Patent Application
20130072607
The present invention relates to nanoclay (nc) hybrids and composites of elastomers and nanoclays.
Efforts to replicate natural rubber led to synthesis of rubbery copolymers such as styrene and butadiene, widely known as SBR, or styrene-butadiene rubber. SBR may be used in producing tires, which accounts for about half of the world consumption, over 10 million tons per year, of synthetic rubber.
A number of ingredients are added to synthetic rubber in order to obtain certain desirable properties. The most important ingredients are those, known as the cure package, that cause interlinking reactions to take place when the mix is “cured.” In order to minimize the risk of premature cure, they are usually added at the end of mixing. The cure package usually consists of sulfur and one or more “accelerators” (e.g., sulfenamides, thiurams, or thiazoles), which make the sulfur interlinking reaction occur faster and more efficiently.
Two other ingredients that play an important role in vulcanization chemistry are known as “activators,” commonly zinc oxide and stearic acid. These compounds react together and with accelerators to form a zinc sulfurating compound, which in turn is the key intermediary in adding sulfur to a diene elastomer and creating sulfur interlinks.
Almost every conceivable material has been added to rubber in attempts to cheapen and stiffen it. Two particulate fillers are outstanding because they also strengthen elastomers to a remarkable degree. The most important, used almost universally, is finely divided carbon black, prepared by incomplete combustion of oil or gas. Another reinforcing filler with particles of similar shape and size is finely divided silica (silicon dioxide, SiO2), prepared either by burning silicon tetrachloride or by acid precipitation from a sodium silicate solution.
Both carbon black and silica, when added to a mix compound at a concentration of about 30 percent by volume, raise the elastic modulus of the rubber by a factor of two to three. They also confer remarkable toughness, especially resistance to abrasion, on otherwise weak materials such as SBR. If greater amounts are added, the modulus will be increased still further, but the strength will then begin to fall. Moreover, there are general disadvantages of reinforcement with carbon black or silica, such as lower springiness (resilience) and a decrease in the initial high stiffness after flexing. Such composites are thus relatively brittle at low temperatures, for example. Elastomeric composites with CB or silica are also relatively difficult to prepare. Many applications may require coloured elastomeric composites.
For a filler to be reinforcing, it appears that the filler particles must be small—for instance, 10-50 nanometres in diameter—and that the elastomer must adhere well to them. If either of these conditions is absent, the reinforcing power will be lessened.
The effect of nanoclays modified by hydrolysed mercaptosilane, as a substitute for carbon black, on the properties of SBR compounds, was reported at the 4th International Conference on nanotechnology for the plastics & rubber industries, http://www.plastic.org.il/nano/nano—02—09_shenkar/PresNano1Feb—09_adam.pptt#2.
In short, modified nanoclays may be produced from reacting nanoclays (NCs), Montmorillonites such as Cloisite 30B, with mercaptosilanes. Such hybrids have been found useful in at least partially substituting for carbon black in elastomeric composites—for example the modified NCs could replace 30 phr (Parts per Hundred) CB by 15 phr NC (7.5 phr of modified NC or 4.2 phr of neat silicate) without reduction of modulus and minor reduction of tensile properties.
The object of the present invention is to further improve and diversify the modified NCs and their production to improve various properties of the products produced with them, as well as to provide new compositions of the NCs and other ingredients that exhibit improved or desired properties.
According to one aspect, a nanoclay (NC) hybrid is provided, the hybrid comprising: silanised montmorillonite and an amine.
The montmorillonite is for example ammonium or aminium-substituted.
The amine is for example selected from a group comprising: p-phenylenediamine (p-PDA), Z2Z′N, 1,1′-(1,2-Ethanediyl)diurea, N,N-dimethyldodecan-1-amine (DDA), combinations thereof and derivatives thereof, in which Z is a 3,5-dihydrocarbyl-4-hydroxyphenalkyl group and Z′ is Z or an alkyl, alkenyl, or aralkyl group of up to 18 carbons.
