WO2005121269A1

WO2005121269A1 - Adhesive comprising adipate ester

Info

Publication number: WO2005121269A1
Application number: PCT/EP2005/005960
Authority: WO
Inventors: Andree Dragon; Oral Aydin; Heiko Diehl
Original assignee: Basf Aktiengesellschaft
Priority date: 2004-06-08
Filing date: 2005-06-03
Publication date: 2005-12-22
Also published as: DE102004027791A1

Abstract

The invention relates to an adhesive, comprising: A) a polymer obtained by radical polymerisation made up of at least 60 wt. % of so-called principal monomer, selected from C1 to C20 alkyl(meth)acrylates, vinyl esters of carboxylic acids of up to 20 C atoms, vinyl aromatics with up to 20 C atoms, ethylenically-unsaturated nitriles, vinyl halides, vinyl ethers of alcohols with 1 to 10 C atoms, aliphatic hydrocarbons with 2 to 8 C atoms and one or two double bonds or mixtures of said monomers and B) an aliphatic mono- or diester formed from a dicarboxylic acid with 4 to 20 C atoms B1) and a C4 to C20 hydroxyalkane B2).

Description

Adhesive containing adipic acid ester

description

The invention relates to an adhesive containing

A) a polymer obtainable by radical polymerization which comprises at least 60% by weight of so-called main monomers selected from Ci to C ₂₀ alkyl (meth) acrylates, vinyl esters of carboxylic acids containing up to 20 C atoms, vinyl aromatics with up to 20 C. -Atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of alcohols containing 1 to 10 C atoms, aliphatic hydrocarbons with 2 to 8 C atoms and one or two double bonds or mixtures of these monomers, and

B) an aliphatic mono- or diester formed from a dicarboxylic acid with 4 to 20 C atoms B1) and a C ₄ to C ₂ o hydroxyalkane B2).

Self-adhesive labels that can be removed without leaving any residue are required for many applications. The absence of residues is of particular importance e.g. when labeling food.

A prerequisite for residue-free removability is that the internal cohesion in the adhesive layer (cohesion) is stronger than the adhesion to the substrate surface. Such properties can e.g. by chemical changes to the binder polymer.

It is possible e.g. the use of crosslinking monomers to increase cohesion. Alternatively, according to EP-A-11 3244 (PF 51222), polymers with ureido groups are used.

A disadvantage of such polymers is that the corresponding modification takes place already during the production of the polymer and the polymers are then only suitable for residue-free self-adhesive articles with low adhesion.

In contrast, it is advantageous to use polymers which are also suitable for other purposes. The residue-free removability must then be set by the adhesive formulation.

The object of the present invention was therefore adhesives for residue-free removable self-adhesive articles; the adhesives should contain simple, universally applicable binders.

Accordingly, the adhesives defined at the outset were found. The adhesive according to the invention contains polymer A) and a mono- or diester B).

The polymer can be obtained by radical polymerization of ethylenically unsaturated compounds (monomers).

The polymer consists of at least 60% by weight, preferably at least 80% by weight, particularly preferably at least 90% by weight, of so-called main monomers.

The main monomers are selected from CrC ₂ o-alkyl (meth) acrylates, vinyl esters of carboxylic acids containing up to 20 C atoms, vinyl aromatics with up to 20 C atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers containing 1 to 10 C atoms Alcohols, aliphatic hydrocarbons with 2 to 8 carbon atoms and one or two double bonds or mixtures of these monomers.

Examples include (Meth) acrylic acid alkyl esters with a C-i-Cio-alkyl radical, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate.

Mixtures of the (meth) acrylic acid alkyl esters are also particularly suitable.

Vinyl esters of carboxylic acids with 1 to 20 C atoms are e.g. Vinyl laurate, stearate, vinyl propionate, vinyl versatic acid and vinyl acetate.

Suitable vinyl aromatic compounds are vinyl toluene, a- and p-methylstyrene, a-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene. Examples of nitriles are acrylonitrile and methacrylonitrile.

