DE10102841A1 - Adhesive with good adhesion, cohesion and tensile-shear properties, for use in adhesive tapes, especially for packaging, comprises aqueous polymer dispersion having low emulsifier content - Google Patents

Abstract

The use of an aqueous polymer dispersion (A) is claimed as an adhesive for the production of adhesive tapes, where (A) contains less than 0.5 wt. % emulsifier(s) based on polymer. An Independent claim is also included for adhesive tapes having an adhesive coating prepared using (A).

Description

The invention relates to the use of an aqueous polymer dis persion as an adhesive for the production of adhesive tapes, because characterized in that the polymer dispersion is less than 0.5 part by weight of an emulsifier or emulsifier mixture, based per 100 parts by weight of polymer.

Aqueous polymer dispersions are used as adhesives for labels, Films, tapes, etc. are used.

Dispersions of polyacrylates and their uses are described dung z. B. in DE-A-196 32 203, DE-A-196 32 202 and EP-A 625 557. Polyacrylate dispersions with emulsifiers according to formulas I and II and their use are known from EP-A-952 199 and EP-A-952 161. The adhesive film produced is often said to have high adhesion, i. H. good adhesion to the substrate, and high cohesion, i.e. H. inner Strength. With packaging tapes, such as for Closing boxes are used, there are special requirements requirements. Adhesive tapes with which the sealing flaps of a Cardboard boxes are glued under a special pull / shear stress. For packaging adhesive tapes are therefore aqueous Adhesives wanted that meet these special requirements len.

Accordingly, the use defined above was found. Ge Adhesive tapes and their use for packaging were also found.

The aqueous polymer dispersion is in particular: the aqueous dispersion of one by radical polymerization available from ethylenically unsaturated compounds (monomers) Chen polymers. The polymer is by emulsion polymerization available or is preferably by emulsion polymerization receive.

The polymer preferably consists of at least 40% by weight, especially preferably at least 60% by weight, very particularly preferably at least 80% by weight of so-called main monomers.

The main monomers are selected from C ₁ -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 from 1 to 10 C Alcohols containing atoms, aliphatic hydrocarbons having 2 to 8 carbon atoms and 1 or 2 double bonds or mixtures of these monomers.

To mention are z. B. (meth) acrylic acid alkyl ester with a C ₁ -C ₁₀ alkyl radical, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate.

In particular, mixtures of the (meth) acrylic acid alkyl esters suitable.

Vinyl esters of carboxylic acids with 1 to 20 carbon atoms are e.g. B. 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 substituted with chlorine, fluorine or bromine, ethylenically unsaturated compounds, preferably vinyl chloride and Vinylidene chloride.

Examples of vinyl ethers include B. vinyl methyl ether or vinyl isobutyl ether. Vinyl ether of 1 to 4 carbon atoms is preferred keeping alcohols.

As hydrocarbons with 2 to 8 carbon atoms and two olefinic Double bonds are butadiene, isoprene and chloroprene, with a double bond z. B. ethylene or propylene.

Preferred main monomers are the C ₁ to C ₁₀ alkyl acrylates and methacrylates, in particular C ₁ 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.

In addition to the main monomers, the radically polymerized Po lymer contain further monomers, for. B. monomers with carboxylic acid, Sulfonic acid or phosphonic acid groups. Carbon is preferred acid groups. May be mentioned for. B. acrylic acid, methacrylic acid, Itaconic acid, maleic acid or fumaric acid.  

Other monomers are e.g. B. also hydroxyl-containing monomers, in particular C ₁ -C ₁₀ hydroxyalkyl (meth) acrylates, (meth) acrylamide.

Phenyloxyethyl glycol are also further monomers mono- (meth) acrylate, glycidyl acrylate, glycidyl methacrylate, Amino (meth) acrylates such as 2-aminoethyl (meth) acrylate called.

Crosslinking monomers may also be mentioned as further monomers.

The polymer is particularly preferably composed of 60 to 99% by weight, entirely particularly preferably 80 to 99% by weight of monomers with a Glass transition temperature below -40 ° C, preferably below -50 ° C and too 1 to 40% by weight, very particularly preferably 1 to 20% by weight Monomers with a glass transition temperature above -40 ° C before moves above 0 ° C.

The above glass transition temperature is each because of the glass transition temperature of the homopolymer of Mo nomers as used in standard works, e.g. B. the Handbook of Polymer is specified and by conventional methods such as differential thermal analysis or differentail scanning calorimetry (see e.g. ASTM 3418/82, so-called "midpoint temperature") can be determined.

The polymers are produced by emulsion polymers tion; it is therefore an emulsion polymer.

