Seamless model and method of making a seamless model

[0001] In the transportation industry (eg, the automotive, rail and space industries), it is a common challenge to produce large, spatially accurate master models. These models are used by engineers to design the concept of each component of the final product. [0002] The highest technical level is often involved in the "basic unit" method in which multiple boards are glued together to produce a coarse model structure and then machined to form the desired shape (shown in Figure 1). This method, however, requires a large amount of labor and requires precise operation, leading to high costs and, in addition, resulting in a model with adhesive lines on the surface, which is an aesthetically undesired appearance. [0003] Thus, there is a need in the industry for models and methods for making models that feature low cost and smooth, seamless surfaces without adhesive lines. U.S. Pat. Nos. 5,707,477 and 5,773,047 disclose methods for making prepreg components for use in the space industry, which include flexible solid padsies prepared from syntactic epoxy materials. Hand-applied to blocks made by stacking continuous layers of aluminum honeycomb cores, all resulting structures are thermoset for effective curing of the paddy. However, this method requires a great deal of labor in involving the manual application of the flexible solid paddy to the honeycomb core, as well as the heating of all structures to cure the applied paddy. .. The resulting model is also relatively dense. [0004] Thus, in this field, those skilled in the art will be provided with models and methods of manufacturing the models that have lower production costs, lower weight and improved smoothness, and are characterized by a more homogeneous surface without adhesive lines. Continue to be needed. [0005] The present invention relates to models and methods of making models that meet these needs of the industry. A method for producing a seamless model without adhesive lines according to the present invention is a step of applying a modeling paste to the outer surface of the foundation structure in the form of a continuous layer, following a step of giving a foundation structure having an exposed outer surface. It includes a step of curing the continuous layer of the applied modeling paste and a step of machining the cured layer of the modeling paste into a desired contour. This method is referred to herein as "net size casting" using a "seamless modeling paste" (SMP). [0006] The modeling paste of the present invention is a syntactic foam containing mechanical bubbles prepared by injecting an inert gas into a resin composition which is a thermosetting resin which can be cured at a low temperature with mechanical stirring. is there. Most preferably, the composition is either a molded polyurethane or an epoxy floss-forming composition comprising microhollow spheres. The polyurethane compositions exemplified here include (1) an organic polyisocyanate component; (2) (a) a polyol component containing a high molecular weight polyol of 50% by weight or more and (b) a polyol component containing a low molecular weight polyol of less than 50% by weight; and ( 3) Contains a sufficient amount of chemical thixotrope to induce thixotrope properties. Preferred epoxy compositions are (1) epoxy resins; (2) sufficient amounts of thixotropic agents to induce thixotropic properties; and (3) (a) at least one polyethyleneimine and (b) at least two aminos. At least one other amine having a hydrogen group contains a curing agent containing a combination amount of (a) and (b) at which the curing of the epoxy resin is sufficiently effective. [0007] Figure 1 shows an example of a traditional basic unit modeling method by gluing multiple boards together. FIG. 2 is a cross section of a seamless model without adhesive lines manufactured according to the present invention. [0008] The miniaturized support structure used in accordance with the present invention, and the method of making the structure, is of the same type as the structure known to those of skill in the art and typically manufactured as a back support for customary board models. It may be a thing. The structure is used as a core to which the modeling paste is applied. Examples of materials from which support structures are made are, but are not limited to, natural wood and low density foam made from, for example, polystyrene, polyurethane or epoxy materials. An example of such a low density nucleus is the Dow HD3000, a polystyrene extended to a density of 0.03. [0009] According to FIG. 2, the layer of modeling paste 2 is applied to the outer surface of the foundation structure 1. Preferably, the layers of modeling paste are distributed on the surface of the foundation structure in the form of continuous layers using a high power measurement mixer. The paste is preferably applied to a thickness of about 0.5 to about 1.5 inches, more preferably about 0.75 