The vinyl halides are chlorine, fluorine or bromine-substituted ethylenically unsaturated compounds, preferably vinyl chloride and vinylidene chloride.

Examples of vinyl ethers include Vinyl methyl ether or vinyl isobutyl ether. Vinyl ethers of alcohols containing 1 to 4 carbon atoms are preferred.

Butadiene, isoprene and chloroprene may be mentioned as hydrocarbons with 4 to 8 carbon atoms and two olefinic double bonds.

Preferred main monomers are the C to C ₁₀ alkyl acrylates and methacrylates, in particular C to C ₈ alkyl acrylates and methacrylates and vinyl aromatics, in particular styrene and mixtures thereof. Methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-hexyl acrylate, octyl acrylate and 2-ethylhexyl acrylate, styrene and mixtures of these monomers are very particularly preferred.

In addition to the main monomers, the polymer may contain other monomers, e.g. Monomers with carboxylic acid, sulfonic acid or phosphonic acid groups. Carboxylic acid groups are preferred. For example, Acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid.

Other monomers are e.g. also monomers containing hydroxyl groups, in particular C 1 -C 4 -hydroxyalky methacrylates, (meth) acrylamide.

Phenyloxyethyl glycol mono (meth) acrylate, glycidyl acrylate, glycidyl methacrylate, amino (meth) acrylates such as 2-aminoethyl (meth) acrylate may also be mentioned as further monomers.

Crosslinking monomers may also be mentioned as further monomers.

The polymer preferably contains hydrophilic groups selected from carboxyl groups, hydroxyl groups, amino groups and carboxamide groups. The content of these hydrophilic groups is in particular 0.001 to 0.5 mol per 100 g of polymer. The content is preferably at least 0.005 mol, particularly preferably at least 0.008 mol and at most 0.2 mol, in particular at most 0.1 mol, very particularly preferably at most 0.05 or 0.03 mol per 100 g / polymer.

The hydrophilic groups selected from carboxyl groups, hydroxyl groups and carboxamide groups are particularly preferred.

At least 20 mol% of the total molar amount of these groups is particularly preferably carboxyl groups.

Carboxyl groups mean both carboxylic acid groups and their salts. In the case of the salts, they are preferably salts with volatile bases, e.g. Ammonia.

The hydrophilic groups can be bound to the polymer by copolymerization of the corresponding monomers.

Preferred monomers with hydrophilic groups are the abovementioned monomers with carboxyl groups and hydroxyl groups, in particular, for example, acrylic acid. In particular, the polymer is composed of at least 60% by weight, particularly preferably at least 80% by weight and very particularly preferably at least 95% by weight of C 1 to C ₂₀ alkyl (meth) acrylates.

In a preferred embodiment, the polymers are prepared by emulsion polymerization, so it is an emulsion polymer.

In emulsion polymerization, ionic and / or non-ionic emulsifiers and / or protective colloids or stabilizers are used as surface-active compounds.

A detailed description of suitable protective colloids can be found in Houben-Weyl, Methods of Organic Chemistry, Volume XIV / 1, Macromolecular Substances, Georg-Thieme-Verlag, Stuttgart, 1961, pp. 411 to 420. Both anionic and cationic come as emulsifiers as well as nonionic emulsifiers. Preferably, only accompanying emulsifiers are used as accompanying surface-active substances, the molecular weight of which, in contrast to the protective colloids, is usually below 2000 g / mol. Of course, if mixtures of surface-active substances are used, the individual components must be compatible with one another, which can be checked by means of a few preliminary tests if in doubt. Anionic and nonionic emulsifiers are preferably used as surface-active substances. Common accompanying emulsifiers are, for example, ethoxylated fatty alcohols (EO grade: 3 to 50, alkyl radical: C ₈ - to C ₃₆ ), ethoxylated mono-, di- and tri-alkylphenols (EO degree: 3 to 50, alkyl radical: C ₄ - to C ₉ ), alkali metal salts of dialkyl esters of sulfosuccinic acid and alkali and ammonium salts of alkyl sulfates (alkyl radical: C ₈ - to C ₁₂ ), of ethoxylated alkanols (EO degree: 4 to 30, alkyl radical: C-, ₂ - to C ₁₈ ), of ethoxylated alkylphenols (EO grade: 3 to 50, alkyl radical: C ₄ - to C _g ), of alkyl sulfonic acids (alkyl radical: C ₁₂ - to C ₁₈ ) and of alkylarylsulfonic acids (alkyl radical: Cg- to C ₁₈ ) ,