In the emulsion polymerization, the monomers are with the help ionic and / or non-ionic emulsifiers dispersed in water yaws and polymerizes.

The amount of emulsifiers used and the content of Emulsifiers in the polymer dispersion is less than 0.5 part by weight, especially less than 0.4 part by weight 100 parts by weight of polymer. The amount is preferably 0.1 to 0.35, particularly preferably 0.2 to 0.3 parts by weight per 100 parts by weight Parts polymer.

Common emulsifiers are e.g. B. 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 grade: 4 to 30, alkyl radical: C ₁₂ - to C ₁₈ ), of ethoxylated Alkylphenols (EO grade: 3 to 50, alkyl radical: C ₄ - to C ₉ ), of alkyl sulfonic acids (alkyl radical: C ₁₂ - to C ₁₈ ) and of alkylarylsulfonic acids (alkyl radical: C ₉ - to C ₁₈ ).

In the present case, preference is given to an emulsifier which is used at least 5% by weight consists of aromatic carbon atoms (in short aromatic called shear emulsifier) or an emulsifier mixture which min at least 10 wt .-% of such an aromatic emulsifier, based on the total amount of emulsifier used.

The aromatic emulsifier preferably consists of at least 10% by weight, particularly preferably at least 20% by weight of aroma table C atoms (i.e. C atoms that are part of an aromatic ring system).

The proportion of aromatic carbon atoms is generally below 80% by weight.

The aromatic emulsifier is preferably a ionic emulsifier, especially an emulsifier with one or two, preferably two sulfate groups.

The molecular weight of the emulsifier is preferably below 2000, especially below 1000 g / mol.

The aromatic is particularly preferred Emulsifier around an ionic compound with a molecular weight below 2000 g / mol, which has at least one sulfate group or sulfo nate groups, preferably two sulfate groups or sulfonate groups with two optionally substituted phenyl groups.

Aromatic emulsifiers with one or two are preferred preferably two sulfonate groups.

It is particularly preferably a compound of the formula:

where X is O, S, CH ₂ , NH or NR ⁷ , one or two of the radicals R ¹ to R ⁶ for a group SO ₃ ^⊖ K ^⊕ and the remaining radicals R ¹ to R ⁶ for H or a C ₁ -C ₁₈ alkyl group, R ⁷ for a C ₁ -C ₁₈ alkyl group K for a counter cation.

X is preferably O. Preferably one or two of the radicals R ¹ to R ^{6 are} a C ₁ -C ₁₈ alkyl group, in particular a C ₆ -C ₁₈ alkyl group and the other radicals R ¹ -R ^{6 are} H atoms and the sulfonate groups.

K is preferably a counter cation; selected from z. B. the alkali metals, ammonium or hydrogen. Be sodium is particularly preferred. For compounds of the formula I han it is usually also a mixture of compounds with different degrees of substitution (mono- or dialkylated) and different substitution position of the substituents (the sulfonate groups and the one or two alkyl groups). Compounds with formula I are under the trademark Dowfax® 2A sold by Dow Chemical Company.

Compared to the sole use of an aromatic emulsifier is the use of a mixture of an aromatic Emulsifier and an emulsifier without aromatic carbon atoms (not aromatic emulsifier) is preferred. The share of the aromatic Emulsifier in the mixture is preferably more than 20, in particular the more than 60 wt .-% and generally does not exceed 95% by weight, based on the emulsifier mixture.

The non-aromatic emulsifier is preferably one of the formula:

R ⁸ -O- (ZO) _n -SO ^- ₃ k ⁺ II,

where the variables have the following meaning:
R ⁸ : C ₁ -C ₁₈ alkyl, preferably C ₁₀ -C ₁₆ alkyl
Z: CH ₂ -CH ₂ or:

preferably CH ₂ -CH ₂
n: an integer from 1 to 40, preferably from 2 to 30
K ⁺ : a cation, e.g. B. H ⁺ an alkali application of z. B. Na, K or ammonium

Among compounds of formula II, compounds with both:

be understood.

Compounds of formula II are, for. B. under the name Dis ponil® FES 77 distributed by Henkel.

The emulsifier mixture preferably consists of:
20 to 95 wt .-% of an aromatic emulsifier, in particular that of the formula I and
5 to 80 wt .-% of a non-aromatic emulsifier, in particular that of the formula II.

The proportion of the aromatic emulsifier is preferably 30 to 95 wt .-%, particularly preferably 50 to 95 wt .-% and the of the non-aromatic emulsifier 5 to 70 wt .-%, especially be preferably 5 to 50 wt .-%, the weight information on the Total amount of emulsifiers are related.

