CH633026A5 - INTERNAL MIXTURE, MOLD MIXTURE, A METHOD FOR THE PRODUCTION OF A MOLDED BODY AND MOLD OBTAINED THEREOF, USED AS A BURN-OUT MOLD BINDING AGENT. - Google Patents

Description

The present invention relates to improved moldings made of sintered particulate solids and to processes and materials for producing these moldings from particulate materials, the moldings having a previously unknown physical cohesion in the uncured, “green” state and having excellent dimensional accuracy as end products, i.e. after burning and sintering. In particular, this invention relates to moldings which are obtained by mixing particulate solids with a thermoplastic material serving as a burnable binder, shaping the mixture into the unfired molded body, burning out the binder and sintering the particulate solids into a uniform solid mass. The invention further relates to a process for the production of such moldings and the new temporary binders which are used in the production of these moldings. The invention can be applied to any particulate solids that can be sintered, the term being defined below.

The burn-out binders according to the invention are plasticized resins and contain as the most important binder resin at least 50% by weight of a thermoplastic, rubber-like block polymer with the physical properties specified below and the structural formula AB 4AB-) r | A, in which tj is zero or an integer, A linear or branched polymer which is glassy or crystalline at 20 to 25 ° C and has a softening point between 80 ° C and 250 ° C, and B is a polymer whose chemical composition is different from that of polymer A and at temperatures between 15 ° below the softening point of A and 100 ° C above the softening point of A as an elastomer. A detailed description of the block polymers, their manufacture, composition and physical properties can be found in the article "Synthesis of Block Polymers by Homogeneous Anionic Polymerization" by L.J. Fetters, Institute of Polymer Science, University of Akron, Akron, Ohio in the Journal of Polymer Science, Part C, No. 26, pages 1-35 (1969) and in «Rubber-

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Related Polymers, I. Thermoplastic Elastomers »from W.R. Hendricks and R.J. Enders, Elastomers Technical Center, Shell Development Company, Torrance, California, published in Rubber Technology, Second Edition, Chapter 20, pages 515-533, published by Van Nostrand Reinhold Company, New York, Cincinnati, Toronto, London and Melbourne (1973 ). For the details of the vacuum reaction apparatus and the procedures for carrying out anionically initiated polymerizations, with the aid of which block polymers can be prepared, reference is made to “Procédures for Homogeneous Anionic Polymerization” by Lewis J. Fetters, Journal of Research of the National Bureau of Standards , Vol. 70A, No. 5, September-October 1966, pages 421-433 and "The Association of Poly-styryllithium, Polyisoprenyllithium, and Polybutadienyllithi-um in Hydrocarbon Solvents" by Maurice Morton, Lewis J. Fetters, RA Fett and J.R. Meier, Institute of Polymer Science, published in Macromolecules, Vol. 3, pages 327-332, American Chemical Society (1970).

The inventive idea is, in particular, that burnable binders are used for the production of sintered shaped bodies from particulate solids, which binders during processing, i.e. when mixing and shaping, behave thermoplastic, because they flow well at the temperatures of these operations and still remain solid when the unfired molded article is stored at room temperature and when this pressed article is first heated until the sintered article has taken on its permanent shape Substances behave. This is achieved by the elastomeric block polymers described above and in detail below and by the oil or wax or a mixture of oil and wax which are present as plasticizers. The oil is used to facilitate processing by lowering the viscosity of the elastomer, which is of particular importance when using shear forces at the temperatures prevailing during mixing and deformation. Accordingly, if the temperature of the material is raised above the glass transition temperature of the elastomeric block polymer, i.e. the glass transition temperature of the A segments in the block polymer, and shear forces are applied, the material becomes less viscous and flows like a thermoplastic resin. If the mixture is cooled to room temperature after shaping, the A segments, such as polystyrene, tend to agglomerate to form areas ("domains") and to adopt a structure that physically behaves like a crosslinked polymer. The oil and / or wax is expelled when it is subsequently heated to a higher temperature. Since there are no shear forces in this heating operation, the areas of the A-segments remain in their agglomerated shape and accordingly retain the shape of the unfired body during the burning out of the binder, and this shape is then sintered by the integrity of the structure of the remaining ones Maintain particulate solids.

The individual components of the mixture are to be explained separately below.

A. The main binder resin

The most important binder resin is a block polymer with the structural formula AB - (AB-) t | A, where t | Zero or an integer and A and B are different polymers. This block polymer makes up at least 50% by weight of the total polymer material in the binder. For the purpose of simplification, these polymers will first be discussed with reference to their simplest form, where r | stands for zero, i.e. the polymer is a block polymer of

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tural formula A-B-A represents. It goes without saying that the descriptions of this three-block polymer also apply to those block polymers in which t | 1 or a larger number means, even if certain segments A are not terminal and certain segments B are not in the middle.

The segments A of these block polymers are linear or branched polymers, which at room temperature, i.e. at 20 to 25 °, glassy or crystalline and whose softening point is in the range of 80 ° C to 250 ° C. When the molded article is in the green body state, i.e. is in the unfired state, namely after shaping and before the binder burns out and at room temperature, for example 20-25 ° C., the segments A generally have a module greater than 109 dynes / cm 2. If the block polymers are prepared by the method of anionic polymerization, suitable materials for the segments A are, for example, the following, the list being not to be interpreted as a restriction, since the person skilled in the art can find other polymers due to the necessary physical and chemical peculiarities: polystyrene, polyacrylonitrile , Poly-p-bromostyrene, polymethyl methacrylate, poly-alphamethylstyrene, poly-2-methyl-5-vinylpyridine and poly-4-vinylpyridine. Other block polymers which are suitable for the purposes of the invention can advantageously be obtained by other synthetic methods, for example by polycondensation, by radical-initiated polymerization and cationic polymerization, based on the procedures known per se. When producing these other syntheses, the following may be mentioned as examples of further segments A: polyvinyl acetate, polyester, polyamides, polyurethanes, polyvinyl chloride, polypropylene, polysulfones, polyphenylene sulfide, poly-4-methylpentene-1 and polyvinyl alcohol and similar polymers, the nature of which, based on the above examples, will be familiar to the person skilled in the art.

