Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-01-07
2004-05-11
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
Reexamination Certificate
active
06734240
ABSTRACT:
DESCRIPTION
The invention relates to the use of an aqueous polymer dispersion as an adhesive for self-adherent peelable films, tapes or labels, characterized in that the polymer dispersion contains from 0.1 to 10 parts by weight, based on 100 parts by weight of polymer, of an emulsifier A) containing a phosphate group.
Many applications call for self-adherent labels, films and tapes which can be later peeled from the substrate.
The self-adherent articles should adhere well to the substrate but on the other hand no residues should remain on the substrate when the labels, tapes or films have been peeled off. To achieve non-residue peelability, use has hitherto often been made of polymer dispersions containing crosslinking agents. However, this requires an additional mixing operation.
Unpublished DE 100109837 (O.Z. 0050/51222) discloses copolymers containing ureido groups which are suitable for peelable labels and films.
WO 99/46337 describes aqueous polymer dispersions containing a phosphate group-containing emulsifier.
The present invention relates to films tapes and labels leaving no residues when peeled from a substrate. However, the protective films tapes and labels should nevertheless stick well to the substrate. Furthermore the adhesive layer should adhere well to the self-adherent articles and should be transparent, resistant to ageing and light-resistant.
Accordingly, we have found the use defined above.
The polymer that is dispersed in the aqueous dispersion preferably consists of so-called main monomers to an extent of at least 40 wt % and more preferably to an extent of at least 60 wt % and most preferably to an extent of at least 80 wt %.
The main monomers are selected from the group comprising C
1
-C
20
alkyl (meth)acrylates, vinyl esters of carboxylic acids containing up to 20 carbons, vinyl aromatic compounds containing up to 20 carbons, ethylenically unsaturated nitrites, vinyl halides, vinyl ethers of alcohols containing from 1 to 10 carbons, aliphatic hydrocarbons containing from 2 to 8 carbons and having 1 or 2 double bonds, or mixtures of these monomers.
The following may be mentioned by way of example: alkyl (meth)acrylates containing a C
1
-C
10
alkyl group, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate.
In particular, mixtures of alkyl (meth)acrylates are suitable.
Vinyl esters of carboxylic acids containing from 1 to 20 carbons are eg vinyl laurate, vinyl stearate, vinyl propionate, vinyl esters of Versatic acid and vinyl acetate.
Suitable vinylaromatic compounds are vinyl toluene, &agr;- and &pgr;-methylstyrenes, &agr;-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene. Examples of nitriles are acrylonitrile and methacrylonitrile.
The vinyl halides are ethylenically unsaturated compounds that are substituted by chlorine, fluorine or bromine, preferably vinyl chloride and vinylidene chloride.
Vinyl ethers which may be mentioned are eg vinyl methyl ether or vinyl isobutyl ether. Preference is given to a vinyl ether of alcohols containing from 1 to 4 carbons.
As hydrocarbons containing from 2 to 8 carbons and two olefinic double bonds there may be mentioned butadiene, isoprene and chloroprene, and those containing one double bond are eg ethylene and propylene.
The main monomers are preferably C
1
-C
10
alkyl (meth)acrylates, particularly C
1
-C
8
alkyl (meth)acrylates and vinyl aromatic compounds, particularly styrene, and mixtures thereof.
Very special preference is given to methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-hexyl acrylate, octyl acrylate and 2-ethylhexyl acrylate, styrene and mixtures of these monomers.
Besides the main monomers the radical-polymerized polymers can contain other monomers, eg monomers containing carboxylic acid, sulfonic acid or phosphonic acid groups. Preference is given to carboxylic acid groups. As examples thereof there may be mentioned acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid.
Other monomers are eg monomers containing hydroxyl groups, particularly C
1
-C
10
hydroxyalkyl (meth)acrylates, and (meth)acrylamide.