Other suitable emulsifiers are compounds of the general formula II

wherein R ⁵ and R ^{6 are} hydrogen or C ₄ - to C ₁₄ -alkyl and are not simultaneously hydrogen, and X and Y can be alkali metal ions and / or ammonium ions. R ⁵ , R ^{6 are} preferably linear or branched alkyl radicals having 6 to 18 carbon atoms. Atoms or hydrogen and in particular with 6, 12 and 16 carbon atoms, where R ⁵ and R ^{6 are} not both hydrogen at the same time. X and Y are preferably sodium, potassium or ammonium ions, with sodium being particularly preferred. Compounds II in which X and Y are sodium, R ^{5 is} a branched alkyl radical having 12 C atoms and R ^{6 is} hydrogen or R ⁵ are particularly advantageous. Industrial mixtures are used which have a share of 50 to 90 wt .-% of the monoalkylated product, for example Dowfax ^® 2A1 (trademark of Dow Chemical Company).

Suitable emulsifiers can also be found in Houben-Weyl, Methods of Organic Chemistry, Volume 14/1, Macromolecular Substances, Georg Thieme Verlag, Stuttgart, 1961, pages 192 to 208.

Trade names of emulsifiers are, for example, Dowfax ^® 2 A1, Emulan ^® NP 50, Dextrol ^® OC 50, Emulsifier 825, Emulsifier 825 S, Emulan ^® OG, Texapon ^® NSO, Nekanil ^® 904 S, Lumiten ^® I-RA, Lumiten ^® E 3065 , Disponil ^® FES 77, Lutensoi ^® AT 18, Steinapol VSL, Emulphor NPS 25.

Ionic emulsifiers or protective colloids are preferred for the present invention. They are particularly preferably ionic emulsifiers, in particular salts and acids, such as carboxylic acids, sulfonic acids and sulfates, sulfonates or carboxylates.

The surface-active substance is usually used in amounts of 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the monomers to be polymerized.

Water-soluble initiators for emulsion polymerization are e.g. Ammonium and alkali metal salts of peroxidic sulfuric acid, e.g. Sodium peroxodisulfate, hydrogen peroxide or organic peroxides, e.g. tert-butyl hydroperoxide.

So-called reduction-oxidation (red-ox) initiator systems are also suitable.

The Red-Ox initiator systems consist of at least one mostly inorganic reducing agent and one inorganic or organic oxidizing agent.

The oxidation component is e.g. the initiators for emulsion polymerization already mentioned above.

The reduction components are, for example, alkali metal salts of sulphurous acid, such as sodium sulphite, sodium hydrogen sulphite, alkali metal salts of disulphurous acid such as sodium disulphite, bisulphite addition compounds of aliphatic aldehydes and ketones, such as acetone bisulphite or reducing agents such as hydroxymethanesulphinic acid and their salts, or ascorbic acid. The Red-Ox initiator systems can be used with the use of soluble metal compounds, the metallic component of which can occur in several valence levels.

Common red-ox initiator systems are e.g. Ascorbic acid / iron (II) sulfate / sodium peroxydisulfate, tert-butyl hydroperoxide / sodium disulfite, tert-butyl hydroperoxide / Na-hydroxymethanesulfinic acid. The individual components, e.g. the reduction component, can also be mixtures e.g. a mixture of the sodium salt of hydroxymethanesulfinic acid and sodium disulfite.

The compounds mentioned are mostly used in the form of aqueous solutions, the lower concentration being determined by the amount of water which is acceptable in the dispersion and the upper concentration being determined by the solubility of the compound in question in water. In general, the concentration is 0.1 to 30% by weight, preferably 0.5 to 20% by weight, particularly preferably 1.0 to 10% by weight, based on the solution.

