Adhesives and use thereof
Adhesives, methods to bond substrates together with the adhesives, and articles of manufacture comprising the adhesives are described. It has been discovered that an adhesive with a polymer content greater than 70 weight percent can be formulated with a blend of (i) a metallocene catalyzed polypropylene polymer that has a density range of about 0.70 to about 0.91 g/cm 3 and a melt viscosity less than 50,000 cP at 190° C. and (ii) a Ziegler-Natta catalyzed amorphous polybutene and/or polypropylene copolymer. Such adhesives have high creep resistance making them particularly well suited for disposable personal care garments.
1. An adhesive comprising:
a) at least 70 wt % of a polymer blend which consists of:
i) a metallocene catalyzed polypropylene homopolymer that has a density range of about 0.70 to about 0.91 g/cm 3 and a melt viscosity less than 50,000 cP at 190° C.,
ii) an atactic polypropylene-polybutene copolymer; and
iii) optionally, a metallocene catalyzed-propylene copolymer with a C 2 , C 4 -C 10 α-olefin comonomer; and
b) less than about 30 wt % of a tackifier and/or plasticizer;
wherein adhesive has a viscosity below about 11,000 centipoise at 150° C. as measured in accordance with ASTM D3236;
wherein the ratio of (i) the metallocene catalyzed polypropylene homopolymer to (ii) the atactic polypropylene-polybutene copolymer is in the range of from about 1:1 to about 1:10; and
wherein the total weight adds to 100 wt %.
2. The adhesive of claim 1 wherein the adhesive comprises less than about 25 wt % of the tackifier and/or plasticizer.
3. The adhesive of claim 1 wherein the metallocene catalyzed polypropylene homopolymer is an isotatic polypropylene.
4. The adhesive of claim 1 wherein the metallocene catalyzed polypropylene homopolymer is an atactic polypropylene.
5. The adhesive of claim 1 wherein the viscosity of the atactic polypropylene-polybutene copolymer is in the range of from about 500 cP to about 3,000 cP at 190° C.
6. The adhesive of claim 1 wherein the tackifier is selected from the group consisting of natural and modified polyterpenes, cyclic or acyclic C 5 resins, cyclic or acyclic C 9 resins, aliphatic and aromatic petroleum hydrocarbon resins, and mixtures thereof.
7. The adhesive of claim 6 wherein the tackifier has a softening point greater than about 80° C.
8. The adhesive of claim 1 further comprising up to about 10 wt % wax.
9. The adhesive of claim 1 wherein the metallocene catalyzed polypropylene homopolymer has medium range isotacticity.
10. A disposable article comprising an adhesive, wherein the adhesive comprises:
a) at least 70 wt % of a polymer blend which consists of:
i) a metallocene catalyzed polypropylene homopolymer that has a density range of about 0.70 to about 0.91 g/cm 3 and a melt viscosity less than 50,000 cP at 190° C.,
ii) an atactic polypropylene-polybutene copolymer having a non-stereospecific morphology; and
iii) optionally, a metallocene catalyzed-propylene copolymer with a C 2 , C 4 -C 10 α-olefin comonomer; and
b) less than about 30 wt % of a tackifier and/or plasticizer;
wherein adhesive has a viscosity below about 11,000 centipoise at 150° C. as measured in accordance with ASTM D3236;
wherein the ratio of (i) the metallocene catalyzed polypropylene homopolymer to (ii) the atactic polypropylene-polybutene copolymer is in the range of from about 1:1 to about 1:10; and
wherein the total weight adds to 100 wt %.
11. The disposable article of claim 10 which is an elastic attachment.
12. The disposable article of claim 11 comprising a substrate wherein the substrate is a film formed from a material selected from the group consisting of rubber, olefin, and a mixture thereof.
13. A method of forming an article comprising:
a) applying the adhesive of claim 1 onto a substrate at a temperature of about 140° C. to about 160° C.;
b) cooling the adhesive to room temperature; and
wherein the cooled adhesive has a creep performance of less than about 40% after 300% strain is applied onto the cooled adhesive at 38° C. for about 4 hours.
14. The method of claim 13 wherein the adhesive is applied by strand coating or spiral coating.
15. The method of claim 13 wherein the adhesive is applied with an add-on level of about 20 to about 100 mg/m/strand.
16. The method of claim 13 wherein the adhesive is applied with an add-on level of about 3 to about 30 mg/inch.
17. The method of claim 13 wherein the cooled adhesive has a creep performance of less than about 30% after 300% strain is applied onto the cooled adhesive at 38° C. for about 4 hours.