JPS62128711A - Molding tool having permeability - Google Patents

Abstract

PURPOSE:To obtain the heat resistance, sufficient strength and good transferring property of a molding tool, by constituting it with porous formed composite sintered member calcined by using a high melting point ceramic powder and a low melting point ceramic powder. CONSTITUTION:A molding tool 23 is constituted as a composite sintered member of a high melting point ceramic powder 21 with a low melting point ceramic powder 22. The low melting point ceramic powder 22 is sintered around the high melting point ceramic powder 21, and the low melting point ceramic powder 22 is sintered each other to bind the high melting point ceramic powder 21 each other. By this binding there is formed a skeleton where the high melting point ceramic powder 21 is an aggregate and the low melting point ceramic powder 22 is a binding member. Therewith pores 24 are formed, and the whole molding tool 23 has breathability. Therefore the gas of the space in the molding tool 23 at the time of molding is uniformly degassed from the whole surface of the porous mold, and is discharged from a hole 28 provided at a mold frame 27. Thereby pin-holes or cavities do not occur on the surface of a moldings, so a beautiful transferring can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a mold that has a good transfer function while maintaining necessary strength, and is particularly suitable for use in vacuum forming, blow molding, injection molding, etc. The present invention relates to a mold having good air permeability.

[Prior Art] Techniques such as vacuum forming, blow molding, and injection molding are generally well known.

For example, in vacuum forming, as shown in FIGS. 9(a) and 9(b), a resin sheet 1 softened by heat is set in a mold 2, and the sheet is passed through a communication hole 3 leading from the back side of the mold 2 to the mold surface side. By suctioning the gas in the space 4 surrounded by the sheet 1 and the mold 2, the sheet 1 is adhered to the mold surface and molded using the H method.

In blow molding, as shown in FIGS. 10(a) and 10(b), a cylindrical resin parison 5 softened by heat is held by a mold 6, and the parison 5 is inflated by an air blow 7 from inside the mold. The parison 5 is attached to the mold surface by discharging the gas between the mold 6 and the parison 5 through the communication hole 8 that communicates the mold surface and the back surface of the mold 6 by the pressure of the expanding parison 5. This is a method of molding.

In index molding, a material 9 such as sea urchin or resin having fluidity is indexed through a spool 12 through a nozzle 10 into a space surrounded by a mold 11 as shown in FIGS. 11(a) and (b). This is a method of molding.

[Problems to be Solved by the Invention] However, in each of the above-mentioned molding methods, when a simple ordinary mold is used as a mold, the following problems arise.

In vacuum forming, gas is sucked through several communicating holes 3 formed on the mold surface, but it is difficult to suck the gas uniformly from all the communicating holes 3, resulting in more or less uneven suction. However, there is a problem that complex shapes may not be transferred sufficiently, and fine patterns (grains, stitches, etc.) cannot be transferred. Furthermore, when transferring using a resin sheet with grains, there is a problem that the grains become wider due to heat when the sheet is heated.

In addition, in blow molding, gas is discharged through several communication holes 8 formed on the mold surface, but the more complex the shape is, the more uneven the gas discharge becomes, which may result in insufficient transfer of the mold. There's a problem.

In order to reduce the unevenness of gas suction or discharge in these vacuum forming and injection molding processes, increasing the number of communication holes 3.8 may be considered, but in reality, this is due to the relationship with the design of the molded product. In many cases, it is difficult to increase the number of communicating holes, and if the number of communicating holes is increased too much, problems will arise in terms of the strength of the mold.

In general, injection molding has a problem in that the gas remaining in the space surrounded by the mold 11 is not sufficiently exhausted, so that pinholes and cavities are easily formed in the molded product.

To solve this problem, a mold having a porous structure is known (for example, JP-A-60-6243@).

However, the proposed mold has a porous structure made of iron-based powder and ceramic powder as aggregates, and although ceramic is a material with excellent heat resistance, iron-based powder has a limited heat resistance. Therefore, there is a problem that the mold as a whole may lack heat resistance. Furthermore, since it is generally considered difficult to increase the bonding strength between ceramics and iron-based materials, there is also the problem that it may be difficult to ensure sufficient strength of the mold.