inches thick. The paste is then cured. [0010] Curing of the curable resin composition is carried out according to a conventional method in a specific application. In general, the composition can be gelled (cured) at ambient temperature or is moderately heated according to customary law to accelerate curing. The curing may then be completed at ambient temperature, moderately elevated temperature or higher temperature, if desired. Room temperature curing is typically preferred. [0011] After curing, the resin layer is machined to the final contour using the cutter 3. Typically approximately 0.25 inch of material is removed during machining. The surface is sealed with a sealant before the model goes into production. [0012] The seamless master modeling paste distributed over the outer surface of the foundation structure consists of mechanically foamed syntactic foam. Foams are prepared by injecting an inert gas into a formed floss-forming composition containing a curable resin composition, microhollow spheres and any other additional additives with mechanical agitation. [0013] Mechanically foamed syntactic foam used in accordance with the present invention is required to exhibit good non-sinkability and sagging resistance when stacked horizontally on a vertical plane. Typically, a 1 inch thickness of sagging resistance on a vertical plane is required. Mechanically foamed syntactic foams made from certain polyurethane, epoxy and polyester floss-forming mixtures have been found to specifically meet these criteria. [0014] Examples of suitable curable polyurethane floss-forming mixtures are (1) organic polyisocyanate components; (2) (a) polyols containing 50% by weight or more of high molecular weight polyols and (b) polyols containing less than 50% by weight of low molecular weight polyols. Ingredients; and (3) include, but are not limited to, those containing sufficient amounts of chemical flossotropic agents to induce thixotrope properties. Preferably, the low molecular weight polyol (b) is present in an amount of less than 40% by weight based on the total weight of the combined polyol components. The polyisocyanate and polyol components are customary liquids under ambient temperature and pressure conditions, and the polyisocyanate components have viscosities in the range of 500-3000 cps to ensure optimal processing volumes in mixers and distributors. The sushi and polyol components have a viscosity of less than 30,000 cps. However, both components may have higher viscosities, such as up to 60000 cps, if suitable measuring pumps are used. [0015] Suitable organic polyisocyanates (1) useful in the present invention include polymethylene polyphenyl isocyanate, 4,4'-diphenylmethane diisocyanate and their species containing carbodiimide bonds, such as toluene diisocyanate, phenylindan diisocyanate. Includes any widely used to make polyurethane plastics containing aliphatic polyisocyanates such as polyarylisocyanates, hexamethylene diisocyanates, isophorone diisocyanates, 2,2,4-trimethylhexamethylene diisocyanates, and blends thereof. To do. Polymeric 4,4'-diphenylmethane diisocyanate is preferred. [0016] Suitable high molecular weight polyols (2a) include those having a hydroxyl number of 300 or less, preferably 100 to 300. Particularly suitable are polyether triols containing aliphatic alkylene glycol polymers having alkylene units containing at least two carbon atoms. Typical are ethylene oxide, propylene oxide, butylene oxide and alkylene oxides such as tetrahydrofuran, and di- and polyfunctional alcohols such as water, propylene glycol, glycerol, trimethylolpropane, hexanetriol, pentaerythritol and sucrose. Prepared through polymerization of. Materials that can be applied generally have a molecular weight in the range of 500 to 7000, preferably 500 to 1700. A typical polyether triol is available from Olin Corp., under the name POLY-O 30-280. [0017] Low molecular weight polyols (2b) include those having at least 300 hydroxyl numbers, preferably 300 to 1000, and even more preferably 350 to 800. Particularly suitable are amine-based polyols, which generally have an equivalent of 30 to 6000 and a viscosity of 1.0 to 20000 centipoise at 25 to 60 ° C. Preferred are those having a molecular weight of 50-400, more preferably 200-350. A wide variety of aromatic and aliphatic polyamines form moieties of amine-based polyols such as di- and polyamines such as ethylenediamine, triethanolamine and toluenediamine, which are reacted with, for example, the alkylene oxides described above. May be good. Amine-based triols are preferred. Typical amine-based polyols are from Texaco Corp., under the name THANOL SF 265, and from BASF Corp., under the name PLURACOL 355. Available. [0018] The chemical thixotrope (3) imparts chemical thixotropy to the mixture of components (1) and (2), which allows sufficient sagging resistance during the final application of the paste to the support structure. It is believed to be caused by the