Microgels in non-crosslinkable organic media
The present invention relates to a composition containing a non-crosslinkable medium and at least one microgel, to a process for its preparation, to uses of the compositions, and to microgel-containing polymers, rubbers, lubricants, coatings, etc. produced therefrom.
The present invention relates to a composition containing a non-crosslinkable medium and at least one microgel, to a process for its preparation, to uses of the compositions, and to microgel-containing polymers, rubbers, lubricants, coatings, etc. produced therefrom.
BACKGROUND OF THE INVENTIONIt is known to use rubber gels, also modified rubber gels, in blends with a very wide variety of rubbers in order, for example, to improve the rolling resistance in the production of motor vehicle tires (see e.g. DE 42 20 563, GB-PS 10 78 400, EP 405 216 and EP 854 171). The rubber gels are always incorporated into solid matrices.
It is also known to incorporate printing ink pigments in finely divided form into liquid media suitable therefore, in order ultimately to produce printing inks (see e.g. EP 0 953 615 A2, EP 0 953 615 A3). Thereby achieving particle sizes of as little as 100 nm.
Various dispersing apparatuses such as bead mills, three-roller mills or homogenizers can be used for the dispersion. The use of homogenizers and the operation thereof is described in the Marketing Bulletin of APV Homogenizer Group—“High-pressure homogenizers processes, product and applications” by William D. Pandolfe and Peder Baekgaard, principally for the homogenization of emulsions.
The above referenced documents do not describe the use of rubber gels as the solids component in mixtures with liquid organic media, with the aim of producing very finely divided rubber-gel dispersions having particle diameters below one μm, and their homogenization by means of a homogenizer.
Chinese Journal of Polymer Science, Volume 20, No. 2, (2002), 93-98 describes microgels fully crosslinked by means of high-energy radiation and their use for increasing the impact strength of plastics. In the preparation of specific epoxy resin compositions, a mixture of a radiation-crosslinked carboxyl-terminated nitrile-butadiene microgel and the diglycidyl ether of bisphenol A, a crosslinkable organic medium, is formed as intermediate. Further liquid microgel-containing compositions are not described.
Similarly, US 2003/0,088,036 A1 discloses reinforced heat-curing resin compositions, the preparation of which likewise comprises mixing radiation-crosslinked microgel particles with heat-curing pre-polymers (see also EP 1 262 510 A1).
Surprisingly it has now found that it is possible to finely distribute microgels in liquid organic media having a specific viscosity using a homogenizer, for example. The division of the microgels in the organic medium to the primary particle range is, for example, a requirement for utilizing the nano properties of the microgels in applications of any kind, for example in incorporation into plastics. The liquid compositions according to the present invention containing the specific microgels are able to open up a large number of novel applications for microgels which were not accessible with the microgels themselves.
SUMMARY OF THE INVENTIONCompositions according to the present invention, owing to the fine distributions that are achievable, can be incorporated into plastics, for example, completely new properties being obtained as a result. The microgel-containing compositions according to the present invention can be used in a large number of fields, such as, for example, in elastomeric PU systems (cold-casting systems and hot-casting systems), in coating compositions or as lubricant additives. In the microgel-containing compositions according to the present invention, materials that are incompatible per se form a homogeneous distribution which remains stable even on prolonged storage (6 months).
P. Pötschke et al., Kautschuk Gummi Kunststoffe, 50 (11) (1997) 787 have shown that, with incompatible materials such as, for example, p-phenylenediamine derivative as the dispersed phase and TPU as the surrounding phase, it is not possible to obtain domains smaller than 1.5 μm. It is surprising that such small dispersed phases are achieved with the microgels of the present invention.
Microgel-containing compositions have been found for which very different rheological behavior has been demonstrated. In suitable microgel-containing compositions, a very strong intrinsic viscosity or thixotropy has surprisingly been found, as well as flow behavior similar to that of Newtonian fluids. This can be used to control the flow behavior, as well as other properties, of any desired liquid compositions in a targeted manner by means of microgels. Surprisingly, plastics produced from the microgel-containing compositions according to the present invention have been found to have improved tear strength.
The present invention accordingly provides a composition containing at least one non-crosslinkable organic medium (A) which has a viscosity of less than 100 mPas at a temperature of 120° C., and at least one microgel (B).
BRIEF DESCRIPTION OF THE DRAWING
The viscosity of the organic medium is preferably less than 200 mPas, more preferably less than 100 mPas, at 120° C. The viscosity of the crosslinkable organic medium (A) is determined at 120° C. at a speed of 5 s−1 by means of a cone/plate measuring system according to DIN 53018.
Microgels (B)
The microgel (B) used in the composition according to the present invention is a crosslinked microgel. Preferably, it is not a microgel crosslinked by means of high-energy radiation. High-energy radiation here means electromagnetic radiation having a wavelength of less than 0.1 μm. The use of microgels crosslinked by means of high-energy radiation, as described, for example, in Chinese Journal of Polymer Science, Volume 20, No. 2, (2002), 93-98, is disadvantageous because it is virtually impossible to produce microgels crosslinked by high-energy radiation on an industrial scale. In addition, the use of high-energy radiation from radioactive radiation sources such as radioactive cobalt is associated with serious safety problems. Furthermore, because the radiation-crosslinked microgels are generally fully radiation-crosslinked microgels, the change in modulus, during incorporation of the composition according to the present invention into plastics, for example, from the matrix phase to the dispersed phase is immediate. As a result, sudden stress can cause tearing effects between the matrix and the dispersed phase, with the result that the mechanical properties, the swelling behavior and the stress corrosion cracking, etc. of the microgel-containing plastics produced using the compositions according to the present invention are impaired.
