JP2010528896A - Method for manufacturing hollow structural parts made of fiber reinforced plastic - Google Patents

Abstract

[Object] To provide a water-dispersible supporting core that can withstand high tensile force when covered with a reinforcing fiber without any hindrance for the RTM method for manufacturing a hollow structure part made of fiber-reinforced plastic.
[Structure] A water-dispersible supporting core prepared with a water-soluble binder consisting of a water-soluble silicate-containing binder and a filler at least partially for the production of hollow structural parts made of fiber reinforced plastic Cover with reinforcing fiber. The fibers on the supporting core are impregnated with a curable plastic, the plastic is cured, and then the supporting core is washed out with water. It is preferred that the binder is at least partially water glass.

Description

  The present invention relates to a method for producing a hollow structure part made of fiber-reinforced plastic according to the premise of claim 1.

  For the production of fiber-reinforced hollow plastic parts, the so-called RTM (resin transfer molding) method and the vacuum injection method are used, among others.

  For this purpose, for example, at least one layer of uniaxially or biaxially oriented reinforcing fibers is placed between the upper and lower molds of a heated press, the fiber layer being between the upper and lower molds. In this state, a thermosetting plastic (for example, an epoxy resin having a curing agent) is injected into the mold cavity under pressure, and the fiber layer is impregnated with the thermosetting plastic. This approach is similar to that in the vacuum injection method, where a vacuum is applied instead of pressurization to cause the fiber layer to draw the thermosetting plastic.

  For example, many hollow structural parts such as support columns, door frames, and bumpers are used in automobiles. Such hollow parts are usually joined. However, junction points can lead to breakage. Furthermore, improvement in the dimensional accuracy of the joined hollow parts is strongly desired.

  For the production of hollow parts by the RTM method, it is customary today to use a wax melt core. The process used for that is very complicated due to the size of the core. Furthermore, due to the high coefficient of thermal expansion of the wax, complicated adjustment of the required production equipment is required. After the actual part manufacture, the material is melted again. This leaves a residue on the inner wall of the mold, which first increases the part weight and is disadvantageous with respect to contaminants and lacquer affinity.

  From WO 02/072328 a supporting core for the production of plastic hollow structural parts containing polyvinylpyrrolidone (PVP) as a water-soluble binder is known.

  A braiding machine can be used to cover the support core, where the support core is placed in the center of the braiding machine while the reinforcing fibers are pulled from the periphery under high tension. However, the supporting core according to WO 02/072328 has a fracture strength that is too low to withstand such a high tensile force.

  Support cores made of low melting point bismuth alloys are also used. However, due to the high input energy for melting the core, the large weight and consequently the handling difficulty, and the health risks of bismuth vapor, such a core cannot be used in practice.

  In addition, a support core made of high-density foam is used, which remains inside the part, thus resulting in a corresponding increase in weight.

  Accordingly, an object of the present invention is to provide a water dispersible support core that can withstand high tensile forces when covered with reinforcing fibers without difficulty for the RTM method for the production of hollow structural parts made of fiber reinforced plastic. is there.

  This is achieved according to the invention by the method of claim 1. In the subclaims, advantageous embodiments of the invention are described.

The supporting core used according to the invention is characterized in that the water-soluble binder comprises at least partly a silicate. The binder preferably used is water glass. The binder is characterized in that the weight ratio of SiO ₂ / M ₂ O is preferably in the range from 1.6 to 4.0, in particular from 1.8 to 3.5, where M is sodium ions and / or Represents potassium ion and / or lithium ion. The binder preferably has a solid content of SiO ₂ and M ₂ O in the range of 30-60 wt%.

  The supporting core preferably has a relatively small binder content of 0.5 to 8 wt.%, In particular 1 to 5 wt.% And thus a correspondingly high filler content. A high strength is thereby achieved, so that the supporting core can withstand high tensile forces when packing, ie covering, and braiding with reinforcing fibers.

  The reinforcing fibers used are preferably carbon fibers. However, it is also possible to use other reinforcing fibers, for example glass fibers. Packing is preferably performed on a braiding machine such as used for braiding cables and ropes, where the support core occupies the position of the cable core or rope core in the center of the braiding machine.

  The production of fiber-reinforced hollow structural parts is then preferably achieved by the RTM method. That is, the packed support core is placed between two molds, for example, an upper mold and a lower mold of a heated press, and the reinforcing fibers on the support core are formed by the support core having two mold parts. In between, it is impregnated with a thermosetting plastic (eg, epoxy resin) injected into the mold cavity. Here, it is possible to perform a resin transfer molding (RTM) method in which a thermosetting plastic is press-fitted into the mold cavity under a pressure of 10 bar or more, or a vacuum injection method in which the thermosetting plastic is sucked into the mold cavity. . After the resin is cured, release is performed, and the supporting core is washed out with water to form a fiber-reinforced hollow structure part.

  The water glass used may be, for example, sodium silicate. However, it is also possible to use other water glasses, in particular potassium silicate or lithium silicate.