formation of adducts from a rapid chemical reaction between the isocyanate and the amine group. It is important that chemical thixotropy is induced after mixing, foaming and distribution onto the underlying structure, as early chemical thixotropy can lead to gelation in the mixing head. Typical examples of such chemical thixotropic agents are 4,4'-methylenedianiline, m-phenylenediamine, 4,4'-methylenebis (2-ethylbenzeneamine), isophoronediamine and most particularly diethyltoludiamine. Aliphatic, alicyclic, aromatic, aromatic aliphatic and heterocyclic amines, including, but not limited to. The amount of the thixotrope required to impart the thixotrope properties depends on the specific polyurethane properties and the specific thixotrope used. The amount is generally 1 to 10% by weight, preferably 2 to 6% by weight, based on the weight of the polyisocyanate (1). [0019] Polyurethanes are prepared by mixing polyisocyanates with polyols. Microhollow spheres and any other additional additives are commonly included with polyols. In general, there is also the possibility of deviation from the theoretical amount by utilizing approximately 2% of the extra polyol in which the theoretical amount of polyisocyanate and polyol is utilized. [0020] To meet all the requirements for an acceptable cured polyurethane foam modeling stock, the cured composition has a heat deflection temperature (HDT) of 40 ° C or higher and preferably 50 ° C or higher, and-. 80 × 10 in the range of 30 ° C to 30 ° C^-6Coefficient of thermal expansion (CTE) below in / in / ° C, preferably 60 × 10^-6Should have less than or equal to in / in / ° C. The cured epoxy foam modeling stock should also meet these criteria. [0021] [0021] Particularly suitable for the use of mechanically foamed syntactic foams are also described, for example, in US Pat. No. 6,077,886, issued June 20, 2000, which is cited herein. (1) Epoxy resin; (2) Sufficient amount of chemical thixotrope to induce thixotrope properties; and (3) (a) at least one polyethyleneimine and (b) at least two aminohydrogens A curing agent consisting of at least one other amine having a group, comprising a curing agent in which the combined amount of (3) (a) and (3) (b) is sufficient to cure the epoxy resin. Epoxy resin / curing agent mixture. [0022] The epoxy resin (1) consists of one or more epoxy resins that are themselves liquid, or a liquid mixture of one or more solid epoxy resins and one or more liquid epoxy resins. It may be, or it may be one or more solid epoxy resins dissolved in a diluting agent such as a diluting agent customarily used in epoxy resin compositions. The epoxy resin may be a polyglycidyl ether of a polyhydric alcohol such as 1,4-butanediol or 1,3-propanediol, or preferably a polyhydric phenol, such as bis (4-hydroxyphenyl). A novolac polyglycidyl ether formed from bisphenols such as methane (bisphenol F) or 2,2-bis- (4-hydroxyphenyl) propane (bisphenol A) or phenols or cresols such as formaldehyde and phenol itself. Polyglycidyl ethers of bisphenol A are particularly preferred. Epoxy resins, especially including solid epoxy resins, are monoepoxides such as one or more epoxy functional epoxides, often monoepoxides and non-epoxides commonly used in curable epoxy resin compositions. Or may contain a non-epoxide dilute. [0023] The thixotrope agent (2) is preferably a thixotrope agent that is believed to exert its thixotrope effect depending largely on hydrogen bonds between particles, and is particularly hydrophilic fumed silica. The amount of thixotrope required to induce thixotrope properties is obtained by the specific epoxy resin properties and the specific thixotrope used. This amount is generally 1 to 20% by weight, preferably 3 to 15% by weight, based on the weight of the epoxy resin (1). [0024] Polyethyleneimine (3) (a) may have a molecular weight (Mw) of 700 to 1000000 or more, more preferably 5000 to 750,000, especially 25000 to 750,000, and particularly approximately 750,000. .. Such polyethyleneimine may be commercially available or prepared from ethyleneimine according to known procedures. [0025] The amount of polyethyleneimine is generally selected so that the epoxy resin composition of the present invention does not flow for the desired time after formation of the composition. Preferably, the amount of polyethyleneimine is such that the epoxy resin composition does not flow for at least 60 minutes after its formation. In certain specific embodiments of the invention, the amount of polyethyleneimine is such that the epoxy resin composition does not flow for several hours in some cases before gelling. The amount of polyethyleneimine required to impart the property of not flowing for a given time can be easily determined by a simple experiment. For the composition of the present invention containing the particularly preferred components (1), (2) and (3) (b) described herein, an amount of 0.2 to 2 parts of polyethyleneimine per 100 parts by weight of the