Preferably, the primary particles of the microgel (B) exhibit approximately spherical geometry. According to DIN 53206:1992-08, primary particles are the microgel particles dispersed in the coherent phase which can be individually recognized by means of suitable physical processes (electron microscope) (see e.g. Römpp Lexikon, Lacke und Druckfarben, Georg Thieme Verlag, 1998). An “approximately spherical” geometry means that the dispersed primary particles of the microgels recognizably have substantially a circular surface when the composition is viewed, for example, using an electron microscope. Because the form or morphology of the microgels does not change substantially during the further processing of the compositions according to the present invention, the comments made hereinabove and herein below apply in the same manner also to the microgel-containing compositions, such as, for example, plastics, coating compositions, lubricants or the like, obtained using the composition according to the present invention.
In the primary particles of the microgel (B) present in the composition according to the present invention, the variation in the diameters of an individual primary particle, defined as
[(d1−d2)/d1]×100,
wherein d1 and d2 are any two diameters of the primary particle and d1>d2, is preferably less than 250%, more preferably less than 100%, most preferably less than 50%.
Preferably at least 80%, more preferably at least 90%, most preferably at least 95%, of the primary particles of the microgel exhibit a variation in the diameters, defined as
[(d1−d2)/d1]×100,
wherein d1 and d2 are any two diameters of the primary particle and d1>d2, of less than 250%, preferably less than 100%, more preferably less than 50%.
The above-mentioned variation in the diameters of the individual particles is determined by the following process. A thin section of the composition according to the present invention is first prepared as described in the Examples. An image is then recorded by transmission electron microscopy at a magnification of, for example, 10,000 times or 200,000 times. In an area of 833.7×828.8 nm, the largest and smallest diameters d1 and d2 are determined on 10 microgel primary particles. If the variation is less than 250%, more preferably less than 100%, most preferably less than 50%, in all 10 microgel primary particles, then the microgel primary particles exhibit the above-defined feature of variation.
If the concentration of the microgels in the composition is so high that pronounced overlapping of the visible microgel primary particles occurs, the evaluatability can be improved by previously diluting the measuring sample in a suitable manner.
In the composition according to the present invention, the primary particles of the microgel (B) preferably have an average particle diameter of from 5 to 500 nm, more preferably from 20 to 400 nm, most preferably from 30 to 300 nm (diameter data according to DIN 53206). Because the morphology of the microgels remains substantially unchanged during the further processing of the composition according to the present invention, the average particle diameter of the dispersed primary particles corresponds substantially to the average particle diameter of the dispersed primary particles in the products of further processing obtained using the composition according to the present invention, such as microgel-containing plastics, lubricants, coatings, etc.. This constitutes a particular advantage of the composition according to the present invention. It is possible to provide customers with liquid, storage-stable microgel formulations which are customized to a certain degree and exhibit a defined morphology of the microgels and which the customer can readily process further in the desired applications. Previous expensive dispersion, homogenization or even preparation of the microgels is no longer necessary, and it is therefore to be expected that such microgels will also be used in fields in which their use hitherto appeared too costly.
In the composition according to the present invention, the microgels (B) advantageously contain at least about 70 wt. %, more preferably at least about 80 wt. %, most preferably at least about 90 wt. %, portions that are insoluble in toluene at 23° C. (gel content).
The portion that is insoluble in toluene is determined in toluene at 23° C. For this purpose, 250 mg of the microgel are swelled in 20 ml of toluene at 23° C. for 24 hours, with shaking. After centrifugation at 20,000 rpm, the insoluble portion is separated off and dried. The gel content is obtained from the difference between the weighed portion and the dried residue and is given in percent.
In the composition according to the present invention, the microgels (B) advantageously exhibit a swelling index in toluene at 23° C. of less than about 80, more preferably of less than 60, most preferably of less than 40. For example, the swelling indices of the microgels (Qi) can preferably be between 1-15 and 1-10. The swelling index is calculated from the weight of the solvent-containing microgel swelled in toluene at 23° C. for 24 hours (after centrifugation at 20,000 rpm) and the weight of the dry microgel:
Qi=wet weight of the microgel/dry weight of the microgel.
In order to determine the swelling index, 250 mg of the microgel are allowed to swell in 25 ml of toluene for 24 hours, with shaking. The gel is removed by centrifugation and weighed and then dried at 70° C. until a constant weight is reached and then weighed again.
In the composition according to the present invention, the microgels (B) preferably have glass transition temperatures Tg of from −100° C. to +100° C., more preferably from −80° C. to +80° C.
Furthermore, the microgels (B) used in the composition according to the present invention preferably have a breadth of glass transition of greater than 5° C., preferably greater than 10° C., more preferably greater than 20° C. Microgels that have such a breadth of glass transition are generally not completely homogeneously crosslinked—in contrast to completely homogeneously radiation-crosslinked microgels. This has the result that the change in modulus from the matrix phase to the dispersed phase in the microgel-containing plastics compositions, for example, produced from the compositions according to the invention is not immediate. As a result, sudden stress on these compositions does not lead to tearing effects between the matrix and the dispersed phase, with the result that the mechanical properties, the swelling behavior and the stress corrosion cracking, etc. are advantageously affected.
