Pressure sensitive adhesives

Details Pressure sensitive adhesives Pressure sensitive adhesives

2001-02-15

2003-01-28

Seidleck, James J. (Department: 1711)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Adhesive outermost layer

C428S343000, C428S352000, C428S3550RA, C428S3550AC

Reexamination Certificate

active

06511744

ABSTRACT:

The invention relates to pressure sensitive adhesives based on a polymer having a glass transition temperature (T
g
) ≦10° C. and obtained by free-radically initiated polymerization of ethylenically unsaturated monomers in a liquid medium in the presence of >0 and ≦5 parts by weight, based on 100 parts by weight of the ethylenically unsaturated monomers used for the polymerization, of at least one oligomeric compound itself obtained by free-radically initiated polymerization of ethylenically unsaturated monomers and having
a) an ethylenically unsaturated double bond content of at least 50 mol % and
b) a number-average molecular weight of from 500 to 50,000 g/mol.
Pressure sensitive adhesives (PSAs) form a permanently tacky film which adheres to a very wide variety of surfaces even—as the name of the adhesives suggests—under slight pressure at room temperature. Pressure sensitive adhesives are used to produce self-adhesive products such as self-adhesive tapes, labels, and films. Products of this kind are very easy to use and make it possible to work rapidly when bonding. In contrast to contact adhesive compositions, no ventilation times are necessary. Moreover, there is no “open time” within which the adhesive bond must be made. The quality of a self-adhesive article depends essentially on whether the cohesion (internal strength of the film of adhesive) and its adhesion (to the surface that is to be bonded) are in tune with one another in accordance with the application.
In the case of pressure sensitive adhesives for tapes and labels, in particular, the level of cohesion must be sufficient to prevent stringing and glue emergence at the edges when stamping and cutting, since otherwise the cutting tools become soiled and the cut faces sticky. At the same time, the adhesion should be at a high level in order to provide good sticking on the substrates that are to bonded.
In general, it is impossible to optimize adhesion and cohesion independently of one another. What are desired are measures which either raise the level of both properties or maintain one property unchanged while improving the other.
Polymers obtained by free-radically initiated polymerization of ethylenically unsaturated monomers in the presence of an ethylenically unsaturated oligomeric compound itself obtained by free-radically initiated polymerization of ethylenically unsaturated monomers are described in the prior art. They are used, for example, as nontacky binders in photosensitive formulations (WO 92/15628), in water-based paints (WO 95/32228, WO 95/32229, and WO 95/32255), or in highly pigmented coating formulations (U.S. Pat. No. 5,412,039).
WO 95/04767 discloses aqueous polymer dispersions obtained by free-radically initiated aqueous emulsion polymerizations of ethylenically unsaturated monomers in the presence of an oligomeric compound itself obtained by free-radically initiated polymerization of ethylenically unsaturated monomers in the presence of a transition metal compound as molecular weight regulator. It makes the general proposal to use these aqueous polymer dispersions, blended with various auxiliaries, as components in binders, polishes, inks, varnishes, paints, sealing compounds, and adhesives.
Adhesives, especially hot-melt adhesives based on a polymer prepared in the presence of an oligomeric propene compound, are disclosed in DE-A 19528369. However, the oligomeric propene derivatives used in that case are obtained by nonfree-radical, metallocene-catalyzed oligomerization of propene.
It is an object of the present invention to provide new pressure sensitive adhesives possessing good adhesion and giving bonds possessing high cohesion.