epoxy resin is preferable. [0026] As examples of amines suitable for use as amine hardeners (3) (b), aliphatic, alicyclic, aromatic, aromatic aliphatic and heterocyclic amines known as hardeners for epoxy resins May be mentioned, alkylenediamines such as ethylenediamine or butane-1,4-diamine; polyalkylene polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine or tripropylenetetramine; triethylenetetramine. N-hydroxyalkyl derivatives of polyalkylene polyamines such as N- (hydroxyethyl) diethylenetriamines or mono-N-2-hydroxypropyl derivatives; polyoxyalkylene polyamines such as polyoxyethylene- and polyoxypropylene-diamines and triamines. N, N-dialkylalkylenediamine such as N, N-dimethylpropane-1,3-diamine or N, N-diethylpropane-1,3-diamine; 3-aminomethyl-3,5,5-trimethylcyclohexyl Alicyclic amines with ring-bound amino or aminoalkyl groups, such as amines (isophoronediamines); aromatic amines, such as bis (4-aminophenyl) methane or bis (4-aminophenyl) sulfones; Epoxy resins and amino-terminated adducts of aliphatic, alicyclic or aromatic aliphatic amines as described; N-aminoalkyl- such as N- (2-aminoethyl) piperazine or N- (3-aminopropyl) piperazine. Piperazins; and reaction products of polyaminoamides, such as polyalkylene polyamines as described above and polymerized unsaturated fatty acids, such as dimerized or trimeric linolenic acid or ricinolenic acid; or theirs. Contains two or more mixtures of such amines. [0027] Polyaliphatic and alicyclic amine hardeners are usually preferred for use as components (3) (b) of the composition and are N-hydroxyalkyl derivatives of polyalkylene polyamines, especially mono-N of triethylenetetramine. -2-Hydroxypropyl derivatives and mixtures thereof with polyaminoamide reaction products of polyalkylene polyamines and polymerized vegetable oils and amine functional reaction products of amines and epoxy group-containing compounds. The amount of (3) (b) is preferably such that (3) (a) and (3) (b) together give approximately 0.75 to 1.25 aminohydrogen equivalents per 1,2-epoxide equivalent of the epoxy resin (1). Is such an amount. [0028] Epoxy resin compositions may also be customarily formed by stirring the preform mixture of (1) and (2) with the preform mixture of (3) (a) and (3) (b). Good. The thixotrope may also be customarily present in the curing agent mixture. [0029] The mechanically foamed syntactic foam used in accordance with the present invention may also be made from a polyester floss-forming mixture. Polyesters and their formation are well known to those of skill in the art. Similar general procedures followed for forming polyurethane and epoxy floss-forming mixtures are applied to polyesters as well, mixed with chemicals to induce chemical thixotropic properties to achieve sufficient sagging resistance. Will be done. [0030] Seamless master modeling pastes prepared according to the present invention contain microhollow spheres or hollow microspheres with a relatively homogeneous distribution. Hollow microspheres are usually acrylic resins such as polyacrylonitrile and polymethylmethacrylate, acrylic modified styrene, polyvinylidene chloride, copolymers of styrene and methylmethacrylate; thermosetting such as phenolic resin, epoxy resin, urea resin and the like. Resin; or a hollow thermoplastic sphere consisting of hollow glass, silica, ceramic or carbon spheres that is very lightweight and acts as a lightweight filler in syntactic foam. Thermoplastic micro hollow spheres are preferred. Examples of suitable micro-hollow spheres are Exapancel, available from Akzo Nobel Corporation; phenolic micro-hollow spheres, available from CQ Technology Corporation; and Yusht-Seiyaku. Includes, but is not limited to, Matsumoto microspheres available from Company. These microhollow spheres preferably have a diameter of about 5 to about 250 micrometers. Microhollow spheres or hollow microspheres suitable for use in the present invention are customary to those skilled in the art, and methods for producing these microhollow spheres are well known. Such microhollow spheres are readily available commercially. These microhollow spheres can be compressed to some extent when exposed to external pressure. However, they are relatively brittle and will foam break or crack at high pressures. Therefore, there is a pressure in the range where the micro hollow sphere works effectively. Microhollow spheres accelerate machining, leading to reduced densities and reducing the coefficient of thermal expansion. The surface of the microhollow spheres may be properly treated for better compatibility with the resin composition. [0031] Microhollow spheres are used in sufficient quantities to produce a product of homogeneous density, but too much creates difficulties in mixing such that a non-homogeneous product is produced. The appropriate amount is about 0.5 to about 5 parts based on 100 parts of resin, preferably about 1 to about 3 parts per 100 parts of resin. The microhollow spheres