The segment B of these polymers A-B-A is formed by rubber-like, flexible, glassy or crystalline polymers, the terms used being defined below, and behave as elastomers at the processing temperatures. The segment B can be straight-chain or branched and, in some embodiments, can also be chemically crosslinked. In these embodiments, a crosslinking agent is added when mixed and made to react when deformed. When the molded article is in the uncured state and at room temperature, it exhibits a modulus of about 106 to 5 x 107 dynes / cm2 when segment B is a rubbery polymer. If segment B is a polymer that is flexible at room temperature, the module is in the range of about IO7 to 109 dynes / cm2. If segment B is glassy or crystalline at room temperature, a modulus above about 109 dynes / cm2 is observed. If the block polymers are prepared by anionically initiated polymerization, suitable substances for the segments B are the following, the list being not intended to be restrictive because the person skilled in the art can find similar polymers on the basis of the physical and chemical properties of the polymers mentioned: polybutadiene, polyisoprene, polydimethylbutadiene , Polyethylene oxide, polyisopropyl acrylate, polyoctamethylcy-clotetrasiloxane and polytetrahydrofuran. As already indicated above, block polymers which are suitable for use in the present invention can also advantageously be obtained by other synthetic methods, for example polycondensation, by free radical polymerization and cationic polymerization. When using these other synthetic routes, suitable substances for segments B are the following: polyisobu

lene, ethylene propylene rubber, ethylene propylene-diene terpolymers, butyl rubber, chlorobutyl rubber, bromo-butyl rubber, chlorosulfonated polyethylene, Epichlorhy-inside rubber, fluorocarbon rubbers, silicone elastomers such as polydimethylsiloxane, further polyurethane elastomers and polypropylene oxide elastomers and similar polymers the person skilled in the art can find them on the basis of the physical and chemical properties of the polymers mentioned in the list above.

The molecular weight of segments A and segments B of the block polymers suitable for use in this invention will vary with the particular polymer segment present, as is known to those skilled in the art, but the physical properties must conform to the definitions given above. For example, if the block polymer has segments A made of polystyrene and segments B made of polybutadiene, the polystyrene segments preferably have molecular weights above about 20,000 and at least two such segments have molecular weights above about 10,000, whereas the polybutadiene segment or the corresponding segments preferably have molecular weights below about 80,000 and at least one such segment has a molecular weight above about 40,000. The lower limit for the molecular weight of the two segments A is determined by the minimum chain length of the segment A, which is necessary to ensure the formation of a heterogeneous phase, while the upper limit of the segments A is determined by the viscosity of the two segments A and B. when this viscosity begins to affect domain formation or processability.

In order to be able to mix the block polymer with each of the other constituents of the burnable binder or with the particulate solids, the block polymer must be heated to at least the softening point of the segments A. When the block polymer has been mixed with the other constituents of the binder, the oil and / or the wax serve as plasticizers and allow the subsequent processing, for example the deformation, etc., at a temperature below the softening point of the segments A. The lower temperature limits of this further processing depend on the chemical composition of the segments A, the extent of the plasticization and the plasticizing properties of the plasticizer. In any case, the lower limit of the processing temperatures of these binders is above the temperature at which the segments B of the block polymer no longer behave as elastomers. In general, the mixing temperature is in the area between 15 ° C below the softening point of the segments A of the block polymer used and 70 ° C above this softening point, unless the mixing is carried out in the absence of gaseous oxygen, in which case the temperature to 100 ° C above the Softening point can be increased. Accordingly, the deformation temperatures of the various suitable block polymers are between 65 ° C and 320 to 350 ° C in the absence of air or other gaseous oxygen. The deformation, with the exception of embossing, can be carried out at temperatures above the softening point of the segments A. The embossing can be carried out at the same temperatures or even below the softening point of the segments A.

In the thermoplastic block polymers of structure A-B-A, the terminal segments A, which are rigid at room temperature, combine to form large aggregates, which are referred to in the literature as "domains". At the normal handling temperatures of the

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molded article after the last deformation in the state before hardening, for example at room temperature or slightly above, these domains are hard and define the ends of the segments B. This definition of the end segments in connection with chain entanglements brings about a physical networking, which protects the unfired article from changes in shape during handling. At higher temperatures, the terminal segments A can soften and be displaced by attacking forces, whereby the polymer begins to flow. This condition enables mixing, shaping, etc., which operations are necessary or possible steps in the production of the uncured molded body. On cooling, an uncured molded body is then obtained which has a hitherto unknown high resistance to physical deformation before heating,

which leads to the burning out of the binder and to the sintering of the shaped body.

B. The plasticizer

The burn-out binder further contains a plasticizer, which is either an oil or a wax or a mixture of oil and wax. The oils and waxes used for this purpose are naphthenic or paraffinic substances or a mixture of paraffinic and naphthenic substances. They are sufficiently volatile that they can be removed easily and quickly when the binder is burned out, but are insufficiently volatile to evaporate in substantial amounts when mixed and / or shaped. The evaporation loss during mixing and / or shaping is preferably less than 20 and in particular less than 10% by weight.

