DUAL-FOAMED POLYMER COMPOSITION
Methods provide a polymer foam having high bonding strength and improved compressive hardness characteristics wherein the polymer foam comprising cavities formed by microballoons, and also 2 to 20 vol. %, based on the total volume of the polymer foam, of cavities surrounded by the polymer foam matrix.
1 - 6 . (canceled)
7 . A method for producing a polymer foam, the method:
a) mixing at least matrix material of the polymer foam with air to form a mixture;
b) mixing microballoons into the mixture from step a);
c) removing air fractions from the mixture, using a pressure gradient; and
d) delivering the mixture,
wherein step c) takes place after step a), and
step d) takes place after steps a) to c).
8 . The method according to claim 7 , wherein the polymer foam, after it has been produced, is shaped between at least two rotating rolls.
9 . The method according to claim 7 , wherein the polymer foam comprising cavities formed by microballoons and also 2 to 20 vol %, based on the total volume of the polymer foam, of cavities surrounded by the polymer foam matrix.
10 . The method according to claim 7 , wherein the polymer foam comprises 6 to 16 vol % of cavities surrounded by the polymer foam matrix.
11 . The method according to claim 7 , wherein at least 90% of all the cavities surrounded by the polymer foam matrix have a maximum diameter of ≦200 μm.
12 . The method according to claim 7 , wherein the polymer foam comprises at least 25 wt %, based on the total weight of the polymer foam, of one or more polymers selected from the group consisting of polyacrylates, natural rubbers and synthetic rubbers.
13 . The method according to claim 7 , wherein the polymer foam is a pressure sensitive adhesive.
14 . The method according to claim 7 , wherein at least 90% of all the cavities formed
15 . The method according to claim 7 , wherein the polymer foam comprising first cavities formed by microballoons, and 2 to 20 vol. %, based on the total volume of the polymer foam, of second cavities surrounded by the polymer foam matrix, wherein the microballons are hollow microspheres having a thermoplastic shell that is elastic, wherein the hollow microspheres have been expanded and at least 90% of all the first cavities formed by microballoons have a maximum diameter of 10 to 500 μm.
16 . The method according to claim 7 , wherein at least 90% of all the first cavities formed by microballoons have a maximum diameter of 15 to 200 μm.
17 . The method according to claim 7 , wherein the polymer foam comprises 10 to 15.5 vol. % of the second cavities surrounded by the polymer foam matrix.
18 . The method according to claim 7 , wherein a volume ratio of the first cavities to the second cavities is from 0.5 to 10.
19 . The method according to claim 18 , wherein a volume ratio of the first cavities to the second cavities is from 2 to 2.6.
20 . The method according to claim 7 , wherein the polymer foam is in the form of a layer having a thickness range from 20 to 5000 μm.
21 . The method according to claim 20 , wherein the polymer foam is in the form of a layer having a thickness range from 400 to 2100 μm.
22 . The method according to claim 7 , wherein a weight per unit volume or overall density of the polymer foam is in a range from 150 to 900 kg/m 3 .
23 . The method according to claim 22 , wherein a weight per unit volume or overall density of the polymer foam is in a range from 350 to 880 kg/m 3 .
24 . The method according to claim 7 , wherein the polymer foam comprises at least 25 wt %, based on the total weight of the polymer foam, of a polyacrylate comprising the following components:
a) acrylic esters and/or methacrylic esters of the following formula
b) CH 2 ═C(R I )(COOR II ),
where R I ═H or CH 3 and R II is an alkyl radical having 4 to 14 carbon atoms,
c) olefinically unsaturated monomers having functional groups that exhibit reactivity with crosslinker substances or with some of crosslinker substances, and
d) optionally, additional acrylates and/or methacrylates and/or olefinically unsaturated monomers, which are copolymerizable with component (a).
25 . The method according to claim 24 , wherein monomers of component (a) are present at a concentration from 45 to 99 wt %, monomers of component (b) are present at a concentration from 1 to 15 wt %, and monomers of component (c) are present at a concentration from 0 to 40 wt %, all concentration based on the total monomer mixture.
26 . The method according to claim 24 , wherein monomers of component (a) consist of acrylic and methacrylic esters with alkyl groups containing 4 to 14 carbon atoms.