Foamable acrylic composition

Abstract

Foamed acrylic materials using both traditional chemical blowing agents as well as foamable microspheres. The acrylic foams have improved density reduction, optical properties, and insulation properties. The acrylic foams can be formed by traditional melt processing methods (extrusion, blow molding, etc.) as well as innovative foaming methods, such as foaming during or after polymerization. One method involves the use of expandable microspheres blended with monomers, the monomers then polymerized through bulk polymerization in cell cast, infusion, or compression molding processes. This method can be effectively used to produce composite foam structures.

1 . A polymeric foamed composite material comprising:
 (a) a foamed polymeric thermoplastic (meth)acrylic matrix   (b) a fibrous material as reinforcement wherein the fibrous material comprises either a fiber with an aspect ratio of the fiber of at least 1000 or the fibrous material has a two dimensional macroscopic structure, and wherein the density of the foamed polymeric thermoplastic (meth)acrylic matrix is at least 5, preferably 10, preferably 20, preferably 30, more preferably 50, more preferably 70, more preferably 90 weight percent less than an unfoamed polymeric thermoplastic (meth)acrylic matrix of the same composition.   
     
     
         2 . The polymeric foamed composite material of  claim 1 , wherein said fibers are selected from the group consisting of natural materials, vegetable fibers, wood fibers, animal fibers mineral fibers, sisal, jute, hemp, flax, cotton, coconut fibers, banana fibers, wool, hair, aliphatic polyamides, aromatic polyamides, polyesters, polyvinylalcohol, polyolefins, polyurethanes, polyvinylchloride, polyethylene, unsaturated polyesters, epoxy resins, vinylesters, mineral fibers, glass fibers, carbon fibers, boron fibers, silica fibers. 
     
     
         3 . The polymeric foamed composite material of  claim 1 , wherein said (meth)acrylic matrix polymer comprises at least 70 weight percent of methyl methacrylate monomer units. 
     
     
         4 . The polymeric foamed composite material of  claim 1 , further comprising 0.1 to 10 weight percent of residual expandable microspheres—based on the weight of the polymeric thermoplastic (meth)acrylic matrix. 
     
     
         5 . A liquid (meth)acrylic syrup comprising:
 e) a (meth) acrylic polymer,   f) a (meth) acrylic monomer,   g) at least one initiator or initiating system for starting the polymerization of the (meth) acrylic monomer,   h) at least one foaming agent said liquid (meth)acrylic syrup having a dynamic viscosity in the range from 10 mPa*s to 10000 mPa*s, preferably from 50 mPa*s to 5000 mPa*s and advantageously from 100 mPa*s to 1000 mPa*s.   
     
     
         6 . The liquid (meth)acrylic syrup of  claim 5 , wherein said foaming agent comprises at least one chemical foaming agent. 
     
     
         7 . The liquid (meth)acrylic syrup of  claim 5 , wherein said chemical foaming agent is selected from the group consisting of azodicarbonamide, azodiisobutyronitile, sulfonylsemicarbazide, 4,4-oxybenzene, barium azodicarboxylate, 5-Phenyltetrazole, p-toluenesulfonylsemicarbazide, diisopropyl hydrazodicarboxylate, 4,4′-oxybis(benzenesulfonylhydrazide), diphenylsulfone-3,3′-disulfohydrazide, isatoic anhydride, N,N′-dimethyl-N,N′dinitroterephthalamide, citric acid, sodium bicarbonate, monosodium citrate, anhydrous citric acid, trihydrazinotriazine, N,N′-dinitroso-pentamethylenetetramine, p-toluenesulfonylhydrazide, and blends thereof. 
     
     
         8 . The liquid (meth)acrylic syrup of  claim 5 , wherein said foaming agent comprises expandable microspheres. 
     
     
         9 . A thermoplastic (meth)acrylic foam article comprising a (meth)acrylic matrix with a density reduction of at least 33%, at least 75%, at least 90%, compared to a non-foamed (meth)acrylic article of the same composition. 
     
     
         10 . The thermoplastic (meth)acrylate foamed article of  claim 9 , comprising thermoplastic (meth)acrylate matrix comprises 0.1 to 10, preferably 1 to 5, weight percent of nanoparticles. 
     
     
         11 . The thermoplastic (meth)acrylate foamed article of  claim 10 , wherein said nanoparticles are conductive nanoparticles. 
     
     
         12 . The thermoplastic (meth)acrylate foamed article of  claim 9 , comprising a (meth)acrylic sheet having a k factor of less than 0.7, preferably less than 0.5, more preferably less than 0.25 at 25° F. 
     
     
         13 . The thermoplastic (meth)acrylate foamed article of  claim 9 , having a class A surface, as measured by ASTM E340. 
     
     
         14 . A process for forming a (meth)acrylic foam comprising the steps of
 a. blending a foaming agent, (meth)acrylic monomers, (meth)acrylic polymer and one or more initiators to form a liquid (meth)acrylic syrup having a dynamic viscosity in the range from 10 mPa*s to 10000 mPa*s, preferably from 50 mPa*s to 5000 mPa*s and advantageously from 100 mPa*s to 1000 mPa*s, b. forming a structure by polymerization of the liquid (meth)acrylic syrup.   
     
     
         15 . The process of  claim 14 , wherein foaming occurs simultaneously with the polymerization process, to form a foamed structure. 
     
     
         16 . The process of  claim 14 , wherein said structure is foamed after polymerization by the addition of energy capable of enabling the foaming agent to expand. 
     
     
         17 . The process of  claim 14 , wherein said foaming agent comprises at least one chemical foaming agent. 
     
     
         18 . The process of  claim 14 , wherein said foaming agent comprises expandable microspheres. 
     
     
         19 . The process of  claim 14 , wherein said structure formation is performed by, cell cast, solid state casting, vacuum infusion, pultrusion, wet compression molding, resin transfer molding, compression resin transfer molding, lay-up/spray-up; or filament winding. 
     
     
         20 . The process of  claim 14 , wherein said liquid (meth)acrylic syrup is combined with long fiber with an claim ratio of the fiber of at least 1000 or the fibrous material has a two or three dimensional macroscopic structure, prior to polymerization. 
     
     
         21 . The process of  claim 14 , wherein said combination of long fibers and liquid (meth)acrylic syrup occurs by Gravure coating, immersion dip coating, slot die coating, curtain coating, or gap coating. 
     
     
         22 . A process for forming a (meth)acrylic foam having improved surface appearance, as measured by ASTM E340, comprising the steps of: a) forming a thermoplastic (meth)acrylic foamed article in a mold, wherein said thermoplastic (meth)acrylic foamed article comprises expandable microspheres, b) curing said article c) enlarging the size of the mold by either opening the mold slightly, or by moving the cured article into a slightly larger mold, d) adding additional heat to the article, causing it to further expand to fill the larger mold, e) cooling the article, and f) demold the article. 
     
     
         23 . The polymeric foamed composite material of  claim 1 , wherein said material is an article for use as an automobile part, boat part, train part, sport article, plane part, helicopter part, space ship part, rocket part, photovoltaic module part, wind turbine part, furniture part, construction part, building part, telephone or cell phone part, computer or television part, printer part or photocopy part.