Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B1/00—Producing shaped prefabricated articles from the material
  • B28B1/52—Producing shaped prefabricated articles from the material specially adapted for producing articles from mixtures containing fibres, e.g. asbestos cement

Definitions

• the present invention relates to a process for the production of molds, models and tools from glass fiber reinforced hard plaster and / or glass fiber reinforced cement, in particular molds, models and tools for the automotive, aircraft and shipbuilding industries and the sanitary sector.
• fiberglass-reinforced materials are composite materials, which are the materials that are created by incorporating a basic material in the form of particles, whiskers, fibers, lamellas or braids into a second material - the matrix.
• cement is used, for example, in the construction sector.
• Their use in laminates in the production of molds, models and tools is not known.
• plastic molds made of glass fiber reinforced epoxy resins or unsaturated polyester resins can also be used, light molds being provided with stiffening ribs.
• the molds are backfilled with more stable materials e.g. with mixtures of epoxy resin and quartz sand.
• Plastic molds are inexpensive compared to steel molds and are a useful addition to the economical production of prototypes.
• Gypsum molds have probably not been used in this area until now because their strength is too low due to their high porosity and the expansion is too high. As a result, their dimensional accuracy and their ability to be demolded are inadequate.
• European patent application 0 124 801 and German patent 77 796 describe the production of molds based on beta calcium sulfate hemihydrate and / or cement. It is characteristic of this and other known methods, however, that only porous forms arise that absorb moisture and are gas permeable. The mechanical properties of such molds do not meet the requirements imposed in vehicle and aircraft construction, even if particles are embedded in the castable molding compounds; For example, whiskers, glass fibers, etc., so that porous composite materials based on gypsum or cement are formed.
• cement-based moldings are produced by first cooling a liquid resin layer consisting of epoxy resin and hardener in a mold to at least 30 ° C., and then pouring a cement-containing layer onto the viscous resin layer becomes. It is essential in this process that both layers solidify at the same time and thereby firmly bond to one another. Moldings produced in this way have a surface layer made of synthetic resin on the cement-containing base layer. However, this method is also unsuitable for the production of molds for large components or models.
• the stated object is achieved in that at least one base layer of a binder is applied to the model to be molded, provided with a release agent, onto which a glass-fiber-reinforced molding composition consisting of 95 to 0% by weight alpha is wet-on-wet Calcium sulfate hemihydrate, 0 to 95% by weight of cement, 0.5 to 8% by weight of glass fibers and 0.5 to 4% by weight of adjusting agent and water, is applied, and the laminate formed is removed from the mold after setting.
• the weight percentages above relate to the dry molding composition.
• the water content of the molding compound is expediently chosen so that a kneadable compound suitable for backfilling molds made of plaster or plastics is produced.
• the water content will be between 20 and 28% by weight, in particular 22 and 26% by weight, based on the dry mixture, but the subject matter of the invention is not restricted to the stated amounts of water.
• the water / gypsum factor or water; cement factor is close to the stoichiometrically necessary water requirement, so that dense forms are created, the mechanical properties of which are further improved by the glass fiber content.
• At least one base layer of a binder is applied to the model coated with release agent, but preferably two are applied.
• the base layers are best applied with a brush to the separating layer, for example a layer of hard wax, whereby the first layer can be about 0.1 to 5 mm thick and the second layer, which is used for reinforcement, 1 to 6 mm.
• the base layers are applied "wet on wet", i.e. the setting process of the layer already applied has not yet ended when the next layer is brushed on. This is the only way to ensure good adhesion between the layers of the laminate. If the setting process has already been completed, an adhesive agent must be used.
• the binder of the base layers can be an epoxy surface resin.
• the dry alpha-calcium sulfate hemihydrate and / or cement-containing molding compound which has not yet been mixed with glass fibers can also be used as a binder, which is then mixed with a little more water than the molding compound and thus becomes spreadable.
• the amount of water added can e.g. between 26 and 31% by weight, based on the dry weight of the binder.
• the second base layer essentially serves to reinforce the first base layer, which is suitable for molding difficult contours and makes it possible to produce shapes with smooth surfaces.
• the glass fiber content of the molding composition is preferably between 2 and 4% by weight. Due to the glass fiber reinforced molding compound, the molded parts are backed in such a way that they can withstand even the heaviest loads, in particular higher pressures.
• the glass fiber length should be 4 to 12 mm, in particular 5 to 8 mm, the diameter about 10 to 15 ⁇ m.
• the molding compound containing glass fiber can also be applied "wet on wet" to the last base layer. Using an adhesion promoter, the molding compound can also be applied to the set base layer, but also in the wet-on-wet process.
• the average grain size of the calcium sulfate hemihydrate crystals and the cement particles is preferably between 15 and 30 ⁇ m.
• Adjustment means are understood here as mixtures which contain accelerators, retarders and plasticizers, possibly also pH regulators and expansion regulators.
• Epo S 1, SW 404, SV 410 and SV 414 are suitable.
• the last base layer consists of an epoxy surface resin that has already set, then after this layer has been roughened, an adhesion promoter must be applied, to which the molding composition according to the invention is then applied using the wet-on-wet method.
• Surface resin can be applied, which can be identical to that of the base layer.
• Example 1 As in Example 1, 5 kg were removed from this mixture and the remaining 10 kg were mixed with 0.3 kg of glass fiber chips and likewise mixed homogeneously. The further processing was carried out in the same way as in Example 1. Here, too, the entire process was completed after about 25 minutes. The demoulding could be carried out after 120 minutes. The following final strengths were measured:
• Example 1 As in Example 1, 5 kg were first removed from this mixture and the remaining 105 kg were mixed with 0.3 kg glass fiber chips of 6 mm length and a maximum of 0.5 mm width for 10 minutes. The further processing of this material was carried out as in Example 1. The entire process was finished after 25 minutes. The demoulding could be carried out after 12 hours. The following final strengths were measured:

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)
• Laminated Bodies (AREA)
• Compositions Of Macromolecular Compounds (AREA)

Applications Claiming Priority (2)

Publications (3)

Family

ID=6271994

Family Applications (1)

Country Status (5)

Cited By (4)

Families Citing this family (11)

Family Cites Families (9)

• 1985
  • 1985-05-30 DE DE19853519367 patent/DE3519367A1/de active Granted
• 1986
  • 1986-04-11 EP EP86105033A patent/EP0203333B1/fr not_active Expired
  • 1986-04-11 DE DE8686105033T patent/DE3665548D1/de not_active Expired
  • 1986-05-28 US US06/867,698 patent/US4749431A/en not_active Expired - Fee Related
  • 1986-05-29 CA CA000510279A patent/CA1282578C/fr not_active Expired - Lifetime
  • 1986-05-30 ES ES555526A patent/ES8801142A1/es not_active Expired

Also Published As

Similar Documents

Legal Events