Patent Application
20070191545
The present invention relates to a composition containing thermoplastic materials and crosslinked microgels that have not been crosslinked by high-energy radiation, to a process for its preparation, to its use in the production of thermoplastically processable molded articles, and to molded articles produced from the composition.
The use of microgels for controlling the properties of elastomers is known (e.g. EP-A-405216, DE-A 4220563, GB-PS 1078400, DE 19701487, DE 19701489, DE 19701488, DE 19834804, DE 19834803, DE 19834802, DE 19929347, DE 19939865, DE 19942620, DE 19942614, DE 10021070, DE 10038488, DE 10039749, DE 10052287, DE 10056311 and DE 10061174). EP-A-405216, DE-A-4220563 and GB-PS-1078400 disclose the use of CR, BR and NBR microgels in mixtures with double-bond-containing rubbers. DE 19701489 describes the use of subsequently modified microgels in mixtures with double-bond-containing rubbers such as NR, SBR and BR.
None of these specifications teaches the use of microgels in the production of thermoplastic elastomers.
Chinese Journal of Polymer Science, Volume 20, No. 2, (2002), 93-98 describes microgels that have been completely crosslinked by high-energy radiation and their use to increase the impact strength of plastics. Similarly, US 20030088036 A1 discloses reinforced heat-curing resin compositions in whose preparation radiation-crosslinked microgel particles are likewise mixed with heat-curing pre-polymers (see also EP 1262510 A1). In these publications, a radioactive cobalt source is mentioned as the preferred radiation source or the preparation of the microgel particles. The use of radiation crosslinking yields very homogeneously crosslinked microgel particles. However, this type of crosslinking has the particular disadvantage that it is not realistic to transfer this process from a laboratory scale to a large-scale installation both from an economic viewpoint and from the point of view of working safety. Microgels that have not been crosslinked by high-energy radiation are not used in the mentioned publications. Furthermore, when completely radiation-crosslinked microgels are used, the change in modulus from the matrix phase to the dispersed phase is immediate. In the case of sudden stress, this can 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 impaired.
DE 3920332 discloses rubber-reinforced resin compositions which comprise (i) a matrix resin having a glass transition temperature of at least 0° C. and (ii) from 1 to 60 wt. % of rubber particles dispersed in the matrix resin. The dispersed particles are characterized in that they consist of hydrogenated block copolymers of a conjugated diene and a vinyl aromatic compound. The particles inevitably have two glass transition microphase structure of separate microphase with segments and temperatures, one being at −30° C. or less. The particles exhibit a soft segments, in which the hard segments and the soft segments are alternately laminated with one another in the form of concentric multiple layers. The preparation of these specific particles is very expensive because it is first necessary to prepare a solution of the starting materials for the particles (block copolymers) in organic solvents. In the second step, water and optionally emulsifiers are added, the organic phase is dispersed in suitable apparatuses, the solvent is then removed and the particles dispersed in water are then fixed by crosslinking with a peroxide. In addition, it is very difficult to produce particle sizes less than 0.25 μm by this process, which is disadvantageous for the flow behavior.
Polymeric materials can be divided into several groups according to their structure, their deformation-mechanical behavior and hence according to their properties and fields of use. Traditionally there are on the one hand the amorphous or semi-crystalline thermoplastics, which consist of long, uncrosslinked polymer chains. Thermoplastics are brittle to viscoelastic at room temperature. These materials are plasticized by pressure and temperature and can then be molded. On the other hand there are the elastomers or rubber materials. Elastomers are a crosslinked rubber product. It may be natural or synthetic rubber. Rubbers can only be processed in the uncrosslinked state. They then exhibit viscoplastic behavior. Only with the addition of crosslinking chemicals such as, for example, sulfur or peroxide is there obtained upon subsequent heating a vulcanization product or the elastic rubber. In this “vulcanization procedure”, the loosely fixed individual rubber molecules are linked together chemically by the formation of chemical bonds. The amorphous preliminary product rubber changes hereby into the elastomer with typical rubber elasticity. The vulcanization procedure is not reversible, except by thermal or mechanical decomposition.
The thermoplastic elastomers (abbreviated to TPE herein below) exhibit completely different behavior. These materials become plastic when heated and elastic again when cooled. In contrast to chemical crosslinkinq, crosslinking in the case of elastomers is physical Accordingly, the TPEs stand between the thermoplastics and the elastomers in terms of their structure and their behavior, and they combine the ready processability of the thermoplastics with the fundamental properties of rubber. Above Tg to the melting point or to the softening temperature, the TPEs behave like elastomers, but they are thermoplastically processable at higher temperatures. As a result of physical crosslinking, for example via (semi-)crystalline regions, a thermoreversible structure with elastic properties is formed on cooling.
In contrast to the processing of rubber, the processing of TPE materials is based not on a cold/warm process but on a warm/cold process. If in the case of soft, highly elastic TPE materials in particular the pronounced intrinsically viscous melting or softening behavior is taken into account, then it is possible when processing TPEs to use the typical thermoplastic processes such as injection molding, extrusion, blow molding and deep drawing. The product properties depend primarily on the structure and phase morphology; in elastomer alloys a large part is played, for example, by the particle size, the particle size distribution or the particle stretching of the disperse phase. These structural features can be influenced to a certain extent during processing. A further fundamental advantage of TPE materials over the conventional, chemically crosslinked elastomers can be seen in their fundamental suitability for recycling. As with all plastics, a fall in viscosity that increases with the number of processing steps is to be observed in the case of the TPE materials, but this does not lead to a significant impairment of the product properties.
Since the discovery of the TPEs, this class of materials has been distinguished by the fact that it is formed by a combination of a hard phase and a soft phase. The TPEs known hitherto are divided into two main groups:
The composition of the comonomers determines the ratio of hard phase to soft phase, determines which phase constitutes the matrix and determines the final properties. A true morphology is recognizable at molecular level when, for example, the deficient component aggregates or crystallizes. The temperature dependence of this physical morphology fixing is a problem with these materials, that is to say there is a limit temperature at which the morphology fixing is undone. This can cause problems during processing owing to changes in the properties associated therewith.