In terms of their function, the oils and / or waxes should be compatible with the rubber-like phase of the most important binder resin if it becomes rubber-like due to plasticization at a temperature slightly below the softening point of the segments A. This gives the binder the ability to absorb large amounts of fillers while remaining strong and flexible.

At least 75% by weight of the oils used as plasticizers boil in the range from 288 ° C to 560 ° C, preferably in the range from 288 ° C to 463 ° C. They have viscosities at 98.9 ° C. in the range from 30 to 220 Saybolt universal seconds (hereinafter abbreviated as SUS), preferably in the range from 35 to 155 SUS and in particular in the range from 35 to 80 SUS. The aniline point of the oils is in the range of 76.6 to 123.8 ° C. The oils can be raffinates from the petroleum industry or vegetable or animal oils and can contain or consist of low molecular weight synthetic polymers such as polystyrene, poly-alphamethylstyrene or a polyolefin.

The waxes used have melting points in the range of 54.4 to 76.6 ° C. At least about 75% by weight of these waxes boil at temperatures in the range from 315 ° C to 483 ° C. The waxes can come from the petroleum refinery or can be vegetable or animal waxes as well as synthetic polymers such as low molecular weight polyolefins.

C. Contingent components

In certain embodiments, the burn-out binders according to the invention advantageously contain certain additional substances such as further resins, further elastomers and antioxidants.

Additional resins are valuable in embodiments in which there is a need to increase the rigidity of the unfired molded article, but the flowability at processing temperatures must still be ensured.

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Suitable additional resins are representatives of the abovementioned polymers which are used as segments A in the block polymers, resins which are similar to those which are suitable for use as segments A and have an affinity for the segments A of the block polymers used, for example coumarone indene -Resins and poly-indene with block polymers which have polystyrene as segments A, and resins with an affinity for the segment or segments B in the block polymers, for example polyterpenes with polybutadiene segments B. It should be mentioned that resins with an affinity for the segments A or B of the block polymer can also be polymers which are valuable for use as segments A or B in other embodiments if they meet the requirements defined above for the segments A or B.

Additional elastomers are valuable in embodiments in which one wants to increase the tensile strength of the unfired molded article. Suitable additional elastomers are, for example, natural rubber and synthetic elastomers such as polybutadiene, polyisoprene, etc.

Antioxidants have the property of delaying an oxidative degradation of the block polymers during mixing and thereby avoiding a loss in strength of the unfired molded article. The antioxidant also allows the binder to escape faster when burned out by reducing the surface oxidation which can clog the surface of the article. Suitable antioxidants are, for example, 2,6-ditert.butylphenol, a polymerized 1,2-dihydro-2,2,4-trimethylquinoline, 2-mercaptobenzimidazole, tetrakis [methylene-3- (3 ', 5'-ditert. butyl-4 '-hydroxy-phenyl) -propionate] -methane etc., where the list can be expanded as desired.

In carrying out the invention, process aids which are usually used in the shaping of polymeric substances are valuable for improving the separation properties of the unfired article from the individual shaping machines with which the unhardened article comes into contact and for improving the flow properties of the mixture of binder and filler extrusion, injection molding, transfer molding, etc. Suitable process aids include, for example, methyl acetyl ricinoleate, stearic acid, polyethylene, polyethylene wax, mixtures of natural waxes and wax derivatives, vegetable fats, partially oxidized polyethylene, etc.

D. Particulate matter

The present invention can be applied to any particulate that is sinterable in accordance with the definition given below. Examples of such substances are ceramic powders such as cordierite powder, alumina, B-spodumene, crystalline or molten silicon dioxide, mullite, kyanite, zircon earth, beryl earth, magnesia, titanium earth, chromium oxide, iron oxide and complex oxides from two or more of the above-mentioned oxides, metal powder such as iron , Iron alloys, copper, copper alloys, aluminum, aluminum alloys, silicon, silicon alloys, nickel super alloys, cobalt super alloys and stainless steels, intermetallic compounds such as nik-kelaluminide and molybdenum silicides, carbides such as silicon carbide, tungsten carbide and iron carbide, nitrides such as silicon nitride and boron nitride as well as substances such as metal nitride and boron nitride Metal nitrides.

An advantage of these binders is that they can absorb large amounts of particulate solids as fillers. The deformable mixture contains 30 to 70

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preferably 50 to 65% by volume of particulate solids, the remainder consisting of the burn-out binder.

E. Properties of the constituents of the binder

The proportions of mainly binder resin or elastomer, i.e. the block polymer, and the plasticizer, i.e. oil, wax or oil and wax can fluctuate within wide limits. If the binder consists only of block polymer and plasticizer, it contains 10 to 90, preferably 30 to 85, in particular 45 to 65% by weight of block polymer, based on the total weight of block polymer and plasticizer, the plasticizer representing the remaining amount, i.e. 90 to 10, preferably 70 to 15 and in particular 55 to 35% by weight, but it should be noted that when using a wax, this wax expediently does not exceed a proportion of about 70% by weight of the binder.

It is possible to replace part of the resin defined above, namely at most below 50% by weight, in particular between 0.1 and 30% by weight, with an equivalent amount by weight of another polymer which meets the definitions for segment A in the above formula.

It is also possible to replace part of the resin defined above, namely less than 50% by weight, in particular between 0.1 and 30% by weight, with the equivalent amount by weight of another polymer which has the properties of the segments B in corresponds to the above formula.