The (p-PDA) derivative may be selected from a group comprising: N,N-dialkyl-p-PDA, N-alkyl-N-aryl-p-PDA and derivatives thereof and combinations thereof. The N-alkyl-N-aryl-p-PDA is for example IPPD and/or 6PPP (N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine).
The aminium is for example any of: dimethyl, benzyl, hydrogenated tallow; dimethyl, dihydrogenated tallow; dimethyl, dihydrogenated tallow; dimethyl, hydrogenated tallow, 2-ethylhexyl; and methyl, tallow, bis-2-hydroxyethyl ammonium salts, and combinations thereof.
In some embodiments, the hybrid further comprises a dispersant. the dispersant is for example: thermoplastic SBS, SIS and combinations thereof. The hybrid may further comprise silicate.
According to another aspect, a method of producing a nanoclay (NC) hybrid is provided, the method comprising: mixing a silanising agent and montmorillonite in an non-flammable solvent at elevated temperature.
According to yet another aspect, a method of producing a nanoclay (NC) hybrid is provided, the method comprising:
mixing an amine and a mortomillonite in a solvent at an elevated temperature;
adding and mixing thereto a silanising agent at an elevated temperature.
The non-flammable solvent is for example selected from chloroform mixtures of: diacetone alcohol, isopropanol, acetone and water of chloroform, mixtures thereof.
In some embodiments, the method further comprises adding acetic acid to the solvent until the solvent has a pH value of 3.
In some embodiments, the method further comprises adding silica to the solvent between mixing the amine and the montmorillonite and adding the silanising agent.
According to an aspect, an elastomeric composite comprising any of the aforementioned nanoclay (NC) hybrids is provided.
The elastomeric composite preferably further comprises an elastomer. The elastomer is for example selected from a group comprising: SBR, isoprene rubbers, butadiene acrylonitrile rubber, EPDM and combinations thereof.
Some composite embodiments further comprise CB.
The elastomeric composites preferably further comprise sulfur, zinc oxide stearic acid, aliphatic-aromatic soft resin and an accelerator.
The accelerator is for example selected from a group comprising: TBBS, MBS and mixtures thereof.
Some composites further comprise silica.
The glossary is not intended to be comprehensive but rather a mere collection to ease reading for those not skilled in the art.
List of Materials:
Rubber Properties
Rheological Properties
mV=minimum viscosity, measured in a rheological test, expressed as the torque applied (lb-inch) to an elastomeric composite, before vulcanization
t2=scorch time=time (minutes) from beginning of vulcanization, until torque increases during the rheological test, to 2 lb/inch
t90=Optimum vulcanization time (time until torque reaches 90% of maximum value)
S1=max value of torque
Tan=the tangent modulus is the slope of a compression stress-strain curve
ML(1+4): Mooney viscosity after (1+4) minutes: Viscosity of rubbers is measured using the shearing disk viscometer. The torque of the rotor is taken after 1 minute pre-heating the rotor plus 4 minute after that.
Mechanical Properties
Tensile=Tensile Strength (Stress at break point) (MPa)
Elongation=Elongation at break (Strain at break point) (%)
M100, M200, M300 (Modula=Stress at 100% strain, 200% strain, 300%)
Tear strength (strength required to initiate a tear in a material)
Yerzley Elasticity (Resilience)—measure of rubber elasticity determined on a Yerzley device.
For a better understanding of the invention and to show how it may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings.
With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention; the description taken with the drawing making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. In discussion of the various figures described herein below, like numbers refer to like parts. The drawings are generally not to scale.
Modified nanoclays may be produced from reacting nanoclays (NCs) such assurface modified montmorillonites, e.g. Cloisite 30A®, with mercaptosilanes. Such hybrids have been found to be useful in substituting at least part of a portion of carbon black (CB) in elastomer formulas, while essentially retaining the desired properties imparted by the CB at the original levels. An advantage of these modified NC is that typically, relatively small portions are required to added to the compounds based on various elastomers to achieve similar qualities. However, there was need to further improve and diversify modified NCs, in particular for manufacture of high-performance elastomeric composites (rubber compounds), e.g elastomeric composites with high tear and/or abrasion resistance.