We have found that this object is achieved by pressure sensitive adhesives based on a polymer having a glass transition temperature ≦10° C. and obtained by free-radically initiated polymerization of ethylenically unsaturated monomers in a liquid medium in the presence of >0 and ≦5 parts by weight, based on 100 parts by weight of the ethylenically unsaturated monomers used for the polymerization, of at least one oligomeric compound itself obtained by free-radically initiated polymerization of ethylenically unsaturated monomers and having
a) an ethylenically unsaturated double bond content of at least 50 mol % and
b) a number-average molecular weight of from 500 to 50,000 g/mol.
Oligomeric compounds obtained by free-radically initiated polymerization of ethylenically unsaturated monomers and having an ethylenically unsaturated double bond content of at least 50 mol % and a number-average molecular weight of from 500 to 50,000 g/mol are much described in the prior art. Reference may be made in this context to the documents WO 87/03605, WO 92/15628, WO 95/04767, WO 95/17435, WO 95/25765, WO 95/27737, WO 95/32228, WO 95/32229, WO 95/32255, WO 96/13527, WO 96/33224, WO 97/31030, WO 97/34934, WO 91/35541, WO 98/04603, WO 98/50436, EP-B 199436, EP-B 196783, EP-B 681601, EP-B 714416, U.S. Pat. No. 4,526,945, U.S. Pat. No. 4,694,054, U.S. Pat. No. 5,412,039, U.S. Pat. No. 5,726,263 and JP-A 9132610, and also Schrauzer and Windgassen, J. Am. Chem. Soc. 1966 (88), 3738 to 3743, Tovrog et al., J. Am. Chem. Soc. 1976 (98), 5144 to 5153, Kukulj et al., Macromolecules 1997 (30), 7661 to 7666, Kukulj et al., Macromolecules 1998 (31), 6034 to 6041, Heuts et al., Macromolecules 1999 (32), 2511 to 2519, and Heuts et al., Macromolecules 1999 (32), 3907 to 3912. In accordance with the invention, oligomeric compounds prepared by bulk, solution, emulsion, or suspension polymerization may be used.
As molecular weight regulators in oligomer preparation it is common to use transition metal compounds whose metal ion is able to exist reversibly in at least two oxidation states. The metal ion is advantageously selected from the group consisting of Fe
2+
, Fe
3+
, Ru
2+
, Ru
3+
, Cr
2+
, Cr
3+
, Mo
2+
, Mo
3+
, W
2+
, W
3+
, Co
2+
, Co
3+
, Re
2+
, Re
3+
, V
2+
, V
3+
, Mn
2+
, Mn
3+
, Zr
2+
, Zr
3+
, Zr
4+
, Ti
2+
, Ti
3+
, Ti
4+
, Ce
2+
, and Ce
3+
. Often, the metal ion is selected from the group consisting of Fe
2+
, Fe
3+
, Co
2+
, Co
3+
, Cr
2+
, and Cr
3+
. Preference is given to the use of organocobalt compounds.
To prepare the oligomeric compounds by free-radically initiated polymerization it is possible in principle to use all ethylenically unsaturated monomers which enter into free-radically initiated polymerization. In particular, these are monomers which are free-radically polymerizable in a simple manner, such as, for example, ethylene, vinyl halides, such as vinyl chloride or vinylidene chloride, vinylaromatic monomers, such as styrene, &agr;-methylstyrene, o-chlorostyrene or vinyltoluenes, esters of vinyl alcohol and monocarboxylic acids having 1 to 18 carbon atoms, such as vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl laurate and vinyl stearate, esters of preferably C
3
to C
6
&agr;,&bgr;-monoethylenically unsaturated mono- and dicarboxylic acids, such as especially acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid, with generally C
1
to C
12
, preferably C
1
to C
8
, and in particular C
1
to C
4
alkanols, such as especially methyl, ethyl, n-butyl, isobutyl and 2-ethylhexyl acrylate and methacrylate, dimethyl maleate and di-n-butyl maleate, nitriles of &agr;,&bgr;-monoethylenically unsaturated carboxylic acids, such as acrylonitrile, and also C
4-8
conjugated dienes, such as 1,3-butadiene and isoprene. Generally, these monomers are of only moderate to low solubility in water under standard conditions (25° C., 1 bar).
Monomers of heightened solubility in water under the abovementioned conditions are, for example, &agr;,&bgr;-monoethylenically unsaturated C
3
to C
5
monocarboxylic and C
4
to C
8
dicarboxylic acids, their water-soluble salts and their amides, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid and their alkali

Affiliated with

Also associated with

Rating

Pressure sensitive adhesives does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Pressure sensitive adhesives, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pressure sensitive adhesives will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3023060