In addition to water glass, the binder may further contain an alkali metal compound, which may be in solid form or as an aqueous solution (eg sodium hydroxide or potassium hydroxide) or in dissolved form (caustic soda or caustic potash). ) May be added. The additive may be used, for example, to control the ratio (ratio of SiO ₂ / M ₂ O) and solids.

  The filler consists of a water-insoluble particulate material, preferably at least partly sand. The sand preferably has an average particle size of 100 to 500 μm.

  In addition to imparting strength to the support core, sand also has an important function in the production of the support core. The supporting core for the process according to the invention is preferably a core shooting machine, as described, for example, in German Offenlegungsschrift 10 2000 97 for the production of cores for casting purposes. Manufactured by. Here, a mixture of foundry sand, magnesium sulfate aqueous solution as a binder and water is shooted into a mold. Subsequently, the water is evaporated to form a casting core for producing a casting.

  The sand content of the filler is at least 30 wt% in order to give the mixture of filler, aqueous binder solution and water preferably used for the injection according to the present invention the fluidity necessary for charging into the mold. Proved convenient.

  Furthermore, the filler preferably contains plastic particles having an average particle size of usually 100 μm to 2 mm. The plastic particles are preferably formed from chopped plastic waste. It is preferred to use plastic pellets in order to give the particles a relatively spherical shape. The spherical shape thus increases the fluidity of the mixture of filler, binder solution and water. The plastic particles further increase the elasticity of the supporting core, ie reduce its brittleness. At the same time, the weight of the support core can be substantially reduced by using plastic particles as the filler. Preferably, the plastic content in the filler is at least 10 wt%. However, the plastic content may be quite high (up to 50 wt% or more). This makes it possible to obtain a core that is significantly lighter and thus easier to handle.

  Reduction of the core weight can be further achieved with ceramic particles or hollow glass spheres. The ceramic particles can be formed by fly ash, for example. Since fly ash particles are also relatively spherical in shape, the fly ash particles also provide the fluidity required for input. This is of course especially true for hollow glass spheres as fillers. The average particle size of the ceramic particles and the hollow glass spheres may be, for example, 50 to 800 μm.

  The water content of the molding material, that is, the mixture of the filler, the binder, and water is preferably 0.2 to 5 wt% with respect to the weight of the filler. This makes it easier to process the molding material when it is inserted into the mold, for example by injection or press fitting. However, the lowest possible moisture content is selected because the supporting core must be dried before it is released to have the required strength.

Preferred molding materials are, for example, 0.5 to 5 wt%, in particular 1 to 2 wt% of silicate-containing water-soluble binders (SiO ₂ / M ₂ O ratio is preferably in the range 1.6 to 4.0 M represents sodium ions and / or potassium ions and / or lithium ions) and 30-60% solids) and the balance consists of sand.

  According to the method of the present invention, any hollow structural part made of fiber reinforced plastic can be produced. In the automotive field, examples of such fiber-reinforced hollow structure parts include in particular struts, ie A pillars, B pillars and C pillars, door frames and bumpers.

International Publication No. 02/072328 German Patent Application Publication No. 10200097

Claims (15)

  A water-dispersible supporting core made of a water-soluble binder and a filler is covered with reinforcing fibers, the fibers on the supporting core are impregnated with a curable plastic, the plastic is cured, and the core A method for producing a hollow structural part made of fiber reinforced plastic, wherein the child is washed out with water, characterized in that the binder consists at least partly of a silicate component.   The method of claim 1, wherein the binder is at least partially composed of water glass.   The binder content is from 0.5 to 8 wt%, preferably from 0.8 to 4 wt%, particularly preferably from 1 to 2.5 wt%, based on the weight of the filler. the method of. The binder has a weight ratio of SiO ₂ / M ₂ O in the range of 1.6 to 4.0, in particular 1.8 to 3.5, where M is sodium ion and / or potassium ion and / or Or a process according to claim 2 or 3 which represents lithium ions. It said binder has a solids content of SiO ₂ and _{M 2} O in the range of 30 to 60 wt%, A method according to any one of claims 1 to 4.   6. A method according to any one of the preceding claims, wherein the binder consists at least in part of sodium silicate and / or potassium silicate and / or lithium silicate.   7. A method according to any one of the preceding claims, wherein the binder comprises at least one further alkali metal compound in addition to the water glass.   The method according to claim 7, wherein the further alkali metal compound is a sodium compound and / or a potassium compound.   9. A method according to any one of the preceding claims, wherein the filler is at least partly composed of sand.   10. A method according to any one of the preceding claims, wherein the filler is at least partially composed of plastic particles.   11. A method according to any one of the preceding claims, wherein the filler is at least partially composed of ceramic particles.   The method according to claim 10 or 11, wherein the plastic particles or ceramic particles have a spherical shape.   13. A method according to any one of the preceding claims, wherein the filler is at least partly composed of ceramic or hollow glass spheres.   The method according to any one of claims 1 to 13, which is performed as a resin transfer molding method.   The method according to any one of claims 1 to 13, which is performed as a vacuum injection method.