The glass transition temperatures (Tg) and the breadth of the glass transition (ΔTg) of the microgels are determined by differential scanning calorimetry (DSC) under the following conditions: For determining Tg and ΔTg, two cooling/heating cycles are carried out. Tg and ΔATg are determined in the second heating cycle. For the determinations, 10 to 12 mg of the chosen microgel are placed in a DSC sample container (standard aluminum ladle) from Perkin-Elmer. The first DSC cycle is carried out by first cooling the sample to −100° C. with liquid nitrogen and then heating it to +150° C. at a rate of 20 K/min. The second DSC cycle is begun by immediately cooling the sample as soon as a sample temperature of +150° C. has been reached. Cooling is carried out at a rate of about 320 K/min. In the second heating cycle, the sample is again heated to +150° C., as in the first cycle. The rate of heating in the second cycle is again 20 K/min. Tg and ΔTg are determined graphically on the DSC curve of the second heating operation. To that end, three straight lines are plotted on the DSC curve. The first straight line is plotted on the part of the DSC curve below Tg, the second straight line is plotted on the branch of the curve passing through Tg with the point of inflection, and the third straight line is plotted on the branch of the DSC curve above Tg. Three straight lines with two points of intersection are thus obtained. The two points of intersection are each characterized by a characteristic temperature. The glass transition temperature Tg is obtained as the mean of these two temperatures, and the breadth of the glass transition ΔTg is obtained from the difference between the two temperatures.
The microgels present in the composition according to the present invention, which microgels have preferably not been crosslinked by high-energy radiation, can be prepared in a manner known per se (see, for example, EP-A-405 216, EP-A-854 171, DE-A 4220563, GB-PS 1078400, DE 197 01 489.5, DE 197 01 488.7, DE 198 34 804.5, DE 198 34 803.7, DE 198 34 802.9, DE 199 29 347.3, DE 199 39 865.8, DE 199 42 620.1, DE 199 42 614.7, DE 100 21 070.8, DE 100 38488.9, DE 100 39 749.2, DE 100 52 287.4, DE 100 56 311.2 and DE 100 61 174.5). In patent (applications) EP-A 405 216, DE-A 4220563 and in GB-PS 1078400, the use of CR, BR and NBR microgels in mixtures with double-bond-containing rubbers is claimed. DE 197 01 489.5 describes the use of subsequently modified microgels in mixtures with double-bond-containing rubbers such as NR, SBR and BR.
Microgels are understood as being rubber particles which are obtained especially by crosslinking the following rubbers:
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- BR: polybutadiene
- ABR: butadiene/acrylic acid C1-4 alkyl ester copolymers
- IR: polyisoprene
- SBR: styrene-butadiene copolymerization products having styrene contents of from 1 to 60 wt. %, preferably from 5 to 50 wt. %
- X-SBR: carboxylated styrene-butadiene copolymerization products
- FKM: fluorine rubber
- ACM: acrylate rubber
- NBR: polybutadiene-acrylonitrile copolymerization products having acrylonitrile contents of from 5 to 60 wt. %, preferably from 10 to 50 wt. %
- X-NBR: carboxylated nitrile rubbers
- CR: polychloroprene
- IIR: isobutylene/isoprene copolymerization products having isoprene contents of from 0.5 to 10 wt. %
- BIIR: brominated isobutylene/isoprene copolymerization products having bromine contents of from 0.1 to 10 wt. %
- CIIR: chlorinated isobutylene/isoprene copolymerization products having chlorine contents of from 0.1 to 10 wt. %
- HNBR: partially and completely hydrogenated nitrile rubbers
- EPDM: ethylene-propylene-diene copolymerization products
- EAM: ethylene/acrylate copolymers
- EVM: ethylene/vinyl acetate copolymers
- CO and ECO: epichlorohydrin rubbers
- Q: silicone rubbers
- AU: polyester urethane polymerization products
- EU: polyether urethane polymerization products
- ENR: epoxidized natural rubber or mixtures thereof.
The preparation of the uncrosslinked microgel starting products is preferably carried out by the following methods:
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- 1. emulsion polymersation
- 2. solution polymerization of rubbers which are not obtainable by variant 1,
- 3. naturally occurring latices, such as, for example, natural rubber latex, can additionally be used.
The microgels (B) used in the composition according to the preferably invention are preferably those which are obtainable by emulsion polymerization and crosslinking.
The following free-radically polymerizable monomers, for example, are preferably used in the preparation of the microgels used according to the invention by emulsion polymerization: butadiene, styrene, acrylonitrile, isoprene, esters of acrylic and methacrylic acid, tetrafluoroethylene, vinylidene fluoride, hexafluoropropene, 2-chlorobutadiene, 2,3-dichloro-butadiene, and also double-bond-containing carboxylic acids, such as, for example, acrylic acid, methacrylic acid, maleic acid, itaconic acid, etc., double-bond-containing hydroxy compounds, such as, for example, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxybutyl methacrylate, amine-functionalized (meth)acrylates, acrolein, N-vinyl-2-pyrrolidone, N-allyl-urea and N-allyl-thiourea, and also secondary amino(meth)acrylic acid esters, such as 2-tert.-butylaminoethyl methacrylate and 2-tert.-butylaminoethylmethacrylamide, etc.. Crosslinking of the rubber gel can be achieved directly during the emulsion polymerization, such as by copolymerization with multifunctional compounds having crosslinking action, or by subsequent crosslinking as described herein below. Preferred multifunctional comonomers are compounds having at least two, preferably from 2 to 4, copolymerizable C═C double bonds, such as diisopropenylbenzene, divinylbenzene, divinyl ethers, divinylsulfone, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, 1,2-polybutadiene, N,N′-m-phenylenemaleimide, 2,4-toluylenebis(maleimide) and/or triallyl trimellitate. There come into consideration also the acrylates and methacrylates of polyhydric, preferably di- to tetra-hydric, C2 to C10 alcohols, such as ethylene glycol, 1,2-propanediol, butanediol, hexanediol, polyethylene glycol having from 2 to 20, preferably from 2 to 8, oxyethylene units, neopentyl glycol, bisphenol A, glycerol, trimethylolpropane, pentaerythritol, sorbitol, with unsaturated polyesters of aliphatic diols and polyols, as well as maleic acid, fumaric acid and/or itaconic acid.