In view of the above-mentioned problems, the present invention has not only heat resistance but also sufficient strength, can withstand multiple uses, and has good transferability even in fine and complicated shapes. Moreover, it is an object of the present invention to provide a mold that has sufficient air permeability so that gases in the mold and the molding material can be easily removed.

[Means for Solving the Problems] The mold having air permeability of the present invention, which meets the above [1], has a high melting point ceramic 3> and a low melting point ceramic powder as main components, which are incinerated during firing. A sintered body is obtained by molding a slurry-like sample containing components as a binder before sintering and sintering it at a temperature that will sinter the low-melting-point ceramic. The fired body has a skeleton in which the high melting point ceramic powder becomes the aggregate and the low melting point ceramic powder is sintered to act as a binding material that connects the high melting point ceramic powder, and this skeleton makes the entire mold porous. It has a quality structure.

Preferably, the fired body has a laminated structure of a mold surface thin layer forming the mold surface of the mold and a back reinforcing layer located on the back side of the mold surface thin layer, and the mold surface thin layer is a thin mold surface layer. The back reinforcement layer is made of coarse-grained, high-melting-point ceramic powder. Further, it is desirable that the above-mentioned fired body be fired in an oxidizing atmosphere.

[For Use] In such a mold, low melting point ceramic powder adheres around the high melting point ceramic material, and pores are generated due to the surface tension horns of the low melting point ceramic material. Since firing is carried out at a temperature at which the low-melting point ceramic powder is sintered, the high-melting point ceramic powder remains as a high-strength aggregate, and the skeleton formed by the low-melting point ceramic part creates a porous structure. This structure ensures air permeability throughout the mold, and the high melting point ceramic powder ensures the desired strength as a mold. Furthermore, since it is constructed as a mold made of ceramic, sufficient heat resistance is achieved, and since it is a bond between high melting point and low melting point ceramics, sufficient internal bonding strength is ensured.

In addition, the porous structure eliminates the need to provide holes for gas suction or gas discharge as in conventional methods, making it possible to suction or discharge gas from the entire mold even with a multi-phase shape. A predetermined mold surface is easily formed. By appropriately setting the particle size of the ceramic powder on the mold surface, it is possible to obtain a smooth skin surface while ensuring the above-mentioned air permeability, and good transferability even for fine and complex shapes71). i'Jt is done.

[Example 1] Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a mold having air permeability according to the present invention, and FIG. 2 shows a schematic cross section of the mold. In Figure 2, 21
indicates a high melting point ceramic powder, and 22 indicates a low melting point ceramic powder, and the air permeable mold 23 in the present invention is a composite sintered body of a high melting point ceramic powder 21 and a low melting point ceramic layer 22. Constructed as. A low melting point ceramic powder 22 is sintered around a high melting point ceramic layer 21, and a low melting point ceramic powder 22 is sintered around the high melting point ceramic powder 21.
They are also sintered to bond the high melting point ceramics 21 together. Through this bonding, a skeleton is formed in which the high-melting-point ceramic powder 21 is used as an aggregate and the low-melting-point ceramic powder 22 is used as a binding material, and the pores 24 are formed by forming this skeleton. Therefore, the mold 23 body has a porous structure and is breathable.

This mold 23 with a porous structure is made of a fired body made of a ceramic powder 21 with a high melting point and a ceramic powder 22 with a low melting point, which are fired as main components, as will be described later. The fired body has a laminated structure of a mold surface thin layer 25 forming the mold surface of the mold 23 and a back reinforcing layer 26 located on the back side of the mold surface thin layer 25. The mold surface thin layer 25 is made of fine grained ceramic powder 2 with a high melting point.
1 is used, and the back reinforcing layer 26 is made of coarse-grained ceramic powder 21 with a high melting point.

