Low-density, class a sheet molding compounds from isophthalate-maleate thermoset resins
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 blends of isophthalate modified, maleic-glycol polyester resin -glycol and maleate-glycol polyester resins that provide low density, thermosetting SMC that yields exterior and structural thermoset articles, e.g. auto parts, panels, etc that have Class A Surface Quality.
1 . A low-density sheet molding compound paste (SMC-paste) comprising:
a phthalate modified, maleic-glycol polyester resin;
a maleic - glycol polyester resin;
an ethylenically unsaturated monomer; and
a nanoclay filler composition.
2 . The low-density sheet molding compound (SMC), according to claim 1 , wherein said phthalate modified, maleic-glycol polyester resin is present at from about 10 mole percent to about 40 mole percent, and wherein said maleate-glycol polyester resin is present at from about 60 mole percent to about 90 mole percent, based on total resin.
3 . The low-density sheet molding compound (SMC), according to claim 1 , wherein said phthalate modified, maleic-glycol polyester resin comprises a phthalic acid, maleic acid, and low molecular weight glycol.
4 . The low-density sheet molding compound (SMC), according to claim 2 , wherein said low molecular weight glycol is selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, dipropylene glycol, 1,3-propane glycol, and mixtures thereof.
5 . The low-density sheet molding compound (SMC), according to claim 4 , wherein said low molecular weight glycol comprises an approximately equimolar mixture of ethylene glycol, dipropylene glycol, and diethylene glycol.
6 . The low-density sheet molding compound (SMC), according to claim 1 , wherein said maleic - glycol polyester resin comprises maleic acid and a low molecular weight glycol.
7 . The low-density sheet molding compound (SMC), according to claim 6 , wherein said low molecular weight glycol is selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, dipropylene glycol, 1,3-propane glycol, and mixtures thereof.
8 . The low-density sheet molding compound (SMC), according to claim 6 , wherein said low molecular weight glycol comprises propylene glycol.
9 . The low-density sheet molding compound (SMC), according to claim 1 , wherein said ethylenically unsaturated monomer is styrene.
10 . The low-density sheet molding compound (SMC), according to claim 1 , further comprising at least one additive selected from the group consisting of low profiling additives, LPA-enhancers, mineral fillers, organic fillers, 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.
11 . The sheet molding compound (SMC) paste, according to claim 1 , wherein said SMC paste has a density of less than about 1.25 g/cm 3 .
12 . A sheet molding compound (SMC) comprising:
the SMC-paste of claim 1; and
a roving reinforcing material.
13 . An article of manufacture comprising the low-density SMC of claim 12 .
14 . The article of manufacture, according to claim 13 , wherein said article has a Class A Surface Quality.
15 . The article of manufacture, according to claim 13 , wherein said article has a surface smoothness quality less than a 80 Ashland LORIA analyzer index.
16 . A process for making molded composite vehicle and construction parts having a density less than 1.6 grams per cm 3 , comprising:
admixing a phthalate modified, maleic-glycol polyester resin; a maleic-glycol polyester resin, an olefinically unsaturated monomer capable of copolymerizing with said glycol resins, 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.
17 . The process of claim 16 wherein said molding pressure for the part is from 200 psi to 1400 psi; preferably from 400 psi to 800 psi.
18 . The process of claim 16 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.
19 . The process of claim 16 wherein said molded part has a surface smoothness quality less than a 100 Ashland LORIA analyzer index.
20 . The method of fabricating a low-density SMC, according to claim 16 , 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.