Methacrylate-based adhesive compositions
An adhesive composition, especially suitable for a two-part adhesive system curable via free radical polymerization comprises; (A) (meth)acrylate ester monomer; (B) chlorinated elastomeric polymer; (C) core-shell impact modifier; and (D) urethane (meth)acrylate oligomer. Example adhesive compositions include urethane (meth)acrylate oligomer (D) derived from (i) a di- or higher isocyanate having at least two isocyanate groups which differ in reactivity; (ii) a chain-extending reagent which has at least two groups selected from hydroxyl and/or amino groups, each capable of reaction with an isocyanate group of (i); (iii) a hydroxymethacrylate component or hydroxyacrylate component. Also urethane (meth)acrylate oligomers, suitable for use in adhesive compositions, and derived from: (i) a diisocyanate having two isocyanate groups which differ in reactivity; (ii) a chain-extending reagent which is a polyether polyol selected from ethoxylated and propoxylated derivatives of tri- and tetra-functional polyols; and (iii) a hydroxyl (meth)acrylate selected from polyethylene glycol (meth)acrylate and polypropylene glycol (meth)acrylate, are disclosed.
1. An adhesive composition, curable via free radical polymerisation, the composition comprising, based on the total weight of components (A), (B), (C) and (D):
(A) from 35% to 65% (meth)acrylate ester monomer(s), at least 70 wt % of which is methyl methacrylate;
(B) from 3 to 32% chlorinated elastomeric polymer(s) selected from chlorinated polyethylenes and polychloroprenes;
(C) from 10 to 35% core-shell impact modifier(s), provided that the combined amount of (B) and (C) is in the range of 30 to 45 wt %; and
(D) from 1% to 20% urethane (meth)acrylate oligomer(s),
wherein the urethane (meth)acrylate oligomer (D) is derived from:
(i) a di- or higher isocyanate having at least two isocyanate groups;
(ii) a branched chain-extending reagent which has at least three hydroxyl groups, each capable of reaction with an isocyanate group of (i), which is selected from a polyester polyol and a polyether polyol; and
(iii) a hydroxymethacrylate component or hydroxyacrylate component.
2. An adhesive composition according to claim 1 , wherein the diisocyanate is selected from isophorone diisocyanate and 2,4-toluene diisocyanate.
3. An adhesive composition according to claim 1 , wherein the chain-extending reagent (ii) is a polyester polyol capable of being obtained by at least one selected from (a) and (b):
(a) by polymerisation of a lactone; and (b) by polymerization of a caprolactone selected from γ-caprolactone, δ-caprolactone, and ε-caprolactone.
4. An adhesive composition according to claim 3 wherein the chain-extending reagent (ii) is derived from at least one selected from (a) and (b):
(a) ε-caprolactone and a tri or higher functional alcohol; and (b) ε-caprolactone and a sugar alcohol.
5. An adhesive composition according to claim 1 , wherein the chain-extending reagent (ii) is a polyether polyol selected from ethoxylated and propoxylated derivatives of at least one selected from (a) and (b):
(a) tri- or higher functional polyols; and (b) tri- or tetra functional polyols.
6. An adhesive composition according to claim 5 , wherein the chain-extending reagent (ii) is a polyether polyol selected from ethoxylated and propoxylated derivatives of trimethylol propane and ethoxylated and propoxylated derivatives of pentaerythritol, and wherein the chain-extending reagent (ii) contains from 3 to 20 units of ethylene oxide (EO), propylene oxide (PO) or combinations thereof.
7. An adhesive composition according to claim 1 , wherein the hydroxyl(meth)acrylate (iii) is selected from a polyethylene glycol methacrylate and polypropylene glycol methacrylate.
8. An adhesive composition according to claim 7 , wherein the polyethylene glycol methacrylate or polypropylene glycol methacrylate contains from 3 to 10 units of ethylene oxide (EO), propylene oxide (PO), or combinations thereof.
9. An adhesive composition according to claim 7 , wherein the urethane (meth)acrylate oligomer (D) is derived from:
(i) a diisocyanate selected from isophorone diisocyanate and 2,4-toluene diisocyanate;
(ii) a polyol selected from ethoxylated and propoxylated derivatives of trimethylol propane and ethoxylated and propoxylated derivatives of pentaerythritol; and
(iii) a polyethylene glycol mono(meth)acrylate or a polypropylene glycol mono(meth)acrylate.
10. An adhesive composition according claim 1 , which includes as component (D) a blend of urethane (meth)acrylate oligomers the blend comprising (a) at least one first oligomer derived from a polyester polyol chain-extending reagent and (b) at least one second oligomer derived from a polyether polyol chain-extending reagent, in a ratio of (a):(b) of 10:1 to 1:10.
11. An adhesive composition according claim 1 , wherein the chlorinated elastomeric polymer (B) is polychloroprene.
12. An adhesive composition according to claim 1 , which comprises one or more of the following additional components:
an acid-functional ethylenically unsaturated monomer;
an unsaturated phosphate-containing monomer;
a chelating agent;
a wax; and
a viscosity control agent.
13. A two part system for an adhesive which comprises first and second parts, which, in combination contain components (A), (B), (C) and (D) as defined in claim 1 , together with
(I) a component capable of initiating free radical polymerisation of components (A) to (D); and
(P) a component capable of promoting the polymerisation, provided that (I) and (P) are contained in different respective parts of the two part system.