The block polymers include, for example, styrene block copolymers (TPE-S), such as butadiene (SBS), isoprene (SIS) and ethylene/butylene (SEBS) types, polyether-polyamide block copolymers (TPE-A), thermoplastic copolyesters, polyether esters (TPE-E) and thermoplastic polyurethanes (TPE-U), which are described in greater detail herein below in connection with the starting materials that can be used according to the present invention.
The second main group of the material TPE are the elastomer alloys. Elastomer alloys are polymer blends which contain both thermoplastic and elastomeric constituents. They are prepared by “blending” the raw materials, that is to say mixing them intensively in a mixing device (internal mixer, extruder or the like). Very different mixing ratios between the hard phase and the soft phase can occur. The soft phase can be either uncrosslinked (TPE-0) or crosslinked (TPE-V). In the ideal TPE blend there are small elastomer particles which are uniformly distributed in finely dispersed form in the thermoplastic matrix. The finer the distribution and the higher the degree of crosslinking of the elastomer particles, the more pronounced the elastic properties of the resulting TPE. These TPE blends are prepared, for example, by so-called “dynamic vulcanization” or reactive extrusion, in which the rubber particles are crosslinked in situ during the mixing and dispersing process. The property profile of these blends is accordingly substantially dependent on the proportion, degree of crosslinking and dispersion of the rubber particles. Very different combinations can be produced by this blend technology. The physico-mechanical properties and the chemical resistance and compatibility with contact media are substantially determined by the individual properties of the blend components. By optimizing the “blend quality” and the degree of crosslinking it is possible to improve specific physical properties. Nevertheless, it is a characteristic of this class that the dispersed phase is present in irregular and coarsely dispersed form. The less compatible the polymers, the more coarse the resulting structure. The non-compatible combinations, such as, for example, a dispersed phase of NBR rubber in a PP matrix, are of particular technical interest. In order to improve the compatibility in such cases and accordingly influence the final properties of the resulting material in the desired manner, a homogenizing agent can be added prior to the dynamic vulcanization. About 1% of the homogenizing agent is sufficient for many applications. The homogenizing agents are generally based on block copolymers whose blocks are compatible with in each case one of the blend phases. Depending on the relative proportions, the two phases may constitute both the continuous and the discontinuous phase. Hitherto it has not been possible to adjust the morphology of this material in a reliable manner. In order to produce particularly finely divided dispersed phases, large amounts of the homogenizing agent may be necessary, which in turn adversely affects the boundary properties of the final material. Industrially produced and commercially available thermoplastic vulcanization products exhibit a maximum distribution of the diameter of the dispersed phase of from 2 μm to 4 μm with individual volume elements up to 30 μm.
Among the elastomer alloys, the most commonly used combinations are based on EPDM with PP. Other elastomer alloys are based on NR/PP blends (thermoplastic natural rubber), NBR/PP blends (NBR=acrylonitrile-butadiene rubber), IIR (XIIR)/PP blends (butyl or halobutyl rubbers as elastomeric phase constituents), EVA/PVDC blends (“Alcryn” blend of ethylene-vinyl acetate rubber (EVA) and polyvinylidene chloride (PVDC) as the thermoplastic phase) and NBR/PVC blends. A targeted adjustment of the morphology of the dispersed phase and hence a targeted adjustment of the desired properties of the TPEs in these polymer blend TPEs is virtually impossible, however, owing to the in situ formation of the dispersed phase and the many parameters involved therein.
The present inventors relates to novel compositions having thermoplastic elastomer properties which can easily be prepared from starting materials known per se and whose properties can be adjusted in a simple and foreseeable manner. The novel compositions can be prepared on an industrial scale, and they should not give rise to problems relating to working safety. Furthermore, there should be no tearing effects in the compositions between the matrix and the dispersed phase on sudden stress so that the mechanical properties, the swelling behavior and the stress corrosion cracking, etc. are impaired. The preparation of the microgels for the composition should be simple and allow the particle size distributions of the microgel particles to be adjusted in a targeted manner to very small average particle sizes.
Surprisingly it has been found in the present invention that, by incorporating crosslinked microgels, which have not been crosslinked by high-energy radiation, based on homopolymers or random copolymers into thermoplastic materials, it is possible to provide compositions having a novel combination of properties. By the provision of the novel composition it is surprisingly possible to overcome the above-mentioned disadvantages of the known conventional thermoplastics and TPEs and at the same time provide thermoplastic elastomer compositions having outstanding use properties. Because thermoplastic elastomer compositions are obtained by the incorporation of microgels into the thermoplastic materials, it is possible to separate the adjustment of the morphology of the dispersed phase from the production of the TPE material in terms of both space and time. The morphology production can be reliably reproduced because the dispersed phase is a microgel whose morphology can be controlled in a manner known per se during preparation and which substantially does not change further on incorporation into the thermoplastic material. In the compositions prepared according to the invention, the polymer microstructure of both the dispersed phase and the continuous phase can be varied within wide limits, so that customized TPEs can be produced from any desired thermoplastic materials, which was not possible according to the known processes for the production of conventional TPEs. By controlling the degree of crosslinking and the degree of fictionalization in the surface and in the core of the dispersed microgels, the desired properties of the resulting TPEs can be controlled further. The glass transition temperature of the dispersed microgel phase can also be adjusted in a targeted manner within the range of from −100° C. to less than 50° C., as a result of which the properties of the resulting TPEs can in turn be adjusted in a targeted manner. As a result, the difference in glass transition temperature between the dispersed phase and the continuous phase can also be adjusted in a targeted manner and can be, for example, from 0° C. to 250° C. With the novel class of TPEs provided by the present invention it is additionally possible to combine thermodynamically compatible and thermodynamically incompatible polymers to form new TPEs which were not obtainable by conventional processes. In the novel TPEs provided by the present invention, the dispersed phase and the continuous phase may each constitute the hard phase and the soft phase. By controlling the properties of the microgels and the relative proportions, the dispersed phase can be present in the matrix in the form of aggregated clusters or in uniformly distributed form and in all intermediate forms.