The amount of initiators is generally 0.1 to 10% by weight, preferably 0.5 to 5% by weight, based on the monomers to be polymerized. Several different initiators can also be used in emulsion polymerization.

Regulators can be used in the polymerization, e.g. in amounts of 0 to 0.8 parts by weight, based on 100 parts by weight of the monomers to be polymerized, is reduced by the molar mass. Suitable are e.g. Compounds with a thiol group such as tert-butyl mercaptan, ethyl thioglycolate, mercaptoethynol, mercaptopropyltrimethoxysilane or tert-dodecyl mercaptan.

The emulsion polymerization is usually carried out at 30 to 130, preferably 50 to 90 ° C. The polymerization medium can consist only of water, as well as mixtures of water and therefore miscible liquids such as methanol. Preferably only water is used. The emulsion polymerization can be carried out either as a batch process or in the form of a feed process, including a step or gradient procedure. Preference is given to the feed process, in which part of the polymerization batch is introduced, heated to the polymerization temperature, polymerized and then the rest of the polymerization batch, usually via a plurality of spatially separate feeds, one or more of which contain the monomers in pure or in emulsified form , continuously, gradually or with superposition of a concentration gradient while maintaining the polymerization of the polymerization zone. In the polymerization, a polymer seed can also be introduced, for example, for better adjustment of the particle size. The manner in which the initiator is added to the polymerization vessel in the course of the free-radical aqueous emulsion polymerization is known to the person skilled in the art. It can either be completely introduced into the polymerization vessel or used continuously or in stages in the course of the free-radical aqueous emulsion polymerization, depending on its consumption. In particular, this depends on the chemical nature of the initiator system as well as on the polymerization temperature. A portion is preferably introduced and the remainder is fed to the polymerization zone in accordance with the consumption.

To remove the residual monomers, usually after the end of the actual emulsion polymerization, i.e. after a conversion of the monomers of at least 95%, initiator added.

The individual components can be added to the reactor in the feed process from above, in the side or from below through the reactor floor.

In emulsion polymerization, aqueous dispersions of the polymer are generally obtained with solids contents of from 15 to 75% by weight, preferably from 40 to 75% by weight.

Dispersions with the highest possible solids content are preferred for a high space / time yield of the reactor. In order to be able to reach solids contents> 60% by weight, one should set a bimodal or polymodal particle size, since otherwise the viscosity becomes too high and the dispersion can no longer be handled. A new generation of particles can be generated, for example, by adding seeds

(EP 81083), by adding excess amounts of emulsifier or by adding mini-emulsions. Another advantage associated with the low viscosity at high solids content is the improved coating behavior at high solids contents. A new / new generation of particles can be generated at any time. It depends on the particle size distribution desired for a low viscosity.

The polymer thus produced is preferably used in the form of its aqueous dispersion,

The average particle size of the polymer particles dispersed in the aqueous dispersion is preferably less than 400 nm, in particular less than 200 nm. The average particle size is particularly preferably between 140 and 200 nm.

By average particle size d ₅ o of the particle size is meant herein, that is 50 wt .-% of the total mass of all particles have a diameter smaller than the d ₅₀ value. The particle size distribution can be known Way with the analytical ultracentrifuge (W. Mäschtle, Makromolekulare Chemie 185 (1984), pages 1025-1039).

The pH of the polymer dispersion is preferably set to a pH greater than 4.5, in particular to a pH between 5 and 8.

The glass transition temperature of the polymer or of the polymer is preferably -60 to 0 ° C, particularly preferably -60 to -10 ° C and very particularly preferably -60 to -20 ° C.

The glass transition temperature can be determined using conventional methods such as differential thermal analysis or differential scanning calorimetry (see, for example, ASTM 3418/82, so-called "midpoint temperature").

The adhesive according to the invention also contains a mono- or diester B).