Crosslinking to form rubber microgels during the emulsion polymerization can also be effected by continuing the polymerization to high conversions or by the monomer feed process by polymerization with high internal conversions. Another possibility consists in carrying out the emulsion polymerization in the absence of regulators.
For the crosslinking of the uncrosslinked or weakly crosslinked microgel starting products following the emulsion polymerization there are best used latices which are obtained in the emulsion polymerization. In principle, this method can also be used with non-aqueous polymer dispersions which are obtainable by other means, e.g. by recrystallization. Natural rubber latices can also be crosslinked in this manner.
Suitable chemicals having crosslinking action are, for example, organic peroxides, such as dicumyl peroxide, tert.-butylcumyl peroxide, bis-(tert.-butyl-peroxy-isopropyl)benzene, di-tert.-butyl peroxide, 2,5-dimethylhexane 2,5-dihydroperoxide, 2,5-dimethylhexane 3,2,5-dihydroperoxide, dibenzoyl peroxide, bis-(2,4-dichlorobenzoyl) peroxide, tert.-butyl perbenzoate, and also organic azo compounds, such as azo-bis-isobutyronitrile and azo-bis-cyclohexanenitrile, and also di- and poly-mercapto compounds, such as dimercaptoethane, 1,6-dimercapto-hexane, 1,3,5-trimercaptotriazine and mercapto-terminated polysulfide rubbers, such as mercapto-terminated reaction products of bis-chloroethylformal with sodium polysulfide.
The optimum temperature for carrying out the post-crosslinking is naturally dependent on the reactivity of the crosslinker and can be carried out at temperatures from room temperature to about 180° C., optionally under elevated pressure (see in this connection Houben-Weyl, Methoden der organischen Chemie, 4th Edition, Volume 14/2, page 848). Particularly preferred crosslinkers are peroxides.
The crosslinking of rubbers containing C═C double bonds to form microgels can also be carried out in dispersion or emulsion with the simultaneous partial, or complete, hydrogenation of the C═C double bond by means of hydrazine, as described in U.S. Pat. No. 5,302,696 or U.S. Pat. No. 5,442,009, or optionally other hydrogenating agents, for example organometal hydride complexes.
Enlargement of the particles by agglomeration can optionally be carried out before, during or after the post-crosslinking.
The preparation process that is preferably employed according to the present invention without the use of high-energy radiation always yields incompletely homogeneously crosslinked microgels which can exhibit the above-described advantages.
Rubbers produced by solution polymerization can also be used as starting materials for the preparation of the microgels. In such cases, solutions of the rubbers in suitable organic solvents are used as starting material.
The desired sizes of the microgels are produced by mixing the rubber solution by means of suitable apparatuses in a liquid medium, preferably in water, optionally with the addition of suitable surface-active auxiliary substances, such as, for example, surfactants, so that a dispersion of the rubber in the appropriate particle size range is obtained. For the crosslinking of the dispersed solution rubbers, the procedure described above for the subsequent crosslinking of emulsion polymerization products is followed. Suitable crosslinkers are the compounds mentioned above, it being possible for the solvent used for the preparation of the dispersion optionally to be removed prior to the crosslinking, for example by distillation.
As microgels for the preparation of the composition according to the present invention there may be used both non-modified microgels, which contain substantially no reactive groups especially at the surface, and microgels modified by functional groups, especially microgels modified at the surface. The latter can be prepared by chemical reaction of the already crosslinked microgels with chemicals that are reactive towards C═C double bonds. These reactive chemicals are especially those compounds by means of which polar groups, such as, for example, aldehyde, hydroxyl, carboxyl, nitrile, etc., and also sulfur-containing groups, such as, for example, mercapto, dithiocarbamate, polysulfide, xanthogenate, thiobenzthiazole and/or dithiophosphoric acid groups and/or unsaturated dicarboxylic acid groups, can be chemically bonded to the microgels. The same is also true of N,N′-m-phenylenediamine. The purpose of modifying the microgels is to improve the microgel compatibility when the composition according to the invention is used to prepare the subsequent matrix, into which the microgel is incorporated, or the composition according to the present invention is used for incorporation into a matrix, in order to achieve a good distribution capacity during preparation as well as good coupling.
Preferred methods of modification are the grafting of the microgels with functional monomers and reaction with low molecular weight agents.
For the grafting of the microgels with functional monomers, there is preferably used as starting material the aqueous microgel dispersion, which is reacted under the conditions of a free-radical emulsion polymerization with polar monomers such as acrylic acid, methacrylic acid, itaconic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, acrylamide, methacrylamide, acrylonitrile, acrolein, N-vinyl-2-pyrrolidone, N-allyl-urea and N-allyl-thiourea, and also secondary amino-(meth)acrylic acid esters such as 2-tert.-butylaminoethyl methacrylate and 2-tert.-butylaminoethylmethacrylamide. In this manner there are obtained microgels having a core/shell morphology, wherein the shell should be highly compatible with the matrix. It is desirable for the monomer used in the modification step to be grafted onto the unmodified microgel as quantitatively as possible. The functional monomers are preferably metered in before crosslinking of the microgels is complete.
Grafting of the microgels in non-aqueous systems is also conceivable in principle, modification with monomers by means of ionic polymerization methods also being possible in this manner.