This is not possible in the TPEs prepared by conventional processes, in which the dispersed phase is formed in situ during the production of the TPEs.
Furthermore, it has been surprisingly found not only that the incorporation of microgels into thermoplastic plastics permits the production of thermopastic elastomers, but also that the incorporation of microgels into, for example, thermoplastic elastomers produced by conventional processes allows a targeted improvement in their properties, such as, for example, dimensional stability and transparency.
The compositions according to the present invention can be prepared on an industrial scale by a simple process, without using microgels crosslinked by high-energy radiation. The microgels used according to the present invention permit a less immediate change in modulus between the matrix phase and the dispersed phase, which leads to an improvement in the mechanical properties of the composition.
Also surprisingly, the physical properties, such as, for example, transparency and oil resistance, can be improved when using thermoplastic elastomers as component (A).
Accordingly, the present invention provides a composition which contains at least one thermoplastic material (A) and at least one microgel (B) based on homopolymers or random copolymers that has not been crosslinked by high-energy radiation.
Microgel or Microgel Phase (B)
The microgel (B) used in the composition according to the present invention is a crosslinked microgel based on homopolymers or random copolymers. Accordingly, the microgels used according to the present invention are crosslinked homopolymers or crosslinked random copolymers. The terms homopolymers and random copolymers are known to the person skilled in the art and are explained, for example, in Vollmert, Polymer Chemistry, Springer 1973.
The crosslinked microgel (B) used in the composition according to the present invention is a microgel that has not been crosslinked by high-energy radiation. High-energy radiation here preferably means electromagnetic radiation having a wavelength of less than 0.1 μm.
The use of microgels completely homogeneously crosslinked by high-energy radiation is disadvantageous because it is virtually impossible to implement on an industrial scale and causes problems associated with working safety. Furthermore, in compositions prepared using microgels completely homogeneously crosslinked by high-energy radiation, tearing effects between the matrix and the dispersed phase occur on sudden stress, with the result that the mechanical properties, the swelling behavior and the stress corrosion cracking, etc. are impaired.
The primary particles of the microgel (B) present in the composition according to the present invention preferably 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 form substantially a circular surface when a thin section is viewed using an electron microscope (see e.g.
In the compositions according to the present invention there may be used, for example, all known TPEs, especially TPE-Us or TPE-As, as the continuous phase. By incorporating the microgels (B) into the known TPEs, preferably TPE-Us or TPE-As, the dimensional stability under heat of the TPEs, preferably TPE-Us or TPE-As, can surprisingly be improved. The transparency of the microgel-containing compositions according to the invention based on TPE-U or TPE-A is also improved. The known TPE-Us are not transparent, while the microgel-containing compositions according to the present invention based on TPE-U are transparent. By incorporating the microgels into TPE-As, it is surprisingly possible to greatly improve their oil resistance, for example, in addition to their optical properties, such as transparency.
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 any desired section of the primary particle and d1>d2, is preferably less than 250%, more preferably less than 200%, most preferably less than 100%.
Preferably at least 80%, more preferably at least 90%, yet more 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 any desired section of the primary particle and d1>d2, of less than 250%, preferably less than 200%, more preferably less than 100%.
The above-mentioned variation in the diameters of the individual particles is determined by the following process. A TEM image of 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, from 10,000 times to 85,000 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 200%, yet more preferably less than 100%, 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 50 to 300 nm (diameter data according to DIN 53206).
Because the morphology of the microgels remains substantially unchanged during incorporation into the thermoplastic material (A), the average particle diameter of the dispersed primary particles corresponds substantially to the average particle diameter of the microgel used.
In the composition according to the present invention, the microgels (B) that are used 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 25 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) that are used advantageously exhibit a swelling index in toluene at 23° C. of less than about 80, more preferably of less than 60, yet more 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) that are used preferably have glass transition temperatures Tg of from −100° C. to +50° C., more preferably from −80° C. to +20° C.
In the composition according to the present invention, the microgels (B) that are used advantageously 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 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 temperature (Tg) and the breadth of the glass transition (ΔTg) of the microgels are determined by differential scanning calorimetry (DSC). For determining Tg and ΔTg, two cooling/heating cycles are carried out. Tg and ΔTg 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 (B) based on homopolymers or random copolymers present in the composition according to the present invention, which microgels have 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-854171, 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 38 488.9, 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:
The preparation of the uncrosslinked microgel starting products is advantageously carried out by the following methods:
The microgels (B) used in the composition according to the present invention are preferably those which are obtainable by emulsion polymerization and crosslinking.
The following free-radically polymerizable monomers, for example, are 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-dichlorobutadiene, 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, 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. 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-dimercaptohexane, 1,3,5-trimercaptotriazine and mercapto-tenminated 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). 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. Nos. 5,302,696 and 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 used according to the present invention always yields incompletely homogeneously crosslinked microgels which can exhibit the above-described advantages.
As microgels for the preparation of the composition according to the 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 compatibility of the microgel with the 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.
Suitable reagents for the surface modification of the microgels with low molecular weight agents are especially 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 dioctyldithiophosphoric acid as well as dodecyldithiophosphoric 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.
Preferably, the microgels are 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 especially preferred in the case of non-polar thermoplastic materials (A), 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 especially preferred in the case of 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 there from can be adjusted.
Adjustment of the morphology of the dispersed phase of the TPEs produced according to the prior art by in situ reactive processing or dynamic vulcanization is not possible with such precision.
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.
Thermoplastic Materials (A)
The thermoplastic materials (A) used in the composition according to the invention preferably have a Vicat softening temperature of at least 50° C., more preferably of at least 80° C., yet more preferably of at least 100° C.
The Vicat softening temperature is determined according to DIN EN ISO 306:1996.
In the composition according to the invention, the thermoplastic material (A) is advantageously chosen from thermolastic polymers (A1) and thermoplastic elastomers (A2).