Otherwise, emulsion polymerization is usually used water-soluble initiators, e.g. B. ammonium and alkali metal salts peroxidic sulfuric acid, e.g. B. sodium peroxodisulfate, water peroxide or organic peroxides, e.g. B. tert-butyl hydropero xid used.

So-called reduction-oxidation (Red-Ox) -In are also suitable itiator systems.

The Red-Ox initiator systems usually consist of at least one inorganic reducing agent and an inorganic or orga African oxidizing agent.

The oxidation component is e.g. B. the already Above initiators for emulsion polymerization.

The reduction components are e.g. B. Alkali metal salts of sulfurous acid, such as. B. sodium sulfite, Sodium hydrogen sulfite, alkali salts of disulfuric acid such as Sodium disulfite, bisulfite addition compounds more aliphatic Aldehydes and ketones such as acetone bisulfite or reducing agents such as Hydroxymethanesulfinic acid and its salts, or ascorbic acid. The  Red-Ox initiator systems can be more soluble when used Metal compounds, their metallic component in several people skill levels can be used.

Common Red Ox initiator systems are e.g. B. Ascorbic acid / egg sen (II) sulfate / sodium peroxydisulfate, tert-butyl hydroperoxide / Na trium disulfite, tert-butyl hydroperoxide / Na hydroxymethanesulfine acid. The individual components, e.g. B. the reduction component, can also be mixtures z. B. a mixture of sodium salt of hydroxymethanesulfinic acid and sodium disulfite.

The amount of initiators is generally 0.1 to 10 wt .-%, preferably 0.2 to 5 wt .-%, based on the polyme rising monomers. Several different In itiators are used in emulsion polymerization.

Regulators can be used in the polymerization, e.g. B. in Amounts from 0 to 0.8 parts by weight, based on 100 parts by weight of the monomers to be polymerized, by means of which the molecular weight is reduced becomes. Are suitable for. B. Compounds with a thiol group such as tert-butyl mercaptan, ethyl thioglycolate, mercapto ethynol, mercaptopropyltrimethoxysilane or tert-dodecylmercap tan.

The emulsion polymerization usually takes place at 30 to 130, preferably 50 to 100 ° C. The polymerization medium can both only from water, as well as from mixtures of water and thus miscible liquids, such as methanol. Preferably only water is used. The emulsion polymerization can be both Batch process as well as in the form of a feed process Lich step or gradient style. The feed process is preferred, in which one part of the bottom submitted to the polymerization temperature heated, polymerized and then the rest of the polymer risk approach, usually over several spatially separated Inlets, one or more of which are in pure monomer or contained in emulsified form, continuously, in stages or by superimposing a concentration gradient under Auf maintenance of the polymerization of the polymerization zone leads. In the polymerization z. B. for better Setting the particle size a polymer seed can be submitted.

The way in which the initiator in the course of the radika Mix aqueous emulsion polymerization the polymerization vessel is added is known to those of ordinary skill in the art. It can both completely placed in the polymerization vessel, as also according to its consumption in the course of the radical  aqueous emulsion polymerization continuously or in stages be used. In particular, this depends on the chemical Na structure of the initiator system and of the polymerization temperature from. A part is preferably presented and the rest after Provided the consumption of the polymerization zone.

To remove the residual monomers is usually also after End of actual emulsion polymerization, d. H. after one Conversion of the monomers of at least 95%, initiator added.

The individual components can the reactor in the feed process from above, in the side or from below through the reactor floor are given.

In the emulsion polymerization, aqueous dispersions of the Polymers usually with solids contents of 15 to 75% by weight, preferably from 40 to 75% by weight.

For a high space / time yield of the reactor are dispersions preferred with the highest possible solids content. At feast to be able to achieve substance contents of <60% by weight, one should or adjust the polymodal particle size, otherwise the viscosity becomes too high and the dispersion is no longer manageable. The Generation of a new generation of particles can, for example by adding seeds (EP 81083), by adding excess Emulsifier amounts or by adding mini emulsions. Another advantage with the low viscosity at high Solid content is accompanied by the improved coating process keep at high solids contents. The creation of a new / new particle generations can occur at any time respectively. It depends on that for a low viscosity desired particle size distribution.

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

The glass transition temperature of the polymer or the emulsion poly merisats is preferably -60 to + 40 ° C, particularly preferred -50 to + 20 ° C and very particularly preferably -50 to + 0 ° C.

The glass transition temperature can be as usual Differential thermal analysis or differential scanning calorimetry (see eg ASTM 3418/82, so-called "midpoint temperature").  

The polymers or polymer dispersions obtained are as Adhesives or pressure-sensitive adhesives for the production of adhesive tapes used.