Suitable reagents for the surface modification of the microgels with low molecular weight agents include the following: elemental sulfur, hydrogen sulfide and/or alkylpolymercaptans, such as 1,2-dimercaptoethane or 1,6-dimercaptohexane, also dialkyl and dialkylaryl dithiocarbamate, such as the alkali salts of dimethyl dithiocarbamate and/or dibenzyl dithiocarbamate, also alkyl and aryl xanthogenates, such as potassium ethylxanthogenate and sodium isopropylxanthogenate, as well as reaction with the alkali or alkaline earth salts of dibutyldithiophosphoric acid and dioctyidithiophosphoric acid as well as dodecyidithiophosphoric acid. The mentioned reactions can also be carried out in the presence of sulfur, the sulfur being incorporated with the formation of polysulfide bonds. For the addition of this compound, free-radical initiators such as organic and inorganic peroxides and/or azo initiators can be added.
There comes into consideration also modification of double-bond-containing microgels such as, for example, by ozonolysis as well as by halogenation with chlorine, bromine and iodine. A further reaction of modified microgels, such as, for example, the preparation of hydroxyl-group-modified microgels from epoxidized microgels, is also understood as being the chemical modification of microgels.
According to the present invention, the microgels can be modified by hydroxyl groups, especially also at the surface thereof. The hydroxyl group content of the microgels is determined as the hydroxyl number with the dimension mg of KOH/g of polymer by reaction with acetic anhydride and titration of the acetic acid liberated thereby with KOH according to DIN 53240. The hydroxyl number of the microgels is preferably from 0.1 to 100, more preferably from 0.5 to 50, mg of KOH/g of polymer.
The amount of modifying agent used is governed by its effectiveness and the demands made in each individual case and is in the range from 0.05 to 30 wt. %, based on the total amount of rubber microgel used, particular preference being given to from 0.5 to 10 wt. %, based on the total amount of rubber gel.
The modification reactions can be carried out at temperatures of from 0 to 180° C., preferably from 20 to 95° C., optionally under a pressure of from 1 to 30 bar. The modifications can be carried out on rubber microgels without a solvent or in the form of their dispersion, it being possible in the latter case to use inert organic solvents or alternatively water as the reaction medium. The modification is preferably carried out in an aqueous dispersion of the crosslinked rubber.
The use of unmodified microgels is preferred in the case of compositions according to the present invention that are used for incorporation into non-polar rubbers or non-polar thermoplastic materials, such as, for example, polypropylene, polyethylene and block copolymers based on styrene, butadiene, isoprene (SBR, SIR) and hydrogenated isoprene-styrene block copolymers (SEBS), and conventional TPE-Os and TPE-Vs, etc.
The use of modified microgels is preferred in the case of compositions according to the invention that are used for incorporation into polar rubbers or polar thermoplastic materials (A), such as, for example, PA, TPE-A, PU, TPE-U, PC, PET, PBT, POM, PMMA, PVC, ABS, PTFE, PVDF, etc.
The mean diameter of the prepared microgels can be adjusted with high accuracy, for example, to 0.1 micrometer (100 nm)±0.01 micrometer (10 nm), so that, for example, a particle size distribution is achieved in which at least 75% of all the microgel particles are from 0.095 micrometer to 0.105 micrometer in size. Other mean diameters of the microgels, especially in the range from 5 to 500 nm, can be produced with the same accuracy (at least 75 wt. % of all the particles are located around the maximum of the integrated particle size distribution curve (determined by light scattering) in a range of ±10% above and below the maximum) and used. As a result, the morphology of the microgels dispersed in the composition according to the present invention can be adjusted virtually “point accurately” and hence the properties of the composition according to the present invention and of the plastics, for example, produced therefrom can be adjusted.
The microgels so prepared can be worked up, for example, by concentration by evaporation, coagulation, by co-coagulation with a further latex polymer, by freeze coagulation (see U.S. Pat. No. 2,187,146) or by spray-drying. In the case of working up by spray-drying, commercially available flow auxiliaries, such as, for example, CaCO3 or silica, can also be added.
In a prferred embodiment of the composition according to the present invention, the microgel (B) is based on rubber.
In a preferred embodiment of the composition according to the present invention, the microgel (B) has been modified by functional groups reactive towards C═C double bonds.
Preferably according to the present invention, the microgel (B) has a swelling index in toluene at 23° C. of from 1 to 15.
The composition according to the present invention preferably has a viscosity at 20° C. of from 2 mPas to 5,000,000 mpas, more preferably from 50 mPas to 3,000,000 mpas, at a speed of 5 s−1 in a cone/plate viscometer according to DIN 53018.
Non-Crosslinkable Organic Medium (A)
The composition according to the present invention contains at least one organic medium (A) which has a viscosity at a temperature of 120° C. of less than 1000 mPas, preferably 200 mPas, more preferably 100 mPas.
Such a medium is liquid to solid at room temperature (20° C.).
Organic medium within the scope of the present invention means that the medium contains at least one carbon atom.
Within the scope of the present invention, non-crosslinkable media are understood as being especially media that do not contain groups crosslinkable via hetero-atom-containing functional groups or C═C groups, such as, especially, conventional monomers or pre-polymers which are crosslinked or polymerized in the conventional manner by means of free radicals, by means of UV radiation, thermally and/or with the addition of crosslinkers (e.g. polyisocyanates) etc. with the formation of oligomers or polymers. Non-crosslinkable media are preferably also solvents, more preferably those according to DIN 55 945.
The non-crosslinkable medium (A) is preferably a non-crosslinkable medium that is liquid at room temperature (20° C.), more preferably a hydrocarbon (straight-chain, branched, cyclic, saturated, unsaturated and/or aromatic hydrocarbons having from 1 to 200 carbon atoms, which may optionally be substituted by one or more substituents selected from halogens, such as chlorine, fluorine, hydroxy, oxo, amino, carboxy, carbonyl, aceto, amido), synthetic hydrocarbon, polyether oil, ester oil, phosphoric acid ester, silicon-containing oil or halogenated hydrocarbon or carbon halide (see e.g. Ullmanns Enzyklopädie der technischen Chemie, Verlag Chemie Weinheim, Volume 20, (1981) 457 ff, 504, 507 ff, 517/518, 524). Such non-crosslinkable media (A) are distinguished especially by viscosities of from 2 to 1500 mm2/s (cSt) at 40° C.