may customarily be added with the curing agent component, or they may be added with the resin component. [0032] The formed defoaming compositions of the present invention are also small amounts of accelerators and customarily used in special applications, such as flame retardants, fillers (such as calcium carbonate), fibers, pigments, dyes, difficulties. It may contain additives such as flame retardants, defoamers, wetting agents and polymeric strengthening agents. Of particular interest are the addition of molecular sieves, which function as a water remover, and zeolites, which are well known to those skilled in the art and have an open network structure. Also of particular interest is the silicon surfactant-like Dabco DC 197 Surfactant, which is available from Air Products, along with others that are commercially available and well known to those in the art. ) Is the addition of a surfactant or antifoaming agent. It has also been found that the addition of calcium stearate improves the mechanical properties of the cured material, and thus their addition is advantageous. These auxiliary materials may be conveniently added with the curing agent component, or they may be added with the resin component. [0033] Techniques for producing mechanically foamed syntactic foam are known to those of skill in the art. For example, the book "Mechanically Frothed Urethane: A New Process for Controlled Gauge, High Density Foam" by Marlin et al., Journal of Cellular Plastics, November / December, 1975, describes such techniques. For example, a mechanically foamed polyurethane foam is prepared by mechanically blending an inert gas such as air into a mixture of isocyanate and polyol, followed by polymerization to form the polyurethane foam. This is different from the customary polyurethane foam, which causes foaming and polymerization at the same time. Surfactants are used in the formulation to allow the formation of bubbles, and urethane polymerization is delayed throughout the expansion step and occurs after the bubbles have been applied to the support. The amount of air in the bubbles determines the density and consistency. The basic device is such that bubbles are continuously generated in a bladed mixer that generates shear stress to disperse the inert gas in a liquid mixture of isocyanate and polyol. The polyol component, including surfactants, additives (classes) and fillers (classes), is weighed as one stream. The isocyanate is weighed as a branched stream, and the inert gas is weighed through a third inlet to achieve a given density. Machines for processing foam are commercially available and well known to those of skill in the art. Mechanically foamed epoxy and polyester foams are prepared in a similar manner. [0034] Inert gases suitable for use in accordance with the present invention include those that are gaseous at room temperature, and preferably do not liquefy at -30 ° C and do not react with resin and curing agent components. They include, for example, air, nitrogen gas, carbon dioxide gas and the like. [0035] Dispersion of the inert gas is a resin, a curing agent under mechanical agitation in order to obtain a foamed floss-forming composition containing the inert gas in which the inert gas is substantially uniformly dispersed. , Introduced into micro hollow spheres and additional additives. [0036] The amount of inert gas introduced into the foamed resin-forming composition may vary according to the desired properties of the final product, especially with the use of a flow meter. In general, suitable amounts include from about 10% to about 70% by volume, preferably from about 20% to about 60% by volume. The bulk density of the obtained cured product is usually 0.3 to 0.9 g / cm.³, Preferably 0.4 to 0.8 g / cm³Is. [0037] Conveniently, separate tanks are filled with resin and hardener. The application of low pressure to the tank promotes inhalation and discharge of material. The gear tank discharges the resin and the curing agent from the tank into a mixing block in which the resin, the curing agent and the inert gas are mixed under high shearing force. Compressed air is injected directly into the mixing block. A dynamic mixer with a hose and a chamber are attached to the mixing block. The amount of compressed air injected into the mixing chamber is controlled using a flow meter to allow controlled changes in the density of the distributed material. The residence time in the mixing block, the high speed mechanical agitation to finally distribute the inert gas to the mixture and the length of the hose attached to the chamber are how well the injected air is resin and hardener. Affects whether it is dispersed in the mixture. [0038] The resulting foamed syntactic resin composition containing an inert gas therein is useful as a seamless master modeling paste distributed over the underlying structure. The curing can be carried out as described above. [0039] Machining or cutting into the desired shape