WO2012128790A1

WO2012128790A1 - High strength polymeric composites

Info

Publication number: WO2012128790A1
Application number: PCT/US2011/058355
Authority: WO
Inventors: Jeffrey Jacob Cernohous
Original assignee: Interfacial Solutions Ip, Llc
Priority date: 2010-10-29
Filing date: 2011-10-28
Publication date: 2012-09-27

Abstract

Compositions and methods for producing polymeric composites having desirable mechanical characteristics. Specifically, the polymeric composites possess superior mechanical properties by admixing polymeric matrix with naturally occurring inorganic materials in combination with a desiccant.

Description

HIGH STRENGTH POLYMERIC COMPOSITES

TECHNICAL FIELD

[001] The composition and methods for producing composites in this disclosure possess superior physical characteristics. Specifically, the composites possess superior mechanical properties by admixing thermoplastics with naturally occurring inorganic materials and a desiccant.

BACKGROUND

[002] Volcanic ash possesses unique material properties attributed to its relatively high surface area, aspect ratio and hardness. Volcanic ash has been applied in various applications such as abrasives and as filtration aids. Additionally, the application of conventional fillers in polymeric composites has not always resulted in properties that one of ordinary skill in the art would consider superior.

SUMMARY

[003] The compositions and methods disclosed herein produce polymeric composites having desirable mechanical characteristics. Specifically, the polymeric composites possess superior mechanical properties by admixing a polymeric matrix with naturally occurring inorganic materials in combination with a desiccant. In one embodiment, polymeric composites produced using volcanic ash as the naturally occurring inorganic material and a desiccant have markedly improved physical properties (e.g., flexural modulus, tensile elongation, etc.) when compared to polymeric materials filled with just volcanic ash or other mineral fillers. The noted composites have utility in many applications. Non-limiting examples include building materials and automotive components. Specific applications of a particular utility includes, extruded sheet products and railroad ties.

[004] In one embodiment, a thermoplastic matrix is melt processed with a naturally -occurring inorganic material and a desiccant to form a useful article. In another embodiment, the thermoplastic matrix is melt processed with a naturally-occurring inorganic material, a desiccant and a coupling agent, a blowing agent, or a combination thereof, to produce a composite.

Conventional melt processing techniques may be employed to generate the polymeric composition.

[005] The following terms used in this application are defined as follows: "Cellulosic Filler" means natural or man-made materials derived from cellulose. Cellulosic materials include, for example: wood flour, wood fibers, sawdust, wood shavings, newsprint, paper, flax, hemp, grain hulls, kenaf, jute, sisal, nut shells or combinations thereof.

"Composite" means a mixture of a polymeric material and a filler or additive.

"Desiccant" means a material that either induces or sustains a state of dryness.

"Filler" Means an organic or inorganic material that does not possess viscoelastic characteristics under the conditions utilized to melt process the filled polymeric matrix.

"Melt Processable Composition" means a formulation that is melt processed, typically at elevated temperatures, by means of a conventional polymer processing technique such as, for example, extrusion or injection molding.

"Naturally Occurring Inorganic Material" means an inorganic material that is found in nature, for example, volcanic ash, and is suitable for forming a composite.

"Polymeric Matrix" means a melt processable polymeric material or resin.

[006] The above summary is not intended to describe each disclosed embodiment or every implementation. The detailed description that follows more particularly exemplifies illustrative embodiments.

DETAILED DESCRIPTION

[007] The compositions and methods disclosed herein are suitable for producing high strength composites. Specifically, the polymeric composites resulting from the admixture of polymeric matrix, naturally occurring inorganic materials, and a desiccant possess superior mechanical properties. In one embodiment, a polymeric matrix is melt processed with a desiccant and volcanic ash as the naturally occurring inorganic material. Surprisingly, polymer composites produced using a mixture of a polymeric matrix, desiccant and volcanic ash have markedly improved flexural and tensile properties when compared to thermoplastic materials filled with conventional inorganic fillers. Specifically, composites having a flexural modulus of greater than 2500 MPa are described. The composites also have markedly improved thermal properties. For example, the coefficients of thermal expansion observed in certain embodiments of the composites are markedly less than polymers filled with conventional inorganic fillers.