Since the mold 23 is fired at a temperature at which the low melting point ceramic powder 22 is sintered, the high melting point ceramic powder 21
The strength of the mold 23 is maintained even after firing, and the high melting point ceramic powder 21 becomes the aggregate at the back of the skeleton that ensures the strength of the mold 23.

Therefore, by adopting the laminated 4'M structure as described above, the mold surface thin layer 25 increases the mold surface with a fine texture by 1q, ensuring sufficient strength for the mold 23 as a whole,
Sufficient ventilation is also maintained.

A mold 23 of 1-g is held by a mold frame 27 in a manner not shown in FIG. The air is more uniformly degassed through the mold and discharged through holes 28 provided in the mold frame 27.

In the mold 23, a high melting point ceramic powder 21
Examples include alumina, mullite, silica, zirconia,
Among oxides such as magnesia and calcia, and composite oxides thereof, those without problems in corrosion resistance and heat resistance are suitable.

The particle size is suitably 50 microns or less for the mold surface thin layer 25 and 200 microns or more for the back reinforcing layer 26. However, depending on the method of use, this particle size is not necessarily in this range, and -C may also be used.

The low melting point ceramic powder 22 is made of oxides such as borax, frit, etc., and composite oxides of oxides including these, which have a much lower melting point than the high melting point ceramic powder 21 and have no problems in corrosion resistance and heat resistance. things are appropriate. The particle size may be the same for both the mold surface thin layer 25 and the back reinforcing layer 26, and is suitably 20 microns or less. It does not necessarily have to be within this range depending on the particle size.

Further, the weight ratio of the high melting point ceramic layer 21 and the low melting point ceramic layer 22 is 100:10 to 1'OO:
50 is appropriate. If the content of ceramic powder 22 with a melting point lower than this range is less, the strength will decrease, and if it is more, the air permeability will be poor. By adjusting this weight ratio, the particle size of the high melting point ceramic powder 21, and the firing temperature, the strength and air permeability of the mold 23 can be adjusted.

Next, an embodiment of a method for manufacturing the mold 23 will be described.

Figure 3 shows the manufacturing process of the mold 23.
In order to form a mold surface thin layer 25, fine grained high melting point ceramic powder 21 and low melting point ceramic powder 22 are added with a binder, plasticizer, etc. to achieve appropriate viscosity and plasticity. Mix thoroughly to obtain a slurry-like sample.

Next, as shown in FIG. 4, the slurry-like sample 29 obtained in the previous step is poured into a mold model 31 which has been molded into a mold frame 30, and subjected to vibration casting to form a thin film of about 'l rTl rTl. A layer is formed and this is semi-solidified to the extent that it will not be destroyed in the next process.

Next, in order to form the back reinforcing layer 26, coarse grained high melting point ceramic powder 21 and low melting point ceramic powder I) are used.
A binder, a plasticizer, etc. are added to obtain a suitable viscosity and plasticity, and the mixture is thoroughly mixed to obtain a slurry-like sample.

Next, as shown in FIG. 5, a slurry-like sample 32 is poured into the semi-solidified grain-shaped surface thin layer 25 in the previous step and subjected to vibration casting, and dried to the extent that the plasticity is not lost. Remove the mold. The demolded product is fired in an oxidizing atmosphere to obtain a mold 23.

Incidentally, the binder, plasticizer, etc. for obtaining appropriate viscosity and plasticity are components that are incinerated during firing, and suitable binders include butyral resin, and suitable plasticizers include phthalate esters.

By the above-described molding method, a mold 23 having good transferability and reproducibility from the mold 31 and sufficient strength can be obtained.

Next, more specific examples in which the present invention is applied to various molding methods will be described.

FIG. 6 shows an embodiment applied to vacuum forming, in which the mold surface thin layer 25a is removed by gas suction 41 from a vacuum pump.
The gas in the mold 23a having the back reinforcing layer 26a is discharged from the mold surface, whereby the resin sheet 42 softened by heat is uniformly adsorbed to the mold surface and molded.

According to this, the resin sheet 42 is attracted to the rest of the mold surface and the unevenness of the mold is transferred, so that even fine and complex shapes are transferred. Note that 43 indicates a formwork, and 44 indicates a clamp.