The aliphatic mono- or diester B) is formed from a dicarboxylic acid with 4 to 20 C atoms B1) and a C ₄ - to C ₂₀ hydroxyalkane B2).

B) can be prepared by a conventional esterification of B1) with B2).

B1) is in particular a dicarboxylic acid with 4 to 8, particularly preferably with 4 to 6, carbon atoms.

It is very particularly preferably a C ₄ dicarboxylic acid, in particular adipic acid.

B2) is in particular a hydroxyalkane with 6 to 15, particularly preferably with 6 to 11, carbon atoms. In particular, it is a hydroxyalkane with 9 carbon atoms.

B) is preferably a linear hydroxyalkane in which the C atom at one chain end is substituted by a methyl group (iso compound) and the C atom at the opposite chain end is substituted by the hydroxy group

B) is particularly preferably a diester, i.e. both carboxylic acid groups of B1) are esterified with a hydroxyalkane B2).

A particularly preferred compound B) is diisononyl adipate (CAS number 33703-08-1), which is available under the trade name Plastomoll® / DNA. The amount of the mono- or diester B) is, for example, 0.1 to 20 parts by weight, preferably at least 0.2, particularly preferably at least 0.3 parts by weight per 100 parts by weight of polymer (solid / solid, ie without solvent); the amount is preferably at most 7 parts by weight, particularly preferably at most 5 parts by weight per 100 parts by weight of polymer, in particular at most 3 or 2.5 parts by weight per 100 parts by weight of polymer.

Very good results are e.g. achieved with an amount of 0.1 to 5 parts by weight, in particular 0.2 to 3 parts by weight per 100 parts by weight of polymer.

The polymer or the aqueous dispersion of the polymer can be mixed in a simple manner with the mono- or diester B).

The mixture obtained is stable on storage.

The adhesives, preferably pressure-sensitive adhesives, can consist solely of the polymer or the aqueous dispersion of the polymer and the mono- or diester B).

The adhesives and pressure sensitive adhesives can contain further additives, e.g. Fillers, dyes, leveling agents, thickeners or tackifiers (tackifying resins). Tackifiers are e.g. Natural resins, such as rosins and their derivatives resulting from disproportionation or isomerization, polymerization, dimerization, hydrogenation. These can be in their salt form (with, for example, mono- or polyvalent counterions (cations) or preferably in their esterified form. Alcohols used for the esterification can be mono- or polyvalent. Examples are methanol, ethanediol, diethylene glycol, triethylene glycol, 1 , 2,3-propanethiol, pentaerythritol.

Furthermore, hydrocarbon resins, e.g. Coumarone indene resins, polyterpene resins, hydrocarbon resins based on unsaturated CH compounds, such as butadiene, pentene, methylbutene, isoprene, piperylene, divinylmethane, pentadiene, cyclopentene, cyclopentadiene, cyclohexadiene, styrene, a-methylstyrene, vinyltoluene Use.

Polyacrylates which have a low molecular weight are also increasingly being used as tackifiers. These polyacrylates preferably have a weight-average molecular weight M _{w of} less than 30,000. The polyacrylates preferably consist of at least 60, in particular at least 80% by weight of dC ₈ alkyl (meth) acrylates.

Preferred tackifiers are natural or chemically modified rosins. Rosin resins consist predominantly of abietic acid or abietic acid derivatives. The amount by weight of the tackifier is preferably 5 to 100 parts by weight. particularly preferably 10 to 50 parts by weight. based on 100 parts by weight of polymer (solid / solid).

The adhesives preferably contain leveling agents (for example lumites) in amounts of 0.05 to 3 parts by weight per 100 parts by weight of polymer.

In particular, the adhesives or pressure-sensitive adhesives according to the invention are suitable for producing self-adhesive articles, such as labels, adhesive tapes or adhesive films, e.g. Protective films.

The self-adhesive articles generally consist of a carrier and a layer of the adhesive applied on one or both sides, preferably on one side.

The carrier material can e.g. are paper or preferably plastic films made of polyolefins or PVC.