The polymers are preferably in the form of their aqueous Dispersion used. The aqueous polymer dispersions can can be used without further additives.

When used, the polymers or the aqueous Dispersions of the polymers a tackifier, d. H. a sticky of the resin can be added. Tackifiers are e.g. B. from "Adhesive Age", July 1987, pages 19-23 or "Polym. Mater. Sci. Eng.", 61 (1989), Pages 588-592 known.

Tackifiers are e.g. B. natural resins such as rosins and their by disproportionation or isomerization, polymerization, Dimerization, hydrogenation resulting derivatives. These can be in their salt form (e.g. with mono- or polyvalent counterions (Cations) or preferably in their esterified form. Alcohols used for the esterification can be one or be multivalued. Examples are methanol, ethanediol, diethylene glycol, triethylene glycol, 1,2,3-propanethiol, pentaerythritol.

Also find hydrocarbon resins, e.g. B. coumarone Inden resins, polyterpene resins, hydrocarbon resins based unsaturated CH compounds, such as butadiene, pentene, methylbutene, Isoprene, piperylene, divinyl methane, pentadiene, cyclopentene, cyclo pentadiene, cyclohexadiene, styrene, α-methylstyrene, vinyl toluene 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 C ₁ -C ₈ alkyl (meth) acrylates.

Preferred tackifiers are natural or chemically modified Rosins. Rosin resins are predominant Part from abietic acid or abietic acid derivatives.

The tackifiers can easily be the inventive Polymers, preferably the aqueous dispersions of the polymers sate are added. The tackifiers are preferably present itself in the form of an aqueous dispersion.  

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).

In addition to tackifiers, e.g. B. other additives such. B. Verdic agents, preferably associative thickeners, defoamers, Plasticizers, pigments, wetting agents or fillers at Find use as a pressure sensitive adhesive. The fiction Appropriate pressure sensitive adhesives therefore contain in addition to the aqueous Polymer dispersion, if necessary, also tackifier and / or the above standing additives.

To produce the adhesive tapes, the pressure sensitive adhesive can be applied by Liche methods, e.g. B. by rolling, knife coating, brushing, etc. on Substrates, e.g. B. paper or polymer films, preferably consisting made of polyethylene, polypropylene, the biaxial or monoaxial ver stretches, polyethylene terephthalate, polyvinyl chloride, Po lystyrene, polyamide or metal can be applied. The water can preferably be removed by drying at 50 to 150 ° C. The substrates can be applied before or after applying the adhesive cut into adhesive tapes. Can be used later the side of the substrates coated with pressure sensitive adhesive, with a Release paper, e.g. B. covered with a siliconized paper become.

The tape-shaped substrates coated with adhesive can rolled up and used at any later time become.

The adhesive tapes are preferably used for packaging purposes used (packaging tapes). In particular, z. B. for closing boxes.

The adhesive tapes according to the invention have very good adhesive properties , in particular good adhesion to the substrates and high cohesion (internal strength in the adhesive layer). In particular, they meet the special requirements for Verpac adhesive tapes, which are characterized by the combined pull / shear result in stress.

In addition, the polymers used for the adhesive tapes dispersions stable despite their low emulsifier content.  

Examples A) Preparation of the polymer dispersions

200 g of water are brought to 90 ° C. in a polymerization reactor heated with stirring. And then with further stirring the 50% portion of feed 2 added. After 10 min. become Inlet 1 and the rest of inlet 2 started and simultaneously with constant feed rate in 180 min. dosed. After the end of feed 1, 30 minutes. at 90 ° C stir. At this temperature, stirring simultaneously 0.15 wt .-% based on monomers of a 10% solution of tert-butyl hydroperoxide in water and 0.25 wt .-%, based on monomers of an aqueous solution of sodium disulfite ace clay adduct metered. The dispersion was then at room temperature temperature cooled and with a 25% aqueous ammonia solution Solution neutralized to pH 7. The solids content is up 52-55% set.

Feed 1 = emulsion feed

511 g water
Total amount of monomers: 1200 g
Type of monomers: see table
Type of emulsifiers: see table

Inlet 2 = initiator inlet

200 g water
3.6 g NaPS

The following abbreviations were used:
BA: n-butyl acrylate
MAS: methacrylic acid
tDMK: tert-dodecyl mercaptan
Disponil FES77: 30% by weight, aqueous solution of the sodium salt of the sulfuric acid half-ester of a C ₁₂ -C ₁₄ -alkyl radical ethoxylated with 30 ethylene oxide units (see formula II)
Dowfax 2A1: 45% by weight aqueous solution of the sodium salt of the diphenyl ether derivatized with a C ₁₂ -C ₁₄ -alkyl radical and with two SO ₃ K radicals (see formula I)
NaPS: sodium peroxodisulfate

Composition and test results are in Table 1 listed.

