Polyurethane hot melt adhesive composition, and preparation method thereof

1 . A polyurethane hot melt adhesive composition, comprising, based on the total weight of the composition:

(A) at least one polyurethane prepolymer obtained by reacting:

(A1) a polyol component comprising:

(a) from 15 wt. % to 20 wt. % of at least one crystalline polyester polyol,

(b) from 15 wt. % to 25 wt. % of at least one liquid polyester polyol, and

(c) from 15 wt. % to 40 wt. % of at least one polyether polyol; and

(A2) from 10 wt. % to 20 wt. % of at least one polyisocyanate having at least two isocyanate groups in one molecule;

(B) from 5 wt. % to 20 wt. % of at least one thermoplastic resin; and

(C) 3 wt. % of calcium carbonate.

2 . The composition of claim 1 , wherein the crystalline polyester polyol has a melting point of more than 40° C., and the liquid polyester polyol has a glass transition temperature of no greater than 0° C.

3 . The composition of claim 1 , wherein the at least one thermoplastic resin is selected from the group consisting of polyesters, phenoxy resins, phenolic resins, acrylic polymers, acrylic block copolymers, acrylic polymers having tertiaryalkyl amide functionality, polysiloxane polymers, polystyrene copolymers, polyvinyl polymers, divinylbenzene copolymers, polyetheramides, polyvinyl acetals, polyvinyl butyrals, polyvinyl acetols, polyvinyl alcohols, polyvinyl acetates, polyvinyl chlorides, methylene polyvinyl ethers, cellulose acetates, styrene acrylonitriles, amorphous polyolefins, thermoplastic urethanes, polyacrylonitriles, ethylene vinyl acetate copolymers, ethylene vinyl acetate terpolymers, functional ethylene vinyl acetates, ethylene acrylate copolymers, ethylene acrylate terpolymers, ethylene butadiene copolymers, ethylene butadiene block copolymers, styrene butadiene block copolymers, polycaprolactone, and any combination thereof.

4 . The composition of claim 1 , further comprising a catalyst selected from the group consisting of triethylamine, tributylamine, dimethylbenzylamine, N-ethyl-, N-methyl-, N-cyclohexylmorpholine, dimethylcyclohexylamine, dimorpholinodiethylether, 2-(dimethylaminoethoxy)-ethanol, 1,4diazabicyclo [2,2,2]octane, 1-azabicyclo [3,3,0]octane, N,N,N′,N′-tetramethyl ethylenediamine, N,N,N′,N′-tetramethyl butanediamine, N,N,N′,N′-tetramethyl hexanel,6-diamine, pentamethyl diethylenetriamine, tetramethyl diaminoethylether, bis-(dimethylaminopropyl)-urea, N,N′-dimethylpiperazine, 1,2-dimethylimidazole, di-(4-N,N-dimethylaminocyclohexyl)-methane, organometallic compounds, and any combination thereof.

5 . The composition of claim 1 , wherein the at least one polyether polyol has a number average molecular weight of between 400 and 8,000 g/mole.

6 . The composition of claim 1 , wherein the at least one thermoplastic resin is free of isocyanate moieties and has a number average molecular weight between 8,000 and 100,000 g/mole.

7 . The composition of claim 1 , wherein the polyurethane hot melt adhesive composition exhibits a tensile strength of between about 3.0 MPa and about 8.0 MPa.

8 . The composition of claim 1 , wherein the liquid polyester polyol has a glass transition temperature of no greater than 0° C.

9 . A cured reaction product comprising the polyurethane hot melt adhesive composition of claim 1 .

10 . An electronic device comprising the polyurethane hot melt adhesive composition of claim 1 .

11 . A method for preparing the polyurethane hot melt adhesive composition of claim 1 , the method comprising:

(i) mixing the polyol component, the at least one thermoplastic resin, and the calcium carbonate under a nitrogen atmosphere at a temperature between about 130 and 150° C.;

(ii) placing the mixture of step (i) under vacuum;

(iii) decreasing the temperature to between about 80 and 120° C.;

(iv) adding the at least one polyisocyanate;

(v) maintaining the temperature between about 100 and 120° C.;

(vi) optionally adding a catalyst and one or more additional additives;

(vii) mixing to obtain a homogeneous mixture; and

(viii) discharging the mixture of step (vii) under a nitrogen atmosphere at a temperature between about 100 and 150° C.

12 . A method of forming an article, the method comprising:

heating the polyurethane hot melt adhesive composition of claim 1 to a molten state;

dispensing the molten polyurethane hot melt adhesive composition as an adhesive bond line on a first substrate, wherein the dispensed bond line has an aspect ratio greater than 50%; and

disposing a second substrate over the first substrate and in contact with the adhesive bond line to form the article.

13 . The method of claim 12 , further comprising cooling the adhesive bond line after disposing the second substrate over the first substrate and in contact with the adhesive bond line.

14 . The method of claim 12 , further comprising curing the adhesive bond line after disposing the second substrate over the first substrate and in contact with the adhesive bond line.

15 . The method of claim 12 , wherein the article is a bezel-less device.

16 . The method of claim 12 , wherein the article is an electronic device.

17 . The method of claim 12 , wherein the bond line aspect ratio is between about 55% and about 98%.

18 . A polyurethane hot melt adhesive composition, comprising, based on the total weight of the composition:

(A) a polyurethane prepolymer obtained by reacting:

(A1) a polyol component consisting of:

(a) from 15 wt. % to 20 wt. % of a crystalline polyol,

(b) from 15 wt. % to 25 wt. % of a liquid polyester polyol, and

(c) from 15 wt. % to 40 wt. % of a polyether polyol; and

(A2) from 10 wt. % to 20 wt. % of at least one polyisocyanate having at least two isocyanate groups in one molecule;

(B) from 5 wt. % to 20 wt. % of at least one thermoplastic resin;

(C) from 0.01 wt. % to 3 wt. % of an aspect ratio promoter comprising calcium carbonate; and

(D) from 0.05 wt. % to 1 wt. % of a catalyst.