Composites having a coefficient of thermal expansion of less that 70 μητ/m are described. The composites have utility in many applications. Non-limiting examples include building materials, transportation materials and automotive components. Preferred examples included concrete forms, railroad ties and automotive sheet stock.

[008] Any naturally occurring inorganic material is suitable in the polymeric composite. Some embodiments incorporate volcanic ash (individually or in combined forms of expanded, unexpanded, or micronized expanded), mica, fly ash, andesiteic rock, feldspars, aluminosilicate clays, obsidian, diatomaceous earth, silica, silica fume, bauxite, geopolymers pumice, perlite, pumicsite and combinations thereof. The various forms of volcanic ash are well suited for many end use applications. In one embodiment, the naturally occurring inorganic material is chosen such that it has an aspect ratio of at least 1.5: 1 (length:width), at least 3: 1, or at least 5: 1. In some embodiments, the inorganic material comprises 5 - 80 wt % of the composition, 20 - 80 wt %, or 30 - 80 wt %.

[009] The polymeric matrix functions as the host polymer and is a primary component of the melt processable composition. A wide variety of polymers conventionally recognized in the art as suitable for melt processing are useful as the polymeric matrix. They include both

hydrocarbon and non-hydrocarbon polymers. Examples of useful polymeric matrices include, but are not limited to, polyamides, polyimides, polyurethanes, polyolefms, polystyrenes, polyesters, polycarbonates, polyketones, polyureas, polyvinyl resins, polyacrylates and polymethylacrylates. Polyolefms are well suited for many applications.

[010] In certain embodiments, polymers suitable as the polymeric matrix include high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), polypropylene (PP), polyolefm copolymers (e.g., ethylene-butene, ethylene-octene, ethylene vinyl alcohol), polystyrene, polystyrene copolymers (e.g., high impact polystyrene, acrylonitrile butadiene styrene copolymer), polyacrylates, polymethacrylates, polyesters, polyvinylchloride (PVC), fluoropolymers, polyamides, polyether imides, polyphenylene sulfides, polysulfones, polyacetals, polycarbonates, polyphenylene oxides, polyurethanes, thermoplastic elastomers (e.g., SIS, SEBS, SBS), epoxies, alkyds, melamines, phenolics, ureas, vinyl esters, liquid crystal polymers or combinations thereof. Polyolefms and thermoplastic elastomers are well suited for certain applications. [Oil] The function of the desiccant in the composite is to address the moisture in the polymer matrix, the naturally occurring inorganic material, fillers, additives or a combination thereof. By addressing the moisture or water present in the other components, the desiccant may

significantly reduce or eliminate moisture causing defects that result in reduced physical properties. The desiccant may be any conventional material capable of moisture uptake and suitable for application in melt processed polymeric matrices. In one embodiment, the desiccant is selected from calcium oxide, magnesium oxide, strontium oxide, barium oxide, aluminum oxide, or combinations thereof. Those of ordinary skill in the art of melt processing polymers are capable of selecting a specific desiccant in combination with a polymer matrix and naturally occurring inorganic material to achieve the beneficial results. The amount of desiccant will vary, but may include a range of about 1 to 20 wt % of the formulation in the composite formulation. In certain embodiments, the desiccant may address bound or interstitial moisture potentially released from the naturally occurring inorganic material during melt processing.

[012] In another aspect, the modified polymer matrix can be melt processed with additional fillers. Non-limiting examples of fillers include mineral and organic fillers (e.g., talc, mica, clay, silica, alumina, carbon fiber, carbon black glass fiber) and conventional cellulosic materials (e.g., wood flour, wood fibers, sawdust, wood shavings, newsprint, paper, flax, hemp, wheat straw, rice hulls, kenaf, jute, sisal, peanut shells, soy hulls, or any cellulose containing material). The amount of filler in the melt processable composition may vary depending upon the polymeric matrix and the desired physical properties of the finished composition. Those skilled in the art of melt processing polymers are capable of selecting appropriate amounts and types of fillers to match with a specific polymeric matrix in order to achieve desired physical properties of the finished material.