If thermoplastic polymers (A1) are used as starting material for the composition according to the invention, then compositions having thermoplastic elastomer properties are first formed by the incorporation of the microgels used according to the present invention.
If, on the other hand, thermoplastic elastomers (A2) are used as starting material for the composition according to the present invention, then thermoplastic elastomer properties are retained, and the properties of the thermoplastic elastomers (A2) can be modified in a targeted manner, as shown herein below, by the addition of the microgels (B) of suitable composition and suitable morphology.
Accordingly, the properties of the known TPEs, such as TPE-U and TPE-A, such as especially the dimensional stability under heat and the transparency of the TPE-Us or the oil resistance of the TPE-As, can be improved by the incorporation of the microgels (B).
In the composition according to the present invention, the difference in glass transition temperature between the thermoplastic material (A) and the microgel (B) is advantageously from 0 to 250° C.
In the composition according to the invention, the weight ratio thermoplastic material (A)/microgel (B) is from 1:99 to 99:1, preferably from 10:90 to 90:10, more preferably from 20:80 to 80:20.
If thermoplastic polymers (A1) are used as the thermoplastic materials (A), the weight ratio (A1)/(B) is preferably from 95:5 to 30:70.
If thermoplastic elastomers (A2) are used as the thermoplastic materials (A), then the weight ratio (A2)/(B) is preferably from 98:2 to 20:80, more preferably from 95:5 to 20:80.
Thermoplastic Polymers (A1)
The thermoplastic polymers (A1) which can be used in the composition according to the present invention include, for example, standard thermoplastics, so-called techno-thermoplastics and so-called high-performance thermoplastics (see H. G. Elias Makromoleküle Volume 2, 5th Edition, Huthig & Wepf Verlag, 1992, page 443 ff).
The thermoplastic polymers (A1) which can be used in the composition according to the present invention include, for example, non-polar thermoplastic materials, such as, for example, polypropylene, polyethylene, such as HDPE, LDPE, LLDPE, polystyrene, etc., and polar thermoplastic materials, such as PU, PC, EVM, PVA, PVAC, polyvinylbutyral, PET, PBT, POM, PMMA, PVC, ABS, AES, SAN, PTFE, CTFE, PVF, PVDF, polyimide, PA, such as especially PA-6 (nylon), more preferably PA4, PA-66 (Perlon), PA-69, PA-610, PA-11, PA-12, PA 612, PA-MXD6, etc.
Preferred thermoplastic polymers (A1) include: PP, PE, PS, PU, PC, SAN, PVC and PA.
Thermoplastic Elastomers (A2)
The thermoplastic elastomers (A2) which can be used in the composition according to the present invention include, for example, the above-mentioned thermoplastic elastomers known from the prior art, such as the block copolymers, such as styrene block copolymers (TPE-S: SBS, SIS, as well as hydrogenated isoprene-styrene block copolymers (SEBS), thermoplastic polyamides (TPE-A), thermoplastic copolyesters (TPE-E), thermoplastic polyurethanes (TPE-U), the mentioned blends of thermoplastics and elastomers, such as thermoplastic polyolefins (TPE-O) and thermoplastic vulcanization products (TPE-V), NR/PP blends (thermoplastic natural rubber), NBR/PP blends, IIR (XIIR)/PP blends, EVA/PVDC blends, NBR/PVC blends, etc. Reference may also be made to the description of the above-mentioned TPEs from the prior art.
Examples of block polymers which can preferably be used according to the invention as the thermoplastic elastomer (A2) include the following:
Styrene Block Copolymers (TPE-S)
The three-block structure of two thermoplastic polystyrene end blocks and an elastomeric middle block characterizes this group. The polystyrene hard segments form domains, that is to say small volume elements having uniform characteristics, which act technically as spatial, physical crosslinking sites for the flexible soft segments. According to the nature of the middle block, a distinction is made between the following styrene block copolymers: butadiene (SBS), isoprene (SIS) and ethylene/butylene (SEBS) types. Branched types of block copolymer can be produced by linking via polyfunctional centers.
Polyether-polyamide Block Copolymers (TPE-A)
The block copolymers based on polyether (ester)-polyamide are formed by insertion of flexible polyether (ester) groups into polyamide molecule chains. The polyether (ester) blocks form the soft and elastic segments, while the hard polyamide blocks assume the function of the thermoplastic hard phase. The hard segments acquire their high strength as a result of a high density of aromatic groups and/or amide groups, which are responsible for the physical crosslinking of the two phases by hydrogen bridge formation.
Thermoplastic Copolyesters, Polyether Esters (TPE-E)
Thermoplastic copolyesters are composed of alternate hard polyester segments and soft polyether components. The polyester blocks, formed from diols (e.g. 1,4-butanediol) and dicarboxylic acids (e.g. terephthalic acid), are esterifies in a condensation reaction by long-chain polyethers carrying hydroxyl terminal groups. Very different hard regions can be established according to the length of the hard and soft segments.
Thermoplastic Polyurethanes (TPE-U)
The block copolymers of polyurethane are synthesized by polyaddition of diols and diisocyanates. The soft segments formed in the reaction between diisocyanate and a polyol act as elastic components under mechanical stress. The hard segments (urethane groups) serving as crosslinking sites are obtained by reaction of the diisocyanate with a low molecular weiaht diol for chain extension. As in the TPE-S types the finely divided hard segments form domains which effect quasi-crosslinking via hydrogen bridges or generally via order states in which two or more domains enter into relationship with one another. Crystallization of the hard segments may occur thereby. A distinction is made between polyester, polyether and chemically combined polyester/polyether types according to the diol used as starting monomer.
Regarding the second group of thermoplastic TPEs (A2), the elastomer alloys, reference may be made to the comments given above in connection with the prior art. Elastomer alloys which can be used according to the invention include, for example, the following:
EPDM/PP Blends
EPDM terpolymers are generally used for the rubber phase, polypropylene is mostly used as the polyolefin. The soft phase can be either uncrosslinked (TPE-0) or crosslinked (TPE-V). Where the PP component is dominant, the thermoplastic constitutes the continuous phase. If the elastomer content is very high, the structure can also be reversed, so that EPDM blends of high PP content result. This class of elastomer alloys therefore covers a wide range of hardnesses. All representatives are distinguished by high resistance to UV radiation and ozone as well as to many organic and inorganic media. On the other hand, resistance to aliphatic and aromatic solvents is poor to moderate.