can be performed using customary tools such as grinders, machining centers, etc. or cutting machines. Particularly preferred is the use of computer numerical control (CNC) machines. The model can be used as a modeling material and is used in the manufacture of master models, design models, tracing models and prototype tools. [0040] From the above description, it will be apparent to those skilled in the art that the total molding cost of the model using the method of the present invention will be more economical than the conventional method using wood or epoxy synthetic foam model blocks. An additional and important advantage is the resulting seamless and glue-free model surface. [0041] This method is even more advantageous in that the amount of syntactic material used is significantly reduced over conventional methods, as a mere thin layer is distributed over the foundation structure. Since syntactic materials are hygroscopic in nature, their water absorption causes some dimensional changes over time. By minimizing the amount of syntactic material used, dimensional changes as a result of moisture absorption are therefore reduced. [0042] In addition to the advantages mentioned above (ie lower and more homogeneous densities, better mechanical properties, smoother surface properties, and even greater overall effect), seamless master pastes produced according to the present invention are low. Even large models that show linear shrinkage and retain high tolerances are manufactured. The final product has excellent edge strength, shore hardness, bending strength, heat deflection temperature, compressive strength and coefficient of thermal expansion. [0043] The present invention will be shown with reference to the following examples, but the scope of the present invention shall not be limited in any case. All parts and percentages are based on weight unless otherwise stated. [0044]<u style="single">Example 1</u>This example shows a typical polyurethane seamless master modeling paste of the present invention. The formulations listed in Table 1 below are prepared by placing a curing agent system containing polyols, microspheres and additional components in a mixing tank and mixing at low speed for 15-30 minutes. The second tank is filled with an isocyanate resin component, and a third tank filled with compressed air is prepared. The curing agent system and resin components are discharged into the mixing block by using a gear pump while applying a low pressure (5 to 10 psi) to the tank to promote the discharge of the material. Compressed air is injected directly into the mixing block. In the mixing block, the material and compressed air are uniformly distributed under high shear (approximately 6900 rpm) with a residence time of 2-5 seconds using a dynamic mixer. The residence time is the time in the mixer that changes conversely with the flow velocity. For easy control of the density of the distributed paste, the amount of compressed air injected into the mixing chamber is controlled by a flow meter. In this formulation, the air reading is 26 mL / min. [0045] The paste is distributed over the foundation structure to a thickness of approximately 1 inch and cured at ambient temperature for at least 10 hours. The crude product is shaped into its final contour using a computer numerically controlled (CNC) machine. [0046] The paste is evaluated as follows. The sagging resistance of the paste is measured prior to curing by distributing the paste horizontally on a vertical plane in a thickness of 0.75 to 1.5 inches. A measurement of 0.75 to 1.5 inches is desirable, and indicates that the material just hangs or drops this much. Paste density, heat deflection temperature (HDT), 66 psi load and coefficient of thermal expansion (CTE) at -30 ° C to + 30 ° C are measured at ambient temperature at 25 ° C after curing for a minimum of 24 hours. Density is measured according to ASTM D792; HDT, ASTM D648; and CTE, ASTM DE831.<img file="JP5118799B2_D0001.tif" /><img file="JP5118799B2_D0002.tif" />[0047] The data show excellent performance characteristics of pastes prepared according to the present invention. In particular, the pastes of the present invention provide excellent sagging resistance. [0048]<u style="single">Comparative example 1</u>This example shows the preparation of a comparative polyurethane formulation. Follow the same common procedure of Example 1 except that the formulations listed in Table 2 below are used. The comparative polyurethane formulation is the same as in the examples except that diethyl toluenediamine is omitted. The properties of the paste thus prepared indicate that this formulation is not suitable for the preparation of seamless master modeling pastes due to the poor distribution properties, as evidenced by the low resistance of the distributed paste to sagging. The sagging resistance is measured as in Example 1.