Finally, it is possible to use a proportion of the resin defined above, in particular between 0.1 and 40% by weight, below 50% by weight, by the equivalent amount by weight of a resin having the structural formula X - [B (AB) t | AJn ', where X is a multivalent low molecular weight link or a polymer A or B, T | stands for zero or an integer and t), for an integer greater than 2 and A and B, as above for segments A and B of the resin of the formula AB - (AB-) t | A are defined. The link X is a multivalent connection, i.e. with more than two functions, and is composed of two or more elements from the following list: carbon, hydrogen, oxygen, halogens, nitrogen, silicon, phosphorus, sulfur. When using anionic polymerization, the link is expediently used as a halogen-functional compound. The following list is given for the purpose of illustration and is not restrictive: silicon tetrachloride, l, 2,4-tri (chloromethyl) benzene, l, 2,4,5-tetra (chloromethyl) benzene, bis- (trichlor -silyl) -ethane, cyclic trimer made of phosphonitrile chloride, benzene, chloromethylated polystyrene, trichloromethylsilane and silicon tetrachloride. The use of these links is described in the aforementioned article "Synthesis of Block Polymers by Homogeneous Anionic Polymerization" by L.J. Fetters discussed and explained. If, as mentioned above, the block polymers are produced on other synthetic routes, other links can be used. In the case of free-radical-initiated polymerization, a polyvalent compound can be used which starts the polymerization of segment B, for example if segment B is polyethyl acrylate, and reacts with segment B, for example a branched azonitrile, as can be obtained by reacting trimethylolpropane with a Diiso-cyanate such as toluene diisocyanate with a glycol such as polyoxypropylene glycol. In the case of polycondensation, it is possible to use a multifunctional compound which reacts with segment B, for example trimellitic anhydride. In the case of the cationically initiated polymerization, polyvinyl chloride can be reacted with trimethylaluminum, the polymerization of segment B being started, for example if this segment B is polyisobutylene, and reacting with segment B. As described above, the symbol X can represent a polymer A, a polymer B or a low molecular weight link. For the purposes of this invention and for the use of such block polymers in the burn-out binders of a deformable mass, the replacement of a polymer A or polymer B by a link X does not appreciably affect the physical properties of the block polymer. In such block polymers, links are usually used and are sufficiently known to the person skilled in the art, as can be seen from the literature reference cited above. According to this teaching, the selection of the respective link for a specific block polymer is within the knowledge of the person skilled in the art.

Taken together, the replacement of the block polymers with such type A polymers, such type B polymers and the other types of block polymers mentioned should account for less than 50% by weight of the main binder resin, namely the initially defined block polymer.

The following table shows preferred ranges of ingredients when additional substances are used.

Burnable binders with contingent components

Material area, preferred especially

% By weight of the area, more preferred

Binder% by weight of the range,

Binder% by weight of the binder

Block polymer

10-90

30-

-85

45-

-65

Plasticizers

90-10

70-

-15

35-

-55

oil

0-90

0-

-70

0-

-55

wax

0-70

0-

-30

0-

-10

Second resin

0-40

0-

-25

0-

-15

Second elastomer

0-40

0-

-15

0-

-10

Antioxidant

0-7

0-

-5

0-

-3

Processing aids

0-15

0-

-10

0-

-7

medium

F. Definitions

The term “sintering” describes the more or less pointwise union of crystalline or amorphous particles under the action of heat and with the formation of a solid body.

The term “deforming” or “deforming” as used herein describes any shaping processes known in the art, for example extrusion molding, injection molding, compression molding, lamination with compression molding, transfer molding, compression molding, deformation by displacement, blow molding, calendering and embossing.

The term “further processing”, insofar as it relates to the present invention, is understood to mean mixing and / or shaping.

The expression “green molded article” or “unfired molded article” denotes a molded article which consists of an intimate mixture of sinterable particulate solids and a binder.

The molecular weights given in this description relate to the average molecular weight Mn.

A room temperature is a temperature in the range of 20-25 ° C.

The term "softening point" describes the glass transition temperature (see below) on the one hand if the polymer is glassy, and on the other hand the melting point "

is

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point of the crystals or crystallites if they are crystalline polymers.

Under the expression «glass transition temperature»,

which is given the symbol Tg is to be understood as the temperature below which a non-crystallizing polymer changes into the state of a supercooled liquid, i.e. in the glassy state.

The term “crystallite melting point”, which is denoted by the symbol Tm, defines the temperature at which a crystalline polymer melts and does not become crystalline.

Both the glass transition temperature and the crystallite melting point represent transition areas, so strictly speaking they are not sharp points, but are used as practical parameters which are sufficiently defined and precise for the description and implementation of the invention and which at most require routine tests but do not require inventive step.

The term “glassy polymer” or “glassy polymer” refers to a non-crystallizing polymer that is below its glass transition temperature at room temperature.

The term “rubber-like polymer” refers to a non-crystalline polymer that is above its glass transition temperature at room temperature.

The term “crystalline polymer” describes a crystallizing polymer that is below its crystallite melting point at room temperature.

Finally, the term "flexible polymer" means a polymer that is at room temperature in the transition region between a glassy or crystalline state and an elastomeric state, i.e. to a rubber.

It is known to those skilled in the art that proportions of certain polymer masses can exist in more than one state at room temperature and not be in a transition state from one to another, for example if it is a polymer mass in which a proportion is as above defined rubber-like polymer and a second portion is a crystalline polymer as defined above. In such cases, the definitions above relate to the predominant proportion of such a polymer mass.

Explanatory examples are then given, in which, unless stated otherwise, the materials used correspond to the definitions given above, which are essential to the invention.

example 1

First, an elastomeric block polymer ABA, which is referred to below as “elastomer”, is produced, namely by anionically started polymerization in a high vacuum system and according to the general procedures for anionic polymerizations, which are described in section 2 (experimental procedures) of the above-mentioned article “Procédures for Homogeneous Anionic Polymeriza-tion »by LJ Fetters are described. In addition, all vessels are connected to the vacuum line via an oil trap, as specified in the aforementioned article "The Association of Polystyryllithium, Polyisoprenyllithium, and Polybutadienyllithium in Hydrocarbon Solvents" by M. Morton and co-workers.