NR/PP Blends (Thermoplastic Natural Rubber)
In a similar manner to EPDM, NR can also be compounded with PP and also with PP/PE mixtures to form a thermoplastically processable natural rubber (TPNR). The dynamic crosslinking of NR generally takes place in the presence of peroxides above 170° C. In comparison with conventional NR vulcanization products, TPNR blends have markedly higher resistance to weathering and ozone.
NBR/PP blends
In these polymer blends, pre-crosslinked or partially crosslinked acrylonitrile-butadiene rubber (NBR) is dispersed as the elastomeric phase in the PP hard phase. Characteristic features of these blends are high resistance to fuels, oils, acids and alkalis as well as to ozone and the effects of weathering.
IIR (XIIR)/PP Blends
Butyl or halobutyl rubbers constitute the elastomeric phase constituents in this class. On the basis of a diene rubber of non-polar nature (comparable NR/IR), the excellent permeation properties of butyl rubber towards many gases are used for the property profile of the TPE blends obtainable in a blend with PP.
EVA/PVDC Blends
These are based on a blend of ethylene-vinyl acetate rubber (EVA) and polyvinylidene chloride (PVDC) as the thermoplastic phase. The property profile in the middle hardness range of from 60 to 80 ShA is marked by good oil resistance and outstanding resistance to weathering.
NBR/PVC Blends
These polymer blends, produced predominantly for improving the properties of plasticized PVC, are mixtures of acrylonitrile-butadiene rubber (NBR) and polyvinyl chloride (PVC). In particular where better oil or grease resistance is required, the plasticized PVC grades having high plasticizer contents are no longer usable (plasticizer extraction). In these NBR/PVC blends, NBR acts as a polymeric, non-extractable plasticizer and can be mixed with PVC in virtually any proportion.
Preferred thermoplastic elastomers (A2) include: TPE-U, TPE-A and TPE-V.
Preferred compositions according to the present invention contain the following combinations of components (A) and (B):
The compositions according to the present invention generally behave like thermoplastic elastomers, that is to say they combine the advantages of thermoplastic processability with the properties of the elastomers, as described in the introduction in connection with the TPEs from the prior art.
The compositions according to the present invention can additionally comprise at least one conventional plastics additive, such as inorganic and/or organic fillers, plasticizers, inorganic and/or organic pigments, flameproofing agents, agents against pests, such as, for example, termites, agents against marten bite, etc., and other conventional plastics additives. These can be present in the compositions according to the invention in an amount of up to about 40 wt. %, preferably up to about 20 wt. %, based on the total amount of composition.
The compositions according to the present invention are obtainable by mixing at least one thermoplastic material (A) and at least one crosslinked microgel (B) that has not been crosslinked using high-energy radiation.
The present invention relates also to the use of crosslinked microgels (B) that have not been crosslinked using high-energy radiation, in thermoplastic materials (A). With regard to the preferred variants of components (A) and (B), reference may be made to the comments hereinbefore.
The present invention also relates also to a process for the preparation of the compositions according to the invention by mixing at least one thermoplastic material (A) and at least one microgel (B). The preparation of the compositions according to the invention is generally carried out in such a manner that the microgel (B) is prepared separately before being mixed with the thermoplastic material (A).
The compositions according to the present invention containing (optionally) modified microgel (B) and the thermoplastic material (A) can be prepared by various methods: on the one hand, it is of course possible to mix the individual components. Apparatuses suitable therefore are, for example, mills, multi-roll mills, dissolvers, internal mixers or mixing extruders.
Suitable as mixing apparatuses are also the mixing apparatuses known from rubber and plastics technology (Saechtling Kunststoff Taschenbuch, 24th Edition, p. 61 and p. 148 ff; DIN 24450; Mixing of plastics and rubber products, VDI-Kunststofftechnik, p. 241 ff), such as, for example, co-kneaders, single-screw extruders (with special mixing elements), twin-screw extruders, cascade extruders, degassing extruders, multi-screw extruders, pin extruders, screw kneaders and planetary extruders, as well as multi-shaft reactors. Preference is given to the use of twin-screw extruders rotating in the same direction, with degassing (planetary extruders with degassing).
The further mixing of the compositions according to the present invention containing (optionally) modified microgel (B) and the thermoplastic materials (A) with additional fillers and optionally conventional auxiliary substances, as mentioned above, can be carried out in conventional mixing apparatuses, such as mills, internal mixers, multi-roll mills, dissolvers or mixing extruders. Preferred mixing temperatures are from room temperature (23° C.) to 280° C., preferably approximately from 60° C. to 200° C.
The present invention relates also to the use of the compositions according to the present invention in the production of thermoplastically processable molded articles, and to the molded articles obtainable from the compositions according to the present invention. Examples of such molded articles include: plug-type connectors, damping elements, especially vibration dampers and shock absorbers, acoustic insulating elements, profiles, films, especially insulating films, foot mats, clothing, especially insoles for shoes, shoes, especially ski shoes, shoe soles, electronic components, housings for electronic components, tools, decorative molded bodies, composite materials, moldings for motor vehicles, etc.
The molded articles according to the present invention can be produced from the compositions according to the invention by conventional processing methods for thermoplastic elastomers, for example by melt extrusion, calendering, IM, CM and RIM.
The present invention is explained further by the following Examples. However, the present invention is not limited to the disclosure of the Examples.
1. Preparation of Microgels (B)
(NBR-based Microgel from Peroxidic Crosslinking (OBR 1102 C))
The preparation of the NBR microgel OBR 1102 C was carried out as described in DE 19701487. An NBR latex was used as starting material. The NBR latex had the following features: content of incorporated acrylonitrile: 43 wt. %, solids concentration: 16 wt. %, pH value: 10.8, diameter of the latex particles (d2): 140 nm, particle density: 0.9984 g/cm3, the gel content of the latex is 2.6 wt. %, the swelling index of the gel portion in toluene was 18.5 and the glass transition temperature (Tg) is −15° C.