The non-crosslinkable medium (A) is preferably a non-crosslinkable medium that is liquid at room temperature (20° C.), preferably a solvent according to DIN 55 495, such as xylene, solvent naphtha, methyl ethyl ketone, methoxypropyl acetate, N-methylpyrrolidone, dimethyl sulfoxide.
Synthetic hydrocarbons are obtained by polymerization of olefins, condensation of olefins or chloroparaffins with aromatic compounds, or dechlorinating condensation of chloroparaffins. Examples of polymer oils are ethylene polymers, propylene polymers, polybutenes, polymers of higher olefins, alkyl aromatic compounds. The ethylene polymers have molecular weights of from 400 to 2000 g/mol. The polybutenes have molecular weights of from 300 to 1500 g/mol.
In the case of the polyether oils, a distinction is made between aliphatic polyether oils, polyalkylene glycols, especially polyethylene and polypropylene glycols, their mixed polymers, their mono- and di-ethers and also ester ethers and diesters, tetrahydrofuran polymer oils, perfluoropolyalkyl ethers and polyphenyl ethers. Perfluoropolyalkyl ethers have molar masses of from 1000 to 10,000 g/mol. The aliphatic polyether oils have viscosities of from 8 to 19,500 mm2/s at 38° C.
Polyphenyl ethers are prepared by condensation of alkali phenolates with halobenzenes. The diphenyl ether and its alkyl derivatives are also used.
Examples of ester oils are the alkyl esters of adipic acid, bis-(2-ethylhexyl) sebacate and bis-(3,5,5-trimethylhexyl) sebacate or adipate. A further class is formed by the fluorine-containing ester oils. In the case of phosphoric acid esters, a distinction is made between triaryl, trialkyl and alkylaryl phosphates. Examples are tri-(2-ethylhexyl) phosphate and bis-(2-ethylhexyl)-phenyl phosphate.
Silicon-containing oils are the silicone oils (polymers of the alkyl- and aryl-siloxane group) and the silicic acid esters.
The halogenated hydrocarbons or carbon halides include chlorinated paraffins, such as chlorotrifluoroethylene polymer oils and hexafluorobenzene.
(Non-reactive) solvents according to DIN 55 945 are hexane, special boiling point gasoline, white spirit, xylene, solvent naphtha, balsam turpentine, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, isophorone, butyl acetate, 1-methoxypropyl acetate, butyl glycol acetate, ethyl diglycol acetate and N-methylpyrrolidone (Brock, Thomas, Groteklaes, Michael, Mischke, Peter, Lehrbuch der Lacktechnologie, Curt R. Vincentz Verlag Hannover, (1998) 93 ff).
Preferred non-crosslinkable media (A) are the large class of the hydrocarbons, the polyether oils, and the solvents according to DIN 55 945.
The composition according to the present invention preferably contains from 0.5 to 90 wt. %, more preferably from 1 to 40 wt. %, most preferably from 2 to 30 wt. %, of the microgel (B), based on the total amount of the composition.
The composition according to the present invention further contains preferably from 10 to 99.5 wt. %, more preferably from 40 to 97 wt. %, most preferably from 50 to 95 wt. %, even more preferably from 60 to 95 wt. %, of the organic medium (A).
The composition according to the present invention preferably contains the non-crosslinkable organic medium (A) and the microgel (B) and optionally the further components mentioned herein below. The presence of water is not preferred, more preferably the presence of water is excluded.
Further, the composition according to the present invention can additionally contain fillers, pigments and additives, such as dispersing aids, de-aerators, flow agents, auxiliary substances for the wetting of substrates, adhesion promoters, anti-settling agents, auxiliary substances for controlling substrate wetting, for controlling conductivity, auxiliary substances for controlling color stability, gloss and floating, oxidation inhibitors, pour-point depressors, high-pressure additives, foam-preventing agents, demulsifying agents.
The mentioned additives can preferably be incorporated into the compositions according to the present invention uniformly, which in turn leads to an improvement in the polymer compositions produced therefrom.
Particularly suitable pigments and fillers for the preparation of the compositions according to the present invention containing the non-crosslinkable medium (A), and of microgel-containing plastics produced therefrom, are, for example: inorganic and organic pigments, silicate-like fillers such as kaolin, talcum, carbonates such as calcium carbonate and dolomite, barium sulfate, metal oxides such as zinc oxide, calcium oxide, magnesium oxide, aluminum oxide, highly dispersed silicas (precipitated silicas and silicas produced by thermal means), metal hydroxides such as aluminum hydroxide and magnesium hydroxide, glass fibers and glass fiber products (laths, threads or glass microspheres), carbon fibers, thermoplastic fibers (polyamide, polyester, aramid), rubber gels based on polychloroprene and/or polybutadiene, and also any other gel particles described above having a high degree of crosslinking and a particle size of from 5 to 1000 nm.
The mentioned fillers can be used alone or in a mixture. Preferably, from 0.5 to 30 parts by weight of rubber gel (B), optionally together with from 0.1 to 40 parts by weight of fillers, and from 30 to 99.5 parts by weight of the non-crosslinkable liquid medium (A) are used to prepare the compositions present according to the invention.