[013] The amount of the filler in the melt processable composition may vary depending upon the polymeric matrix and the desired physical properties of the finished composition. Those skilled in the art of melt processing polymers are capable of selecting an appropriate amount and type of filler(s) to match with a specific polymeric matrix and naturally occurring inorganic material in order to achieve desired physical properties of the finished material. Typically, the filler may be incorporated into the melt processable composition in amounts up to about 80 % by weight. Preferably, the filler is added to the melt processable composite composition at levels between 5 and 80 %, more preferably between 15 and 80 % and most preferably between 25 and 70 % by weight of the formulation. Additionally, the filler may be provided in various forms depending on the specific polymeric matrices and end use applications such as, for example, powder and pellets.

[014] Cellulosic materials are commonly utilized in melt processable compositions as fillers to impart specific physical characteristics or to reduce the cost of the finished composition.

Cellulosic materials generally include natural or wood based materials having various aspect rations, chemical composition, densities, and physical characteristics. Non-limiting examples of cellulosic materials include wood flour, wood fibers, sawdust, wood shavings, newsprint, paper, flax, hemp, rice hulls, kenaf, jute, sisal, and peanut shells. Combinations of cellulosic materials and a modified polymer matrix may also be used in the melt processable composition. In a preferred embodiment, the cellulosic filler comprises 5 - 60 wt % of the composition, 5 - 40 wt %, or 5 - 20 wt %.

[015] In another aspect, the melt processable composition may include coupling agents to improve the compatibility and interfacial adhesion between the thermoplastic matrix and the naturally-occurring inorganic material and any other fillers. Non-limiting examples of coupling agents include functionalized polymers, organosilanes, organotitanates and organozirconates. Preferred functionalized polymers include functionalized polyolefins, polyethylene-co-vinyl acetate, polyethylene-co-acrylic acid, and polyethylene-co-acrylic acid salts.

[016] In yet another embodiment, the melt processable composition may contain other additives. Non-limiting examples of conventional additives include antioxidants, light stabilizers, fibers, blowing agents, foaming additives, antiblocking agents, heat stabilizers, impact modifiers, biocides, compatibilizers, flame retardants, plasticizers, tackifiers, colorants, processing aids, lubricants, coupling agents, and pigments. The additives may be incorporated into the melt processable composition in the form of powders, pellets, granules, or in any other extrudable form. The amount and type of conventional additives in the melt processable composition may vary depending upon the polymeric matrix and the desired physical properties of the finished composition. Those skilled in the art of melt processing are capable of selecting appropriate amounts and types of additives to match with a specific polymeric matrix in order to achieve desired physical properties of the finished material.

[017] In certain embodiments, a blowing agent, or agents, may be incorporated into the melt processable composition. The blowing agent, or combination of blowing agents, lead to the development of cells through the release of a gas at the appropriate time during processing. The amount and types of blowing agents influences the density of the finished product by its cell structure. Both physical and chemical blowing agents may be employed in forming the composition of this disclosure. Physical blowing agents tend to be volatile liquids or compressed gases that change state during melt processing to form a cellular structure. Chemical blowing agents tend to be solids that decompose thermally to form gaseous decomposition products. The gases produced are finely distributed in the melt processable composition to provide a cellular structure. Those of ordinary skill in the art are capable of selecting a specific type and amount of blowing agent to achieve a desired result in the melt processable composition.

[018] Chemical blowing agents can be divided into two major classifications; organic and inorganic. Organic blowing agents are available in a wide range of different chemistries, physical forms and modification, such as, for example, azodicarbonamide. Inorganic blowing agents tend to be more limited. An inorganic blowing agent may include one or more carbonate salts such as Sodium, Calcium, Potassium, and/or Magnesium carbonate salts. Preferably, sodium bicarbonate is used because it is inexpensive and readily decomposes to form carbon dioxide gas. Sodium bicarbonate gradually decomposes when heated above about 120 °C with significant decomposition occurring between 150 °C and 200 °C. In general, the higher the temperature, the more quickly the sodium bicarbonate decomposes. An acid such as citric acid may also be included in the foaming additive (or added directly to the melt processable composition) to facilitate decomposition of the blowing agent. Chemical blowing agents are usually supplied in powder form or pellet form. The specific choice of the blowing agent will be related to the cost, desired cell development and gas yield and the desired properties of the foamed material.