Antioxidant is a substance added in small quantities to hydrocarbons-which are susceptible to oxidation, such as rubbers, to inhibit or slow oxidative processes, while being itself oxidized. In primary antioxidants (also called free-radical scavengers), antioxidative activity is implemented by the donation of an electron or hydrogen atom to a radical derivative. These antioxidants are usually sterically hindered amines (p-Phenylene diamine, trimethyl dihydroquinolines, alkylated diphenyl amines) or substituted phenolic compounds with one or more bulky functional groups such as a tertiary butyl.
The inventor has now found that surprisingly, improvement of elastomeric composites containing modified NCs may be performed by changes in the production of the modified NCs, for example by adding IPPD (N-isopropyl-N′-phenyl-paraphenylenediamine) or DDA (dodecyl amine) or other amines during the manufacture of the NCs, and optionally by performing further changes to the production of the modified NCs.
In particular, some embodiments exhibit very high tear resistance, some even over 60 N/mm. Whereas prior art elastomer compositions, not containing NCs, that were designed to have such high tear resistance, typically contained as much as 50-60 parts CB (carbon black), nevertheless they sometimes failed to accomplish the desired mechanical properties. In contrast, some embodiments are now found to reliably replace up to 35 parts of the CB or about 30 phr silica, with merely about 15-20 NC to achieve the same strength. In general, the elastomeric composition embodiments generally exhibit improved qualities over elastomeric compositions of similar content that do not include NCs with amines.
In some embodiments, elastic properties such as rebound (Yerzley resilience, tangent) were greatly improved. In some embodiments, ageing properties were also improved. In some embodiments, lighter products are obtained for the same degree of reinforcement, as compared to elastomer composites with prior art components.
Elastomeric Composites with Carbon Black (CB)
Table 1 presents the ingredients of 5267-1 and S257-2R, SBR rubber composites with some CB (HAF N330), and prepared from RRA 10 and RRA 181-1, respectively.
Table 2 presents the properties of the compositions S267-1 and 5257-2R measured at 150° C. Some key features are also shown in graphic form in
The addition of the amine significantly improved the tear resistance, modulus at various stretching lengths, tensile strength and hardness. In addition, ageing properties of the compound are improved
It may be important that an amine such as DDA (dodecylamine) be added to NC (e.g. Cloisite 15A) before adding the TESPT (Si69), perhaps because in such way the long-chain amine continues the process of increasing distance between the layers of NC (a process begun during production of the NC hybrid by treating MMT with quaternary tallow ammonium salt). The silanisation of NC may thereby occur on a larger surface.
However, note that the reactions to prepare the RRA compositions are not necessarily carried out to completion, since experiments have so far shown that after 7 hours of reaction with the TESPT there were no significant improvements in the mechanical properties of the products.
Alternative NC materials that may provide similar advantageous properties: Commercially treated NCs such as: Cloisite 10A, 15A, 20A, 25A and 30B of Southern Clays; Nanomer 1.31 ps, 1.28E and 1.34 TCN of Nanocor. In general, the Commercially treated NCs are montmorillonites in which sodium ions are exchanged with ammonium or aminium ions.
Elastomers such as the entire range of NBR Krynac with ACN content 28, 33, 38, 44 and of various viscosities-of Lanxess, Nipol of Zeon), and EPDM (Keltan 512, 512/50 of DSM, Du Pont, Dow Elastomers, Bayer) may also be improved by incorporation of the improved modified NCs.
