Amorphous copolyester resins for use as a cold seal adhesive, coating compositions
A method of adhering substrate surfaces to one another comprises applying a copolyester resin mixture to the surfaces and contacting the surfaces with one another in the absence of heat to form a cold seal. The copolyester resin may be sulfonated and the reaction product of (a) at least two diols comprising ethylene glycol at a mole fraction of at least about 0.25 and (b) at least three diacids or diesters comprising: (i) a sulfomonomer at a mole fraction of at least 0.02, preferably at least 0.07; (ii) at least one aromatic diacid or diester; and (iii) at least one aliphatic diacid or diester. The ratio of aromatic to aliphatic diacids or diesters may be between about 75/25 and about 45/55, and the glass transition temperature of the resin may be between about −25° C. and about 15° C. The resin may be solvated and preferably is food grade compliant and compostable.
1 . A method of adhering a first substrate surface to a second substrate surface: applying a copolyester resin mixture to the first substrate surface and the second substrate surface; and contacting the first substrate surface with the second substrate surface to form a laminate, wherein the method is carried out at ambient temperature, wherein the first substrate and the second substrate are compostable substrates, wherein a copolyester resin in the copolyester resin mixture comprises the reaction product of: (a) at least two diols comprising ethylene glycol at a mole fraction of at least about 0.25 based on the diols and neopentyl glycol and the molar ratio of ethylene glycol: neopentyl glycol is from about 3:1 to about 20:1 and (b) at least three diacids or diesters comprising: (i) at least one sulfomonomer at a mole fraction based on the diacids or diesters of at least 0.02; (ii) at least one aromatic diacid or diester; and (iii) at least one aliphatic diacid or diester.
2 . The method of claim 1 , wherein the contacting step is done at a time and at a pressure sufficient to bond the first substrate surface to the second substrate surface.
3 . The method of claim 2 , wherein the time of the contacting step is from about 0.1 seconds to about 20 seconds, and the pressure of the contacting step is from about 40 psi to about 120 psi.
4 . The method of claim 1 , wherein the copolyester resin mixture further comprises a solvent and the solvent is water, an organic solvent, or both.
5 . The method of claim 4 , wherein the solvent is water and an organic solvent, and the organic solvent comprises acetone and isopropyl alcohol.
6 . The method of claim 1 , wherein the overall Tg of the copolyester resin is from about −25° C. to about 15° C.
7 . The method of claim 1 , wherein: the at least one sulfomonomer is at least one of dimethyl-5-sulfoisophthalate sodium salt (DMSIP) or 5-sulfoisophthalic acid (SIP A); the at least one aliphatic diacid or diester is selected from the group consisting of sebacic acid, azelaic acid, and adipic acid; the at least one aromatic diacid or diester is selected from the group consisting of at least one of isophthalic acid, dimethyl terephthalate, terephthalic acid, and dimethyl isophthalate; and the at least two diols further comprise at least one of diethylene glycol, trimethylol propane, and cyclohexane dimethanol.
8 . The method of claim 1 , wherein the ratio of aromatic to aliphatic diacids or diesters is between about 75/25 and about 45/55.
9 . The method of claim 8 , wherein the ratio of aromatic to aliphatic diacids or diesters is between about 70/30 and about 50/50.
10 . The method of claim 1 , wherein: the at least one sulfomonomer is dimethyl-5-sulfoisophthalate sodium salt; the at least one aliphatic diacid or diester is sebacic acid; and the at least one aromatic diacid or diester is isophthalic acid and dimethyl terephthalate.
11 . The method of claim 10 , wherein: dimethyl-5-sulfoisophthalate sodium salt is present in an amount from about 0.07 to 0.2 mole fraction based on the total amount of diacids and diesters; isophthalic acid is present in an amount from about 0.02 to 0.2 mole fraction based on the total amount of diacids and diesters; dimethyl terephthalate is present in an amount from about 0.25 to 0.55 mole fraction based on the total amount of diacids and diesters; sebacic acid is present in an amount from about 0.18 to 0.4 mole fraction based on the total amount of diacids and diesters;
ethylene gylcol is present in an amount from about 0.75 to 0.97 mole fraction based on the total amount of diols; and neopentyl gylcol is present in an amount from about 0.03 to 0.25 mole fraction based on the total amount of diols.
12 . The method of claim 11 , wherein: dimethyl-5-sulfoisophthalate sodium salt is present in an amount from about 0.08 to about 0.15 mole fraction based on the total amount of diacids and diesters; isophthalic acid is present in an amount from about 0.03 to about 0.15 mole fraction based on the total amount of diacids and diesters; dimethyl terephthalate is present in an amount from about 0.3 to about 0.5 mole fraction based on the total amount of diacids and diesters;
sebacic acid is present in an amount from about 0.2 to about 0.38 mole fraction based on the total amount of diacids and diesters; ethylene gylcol is present in an amount from about 0.8 to about 0.95 mole fraction based on the total amount of diols; and neopentyl gylcol is present in an amount from about 0.05 to about 0.2 mole fraction based on the total amount of diols.
13 . The method of claim 1 , wherein the at least two diols further comprise diethylene glycol present in an amount from about 0.01 to about 0.2 mole fraction based on the total amount of diols.
14 . The method of claim 1 , wherein the copolyester resin mixture comprises a blend of two or more copolyester products.
15 . A method of adhering a first substrate surface to a second substrate surface: applying an amorphous sulfonated copolyester resin mixture, comprising the reaction product of: (a) at least two diols comprising ethylene glycol at a mole fraction and (b) at least three diacids or diesters comprising: (i) at least one sulfomonomer; (ii) at least one aromatic diacid or diester; and (iii) at least one aliphatic diacid or diester, to the first substrate surface and the second substrate surface; and contacting the first substrate surface with the second substrate surface to form a laminate, wherein the method is carried out at ambient temperature, wherein the first substrate and the second substrate are compostable substrates and an amorphous sulfonated copolyester resin in the amorphous sulfonated copolyester resin mixture has a Tg of between about −25° C. and about 15° C.
16 . The method of claim 15 , wherein the amorphous sulfonated copolyester resin mixture comprises a blend of two or more copolyester products.