Low-density, class a sheet molding compounds containing divinylbenzene
The present disclosure relates generally to resin formulations for sheet molding compounds. Particularly, but not by way of limitation, the invention relates to low-density thermosetting sheet molding compounds (SMC) comprising an organic-modified, inorganic clay, a thermosetting resin, a low profile agent, a reinforcing agent, a low-density filler, and substantially the absence of calcium carbonate. The present disclosure relates particularly to the use of alternative reactive monomers present as aromatic, multiethylenically-unsaturated compounds that aid thermosetting SMC in yielding exterior and structural thermoset articles, e.g. auto parts, panels, etc that have Class A Surface Quality.
1 . A sheet molding compound paste formulation comprising:
a thermosetting resin;
an ethylenically unsaturated monomer;
an alternative reactive monomer;
a low profiling additive; and
a nanoclay filler composition, wherein said SMC paste has a density less than about 1.25 g/cm 3 .
2 . The paste formulation, according to claim 1 , wherein said alternative reactive monomer is an aromatic, multiethylenically-unsaturated monomer.
3 . The paste formulation, according to claim 2 , wherein said alternative reactive monomer is selected from the group consisting of di-, tri-, tetra-, and higher multi functional ethylenically unsaturated aromatic compounds, and mixtures thereof.
4 . The paste formulation, according to claim 3 , wherein said ethylenically unsaturated aromatic compound is selected from the group consisting of benzene, toluene, naphthalene, anthracene, higher order aromatics, and mixtures thereof.
5 . The paste formulation, according to claim 3 , wherein a preferred ethylenically unsaturated aromatic compound is divinylbenzene.
6 . The paste formulation, according to claim 1 , further comprising a low-profiling additive enhancer.
7 . The paste formulation, according to claim 1 , further comprising at least one additive selected from the group consisting of mineral fillers, organic fillers, resin tougheners, rubber impact modifiers, organic initiators, stabilizers, inhibitor, thickeners, cobalt promoters, nucleating agents, lubricants, plasticizers, chain extenders, colorants, mold release agents, antistatic agents, pigments, fire retardants, and mixtures thereof.
8 . A sheet molding compound (SMC) comprising:
the paste formulation, according to claim 1; and
a roving reinforcing material.
9 . An article of manufacture comprising the low-density SMC of claim 8 .
10 . The article of manufacture, according to claim 9 , wherein said article has a Class A Surface Quality.
11 . A process for making molded composite vehicle and construction parts having a density less than 1.6 grams per cm 3 , comprising:
admixing unsaturated polyester thermosetting resin, an olefinically unsaturated monomer capable of copolymerizing with said unsaturated polyester resin, an alternative reactive monomer, a thermoplastic low profile additive, free radical initiator, alkaline earth oxide or hydroxide thickening agent, and a nanoclay composite filler composition;
forming a paste;
dispensing said paste on a carrier film above and below a bed of roving, forming a molding sheet;
enveloping said sheet in the carrier film;
consolidating said sheet;
maturing said sheet until a matured molding viscosity of 3 million to 70 million centipoise is attained and said sheet is non-tacky,
releasing said sheet from said carrier film;
compression molding said sheet into a part in a heated mold under pressure whereby a uniform flow of resin, filler and glass occurs outward to the edges of said part; and
removing said molded part.
12 . The process for making molded composite vehicle and construction parts, according to claim 11 , wherein said alternative reactive monomer is an aromatic, multiethylenically-unsaturated monomer.
13 . The process for making molded composite vehicle and construction parts, according to claim 11 , wherein said alternative reactive monomer is selected from the group consisting of di-, tri-, tetra-, and higher multi functional ethylenically unsaturated aromatic compounds, and mixtures thereof.
14 . The process for making molded composite vehicle and construction parts, according to claim 11 , wherein said ethylenically unsaturated aromatic compound is selected from the group consisting of benzene, toluene, naphthalene, anthracene, higher order aromatics, and mixtures thereof.
15 . The process for making molded composite vehicle and construction parts, according to claim 11 , wherein a preferred ethylenically unsaturated aromatic compound is divinylbenzene.
16 . The process of claim 11 wherein said molding pressure for the part is from 200 psi to 1400 psi; preferably from 400 psi to 800 psi.
17 . The process of claim 11 wherein said molding temperature for the part is from 250° F. to 305° F.; preferably from 270° F. to 290° F; and most preferably from 275° F. to 285° F.
18 . The process of claim 11 wherein said molded part has a surface smoothness quality less than a 100 Ashland LORIA analyzer index.
19 . The method of fabricating a low-density SMC, according to claim 11 , further comprising providing auxiliary components selected from the group consisting of LPA-enhancers, mineral fillers, organic fillers, auxiliary monomers, rubber impact modifiers, resin tougheners, organic initiators, stabilizers, inhibitor, thickeners, cobalt promoters, nucleating agents, lubricants, plasticizers, chain extenders, colorants, mold release agents, antistatic agents, pigments, fire retardants, and mixtures thereof.
20 . The article of manufacture, according to claim 10 , wherein said article has a surface smoothness quality less than a 100 Ashland LORIA analyzer index.
21 . A method of fabricating an article of manufacture comprising heating under pressure the low-density SMC of claim 8 .
22 . The method of claim 12 wherein said molded part has a surface smoothness quality less than a 100 Ashland LORIA analyzer index.