MELT IN PLACE BINDERS FOR BINDING PARTICULATE FILLERS TO SUBSTRATES
The invention relates to the use of a melt-in-place acrylic binder that is applied to a substrate in the form of a powder, followed by a fusing together of the binder powder by heat or radiation. Particulate filler is present either on the substrate, mixed with the binder powder, or admixed into the binder powder prior to fusion. The fused binder helps adhere the particulate fillers to the substrate, and may or may not cover the particulate filler.
1 . A coated substrate comprising a substrate material having applied on at least one side a mixture comprising:
a. 1 to 50 weight percent of a acrylic polymer powder, wherein said acrylic polymer powder is a homo- or co-polymer comprising from 30 to 100 weight percent of methylmethacrylate units, wherein the average acrylic polymer powder particle size is from 1 to 1000 microns, and wherein said acrylic polymer powder is capable of melting during a process step prior to the coated substrate becoming a final article; and
b. 50 to 99 weight percent of particular fillers.
2 . The coated substrate of claim 1 , wherein said acrylic polymer powder has a Tg of from 40 to 100° C.
3 . The coated substrate of claim 1 , wherein said acrylic polymer powder has a molecular weight of from 20,000 to 200,000 g/mol.
4 . The coated substrate of claim 1 , wherein said acrylic polymer powder has an average particle size of from 50 to 500 microns.
5 . The coated substrate of claim 1 , wherein said acrylic polymer powder particles are spherical.
6 . The coated substrate of claim 1 , wherein said acrylic polymer powder particles are granular and irregular.
7 . The coated substrate of claim 1 , wherein said acrylic polymer powder contains latent functionality capable of crosslinking.
8 . The coated substrate of claim 1 , further comprising 5 to 50 weight percent impact modifiers, based on the weight of the acrylic polymer powder.
9 . The coated substrate of claim 1 , wherein said substrate comprises a polymer.
10 . The coated substrate of claim 1 , wherein said substrate comprises a bituminous material.
11 . A process for forming a melt-in-place acrylic coating on a substrate comprising:
a. placing an effective amount of particulate filler and acrylic polymer powder onto a substrate;
b. heating said acrylic polymer powder above the Tg of the acrylic polymer for a time sufficient to allow the acrylic polymer powder to melt and flow into a continuous, non-continuous or semi-continuous coating; and
c. cooling the substrate, acrylic polymer coating and particulate filler below the Tg of the acrylic polymer.
12 . The process of claim 11 , wherein said substrate is contacted with said particulate filler prior to the addition of the acrylic polymer powder.
13 . The process of claim 11 , wherein said substrate is contacted with said acrylic polymer powder, and said acrylic polymer powder is melted prior to the addition of the particulate filler.
14 . The process of claim 11 , wherein said acrylic polymer powder and said particulate filler are admixed prior to the addition of the admixture onto the substrate.