To produce the adhesive layer on the carrier material, the carrier material can be coated in the usual way. Usual layer thicknesses (after drying) are, for example, 5 to 30 g / m ²

The coated substrates obtained are e.g. used as self-adhesive articles, such as labels, adhesive tapes or foils.

The self-adhesive articles according to the invention have good performance properties.

In particular, they can be removed again without residue after being glued to a wide variety of substrates. You have reduced adhesion, but good cohesion. This is achieved in particular with a small amount B). The self-adhesive articles, for. B. labels, for food.

Examples

The feedstocks were mixed.

The amounts given in the table are the parts by weight of the aqueous dispersion (with water) and the parts by weight of Plastilit or Plastomoll.

All formulations additionally contain 1 part by weight of Lumiten 1-SC (leveling agent) per 100 parts by weight of the total of dispersion and plastilite or plastomoll.

Test Methods

Peel and shear strength

Paper was coated with the formulation (18 g / m ² dry, drying for 3 minutes, 90 ° C.).

The peel strength (adhesion) and shear strength (cohesion) were then determined.

The coated carrier was cut into 25 mm wide test strips. To determine the shear strength, the test strips with a bonded area of 25 mm ^{2 were} glued to a V2A test plate, rolled up once with a 1 kg roll, stored for 10 minutes (in a standard atmosphere, 50% relative atmospheric humidity 1 bar, 23 ° C) ) and then suspended with a 1 kg weight (in a normal climate). The measure of the shear strength was the time until the weight dropped; the average of 5 measurements was calculated.

When determining the peel strength (adhesion), a 2.5 cm wide test strip was glued to a steel test specimen and with a roll weighing 1 kg Rolled up once. After 20 minutes or after 24 hours of storage in a standard atmosphere, it was clamped with one end in the upper jaws of a tensile strain test apparatus. The adhesive strip was peeled off the test surface at 300 mm / min at a 180 ° angle, ie the adhesive strip was bent over and pulled off parallel to the test plate and the force required was measured. The measure for the peel strength was the force in N / 2.5 cm, which resulted from the average of five measurements. The test was also carried out in a standard atmosphere.

Claims

claims

1. Adhesive containing A) a polymer obtainable by radical polymerization which comprises at least 60% by weight of so-called main monomers selected from C 1 to C ₂₀ alkyl (meth) acrylates, vinyl esters of carboxylic acids containing up to 20 C atoms, vinyl aromatics with up to 20 carbon atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of alcohols containing 1 to 10 carbon atoms, aliphatic hydrocarbons with 2 to 8 carbon atoms and one or two double bonds or mixtures of these monomers, and

B) an aliphatic mono- or diester formed from a dicarboxylic acid having 4 to 20 C atoms B1) and a C ₄ to C ₂₀ hydroxyalkane B2).

2. Adhesive according to claim 1, characterized in that the polymer is an emulsion polymer and is composed of at least 60% by weight of Ci to C ₂₀ alkyl (meth) acrylates.

3. Adhesive according to claim 1 or 2, characterized in that the polymer contains 0.001 to 0.5 mol of hydrophilic groups selected from carboxyl groups, hydroxyl groups and amino and amide groups per 100 g of polymer.

4. Adhesive according to one of claims 1 to 3, characterized in that the aliphatic dicarboxylic acid B1) is adipic acid (C4 dicarboxylic acid).

5. Adhesive according to one of claims 1 to 4, characterized in that B2) is a C6 to C15 hydroxyalkane.

6. Adhesive according to one of claims 1 to 5, characterized in that the first C atom of the hydroxyalkane B2) is substituted by a methyl group (iso compound) and the last C atom by a hydroxy group.

7. Adhesive according to one of claims 1 to 6, characterized in that B) is a diester.

8. Adhesive according to one of claims 1 to 7, characterized in that the mono- or diester B) is present in amounts of 0.1 to 20 parts by weight, based on 100 parts by weight of polymer.

9. Adhesive according to one of claims 1 to 8, characterized in that it is a pressure sensitive adhesive.

10. Self-adhesive articles obtainable using the adhesive according to one of claims 1 to 9.