The reaction vessel is first flamed in a vacuum. The reaction vessel is then cooled, disconnected from the vacuum line and rinsed with a solution of lithium ethyl in n-hexane, all impurities which could break off growing polymer chains being inactivated by reaction. The monomers and solvents used to make the elastomer are

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according to the article by L.J. Fetter's way of working cleaned.

The reaction vessel is reconnected to the vacuum line. A solution is then added to the reactor which contains 0.036 gram of lithium ethyl in 3 ml of benzene. 370 ml of benzene are added to the reactor. Then 15 g of monomeric styrene are distilled through a breakable seal into the reaction vessel onto the benzene. The contents of the vessel are then cooled to a temperature between -65 and -78 ° C using a cold bath made of dry ice and alcohol. Then the reaction vessel is separated from the vacuum line and the contents of the vessel are allowed to warm up.

After thawing the content, add 0.65 g of anisole in 4 ml of benzene and combine by shaking. Polymerization of the styrene is allowed to proceed at 30 ° C for 4 hours. Then the reaction vessel is reconnected to the vacuum line and 60 g of butadiene are distilled in. The contents of the vessel are cooled with liquid nitrogen and the connection to the vacuum line is closed. The mixture is allowed to thaw again and the butadiene is polymerized after stirring at 30 ° C. for 16 hours.

The mixture is then cooled to the temperature of a cold mixture of dry ice and alcohol, and after connecting the reaction vessel to the vacuum line, a further 15 g of styrene are distilled in. Now the reaction vessel is again separated from the vacuum line, the contents are thawed and mixed, and the styrene is polymerized at 30 ° C. for 4 hours. The elastomer in the reactor is then coagulated by slowly pouring the benzene solution into methanol, which contains a small amount of phenyl-beta-naphthylamine as a stabilizer of the elastomer. The elastomer is then dried and is ready for use as a binder resin.

This polystyrene-polybutadiene-polystyrene elastomer, which contains about 33.3% by weight of polystyrene, is rolled out in a quantity of 14.5 g on a roller mill heated to 150 ° C. to form a strip. About 10 g of a cordierite glass frit is then added to the rolling mill and worked into the strip. 12.5 g of a commercially available paraffinic mineral oil Flexon 845 - a trade name of the Exxon Company, USA, are mixed with 50 g of the cordierite frit mentioned with stirring. This oil has the following properties: specific gravity (15.6 / 15.6 ° C) of 0.8649-0.8811; ASTM color 1-4; Viscosity at 98.9 ° C: 43.4-61.5 SUS; Aniline point: 104-115.5 ° C and aromatic content (silica gel adsorption) of 14.9-16.1% by weight. About half of the mixture of oil and cordierite is placed in the roller mill and mixed with the belt. As the viscosity decreases, the roller temperature is lowered to 143 ° C to reduce the evaporation of the oil. The rest of the dry cordierite (40 g) and the rest of the mixture of cordierite and oil are alternately fed into the rolling mill in portions of a few grams. When the mixing is complete after about 20-30 minutes, the mixture is removed as a film from the roller mill and cooled.

This mixture is used to produce corrugated foils by compression molding. The films obtained from the above-mentioned mixer are laminated on a rolling mill, the rolls of which are heated to 143 ° C., and the roll gap is gradually reduced until a film with a thickness of 0.76 mm is obtained. A square with a side length of 9 cm is cut out of this 0.76 mm thick film, and this sample is suitable for producing a ribbed body due to its excess material. The punch of a press with a diameter of 9.2 cm and the lower half of the press mold are heated to 121 ° C. The sample described above

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is then placed on the preheated lower half of the mold for 15 seconds, and then the non-preheated upper half of the mold is placed on the sample and lower mold half. Both parts of the mold are coated with polytetrafluoroethylene. Then the press is closed and a pressure of 140 atm is applied. This press pressure is maintained for 15 seconds. It is then depressurized and the ribbed film is removed from the mold.

This sample of a ribbed film is then heated according to the following cycle:

Table I

Heating step temperature, ° C

Time, hours

1 71

4th

2 127

4th

3 204-232

4th

Now the molded article obtained is as follows

Burned scheme:

Table II

Burning process temperature rise

Temperature range

° C / h

° C

1 333-444

ZT-1200

2 55.5

1200-1370

Finally, you get a firm, dense, ribbed cordierite sheet.

Example 2

The procedure of Example 1 is repeated with the only difference that the elastomeric block polymer used is a commercial three-block polymer (ABA) with a polybutadiene segment in the middle and two terminal polystyrene segments. This block polymer contains 30% by weight of polystyrene and bears the name Kraton 1101, a trade name of the Shell Oil Company. This block polymer has a specific gravity of about 0.95 and an intrinsic viscosity of about 1.00 dl / g (measured at 30 ° C in toluene).

A firm, dense, ribbed sheet of cordierite is obtained.

Example 3

The procedure of Example 2 is repeated with one difference. Thereafter, the elastomer, the oil and the frit are first stirred together and then homogeneously mixed in a Banbury mixer which had previously been heated to 154-160 ° C for 15 minutes. The mixture obtained is then processed into skins on a two-roll mill, the rolls of which have been preheated to 143 ° C. After mixing on the rollers for 2-5 minutes, the skins are removed and cooled. You are now ready for compression molding according to the previous examples. Solid, dense discs of cordierite are obtained.