The polymer dispersion obtained was further without addition sets used as glue.

B) Application test as an adhesive for packaging tapes Production of the adhesive tape

Carrier: biaxially oriented 30 µ polypropylene film (OPP film) corona-pretreated inside
Adhesive application: 22 g / m ²

Drying: 3 min at 90 ° C
Cover the adhesive layer with unprepared OPP film 40 µ
Conditioning: storage in standard climate (NK) for 16 hours
Strip width: 25 mm
Substrate: cardboard (Testliner 8283, Juwe, Korschenbroich)
Bonding area: 25 × 25 mm
Number of samples: at least 2
Load: 300 g (corresponds to 500 g on the bonding surface via leverage)
Test condition: standard climate (23 ° / 50% relative humidity)

procedure

The dispersion is drawn onto the OPP film after a Drying time of 3 minutes at 90 ° C the adhesive film with OPP film (40 µ covered) and along the streak direction in strips of 25 mm wide cut. The strips are 16 hours in the NK stored. The test is carried out in a standard climate (NK).  

From a box (Testliner 8283) 35 mm wide by 110 mm Length becomes an end in a so-called rocker with egg permanently attached to a stamp. The box and one on the same Height opposite, movable, but still locked Metal plates are glued and bonded with an adhesive strip the. The adhesive strip is rubberized with a 2.5 kg weight Rolled up and down 2 times. Hangs on the metal plate Weight of 300 g. The metal plate is unlocked. The Ge important now pulls one end of the movably suspended metal plate down and pushes the other end on which the adhesive tape sticks up. The bond is now under one Tensile / shear stress, as with the opening flaps of a Kar tons, which are held together with an adhesive strip. The The adhesive surface is loaded with 500 g via the leverage effect.

The table shows the time until the bond is loosened ben.

The composition and test results are as follows Take the table.

Monomer composition 98.5% by weight BA; 1.5 wt% MAS

The quantities for Dowfax and Disponil are parts by weight based on 100 parts by weight of monomers.

Claims (10)

1. Use of an aqueous polymer dispersion as an adhesive for the production of adhesive tapes, characterized in that the polymer dispersion contains less than 0.5 part by weight of an emulsifier or emulsifier mixture, based on 100 parts by weight of polymer. 2. Use according to claim 1, characterized in that the polymer dispersion is the dispersion of a polymer which comprises at least 40% by weight of so-called main monomers selected from C ₁ to C ₂₀ alkyl (meth) - Acrylates, vinyl esters of up to 20 carbon atoms containing carboxylic acids, 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 is built up. 3. Use according to one of claims 1 or 2, characterized ge indicates that it is 60 to 99 wt .-% of the monomers ren, from which the polymer is built to monomers with egg ner glass transition temperature is below -40 ° C and at 1 up to 40% by weight of the monomers around those with a glass over transition temperature is above -40 ° C. 4. Use according to any one of claims 1 to 3, characterized characterized in that the emulsifier at least 5 wt .-% of aro there are matical C atoms (in short aromatic emulsifier ge mentioned) or the emulsifier mixture from at least 10 wt .-% the aromatic emulsifier. 5. Use according to one of claims 1 to 4, characterized in that the aromatic emulsifier is a compound of the formula:
where X is O, S, CH ₂ , NH or NR ⁷ , one or two of the radicals R ¹ to R ⁶ for a group SO ₃ ^- K ⁺ and the remaining radicals R ¹ to R ⁶ for H or a C ₁ -C ₁₈ alkyl group, R ⁷ for a C ₁ -C ₈ alkyl group and K for a counter cation. 6. Use according to one of claims 1 to 5, characterized in that it is an emulsifier mixture of:
20 to 95 wt .-% of an aromatic emulsifier and
5 to 80% by weight of a sulfate of the formula:
R ⁸ -O- (ZO) _n -SO ^- ₃ k ⁺ II
the variables have the following meaning:
R ⁸ : C ₁ -C ₁₈ alkyl
Z: CH ₂ -CH ₂ or
n: an integer from 1 to 40
k: a cation. 7. Adhesive tapes with an adhesive coating available through a use according to one of claims 1 to 6. 8. Use of the adhesive tapes according to claim 7 as packaging tapes. 9. Process for the production of packaging, characterized records that an adhesive tape according to claim 7 is used. 10. Method of closing boxes, characterized net that an adhesive tape according to claim 7 is used.