HEAT-SEALABLE COATING SYSTEM SUITABLE FOR THE SEALING OF VARIOUS TYPES OF SUBSTRATES
The present invention is directed to a heat-sealable coating system suitable for the sealing of various types of substrates, comprising a film-forming dispersion, comprising a polyester or polyester mixture as polymer type A, a poly(meth)acrylate as polymer type B, a graft copolymer of polymer type A and polymer type B as polymer type AB, a polyolefin or a polyolefin mixture as polymer type C, and a graft copolymer as polymer type CD, composed of polymer type C and of a poly(meth)acrylate as polymer type D, wherein said dispersion comprises of from 30% to 60% by weight of ethyl acetate based on the total weight of the dispersion, and wherein said dispersion comprises of from 20% to 50% by weight of polymer type A, from 10% to 20% by weight by weight of polymer type B, from 10% to 20% by weight of polymer type AB, from 5% to 25% by weight by weight of polymer type C, and from 15 to 35% by weight by weight of polymer type CD, based in each case on the total mass of the polymer types A, B, C, AB, and CD, and to a process for the sealing of various types of substrates, wherein the foil is coated with a coating system according to the invention.
1 . A heat-sealable coating system suitable for the sealing of various types of substrates, comprising a film-forming dispersion, comprising
a polyester or polyester mixture as polymer type A,
a poly(meth)acrylate as polymer type B,
a graft copolymer of polymer type A and polymer type B as polymer type AB,
a polyolefin or a polyolefin mixture as polymer type C, and
a graft copolymer as polymer type CD, composed of polymer type C and of a poly(meth)acrylate as polymer type D,
wherein said dispersion comprises of from 30% to 60% by weight of ethyl acetate based on the total weight of the dispersion, and wherein said dispersion comprises of from 20% to 50% by weight of polymer type A,
from 10% to 20% by weight by weight of polymer type B,
from 10% to 20% by weight of polymer type AB,
from 5% to 25% by weight by weight of polymer type C, and
from 15 to 35% by weight by weight of polymer type CD,
based in each case on the total mass of the polymer types A, B, C, AB, and CD.
2 . The coating system as claimed in claim 1 , wherein said dispersion comprises of from 50% to 55% by weight of ethyl acetate.
3 . The coating system as claimed in claim 1 , wherein that said dispersion comprises of from 0.5% to 10% by weight, preferably of from 5% to 7.5% by weight of cyclohexane.
4 . The coating system as claimed in claim 1 , wherein said dispersion comprises of from 25% to 40% by weight of polymer type A,
from 10% to 15% by weight of polymer type B,
from 10% to 20% by weight of polymer type AB,
from 10% to 15% by weight of polymer type C, and
from 20% to 30% by weight of polymer type CD,
based in each case on the total mass of the polymer types A, B, C, AB, and CD.
5 . The coating system as claimed in claim 1 , wherein the proportion of the polymer type C, inclusive of the proportions in polymer type CD, based on the total mass of the polymer types A, B, C, AB, and CD, is from 5 to 40% by weight, preferably of from 10 to 20% by weight.
6 . The coating system as claimed in claim 1 , wherein from 1% to 15%, preferably 2.5% to 9% of the carbons of the main chain of the polymer type C are tertiary carbon atoms.
7 . The coating system as claimed in claim 1 , wherein the polymer type A is a mixture of a two polyesters and polymer type C is a mixture of two polyolefines.
8 . The coating system as claimed in claim 1 , wherein the polymer type AB is a graft copolymer with a polyester main chain and poly(meth)acrylate side chains.
9 . The coating system as claimed in claim 1 , wherein polymer type C is an EPM, a hydrogenated polybutadiene, or a copolymer of ethylene and of an α-olefin having from 4 to 12, preferably 4 to 6 carbon atoms.
10 . The coating system as claimed in claim 1 , wherein polymer type C comprises a proportion of from 60 to 90%, preferably of from >70 to 85 by weight of repeating ethylene units, and its weight-average molecular weight M w is from 10 000 to 250 000.
11 . The coating system as claimed in claim 1 , wherein in order to produce the graft copolymers AB and CD, grafting of polymer type B onto polymer type A and of polymer type D onto polymer type C is carried out simultaneously, and that polymer type B and polymer type D preferably have the same composition.
12 . The coating system as claimed in claim 1 , wherein it has a dynamic viscosity of from 200 to 10000 mPas, preferably of from 500 to 5000 mPas, and more preferably 1000 to 4000 mPas, as determined by the method given in the description.
13 . A process for the sealing of various types of substrates, wherein a foil is coated with a coating system as claimed in claim 1 , the coating is dried at a temperature of below 100° C., preferably at a temperature of from 80 to 98° C., and the coated side of the foil is placed onto the material to be sealed, and is sealed at a temperature of from 120 to 220° C. and with a pressure of from 0.2 to 0.6 MPa over a period of from 0.1 to 1 s.
14 . A process according to claim 13 , wherein the foil and the material to be sealed, both coming in to contact with the coating system, are made from the same kind of polymer, preferably polyethylene terephthalate.
15 . A process according to claim 13 , wherein aluminum foils, polyester foils, PET foils, or PET-coated foils are used as foils and substrates made from polystyrene, polyester, PET, or polyvinyl chloride are used as material to be sealed.