Example 4

The procedure of Example 3 is repeated with the following differences: 29.0 parts by weight of the elastomeric three-segment polymer made of polystyrene-poly-butadiene-polystyrene are mixed with 27.3 parts by weight of a paraffin wax with a melting point of 54.4 ° C. and 200 parts by weight a cordierite glass frit. A firm, dense cordierite disc is obtained. The paraffin wax also serves as a processing aid and plasticizer and allows smoother extrusions. It further increases the strength of the unfired molded article.

Example 5

The procedures of Example 3 are repeated, except that the following deviations are made: Test bars are produced using a pressure stamp injection molding machine. The housing and the nozzle of the injection molding machine are heated to 160 ° C, and this temperature is maintained by regulation. A mold for injection molding two test bars is preheated to 37.8 ° C and held together under a pressure of 1055 atm. Pieces weighing about 20 g, cut out of the above-mentioned fur, are placed in the injection cylinder and allowed to warm up for about 5 minutes. The material is then injected into the mold while maintaining the piston pressure of 56 atm for one minute. The test bars are then first heated and then fired, according to the cycles given in the previous examples. This gives firm, dense cordie bars.

Example 6

The procedure of Example 2 is repeated with the following deviations: In a screw extruder with a clear width of 50.5 mm, a film is first produced. For this purpose, the mixture of binder and cordierite is brought into the form of a lozenge and the lozenges are filled into the feed hopper of the extruder. They are then passed through the extruder and extruded through a slot die with a width of approximately 100 mm and a slot width of approximately 0.5 mm. The following temperatures are maintained in the extruder: feed area 80 ° C, screw area 121 ° C and die 150 ° C. The film strip is then cooled to room temperature and stored temporarily. The tape is flexible and is suitable for subsequent processing such as cutting, winding and embossing, and after firing results in a firm and tight cordierite tape.

Example 7

The procedure of Example 2 is repeated, but another elastomer is used, namely Kraton 1102, a commercially available block polymer with three segments, polystyrene-polybutadiene-polystyrene. This elastomer contains about 28% by weight of polystyrene and has a lower viscosity, namely an intrinsic viscosity of 0.84 dl / g (30 ° C in toluene), than the elastomer in the previous examples, which is 30% by weight of polystyrene contains. Because of the lower viscosity of the elastomer, the entire binder also has a lower viscosity and is easier to process. The product obtained is less stiff in the unfired state, but results in a firm, tight, ribbed cordierite disc after firing.

Example 8

The procedure of Example 2 is repeated, but a commercially available block polymer consisting of three segments, namely polystyrene-polyisoprene-polystyrene from the Kraton 1107 brand, which contains about 14% by weight of polystyrene, is used as the elastomer. When mixed with the oil and frit, this elastomer gives a blend with a lower modulus and lower strength in the green state than in the previous examples. One s

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However, after firing, it still receives a firm, dense, ribbed cordierite disc.

Example 9

The procedure of Example 2 is repeated,

however, the product used is Kraton GX-7820, a commercially available, elastomeric block polymer with three segments, in which a polyethylene-butylene rubber is present as the central segment and polystyrene as the terminal segments. The polymer contains 12-14% by weight polystyrene. Instead of the oil used in Example 2, Shellflex 790, a paraffinic oil, is used as the plasticizer. Shellflex is a trademark of Shell Chemical Company. The use of this oil reduces the evaporation that would occur because higher mixing temperatures, namely approximately 177 ° C., are more suitable for processing this plasticized elastomer. The unfired molded body is stiffer than that of Example 2, and the distribution of the filler is not quite as smooth. The ribbed disc obtained after firing is less dense and has a lower strength than that obtained according to the above examples.

Example 10

The procedure of Example 2 is repeated, but the weight ratios of the elastomer, the oil and the cordierite frit are as follows: 2.75 parts of elastomer, 22.77 parts of oil and 100.00 parts of frit. This example illustrates the approximation of the minimum amount of elastomer and the maximum amount of oil in the binder. The green blank is soft and has little strength and weak cohesion. The ribbed disc obtained after firing is less dense and less strong than that obtained in the previous examples.

Example 11

The procedure of Example 2 is repeated, but the parts by weight of the elastomer, the oil and the cordierite frit are as follows: 24.78 parts of elastomer, 2.53 parts of oil and 100.00 parts of frit. This example illustrates the approximation of the maximum amount of elastomer and the minimum amount of oil in the binder. The mixture is stiffer and is less easy to process than that given in the examples above.

Example 12

The procedure of Example 2 is repeated, but using paraffin wax with a melting point of 54.4 ° C. instead of the oil in the binder as a plasticizer, and the weight ratios of elastomer, wax and frit being the following: 8.26 parts of elastomer, 19.07 parts wax and 100.00 parts frit. The mixture gives a firmer green blank with less tendency to crack during heating and burning.

Example 13

In a closed rolling mill, a commercially available polystyrene with an amount of 12.17 g is processed into a fur, and the rolling mill has previously been heated to 160.degree. The polystyrene has a specific gravity of about 1.05, a Vicat softening point of about 97 ° C and a melt flow viscosity of about 3.5 g / 10 min (ASTM-D123 8 mode of operation G). The temperature in the rolling mill is reduced to 154.5 ° C. and 12.39 g of the elastomer made of polystyrene, polybutadiene and polystyrene according to Example 2 (30% by weight polystyrene) are added and mixed in the rolling mill with the polystyrene. 2 g of the 100 g of cordierite glass frit to be used are then placed in the rolling mill in order to stabilize the skin. Now stir 3.8 g of the paraffinic mineral oil shown in Example 2 with 50 g of the cordierite frit. About half of this mixture of oil and cordierite is added to the rolling mill and worked in. The remaining dry cordierite and the remaining mixture of cordierite and oil are then incorporated by alternately adding a few grams of these two components. After completing the incorporation after about 20-25 minutes, the mixture in the form of skins is removed from the rolling mill and allowed to cool. Further processing is carried out according to the instructions in Example 2. A solid green blank is also obtained in this way, but with improved green strength and better dimensional stability when burned out. The processability of the mixture improved as the mixing progressed.