[019] Suitable, non- limiting examples of blowing agents include water, carbonate salts and other carbon dioxide releasing materials, diazo compounds and other nitrogen producing materials, carbon dioxide, decomposing polymeric materials such as poly (t-butylmethacrylate) and polyacrylic acid, alkane and cycloalkane gases such as pentane and butane, inert gases such as nitrogen, and the like. The blowing agent may be hydrophilic or hydrophobic.

[020] The melt processable composition can be prepared by any of a variety of ways. For example, the modified polymeric matrix, desiccant, and naturally occurring inorganic material may be combined together by any of the blending means usually employed in the plastics industry, such as with a compounding mill, a Banbury mixer, or a mixing. The materials may be used in various forms, for example, a powder, a pellet, or a granular product. The mixing operation is most conveniently carried out at a temperature above the melting point or softening point of the processing additive, though it is also feasible to dry-blend the components in the solid state as particulates and then cause uniform distribution of the components by feeding the dry blend to a twin-screw melt extruder. The resulting melt-blended mixture can be either extruded directly into the form of the final product shape or pelletized or otherwise comminuted into a desired particulate size or size distribution and fed to an extruder, which typically will be a single-screw extruder, that melt-processes the blended mixture to form the final product shape.

[021] Melt-processing typically is performed at a temperature from 120 °C to 300 °C, although optimum operating temperatures are selected depending upon the melting point, melt viscosity, and thermal stability of the composition. Different types of melt processing equipment, such as extruders, may be used to process the melt processable compositions. Extruders suitable for use with the compositions are described, for example, by Rauwendaal, C, "Polymer Extrusion," Hansen Publishers, p. 11 - 33, 2001. Melt processing may also include injection molding, batch mixing, blow molding or rotomolding.

[022] The composites are suitable for subsequent melt processing and manufacturing into articles for various industries, including the construction and automotive industries. For example, in the construction industry, articles incorporating the composition may include:

concrete forms, decking, sheeting, structural element, roofing tiles, and siding. The improved mechanical properties of the composite enable thin and or hollow profiles, thereby reducing cost and weight for particular end use application. Those of ordinary skill in the art of designing construction articles are capable of selecting specific profiles for desired end use applications. Applications in the automotive industry include: body and interior panels and decorative articles. The composites have particular utility for producing sheet articles that are utilized as concrete forms. Typically sheet articles have a thickness greater than 15 mm. Additionally, railroad ties may be formed using the composites.

[023] The resulting articles produced by melt processing the inventive composition exhibit superior mechanical characteristics in the field of composite structures. In one embodiment, the flexural modulus is as much as 30 % higher over conventional composite materials. Certain embodiments may exhibit one or more of, and preferably two or more of, a flexural modulus of greater than 2500 MPa, an impact strength of at least 300 J/m, a tensile elongation of at least 4%, a tensile strength greater than 50 MPa, a specific gravity of 0.9 g/cm³, and a coefficient of thermal expansion of less than 70 μιη/m. Additionally, the composite may exhibit a ratio of flexural modules to specific gravity of greater than 2100: 1.

[024] The articles of the invention also possess unexpected physical characteristics over conventionally filled polymer composites. For example, an increase in tensile elongation is not typically achieved with greater loading levels of fillers or additives. In certain embodiments, the composition may exhibit tensile elongation properties of more than 4% with greater than 30% by weight of the naturally-occurring inorganic material.

[025] MATERIALS

[026] PREPARATION OF COMPARATIVE EXAMPLES CE1 AND EXAMPLES 1-6. Composite samples were prepared and tested using the following protocol. A selected polypropylene and coupling agent were pre -blended and then coated with mineral oil (0.25 wt% mineral oil/ 99.75 wt% resin) in a polyethylene bag. The filler subsequently dry blended with the coated resin (i.e., volcanic ash, desiccant). The resulting blend was volumetrically fed into the feed zone of a 27 mm co-rotating twin screw extruder fitted with three strand die