<img file="JP5118799B2_D0003.tif" /> 【0049】<u style="single">Example 2</u>This example illustrates the preparation of other typical polyurethane seamless master modeling pastes of the present invention. The formulations shown in Table 3 below are prepared in the same common procedure as in Example 1 except that the amounts of various components are changed. The properties of the paste thus prepared indicate that this formulation is suitable for the preparation of seamless master modeling pastes, with excellent dispensing properties, as evidenced by the high resistance of the dispensed paste to sagging. The sagging resistance is measured as in Example 1.<img file="JP5118799B2_D0004.tif" /> 【0050】<u style="single">Example 3</u>Table 4 below shows the results of the machining tests performed in Formulation 1. The machining test is carried out as follows. Weight% of dust (ie particles less than 0.5 mm in size) is measured during normal CNC machining operations. High density modeling material XD4503 (epoxy / amine based) with a density of 0.8 g / cc available from Vantico Inc., commercially available using several spindle speeds and feed rates, and a percentage of dust. ).<img file="JP5118799B2_D0005.tif" />The test results show very good machining performance, similar to the XD4503. Other properties observed during machining, such as surface smoothness, edge sharpness and odor, indicate that polyurethane formulations prepared according to the present invention have excellent overall machinability. ing. [0051]<u style="single">Example 4</u>This example shows that pastes of variable densities can easily be produced according to the present invention. The same common procedure as in Example 1 is followed using the ingredients of Formulation 1, except that the amount of air injected into the mixing chamber is varied through the use of a flow meter. Table 5 below shows the resulting density of airflow and pastes so produced. The density is measured as in Example 1.<img file="JP5118799B2_D0006.tif" /> 【0052】<u style="single">Example 5</u>This example shows that the exotherm of the system can be controlled by varying the ratio of high molecular weight polyols to low molecular weight polyols while maintaining acceptable chemical thixotropic properties. Table 6 below shows the exothermic peaks of formulations 1 to 3. The exothermic peak is measured during the reaction of the resin and the curing agent component.<img file="JP5118799B2_D0007.tif" />¹Formulations 1, 2 and 3 have high molecular weight to low molecular weight polyol ratios of 62: 38; 83.5: 16.6; and 95: 5, respectively. [0053]<u style="single">Example 6</u>Table 7 below shows the use of various isocyanates in combination with the curing agent systems of Examples 1 and 3. The paste is produced according to the same common procedure as in Example 1. The data show that the use of different isocyanates allows control of the exothermic peaks of the resin / curing agent reaction while maintaining good chemical thixotropy.<img file="JP5118799B2_D0008.tif" />¹Prepolymers are made using Isonate 143L (modified MDI), available from Dow, and Arcol 24-32 polyols, available from Bayer. The NCO content is varied by blending the prepolymer with other isocyanates in various ratios. [0054]<u style="single">Example 7</u>The following materials are blended for their non-depressing properties after mixing and before curing and their ability to retain the air once dispersed therein.<img file="JP5118799B2_D0009.tif" />The pre-prepared and filled material is loaded into a 2KM 1900 metering mix metering distributor in a 50 liter steel drum. The resin and hardener components are pumped to the mixing block at low pressure (5-20 bar), which gives the material a flow rate of approximately 100 g / min. Air from the compressed air line is supplied directly into the mixing block. The speed of the rotating mixer in the block is varied to provide the desired foaming together with the resin, hardener and air components. Compressed air is regulated using a flow meter, and the speed of the rotary mixer is controlled via a metering mixer. The following parameters are used in this example: Air flow: 4bar Material pressure A: 16bar Material pressure B: 5bar Flow rate: 100g / min Mixer speed: 1400 rpm The paste is extruded onto a solid support covered with release paper and cured at ambient temperature for at least 10 hours. The material is evaluated as follows. Density is measured using a specific gravity cup (pycnometer). The uncured material from the machine, 0.67 g / cm showing a good mix of air into the mixed material³Measured at the density of. In the inspection of the cutting of the material, it can be seen that there is a homogeneous dispersion of air within the sample. The cell size is homogeneous. [Simple explanation of drawings] FIG. 1 shows an example of a conventional basic unit modeling method by bonding a large number of boards together. FIG. 2 is a cross section of a seamless model without adhesive lines manufactured according to the present invention.