Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1994-04-14
1996-07-16
Schofer, Joseph L.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
524460, C08F22006, C08F22010
Patent
active
055368000
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to water- or alkali-dispersible emulsion polymer systems which are functional as pressure-sensitive adhesives. The adhesives of the instant invention provide an ecologically friendly replacement for pressure-sensitive adhesives which hinder clean paper recovery during repulping.
For a label or tape constructions to be repulpable, the adhesive must, for some markets, be water dispersible or cold water soluble and, for such markets, pass Tappi Useful Method 213 (Tappi UM 213) "Repulpability of Splice Adhesive Compositions," incorporated herein by reference.
Other markets which utilize hot water or alkali for repulping accept a different test. A product which passes a Tappi Useful Method 204 (Tappi UM 204), a de-inking and repulping test incorporated herein by reference will also satisfy requirements for elevated temperature alkali repulping.
Most rubber-based and acrylic adhesive systems are not repulpable. During the repulping process (fiber shearing), the adhesives tend to agglomerate and form globules, commonly referred to in the trade as "stickies." Stickies adversely affect paper quality and have a negative impact on the process of recycling paper.
Several approaches can be taken to remove adhesive stickies. One has been to use water-dispersible adhesive microspheres prepared by processes described in U.S. Pat. Nos. 3,691,140 to Silver, 4,155,152 to Baker et al., 4,495,318 and 4,598,212 to Howard, and 4,810,763 to Mallya et al., each incorporated herein by reference, and applied at appropriately low coat weights. While the adhesives disperse in the paper fiber adequately during the repulping process, the adhesive is not removed from the paper fibers. Rather, the adhesive microspheres accumulate in the paper fibers, reducing paper quality and limit the number of times the paper fibers can be repulped or recycled.
Water-soluble adhesive systems which provide for complete adhesive removal from the fiber have been used commercially. Typically, commercial water-soluble products have suffered from (a) poor shelf life (the tape or label is sold in a sealed plastic bag); (b) poor humidity and/or heat-aged performance; and (c) a propensity to bleed into the paper facestock (which reduces peel performance). Each of these problems is related to the high water-sensitivity of the respective products. Such water-soluble adhesives and tapes are described, for instance, in U.S. Pat. No. 3,441,430 to Peterson; U.S. Pat. No. 3,865,770 to Blake, U.S. Pat. No. 4,052,368 to Larson, U.S. Pat. No. 4,413,080 to Blake, and U.S. Pat. No. 4,569,960 also to Blake, each incorporated herein by reference.
There is a need therefore to provide adhesives for a general purpose label and tape construction which are repulpable and not sensitive to changes in relative humidity and where no special precautions are required for storage or use as an adhesive for a label or tape.
SUMMARY OF THE INVENTION
According to the present invention, there is provided an adhesive system which comprises inherently tacky water-dispersible pressure-sensitive adhesives formed by emulsion polymerization of from about 55% to about 90% by weight of nonacid monomers, predominantly alkyl acrylates, interpolymerized with from about 10% to about 20% of a mixture of acrylic acid and at least one oleophilic unsaturated carboxylic acid, preferably a mixture of acrylic acid with methacrylic acid, with some portion of the polymerization occurring in the presence of a chain transfer agent. The repulpable pressure-sensitive adhesives have a glass transition temperature in the range of about -15.degree. to -50.degree. C. and are preferably formed in the presence of a mixture of nonionic and anionic surfactants.
Useful repulpable pressure-sensitive adhesive polymers may be prepared by one stage of emulsion polymerization, sequential polymerization or by blending separately formed emulsion polymers. Sequential emulsion polymerization is preferred. However formed, the emulsion pressure-sensitive adhesives may be ble
REFERENCES:
patent: 3299010 (1967-01-01), Samour
patent: 3400103 (1968-09-01), Samour et al.
patent: 3983297 (1976-09-01), Ono et al.
Randall, legal representative Richard P.
Scholz William F.
Van Ham, deceased Robert H.
Van Ham, legal representative Louis C.
Avery Dennison Corporation
Sarofim N.
Schofer Joseph L.
LandOfFree
Repulpable pressure-sensitive adhesive compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Repulpable pressure-sensitive adhesive compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Repulpable pressure-sensitive adhesive compositions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1785292