Elastomeric Composites without Carbon Black (CB), Accelerator TBBS
Another group of elastomeric composite embodiments that were produced were devoid of CB. Three elastomeric composites were made, S96-1G comprised of (prior art) RRA 10, S266-1G comprised afore mentioned RRA 181-1, and S270-1G comprised RRA 189-2, whose production is schematically presented in
Table 3 lists the ingredients in the three elastomeric composites
In production of RRA 189-2, SBS as dispersant was added to the mix of nanoclay and the amine DDA before the mixing for two hours at 80° C. Note that the amine DDA is used to make RRA 189-2, compared to the amine IPPD used in making RRA 181-1.
Table 4 and
As with the elastomeric composites having CB, the elastomeric composite embodiments with the modified NC that comprises amine (DDA or IPPD) have improved tear resistance, shear modulus at various stretching lengths, and hardness, with essentially no change in elasticity. The two embodiments S266-1G and S270-1G have similar tear resistance, tensile strength, hardness and elasticity. The main improvement resulting from the incorporation of DDA and SBS over incorporation of IPPD was increasing scorch time (t2) and reducing of vulcanization time (DDA as amine is also a strong accelerator). However, IPPD has anti-ozone properties that may improve the wear resistance of the elastomeric composites.
Elastomeric Composites without Carbon Black (CB), and with Accelerator MBS
The elastomeric composites S96-1G, S266-1G and S270-1G mentioned above were made with, amongst other ingredients, accelerator TBBS. Additional elastomeric composites were prepared without CB, in which the accelerator TBBS is replaced with accelerator MBS.
Silica (SiO2) was added in the mix containing NC, DDA. We may presume that OH functional groups present on the surface of SiO2, activated with amine, may also react with silane further along in the reaction step, i.e. there may be an advantage to adding silica to the NC in producing the hybrid, rather than adding the silica to the elastomer during vulcanization.
Table 5 list the ingredients used to prepare two elastomeric composites, S278-1G, that includes prior art NC, RRA 50R, and embodiment S274-5G, that includes RRA 190-5.
Table 6 and
Similar to the tendency observed with elastomeric composites with accelerant TBBS, in the elastomeric composites made with the accelerant MBS, a general improvement in physical properties appears, upon addition of the amine: a significant improvement of tear resistance, tensile strength and modulus, while retaining elasticity.
Note that in addition to amine DDA, the dispersant SBS and filler SiO2 are added to the NC in RRA 190-5. The dispersant added in some modified NC embodiments may further improve properties of the elastomeric composites.
Modified NCs with/without Acetic Acid and Elastomeric Composites Produced Thereof
Referring back to the modified NC embodiments RRA 181-1 and RRA 189-2, described above, they were prepared using acetic acid as a catalyst for the reaction of the mercaptosilane with the NC. However, RRA 190-5 was prepared without use of the acetic acid. The following examples investigate role of acetic acid in the properties of the elastomeric composites with modified NCs.
Table 7 lists the ingredients in non-CB composites made from the modified NCs with/without acetic acid.
Table 8 shows the properties of the compositions S270-5G and S270-7G as measured at 150° C.
Tables 9-12 compare various additional compositions made with acetic acid, RRA 189-2, and without acetic acid added, RRA 189-4. In S268-2 and S269-2, the compositions include carbon black (HAF N330); and in S269-11 and S269-21, the compositions include both carbon black and silica.
Note that Struktol is a dispersant.
Tables 8, 12 results indicate that in some compositions, adding acetic acid during preparation of modified NCs may improve the elastomeric composites; however, in other compositions omitting the acetic acid may actually overall improve the properties of the elastomer-NC composites. An improvement of tensile strength and tear resistance is apparent in the compositions S270-7G and S269-21, wherein the modified NC is prepared without acetic acid. Note the particularly high tear threshold of S269-21, which is suitable for tires, despite the elastomeric composite containing only 15 phr of CB.