7 phr of dicumyl peroxide (DCP) was used in the preparation of OBR 1102 C.
Characteristic data of the resulting microgel are summarized in Table 1.
(SBR-based Microgel from Peroxidic Crosslinking (OBR 1046 C))
The preparation of the microgel was carried out by crosslinking an SBR latex containing 40 wt. % of incorporated styrene (Krylene 1721 from Bayer France) in latex form with 1.5 phr of dicumyl peroxide (DCP) and subsequently grafting with 5 phr of hydroxyethyl methacrylate (HEMA).
The crosslinking of Krylene 1721 with dicumyl peroxide was carried out as described in Examples 1) to 4) of U.S. Pat. No. 6,127,488, 1.5 phr of dicumyl peroxide being used for the crosslinking. The underlying latex Krylene 1721 has the following features:
After reaction with 1.5 phr of dicumyl peroxide, the product had the following characteristic data:
The hydroxyl modification of the 1.5 phr-crosslinked SBR latex was carried out by grafting with 5 phr of hydroxyethyl methacrylate. The reaction with HEMA, stabilization and working up of the hydroxyl-modified latex were carried out as described in U.S. Pat. No. 6,399,706, Example 2.
The characteristic data of the hydroxyl-modified SBR gel are summarized in Table 1.
Before the microgel is used in TPU, it is dried to constant weight at 100 mbar in a vacuum drying cabinet from Haraeus Instruments, type Vacutherm VT 6130.
(SBR-based Microgel from Direct Polymerization; Crosslinking with DVB (OBR1126E)
The preparation of this microgel was carried out by copolymerization of 23% styrene, 76% butadiene and 1% divinylbenzene in emulsion.
Microgel based on hydroxyl-modified BR, prepared by direct emulsion polymerization using the crosslinking comonomer ethylene glycol dimethacrylate (OBR 1118).
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 was evacuated three times and charged with nitrogen. Then 9.200 kg of butadiene, 550 g of ethylene glycol dimethacrylate (90%), 312 g of hydroxyethyl methacrylate (96%) and 0.75 g of hydroquinone monomethyl ether are added. The reaction mixture was heated to 30° C., with stirring. An aqueous solution consisting of 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 is then metered in. The reaction was started by addition of an aqueous solution of 2.8 g 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 consisting of 250 g of water in which 10.53 g of Mersolat K30/95 and 2.8 g of p-menthane hydroperoxide (Trigonox NT 50) are dissolved. When a polymerization conversion of 95-99% is 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.
The characteristic data of the SBR gel are summarized in Table 1.
(NBR-based Microgel from Peroxidic Crosslinking (OBR 1102 B))
An NBR-based microgel from peroxidic crosslinking was prepared as in Preparation Example 1 using DCP of 5 instead of 1.5 phr.
The abbreviations used in the table have the following meanings:
DCP: dicumyl peroxide
EGDMA: ethylene glycol dimethacrylate
phr: parts per 100 rubber
Ospec.: specific surface area in m2/g
dz: The diameter
QI: swelling index
Tg: glass transition temperature
ΔTg: breadth of the glass transition
For the determination of Tg and ΔTg, a DSC-2 device from Perkin-Elmer is used.
Swelling Index QI
The swelling index QI was determined as follows:
The swelling index was calculated from the weight of the solvent-containing microgel swelled for 24 hours in toluene at 23° 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 for 24 hours in 25 ml of toluene, with shaking. The (wet) gel swelled with toluene is weighed, after centrifugation at 20,000 rpm, and then dried to constant weight at 70° C. and weighed again.
OH Number (Hydroxyl Number)
The OH number (hydroxyl number) was determined according to DIN 53240 and corresponds to the amount of KOH, in mg, that is equivalent to the amount of acetic acid liberated in the acetylation of 1 g of substance using acetic anhydride.
Acid Number
The acid number is determined as already mentioned above according to DIN 53402 and corresponds to the amount of KOH, in mg, that was required to neutralize 1 g of the polymer.
Gel Content
The gel content corresponds to the portion that was insoluble in toluene at 23° C. It was determined as described above.
Glass Transition Temperature
The glass transition temperatures were determined as mentioned above.
Breadth of the Glass Transition
The breadth of the glass transition was determined as described above.
2. General Procedure for the Mixing Process in an Internal Mixer:
The preparation of the compositions according to the invention was carried out by means of a laboratory internal mixer (Rheocord 90, Rheomix 600 E mixing chamber, Haake) with tangent rotors, compressed-air cooling and a chamber volume of 350 cm3. Mixing was carried out at a speed of 100 rpm, an initial chamber temperature of 160° C. and a degree of filling of 70%. Mixtures comprising a rubber microgel (B)/thermoplastic material (A) in the indicated ratios of, for example, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, 20/80, 10/90 are prepared. To that end, the thermoplastic was first placed in the mixer and melted in the course of 4 minutes. Then the microgel is metered in, the die was closed and mixing was carried out for 8 minutes. A rise in temperature occurs thereby. The torque passes through a maximum with a final plateau. After mixing, visually homogeneous samples are removed, which exhibit approximately the coloring of the microgel.
3. Determination of Morphology
The morphology was determined by means of transmission electron microscope images (TEM) and by means of atomic force microscopy (AFM).
1. TEM:
Sample preparation for transmission electron microscopic investigations
Cryo-ultramicrotomy
Procedure:
Under cryo conditions, thin sections having a section thickness of about 70 nm were prepared by means of diamond knives. In order to improve the contrast, contrasting with OsO4 can be carried out.
The thin sections were transferred to copper nets, dried and first assessed over a large area in the TEM. Then, with 80 kV beam potential at 12,000 times magnification, displayed area=833.7*828.8 nm, characteristic image sections were stored by means of digital imaging software for documentation purposes and evaluated.