(commercially available from American Leistritz Extruder Corporation, Sommerville, NJ). All samples were processed at 150 rpm screw speed using the following temperature profile: Zone 1-2 = 170 °C, Zone 3-4 = 180 °C, Zone 5-6 = 190 °C, Zone 7-8= 190 °C. The resulting strands were subsequently cooled in a water bath and pelletized into 0.63 cm pellets to produce the composite formulation. For samples 4-6, the same procedure was utilized for compounding with the exception that carbon dioxide as the PBA was delivered into zone 3 of the extruder using a metering system at 5 g/min dosage rate (commercially available from American Leistritz Extruder Corporation, Sommerville, NJ). For example CE1 and examples 1-3, the resulting pellets were extruded into a sheet having a thickness of 6.25 mm using a laboratory 1.95 cm single screw extruder equipped with a 76 mm x 6.25 mm die and three roll sheet take off unit (commercially available from CW Brabender, Hackensack, NJ). The samples were processed at 75 rpm and 180°C for all zones. The resulting sheet samples were machined into test specimens and tested for tensile, flexural and impact properties following ASTM D638, D790 and D256. The tensile, flexural impact properties, along with bulk density, were subsequently tested as specified in the ASTM methods. Table 1 gives the formulations that were produced following this procedure. Table 2 gives the mechanical properties of these composite formulations. Table 3 gives the formulations that were produced in Examples 4-6. Table 4 provides the specific gravity and bulk density of pellets produced in Examples 4-6. TABLE 1. Formulation for Comparative Examples CEl and Example 1-3

TABLE 2. Tensile and Flexural Properties for Comparative Example CEl and Examples 1-3

TABLE 3. Formulation for Exampli

TABLE 4. Formulation for Exampli

Claims

WHAT IS CLAIMED IS:

1. A composition comprising:

(a) a polymeric matrix,

(b) a naturally-occurring inorganic material, and

(d) a desiccant.

2. The composition of claim 1, wherein the naturally-occurring inorganic material is volcanic ash, mica, fly ash, andesiteic rock, feldspars, aluminosilicate clays, obsidian, diatomaceous earth, silica, silica fume, bauxite, geopolymers pumice, perlite, pumicsite or combinations thereof.

3. The composition of claim 1, wherein the naturally-occurring inorganic material is volcanic ash.

4. The composition of claim 1, wherein the polymeric matrix is high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, polyolefin copolymers, polystyrene, polystyrene copolymers, polyacrylates, polymethacrylates, polyesters,

polyvinylchloride, fluoropolymers, liquid crystal polymers, polyamides, polyether imides, polyphenylene sulfides, polysulfones, polyacetals, polycarbonates, polyphenylene oxides, polyurethanes, thermoplastic elastomers, epoxies, alkyds, melamines, phenolics, ureas, vinyl esters, liquid crystal polymers or combinations thereof.

5. The composition of claim 1, wherein the desiccant is calcium oxide, magnesium oxide, strontium oxide, barium oxide, aluminum oxide, or combinations thereof.

6. The composition of claim 1, wherein the naturally-occurring inorganic material has an aspect ratio of 1.5: 1.

7. The composition of claim 1, further comprising a coupling agent, a blowing agent or a combination thereof.

8. The composition of claim 1, wherein the composition exhibits at least two of flexural modulus of greater than 2500 MPa, an impact strength of at least 300 J/m, a tensile elongation of at least 4%, and a coefficient of thermal expansion of less than 70 μπι/m.

9. The composition of claim 1, wherein composition has at least 30% by weight of the naturally- occurring inorganic material and a tensile elongation of at least 4%.

10. The composition of claim 7, wherein the composition has a specific gravity of 0.9 g/cm³.

11. A method of forming a composite, comprising melt processing a polymeric matrix, a naturally-occurring inorganic material, and a desiccant.

12. The method of claim 11, wherein the melt processing includes extrusion, injection molding, batch mixing, blow molding or rotomolding.

13. The method of claim 11, further comprising a coupling agent, blowing agent, or

combination thereof.

14. An article comprising a melt processable composition of a polymeric matrix, a naturally- occurring inorganic material, and a desiccant.

15. The article of claim 14, wherein the article is a sheet, railroad tie, concrete form, building material or an automotive component.

16. The article of claim 15, wherein the sheet is greater than 15 mm in thickness.

17. The article of claim 15, wherein the has at least 30% by weight of the naturally occurring inorganic material and the sheet exhibits a tensile elongation of at least 4%, a flexural modulus of greater than 2500 MPa, specific gravity of 0.9 g/cm³, and a coefficient of thermal expansion of less than 70 μπι/m.