Modified NCs with/without Silica and Elastomeric Composites Produced Thereof
Comparing S270-7G (Table 8) with S274-5G (Table 6), RRA 189-4 in S270-7G is made with DDA and SBS added to the NC, before adding the mercaptosilane. RRA 190-5 is prepared from the same ingredients under similar conditions, however, silica is also added in manufacture of RRA 190-5, after the two hours of mixing the NC with DDA and SBS at elevated temperature (considerably above room temperature), and then the mix with the silica is stirred for 10 hours at 90° C., before the mercaptosilane is added. The other ingredients are identical in the two compared elastomeric composites.
S274-5G, containing RRA 190-5, has a significantly higher tear threshold, and somewhat higher tensile strength, indicating that the addition of silica in production of the modified NC may be beneficial to strength of elastomeric composites made with the NCs embodiments.
Modified NCs Produced with Various Solvents and Elastomeric Composites Produced Thereof
The modified NCs are prepared using at least one solvent: The solvent and the NC are mixed together with at least one amine. Solvents such as Isopropyl alcohol, diacetone alcohol (DAA), chloroform or mixtures thereof may be used, for example, instead of acetone in formerly described hybrids.
Two similar modified NCs were prepared, one in which the solvent was chloroform, and another in which the solvent was a mixture of isopropanol (IPA) and water. The reactions to produce the modified NCs are shown in
In both hybrids RRA 194-1 and RRA 202-1, Cloisite 15A (30 g) and IPPD (isopropyl p-phenylene diamine)—1.14 g were mixed together in solvent for 2 h at 80° C. After that Si69 (TESPT) 10 g, water—1 g was added. The silanization reaction was conducted 7 hours at 80° C. (measured in glycerin bath). After the 7 hour's reaction the content was poured into a tray and dried approximately 16 h at RT.
Table 13 lists ingredients in elastomeric composites made from the hybrids.
Properties of non-CB elastomeric composites S298-1G and S311-4G comprising the hybrids are listed in Table 14 and presented in
The elastomeric composites have similar properties, which are also similar to the properties of S274-5G, Table 6, which is also without CB and made with MBS, but using acetone as a solvent. Since RRA 190-5 in S274-5G comprises silica, which appears to augment the strength of the elastomeric composites, whereas the hybrids in S298-1G and S311-4G do not contain silica, the solvents IPA+water and chloroform may provide better properties than the solvent acetone. In addition, IPA:water (1:2) and chloroform are much less of a fire hazard.
Further hybrids were made with mixtures of acetone and other solvents. RRA 194-2, whose production is schematically shown in
Table 15 lists properties of elastomeric composites made from the hybrids RRA 194-2 and RRA 195-1;
Compared to RRA 190-5, the composites with the new hybrids—10 phr on basis of SBR without filler, gave essentially the same behavior: approximately the same tensile Strength, Elongation at break, somewhat better Modulus at 200%, and a slight lower elasticity. Vulcanization time was improved.
In general, then, in production of NC hybrids from nanoclays and silanising agents, solvent mixtures containing water, such as the solvents IPA: water, and acetone: water, may be preferable over use of acetone solvent.
In some embodiments, the amine molecules added to the NCs contain two or more amine groups (nitrogen atoms bonded to an organic substituent). Such amine molecules may serve dual purposes: to bond to the nanoclay (first, bonded amine), and to be an antioxidant (second, non-bonded amine). Multi-bonding by many amine groups in an amine molecule may improve the strength of the elastomeric composite.
SBS may be particularly suitable for use in elastomeric composites based on SBR, due to the similarity in structures. For other elastomers, likewise other dispersants may be selected accordance with the similarity to the elastomer structure. For example, SIS (styrene isoprene styrene block copolymer) may be most suitable for use with isoprene rubbers.
The scope of the present invention includes both combinations and sub combinations of the various features described hereinabove as well as variations and modifications thereof, which would occur to persons skilled in the art upon reading the foregoing description.
The word “comprise”, and variations thereof such as “comprises”, “comprising” and the like indicate that the components listed are included, but not generally to the exclusion of other components.
| Number | Date | Country | |
|---|---|---|---|
| 61506377 | Jul 2011 | US |