2. AFM: Topometrix Model TMX 2010.
For the investigation, glossy sections were prepared and transferred to the AF microscope. The images were prepared by the layered imaging process.
If the microgel was too highly concentrated, i.e. if the primary particles overlap, dilution can be carried out beforehand.
(PP-based Composition According to the Invention)
The microgel OBR 1118 from Preparation Example 4 was mixed with PP Atofina PPH 3060 (produced by ATOFINA) as indicated below. The preparation of the composition was carried out using a laboratory extruder (ZSK 25, manufacturer: Krupp Wemer u. Pfleiderer, Stuttgart; screw diameter d=25 mm, L/d>38; throughputs: 2.0 to 5.0 kg/h, speeds: 100 to 220 rpm) having shafts running in the same direction. Mixing is carried out at a speed of from 100 to 220 rpm, an intake-zone temperature of 160° C. and a throughput of 5 kg/h. Mixtures having a MG/PP weight ratio of 5/95%, 10/90%, 15/85%, 20/80%, 25/75%, 30/70%, 35/65% are prepared. To that end, the PP and MG are first metered into the extruder continuously by means of gravimetric metering scales. In the extruder, a rise in temperature to 180 to 195° C. takes place. After processing, visually homogeneous samples are removed, which have approximately the coloring of the microgel.
A conventionally prepared TPE-V (Santoprene Rubber 201-87) from Advanced Elastomer Systems (M1) was used as a reference for the microgel-based TPE-Vs.
The resulting compositions/test specimens exhibited the following properties.
(PP-based Composition According to the Invention)
The microgel from Example 2 (OBR 1046 C) was mixed with a PP Atofina PPH 3060 (produced by Atofina) as indicated below. The preparation of the composition is carried out using a laboratory extruder (ZSK 25, manufacturer: Krupp Wemer u. Pfleiderer, Stuttgart; screw diameter d=25 mm, L/d>38; throughputs: 2.0 to 3.5 kg/h, speeds: 100 to 200 rpm) having shafts running in the same direction. Mixing was carried out at a speed of from 100 to 220 rpm, an intake-zone temperature of 165° C. and a throughput of 5 kg/h. Mixtures having a MG/PP weight ratio of, for example, 5/95%, 10/90%, 15/85%, 20/80%, 25/75%, 30/70%, 35/65% are prepared. To that end, the PP and MG were first metered into the extruder continuously by means of gravimetric metering scales. In the extruder, a rise in temperature to 190 to 210C. took place. After processing, visually homogeneous samples were removed, which have approximately the coloring of the microgel.
A conventionally prepared TPE-V (Santoprene Rubber 201-87) from Advanced Elastomer Systems (M1) was used as a reference for the microgel-based TPE-Vs.
The resulting compositions/test specimens exhibited the following properties.
(PP-based Composition According to the Invention)
Microgels (OBR 1126 E) from Example 3 were mixed with a PP Moplen Q 30 P (produced by Montel Polyolefins) as indicated below. The preparation of the composition was carried out using a laboratory extruder (ZSK 25, manufacturer: Krupp Werner u. Pfleiderer, Stuttgart; screw diameter d=25 mm, L/d>38; throughputs: 2.0 kg/h, speeds: 100 to 190 rpm) having shafts running in the same direction. Mixing was carried out at a speed of from 100 to 220 rpm, an intake-zone temperature of 165° C. and a throughput of 5 kg/h. Mixtures having a MG/PP weight ratio of, for example, 5/95%, 10/90%, 1 5/85%, 20/80%, 25/75%, 30/70%, 35/65% are prepared. To that end, the PP and MG are first metered into the extruder continuously by means of gravimetric metering scales. In the extruder, a rise in temperature to 175 to 190° C. takes place. After processing, visually homogeneous samples were removed, which have approximately the coloring of the microgel.
A conventionally prepared TPE-V (Santoprene Rubber 201-87) from Advanced Elastomer Systems (M1) was used as a reference for the microgel-based TPE-Vs.
The resulting compositions/test specimens exhibited the following properties.
(TPE-U-based Compositions According to the Present Invention)
The microgel from Preparation Example 2 (OBR 1046C) was used as the microgel. As the TPU added to the microgel there was used Desmopan 385, a TPE-U from Bayer AG.
The preparation of the composition was carried out using a laboratory extruder (ZSK 25, manufacturer: Krupp Wemer u. Pfleiderer, Stuttgart; screw diameter d=25 mm, L/d>38; throughputs: 2.0 to 5.0 kg/h, speeds: 100 to 220 rpm) having shafts running in the same direction. Mixing was carried out at a speed of from 100 to 220 rpm, an intake-zone temperature of 160° C. and a throughput of 5 kg/h. Mixtures having a MG/PP weight ratio of 5/95%, 10/90%, 15/85%, 20/80%, 25/75%, 30/70% are prepared. To that end, the PP and MG are first metered into the extruder continuously by means of gravimetric metering scales. In the extruder, a rise in temperature to 195° C. takes place. After processing, visually and physically homogeneous samples were removed, which have approximately the coloring of the microgel and were transparent.
A conventionally prepared TPU (Desmopan 385) (M1) was used as a reference for the microgel-based TPE-Us.
Injection Molding:
Standard tensile test specimens were injection-molded from the resulting granules of the MG-based TPE-Us and of the pure Desmopan 385. This was carried out using an injection-molding machine (type 320S from Arburg) at a machine temperature of 205-215° C., a ram pressure of 10 bar and a tool temperature of 60° C. The residence time of the sample in the machine and in the tool was 50 seconds. The shot was 29.5 g.
Preparation of the Test Specimens:
50% F3 standard test rods were prepared from all the samples. This was carried out for all materials by injection-molding of test sheets. The test specimens were prepared from the test sheets. All the standard rods have a width of 14 mm in the head region and a web width of 7 mm. The thickness of the standard rods was 2 mm.