The compositions according to the present invention can contain further auxiliary substances, such as anti-ageing agents, heat stabilizers, light stabilizers, anti-ozonants, processing aids, plasticizers, tackifiers, blowing agents, colorings, waxes, extenders, organic acids and also filler activators, such as, for example, trimethoxysilane, polyethylene glycol, or other auxiliary substances known in the described industries.
The auxiliary substances are used in the conventional amounts, which are governed inter alia by the intended use. Conventional amounts are, for example, amounts of from 0.1 to 50 wt. %, based on the amounts of liquid medium (A) used.
Preferably, the composition according to the present invention is prepared by means of a homogenizer, a bead mill or a three-roller mill. Disadvantages of bead mills are the comparatively limited viscosity range (tendency towards thin compositions), the high outlay in terms of cleaning, the expensive change-over of the compositions that can be used, and wear of the beads and the grinding apparatus. Homogenization of the compositions according to the present invention is preferably carried out by means of a homogenizer or a three-roller mill. Disadvantages of three-roller mills are the comparatively limited viscosity range (tendency towards very thick compositions), the low throughput and the fact that the procedure is not closed (poor working protection). Homogenization of the compositions according to the present invention is more preferably carried out by means of a homogenizer. The homogenizer allows thin and thick compositions to be processed with a high throughput (high flexibility). Product change-over is possible relatively quickly and without difficulty.
The dispersion of the microgels (B) in the liquid medium (A) takes place in the homogenizer in the homogenizing valve (The FIGURE).
In the process used according to the present invention, agglomerates are comminuted into aggregates and/or primary particles. Agglomerates are physically separable units which undergo no change in primary particle size during dispersion.
The product to be homogenized enters the homogenizing valve at low speed and is accelerated to high speeds in the homogenizing gap. Dispersion takes place downstream of the gap, principally as a result of turbulence and cavitation (William D. Pandolfe, Peder Baekgaard, Marketing Bulletin of APV Homogenizer Group—“High-pressure homogenizers processes, product and applications”).
The temperature of the composition according to the present invention on introduction into the homogenizer is advantageously from −40 to 140° C., preferably from 20 to 80° C.
The composition according to the present invention to be homogenized is preferably homogenized in the apparatus at a pressure of from 200 to 4000 bar, preferably from 500 to 2000 bar, more preferably from 900 to 2000 bar. The number of passes is governed by the desired dispersion quality and can vary from 1 to 20, preferably from 1 to 10, passes.
The compositions prepared according to the present invention have a fine particle distribution, which is achieved especially with the homogenizer and is extremely advantageous also in respect of the flexibility of the process with regard to varying viscosities of the liquid media and of the resulting compositions and necessary temperatures as well as the dispersion quality.
The present invention relates also to the use of the composition according to the present invention in the production of microgel-containing polymers or plastics, as discussed above.
If the compositions according to the present invention are incorporated into thermoplastic polymers, it is surprisingly found that microgel-containing polymers that behave like thermoplastic elastomers are obtained.
The present invention relates also to the molded bodies and coatings produced therefrom by conventional processes.
The invention is further illustrated but is not intended to be limited by the following examples in which all parts and percentages are by weight unless otherwise specified.
EXAMPLES Example 1In Example 1 described herein below it is shown that compositions according to the present invention having specific rheological characteristics, such as intrinsic viscosity, thixotropy and approximately Newtonian flow behavior, are obtained using microgels based on SBR.
The composition of the microgel phase is given in the table below:
T 110 is hydrogenated naphthenic oil from Nynas Naphthenics AB. Micromorph 5P is an SBR-based crosslinked rubber gel having an OH number of 4 from RheinChemie Rheinau GmbH. Micromorph 5P consists of 40 wt. % styrene, 57.5 wt. % butadiene and 2.5 wt. % dicumyl peroxide. Micromorph 1P is an SBR-based, crosslinked, surface-modified rubber gel from RheinChemie Rhienau GmbH.
Micromorph 1P consists of 80 wt. % styrene, 12 wt. % butadiene, 5 wt. % ethylene glycol dimethacrylate (EGDMA) and 3 wt. % hydroxyethyl methacrylate (HEMA).
Preparation Example 1 Relating to Micromorph 1PMicrogel based on hydroxyl-modified SBR, prepared by direct emulsion polymerization using the crosslinking comonomer ethylene glycol dimethacrylate (Micromorph 1P).
325 g of the Na salt of a long-chain alkylsulfonic acid (330 g of Mersolat K30/95 from Bayer AG) and 235 g of the Na salt of methylene-bridged naphthalenesulfonic acid (Baykanol PQ from Bayer AG) were dissolved in 18.71 kg of water and placed in a 40-litre autoclave. The autoclave is evacuated three times and charged with nitrogen. Then 8.82 kg of styrene, 1.32 kg of styrene, 503 g of ethylene glycol dimethacrylate (90%), 314 g of hydroxyethyl methacrylate (96%) and 0.75 g of hydroquinone monomethyl ether were added. The reaction mixture was heated to 30° C., with stirring. An aqueous solution containing 170 g of water, 1.69 g of ethylenediaminetetraacetic acid (Merck-Schuchardt), 1.35 g of iron (II) sulfate * 7H2O, 3.47 g of Rongalit C (Merck-Schuchradt) and 5.24 g of trisodium phosphate * 12H2O was then metered in. The reaction was started by addition of an aqueous solution of 2.89 of p-menthane hydroperoxide (Trigonox NT 50 from Akzo-Degussa) and 10.53 g of Mersolat K 30/95, dissolved in 250 g of water. After a reaction time of 5 hours, activation was carried out using an aqueous solution containing 250 g of water in which 10.53 g of Mersolat K30/95 and 2.8 g of p-menthane hydroperoxide (Trigonox NT 50) were dissolved. When a polymerization conversion of 95-99% was reached, the polymerization was stopped by addition of an aqueous solution of 25.53 g of diethylhydroxylamine dissolved in 500 g of water. Unconverted monomers were then removed from the latex by stripping with steam. The latex was filtered and stabilizer was added as in Example 2 of U.S. Pat. No. 6,399,706, followed by coagulation and drying.