Example 14

10.67 g of natural rubber (No. 1 ribbed smoke sheet) is worked through in a closed roller mill that has been preheated to 150 ° C. The fur obtained is then removed from the roller mill and set aside. At the same temperature, 13.77 g of the elastomer from Example 2 are worked through in the same rolling mill. Then half of the natural rubber is fed into the rolling mill. The rest of the dry cordierite and natural rubber are then incorporated by alternately adding a few grams of one and then the other ingredient. When the mixing is complete after 20-25 minutes, the mixture is taken out of the mill as a skin and allowed to cool. Further processing takes place according to the technique given in Example 2. The use of natural rubber results in improved tensile strength in the green blank, which has a lower modulus than that according to Example 2.

Example 15

The procedure of Example 2 is repeated with the following changes: the total amount of cordierite is added initially and no frit is added separately mixed with the oil. The weight ratios of elastomer, oil and cordierite are as follows: 27.54 parts elastomer, 25.30 parts oil and 2.72 parts frit. An extremely soft mixture is obtained, with the tendency to provide a porous ceramic molded body after firing.

Example 16

The procedure of Example 1 is repeated with the following changes: The weight ratios of elastomer, oil and glass frit are as follows: 12.39 parts of elastomer, 13.92 parts of oil and 123.81 parts of frit. With this high content of glass frit, the unfired blank is very stiff and very brittle and is difficult to process further.

Example 17

The procedure of Example 2 is repeated with the following changes: The weight ratios of elastomer, oil and frit are as follows: 13.77 parts of elastomer, 12.53 parts of oil and 100.00 parts of frit. In addition, the mixture contains 0.14 part by weight of an antioxidant, namely 4,4'-methylenebis (2,6-ditert.butylphenol). The use of the antioxidant results in better retention of strength when mixed and better resistance to sagging when the binder burns out.

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Example 18

The procedure of Example 2 was repeated with the following changes: The weight ratios of the constituents of the binder and the frit are as follows: 13.77 parts of elastomer, 11.39 parts of oil and 100.00 parts of frit. The mixture also contains 1.36 parts of methyl acetylricinoleate as processing aid. The use of the processing aid results in better processing during calendering and extrusion.

Example 19

Sintered modified tubes of beta alumina are produced by extruding the elastomer and oil of Example 2, a wax, an antioxidant and particulate beta alumina in tube form. The composition of the extruded mixture is as follows:

Table I

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Weight

parts

Example 2 elastomer

4.7

Example 2 oil

3.2

Paraffin wax (melting point 57.2 ° C)

3.5

Antioxidants,

Poly-1,2-dihydro-2,2,4-trimethylquinoline

0.5

Pul shaped lithium-modified beta-alumina

(9.0% Na, 0.8% LiîO and 90.2% AhOa)

50.0

The substances mentioned are mixed at 154 ° C on a two-roll mill. The mixture is shaped into a tube in an extruder. The nozzle temperature is 154 ° C and the chamber temperature is 171 ° C. The tubes are then burned out and sintered according to the following scheme:

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range, ° C

1

50

100-700

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Hold for 15 hours

700

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Course of 3 hours

The tube obtained is placed in a platinum tube and mechanically closed. The sealed tube is then placed in an oven which is heated to 1100 ° C for 15 hours. The temperature is then increased from 1100 ° C. to 1570 ° C. in the course of 4 hours and 45 minutes, held at this level for 15 minutes and then lowered to 1420 ° C. in the course of 15 minutes. Then one maintains this temperature for 8 hours and then cools down to 360 ° C in the course of 7 hours, and finally the tube is allowed to come to room temperature in air.

Example 20

The procedures of the above examples are repeated with the only change that particulate alumina is used instead of cordierite and the sintering is carried out at temperatures of 1600-1700 ° C.

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Example 21

The procedures of the previous examples are repeated 25, with the only change that particulate silicon carbide is used instead of cordierite and that the sintering is carried out at temperatures of 2000-2200 ° C.

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Example 22

The procedures of the above examples are repeated 35, with the change that particulate alumina is used instead of cordierite and the sintering is carried out at temperatures between 550 and 650 ° C.

Example 23

The procedures of the above examples are repeated, with the change that particulate stainless steel is used instead of cordierite and that the sintering is carried out at temperatures between 1400 and 1500 ° C.

B

Claims (24)