Physical Testing:
The tensile test of the samples was carried out on 50% F3 standard test rods (see above) according to DIN 53455. The testing was carried out using a universal testing machine (type 1445, Frank) with optical length pick-ups. The measuring range of the force pick-up was 0 to 1000 N. The results of the measurements were summarized in Table 5. The following machine parameters were specified:
The breaking elongation and stress at break values of the microgel-based TPE-Us were above the values of the pure constituent TPU phase even at high loads. The calculated values were summarized in Table 2.
Shore A Hardness:
As a comparison with room temperature, the test specimens were additionally stored at +80° C. and at −2° C. in each case for 64 hours and conditioned for 1 hour at RT before the measurement. Within the scope of measuring accuracy, the samples with microgel exhibit no significant changes in Shore A hardness. The calculated values were summarized in Table 6.
Determination of Color:
The color of the test sheets was determined according to DIN standards DIN 5033 and DIN 6174 using a Match Rite CFS57 colour-measuring device from X-Rite GmbH. The calculated color values were summarized in Table 6. Although the microgel-containing test sheets have an inherent color, they remained transparent even with a content of 30% MG.
Hot-air Ageing:
Hot-air ageing was carried out at 130° C. and 180° C., in each case for one hour. The test specimens were then evaluated for appearance, shape and color. Test specimens which had not been stored in hot air were evaluated at the same time for comparison purposes. The results are shown in
(TPE-A-based Compositions According to the Present Invention and Comparison Compositions)
Preparation Process
The preparation of the TPE-As was carried out by means of a laboratory internal mixer (Rheocord 90, Rheomix 600 E mixing chamber, Haake) with tangent rotors, compressed-air cooling and a chamber volume of 350 cm3. Mixing was carried out at a speed of 100 rpm, an initial chamber temperature of 190° C. and a degree of filling of 70%. Mixtures having a rubber microgel/thermoplastic ratio of 70/30 were prepared (samples 1 and 2). To that end the thermoplastic (Grilamid L 112 G) was first placed in the mixer and melted in the course of 4 minutes. Then the microgel was metered in, the die was closed and mixing was carried out for 8 minutes. A rise in temperature occurred thereby (samples 1 and 2: Tmax=251° C.). The torque passed through a maximum. After mixing, visually and physically homogeneous samples were removed, which exhibited approximately the coloring of the microgel. This material was then granulated.
A conventional TPE-A (sample 5) having the same rubber/thermoplastic ratio was prepared as a reference for the microgel-based TPE-As according to the present invention. The PA used had the name (Grilamid L 1120 G) from EMS-GRIVORY and the nitrile rubber used has the name (Perbunan NT 3465) from BAYER AG. The crosslinker used is a dicumyl peroxide. It has the name Poly-Dispersion E(DIC)D-40 from Rhein Chemie Corporation. It is a 40% blend of DCP in an EPM binder. 5 phr of the chemical were metered in. Mixing of these TPE-As was carried out in the same mixer, but an initial temperature of 180° C., a rotor speed of 75 rpm and a total mixing time of 12 minutes were chosen. The Grilamid L 1120 G (64.3 g) was first placed in the vessel. After it had melted, the NBR rubber (Perbunan NT 3465 (149 g) and the Poly-Dispersion E(DIC)D-40 crosslinker (18.6 g) were metered in succession and the die was closed. After mixing, visually and physically homogeneous samples were removed. This material was then granulated. The resulting morphology is shown in
As a further reference for the microgel-based TPE-As according to the present invention, pure PA (Grilamid L 1120 G (sample 3)) and pure NBR vulcanization product (Perbunan NT 3465 crosslinked with 5 phr of Poly-Dispersion E(DIC)D-40 (sample 4)) were used.
Injection Molding
Rods were injection-molded from the granules of the TPE-As and the pure thermoplastics. This was carried out using a laboratory injection-molding machine (Injektometer, Göttfert) at a machine temperature of 230-240° C., a pressure of 10 bar and a tool temperature of 120° C. The residence time of the sample was about one minute in the machine and in the tool.
Preparation of the Test Specimens
S2 standard rods were prepared from all the samples. This was carried out by cutting in the case of the pure thermplastic materials (sample 3). The standard rods of all the other samples were stamped out. All the prepared standard rods had a width of only 10 mm in the head region because the injection-molded blanks had a diameter of only 10 mm. The thickness of the standard rods is 4 mm.
Physical Testing
Tensile Test
The tensile test of the samples was carried out on S2 standard rods (see above) according to DIN 53504. The testing was carried out using a universal testing machine (type 1445, Frank) with optical length pick-ups. The measuring range of the force pick-up is 0 to 2000 N. The results of the measurements are summarized in Table 1.
The breaking elongation and stress at break values of the microgel/PA-based TPE-As were between the values of the pure constituent elastomer and thermoplastic phase. The level of properties of a conventionally prepared TPE-A having the same polymers (sample 5) can be reached. When the microgel OBR1102C (Preparation Example 1) having the high ACN content was used, the stronger TPE-A was achieved.
Swelling
The swelling of the samples was carried out on S2 standard rods (see above) according to DIN 53521 at a temperature of 125° C. and for a duration of 4 days in the reference test liquid IRM 903 (Industry Reference Material, highly hydro-treated heavy naphthene distillate). When the contact time has elapsed, the test specimens were tempered by storage in unused test agent for 30 minutes at 23° C.
The results of the swelling test in oil are summarized in Table 6. The swelling in oil of the microgel/PA-based TPE-As was very slight. The swelling resistance of a conventionally prepared TPE-A containing the same polymers (PA (Grilamid L 1120 G) from EMS-GRIVORY and (Perbunan NT 3465) from BAYER AG) (sample 5) was exceeded by far. When the microgel OBR1102C having the high ACN content was used, the lower swelling in oil was noted.
As illustrated in the Examples above according to the present invention, the microgel domains, that is to say the domains of the elastomer phase, are smaller and more uniform by orders of magnitude than the elastomer domains, formed by dynamic vulcanization, of conventional dynamically vulcanized TPVs, both with (>5 to 30 μm) and without phase mediator (>10 to 35 μm,
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 103 45 043.2 | Sep 2003 | DE | national |
