium (ethyl acetate) and mixed by applying heat set. After 2 hours of reaction, the aluminum β-car boxyethyl acrylate isolated. It had a breakdown point of approx. 210 degrees C.

Production of zirconium β-carboxyethyl acrylate

72 g of β-carboxyethyl acrylate were mixed with 260 g of zirconium acetyl Acetonate implemented in ethyl acetate and the zirconium β-carboxy ethyl acrylate isolated after 3 hours. It had a disintegration point of approx. 320 degrees C and is characterized by a high temperature resistance.

Production of iron β-carboxyethyl acrylate

100 g of β-carboxyethyl acrylate were mixed with 336 g of iron acetyl mixed acetonate in ethyl acetate and heated. That ent The iron β-carboxyethyl acrylate in question had a decomposition point of 250 degrees C.

Claims (12)

1. Salt-containing crosslinker for the radical polymerization of ethylenically unsaturated monomers, with at least two unsaturated anionic groups and a polyvalent cation, characterized in that the crosslinker has the following general formula: where R₁ and R₂ are the same or different and = H or Cl, F, Br, J; R₃ and R₄, which are the same or different, can be a methyl group, a hydrogen atom, a halogen atom or -CN, m is an integer between 2 and 4 and K is a polyvalent central group with a polyvalent metal atom from the group Ca, Ba, Sr. , Mg, Zn, Al, Sn, Cu, Zr, Fe, Cr, Cd, Mo, Mn, Co, Ni, Bi, Ti, Hf, V or Pb with the valency m + x, where x is an integer between 0 and 4 and the valences of the central atom can also be partially saturated by other atoms A. 2. Crosslinker according to claim 1, characterized in that the central group is a metal oxycation, ZrO ²⁺ , TiO ²⁺ . 3. Crosslinker according to claim 1 or 2, characterized characterized in that the crosslinker aluminum-β- carboxyethyl acrylate, zirconium β-carboxyethyl acrylate or iron β-carboxyethyl acrylate. 4. Process for radical networking from produced ethylenically unsaturated monomers Polymers with a crosslinker, characterized by Mixing the monomers with 0.01 to 30 wt .-% one or several crosslinkers according to one of the previous claims and implementation of Polymerization. 5. Process for radical networking from produced ethylenically unsaturated monomers Polymers with a crosslinker, characterized by Mix the homo / copolymer with 0.01 to 30 % By weight of one or more crosslinkers according to one of the Claims 1-3 and subsequent implementation of the Networking. 6. The method according to claim 5, characterized in that crosslinking by irradiation with UV, visible Light, electrons, highly accelerated ions, Neutrons, deuterons or alpha particles is carried out. 7. The method according to any one of claims 4 or 5, characterized characterized in that the radical homo / copolymerization the ethylenically unsaturated Monomers carried out in solution or in bulk becomes.   8. The method according to any one of claims 5 to 7, characterized characterized in that the mixture of homo / copolymers and crosslinker on a support applied and then on this by irradiation is networked. 9. The method according to any one of claims 5 to 8, characterized characterized in that the crosslinker content is preferred 0.05 to 25% by weight and very particularly preferably 0.1 is up to 50 wt .-% of the total polymer. 10. The method according to any one of claims 4 to 9, characterized characterized in that the crosslinker (s) as complex (s) with a compound from the group of 1,2,3-triols and / or glycerol monoether / or thioether with at least 6 carbon atoms and / or a vicinal diol with at least 6 carbon atoms. 11. Use of the crosslinking agent according to one of claims 1-3 for the crosslinking of ethylenically unsaturated Monomers by adding from 0.01 to 30% by weight, based on the monomer proportions before or after the Solution or block polymerization. 12. Use according to claim 11, characterized characterized in that the ethylenically unsaturated Have monomeric acrylates and that the polymer is an acrylic adhesive.