For the preparation of the composition according to the present invention, T110 was placed in the vessel and Micromorph 5P was added with stirring by means of a dissolver. The composition was passed through the homogenizer four times at 950 bar.
The rheological properties of the composition were determined by means of a rheometer, MCR300, from Physica. A plate/cone system, CP25-1, was used as the measuring body. The measurements were carried out at 20° C.
(For the composition consisting of 80% T110 and 20% Micromorph 1P or Micromorph 5P, some measuring results are shown in the following table).
As a comparison, the greases Li-120H AK33, Fuchs-Lubritech GmbH, and E301 (15%), laboratory product of RheinChemie Rheinau GmbH, were measured concomitantly.
The table shows the viscosities v′, which were measured at shear rates of 5 s−1, 100 s−1, 1000 s−1, 3000 s−1 and 0.1 s−1. The quotient v′(0.1 s−1)/v′(3000 s−1) was defined as an arbitrary measure of the viscosity-increasing action of microgel.
The composition containing 80% T110 and 20% Micromorph 5P, which was passed through the homogenizer four times at 950 bar, exhibits Theological behavior comparable to that of Li-120H AK33 or E301. Micromorph 1P, on the other hand, exhibits no appreciable thickening in Nynas T110.
1)Micromorph 5 P
2)Micromorph 1 P
The measured values show a thickening which, with suitable selection of the microgel/lubricant combination, is suitable for the production of lubricating greases.
In addition, it is possible to control rheological properties in the described liquid media using microgels. The compositions according to the present invention are valuable as thickeners, as anti-dripping and anti-settling agents and as a rheological additive.
The described compositions can advantageously be used in lubricants, paints and inks, adhesives, rubber and gel coats.
The compositions prepared in Example 1 can be used in lubricating greases. They result in advantageous properties therein, such as high intrinsic viscosity.
Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.
Claims
1. Composition comprising at least one non-crosslinkable organic medium (A) which has a viscosity of less than 1000 mPas at 120° C., and at least one microgel (B).
2. Composition according to claim 1, the microgel (B) has primary particles exhibiting approximately spherical geometry.
3. Composition according to claim 2, wherein the microgel (B) has a variation in diameters of an individual primary particle of the microgel (B), defined as [(d1−d2)/d1]×100, wherein d1 and d2 are any two diameters of the primary particle and d1>d2, is less than 250%.
4. Composition according to claim 2, wherein the primary particles of the microgel (B) have an average particle size of from 5 to 500 nm.
5. Composition according to claim 1, wherein the microgel (B) comprise at least about 70 wt. % portions that are insoluble in toluene at 23° C.
6. Composition according to claim 1, wherein the microgel (B) has a swelling index in toluene at 23° C. of less than about 80.
7. Composition according to claim 1, wherein the microgel (B) has glass transition temperatures of from −100° C. to +100° C.
8. Composition according to claim 1, wherein the microgel (B) is a crosslinked microgel that has not been crosslinked by means of high-energy radiation.
9. Composition according to claim 1, wherein the microgel (B) has a breadth of the glass transition range of greater than about 5° C.
10. Composition according to claim 1, wherein the microgel (B) is prepared by emulsion polymerization.
11. Composition according to claim 1, wherein the microgel (B) is based on rubber.
12. Composition according to claim 1, wherein the microgel (B) is based on homopolymers or random copolymers.
13. Composition according to claim 1, wherein the microgel (B) is modified by functional groups reactive towards C═C double bonds.
14. Composition according to claim 1, wherein the non-crosslinkable medium (A) is at least one compound selected from the group consisting of solvents, saturated or aromatic hydrocarbons, polyether oils, ester oils, polyether ester oils, phosphoric acid esters, silicon-containing oils and halogenated hydrocarbons.
15. Composition according to claim 1 comprising from 0.5 to 90 wt. % of the microgel (B), based on the total amount of the composition.
16. Composition according to claim 1 comprising from 10 to 99.5 wt. % of the non-crosslinkable organic medium (A).
17. Composition according to claim 1 further comprising fillers and additives.
18. Composition according to claim 1 prepared a homogenizer, a bead mill (agitator ball mill) or a three-roller mill.
19. Composition according to claim 1, wherein the composition has a viscosity at 20° C. of from 2 mPas to 5,000,000 mPas at a speed of 5 s−1, determined by means of a cone/plate measuring system according to DIN 53018.
20. Composition according to claim 19, wherein the microgel (B) has a swelling index in toluene at 23° C. of from 1 to 15.
21. Composition according to claim 1, wherein the composition is a thermoplastic plastics, rubbers or thermoplastic elastomers.
22. Microgel-containing polymers comprising compositions according to claim 1.
23. Use according to claim 22 in the production of microgel-containing rubbers.
24. Plastics, rubbers, coating compositions or lubricants comprising the compositions according to claim 1.
25. Process for the preparation of the composition according to claim 1, comprising subjecting components (A) and (B) \to treatment by means of a homogenizer, a bead mill or a three-roller mill.
Type: Application
Filed: Sep 23, 2004
Publication Date: Sep 8, 2005
Inventors: Torsten Ziser (Birkenau), Thomas Fruh (Limburgerhof), Patrick Galda (Karlsruhe), Werner Obrecht (Moers)
Application Number: 10/947,876