As examples of further monomers there may be mentioned phenyloxyethyl glycol mono(meth)acrylate, glycidyl acrylate, glycidyl methacrylate and amino (meth)acrylates such as 2-aminoethyl (meth)acrylate.
Other possible monomers include crosslinking monomers; however, the presence of crosslinking monomers or other crosslinking agents is not absolutely necessary for the purposes of the present invention.
Synthesis of the polymers is carried out in a preferred embodiment by emulsion polymerization, and they are consequently emulsion polymers.
The glass transition temperature of the polymer or emulsion polymer is preferably from −60° to +20 ° C. and more preferably from −50 ° to 0° C. and most preferably from −50° to −10° C.
The glass transition temperature can be determined by conventional methods such as differential thermal analysis or differential Scanning Calorimetry (cf eg ASTM 3418/82, “midpoint temperature”).
The aqueous polymer dispersion contains from 0.1 to 10 parts by weight and preferably from 0.1 to 5 parts by weight and more preferably from 0.2 to 3 parts by weight of an emulsifier A) contaning at least one phosphate group.
The emulsifier also comprises, preferably to an extent of at least 50 wt %, alkylene oxide groups, particularly ethylenoxide groups, propylene oxide groups or mixtures thereof.
The emulsifier is preferably a compound comprising, to an extent of at least 70 wt %, ethylene oxide and/or propylene oxide groups.
Particular preference is given to an embodiment in which the emulsifier contains both ethylenoxide groups and propylene oxide groups.
The proportion of ethylenoxide groups is at least 10 wt % and preferably at least 40 wt %, based on the molecular weight of the emulsifier.
The proportion of propylene oxide groups is at least 10 wt %, preferably at least 20 wt %, based on the molecular weight of the emulsifier.
The molecular weight of the emulsifier is preferably from 400 to 2000 g/mol and more preferably from 600 to 1600 g/mol.
It is preferably an emulsifier of the formula
in which the variables have the following meanings:
E: CH
2
—CH
2
R:
C
1
-C
18
alkyl
x, y, w, z:
each denote an integer from 0 to 30,
x + w:
at least 1
y + z:
at least 1
n:
1 or 2
B:
a monovalent or divalent cation
a, c:
each denote 1 or 2, a*c being equal to 3-n
Preferably R stands for C
10
-C
16
alkyl. The term x+w is preferably equal to from 6 to 20 and more preferably from 10 to 14. The term y+z is preferably equal to from 2 to 10 and more preferably from 3 to 7. Preferably both w and z are equal to 0.
B is preferably a monovalent cation, particularly of Na, K, NH
3
or H, correspondingly c is equal to 1 and a is equal to 1 or 2.
Compounds of this kind are available, eg, under the Trade Name Lutensit® (BASF).
The emulsifier is preferably used when the emulsion polymerization of the monomers takes place. The monomers are dispersed in aqueous phase with the aid of the emulsifier and then polymerized.
In addition to emulsifier A), other emulsifiers or other surface-active compounds can be used.
However, the additional use of other emulsifiers or surface-active compounds is not absolutely necessary.
A detailed description of suitable protective colloids is given in Houben-Weyl, Methoden der organischen Chemie, Vol. XIV/1, “Makromolekulare Stoffe”, Georg-Thieme-Verlag, Stuttgart, 1961, pp 411 to 420. Suitable emulsifiers are anionic, cationic and non-ionic emulsifiers. Preferably, supplementary surfactants used are exclusively emulsifiers, whose molecular weight, unlike the protective colloids, is usually below 2000 g/mol. Of course, when use is made of mixtures of surfactants, the constituents have to be compatible with each other, which can be checked if necessary by a few preliminary tests. Preferably, anionic and non-ionic emulsifiers are used as surfactants. Commonly used supplementary emulsifiers are for example etho
Centner Alexander
Hartz Oliver
Schlarb Bernhard
Schumacher Karl-Heinz
Staller Christelle
BASF - Aktiengesellschaft
Sanders Kriellion A.
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