633026 PATENT CLAIMS 1. intimate mixture, usable as a burnable mold binder, containing 10 to 90 parts by weight of a resin 90 to 10 parts by weight of a plasticizer for this resin, characterized in that (1) the resin consists of at least 50% by weight of a block polymer of the structural formula AB - (AB ^ ri A, in which t) for zero or an integer, A for a linear or branched, at 20 to 25 ° C. glassy or crystalline polymer with a softening point of 80 to 250 ° C and B for a polymer with a different chemical composition than A, which is at temperatures between 15 ° C below the softening point of A and 100 ° C above the softening point of A as Elastomer behaves, and (2) the plasticizer (a) an oil, of which at least 75% by weight boils in the range from 288 ° C to 560 ° C, at 98.9 ° C a viscosity of 30 to 220 Saybolt universal seconds and an aniline point of 76.6 to 123.8 ° C, or / and (b) a wax with a melting point of 54.4 to 76.6 ° C, of which at least 75% by weight boils between 315 ° C and 483 ° C. 2. Mixture according to claim 1, characterized in that the said block polymer is one in which T | has the value zero, A stands for polystyrene and B for polybutadiene or polyisoprene. 3. Mixture according to claim 1, characterized in that the oil is a paraffin oil or naphthenic oil and boils in the range from 288 to 462.5 ° C. 4. Mixture according to claim 1, characterized in that it contains 70 to 15 parts by weight of plasticizer per 30 to 85 parts by weight of resin, and that B is a polymer which ■ is at temperatures between 15 ° C below the softening point of A and 70 ° C above the softening point of A as an elastomer. 5. Mixture according to claim 1, characterized in that it consists of 45 to 65 parts by weight of resin and 55 to 35 parts by weight of plasticizer. 6. Mixture according to claim 1, characterized in that said block polymer makes up more than 50% by weight of the mixture. 7. Mixture according to claim 1, characterized in that said block polymer makes up more than 50% by weight of the mixture, and that the mixture contains a second polymer which corresponds to the definitions given for polymer A. 8. Mixture according to claim 1, characterized in that said block polymer makes up more than 50% by weight of the mixture, and that the mixture further contains a second polymer which corresponds to the definitions given for polymer B. 9. Mixture according to claim 1, characterized in that it further contains an antioxidant. 10. Molding mixture for the production of sintered moldings, which consists of 30 to 70 vol .-% sinterable particulate solids and 70 to 30 vol .-% of a burn-out binder, characterized in that it contains a mixture according to claim 1 as a binder. 11. Molding mixture according to claim 10, characterized in that in the mixture according to claim 1 up to below 50 wt .-% of the resin mentioned in claim 1 consists of a polymer which corresponds to the definition given for polymer A in claim 1, and furthermore, up to below 50% by weight of the said resin can consist of a polymer which corresponds to the definitions of the polymer B as stated in claim 1, the sum of the proportions by weight of these latter two polymers, taken together less than 50% by weight of the make up mentioned resin. 12. Molding mixture according to claim 10, characterized in that the polymer B in the block polymer according to claim 1 behaves as an elastomer at temperatures between 15 ° C below the softening point of A and 70 ° C above the softening point of A. 13. Molding mixture according to claim 10, characterized in that in the mixture according to claim 1 up to below 50 wt .-% of the resin mentioned in claim 1 consists of a polymer which corresponds to the definition given for polymer A in claim 1 that furthermore, up to below 50% by weight of said resin can consist of a polymer which corresponds to the definition given for polymer B in claim 1, and that up to below 50% by weight of said resin can consist of an elastomer having the structural formula X. [B (AB) rç A] if, where X is a polyvalent low molecular weight link or a polymer A or B, t) is zero or a positive integer, and t | ' stand for a positive integer greater than 2 and A and B have the meanings mentioned in claim 1, with the proviso that the polymer B in the latter elastomer is at temperatures between 5 ° C below the softening point of A in the block polymer according to claim 1 and 90 ° C above the softening point of polymer A in the block polymer according to claim 1 behaves as an elastomer, and that the sum of the aforementioned polymers is less than 50% by weight of the resin. 14. Molding mixture according to claim 13, characterized in that the burn-out binder consists of an intimate mixture of 30 to 85 parts by weight of resin and 70 to 15 parts by weight of plasticizer. 15. Molding mixture according to claim 13, characterized in that the burn-out binder consists of an intimate mixture of 45 to 65 parts by weight of resin and 55 to 35 parts by weight of plasticizer. 16. A process for the production of a sintered shaped body starting from solid sinterable particles, characterized in that a molding mixture according to claim 10 is first prepared by mixing these solid particles with a corresponding burnable binder, that this molding mixture is shaped into a raw molded body, the binder by the action of heat removed from the blank and finally sintering the particulate solids in the blank by firing. 17. The method according to claim 16, characterized in that in the binder, the polymer B of the block polymer mentioned in claim 1 behaves as an elastomer at temperatures between 15 ° C below the softening point of polymer A and 70 ° C above the softening point of polymer A. 18. The method according to claim 16, characterized in that firstly a molding mixture according to claim 13 is prepared, that the mixture obtained is processed into a crude, unfired molded body, then the burnable binder is removed from it by the action of heat and finally by firing the particulate solids mentioned produces a sintered molded body. 19. The method according to claim 18, characterized in that the polymer B of the block polymer mentioned in claim 1 at temperatures between 15 ° C below the softening point of polymer A in the block polymer and 70 ° C above the softening point of 2nd s 10th 15 20th 25th 30th 35 40 45 50 55 60 65 Polymer A behaves as an elastomer in the block polymer, and that the polymer B of the elastomer mentioned in claim 13 behaves as an elastomer at temperatures between 5 ° C below the softening point of the polymer A in the former block polymer and 70 ° C above the softening point of the former block polymer. 20. The method according to claim 18, characterized in that 0.1 to 30 wt .-% of the resin mentioned in claim 1 consists of the polymer mentioned in claim 1, which falls under the definition of polymer A. 21. The method according to claim 18, characterized in that 0.1 to 30 wt .-% of the resin mentioned in claim 1 consists of the polymer mentioned in claim 1, which falls under the definition of polymer B. 22. The method according to claim 18, characterized in that 0.1 to 40 wt .-% of the resin mentioned in claim 1 from the polymer of the formula X [B (AB) n A] t) '. 23. Sintered molded body produced by the method according to claim 16. 24. Shaped body according to claim 23, produced by the method according to claim 18.