FIG. 7 shows an embodiment in which the present invention is applied to blow molding, in which a cylindrical resin parison 51 softened by heat is placed in a mold 23 having a mold surface thin layer 25b and a back reinforcing layer 26b.
The resin 51 is inflated and molded into a bag shape by inserting the resin 51 into the bag and blowing gas through the regular needle 52 inserted into the inside thereof.

In this case, the gas between the bag-shaped resin 51a and the mold 23b is discharged from the entire mold surface of the mold 23b, so that the bag-shaped resin 51a can be neatly transferred even at the corners. I can do it. Note that r3.53 indicates the formwork, and 54 indicates the gas to be handled.

FIG. 8 shows an embodiment in which the present invention is applied to index molding, in which a +A material 61 made of fluidized resin or the like is surrounded by a mold 23c having a thin mold surface layer 25c and a back reinforcing layer 26c. It is molded by injecting it from a nozzle 62 into a spool 63.

In this case, the gas remaining in the mold 23C or the gas trapped in one or more fats is discharged from the entire surface of the mold 23G, causing pinballs or cavities to form on the surface of the molded product. , a beautiful transcription. In addition, 64 shows a formwork, and 65 shows the gas discharge|emitted.

Note that the above-mentioned examples are representative examples of the present invention, and the present invention is not limited thereto. For example, in the present invention, molten metal, rubber, glass, or a molten or softened plastic material such as rutal or nitric acid is poured into the mold using a mold with a gap, and the material is poured under pressure. Alternatively, it can also be applied to molds that require degassing and dewatering properties in molding methods that involve plastic flow.

[Effects of the Invention] When using the air-permeable mold of the present invention as described above, the mold is a composite sintered mold with a porous structure fired using a high-melting point ceramic material and a low-melting point ceramic powder. Since it is composed of a solid body, it is possible to obtain a mold that has sufficient strength as well as heat resistance, and has the advantage of being able to have good transferability even for minute and complex shapes. It will be done.

In addition, it has sufficiently good air permeability to prevent the mold surface from drying, making it possible to easily and uniformly remove gas inside the mold and during the molding process, allowing the design surface of fine and complex shapes to be easily and evenly removed. Another effect is that it becomes possible to easily mold objects having the following properties.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a breathable mold according to an embodiment of the present invention, FIG. 2 is a partially enlarged cross-sectional view showing the internal structure of the mold shown in FIG. 1, and FIG. 3 is a cross-sectional view of the mold shown in FIG. Figure 4 is a flow diagram of the manufacturing process of 176 molds.
Figure 5 is a cross-sectional view of the apparatus in step 1 of the manufacturing process shown in Figure 3. Figure 6 is a cross-sectional view of the mold when the present invention is applied to vacuum forming. Figure 7 is a cross-sectional view of a mold when the present invention is applied to blow molding, Figure 8 is a cross-sectional view of a mold when the present invention is applied to injection molding, and Figure 9 (a) is a cross-sectional view of a mold when the present invention is applied to injection molding. ) is a cross-sectional view of a mold used in conventional vacuum forming, Figures 10 (a) and (b) are cross-sectional views of a mold used in conventional blow molding, and Figures 11 (a) and (b) are cross-sectional views of a mold used in conventional injection molding. A cross-sectional view of the mold used for this. 21... Ceramic powder with high melting point 22...
...Low melting point ceramic powder 23.23a, 23b, 2
3 G--Molding mold 24... Pores 25.25a, 25b, 25c--The thin layer 2
6.26a, 26b, 26G... Back reinforcement layer 2
7... Formwork 2B... Hole 29. 32... Slime sample 30... Formwork 31... Mold hidden 42. ... Resin sheet 51 ... Resin parison 62 ... Nozzle 63 ... Spool Fig. 6 230 +1'l: Itchi 1 Fig. 7

Claims (3)

[Claims] (1) A slurry-like sample containing a high melting point ceramic powder and a low melting point ceramic powder as main components and a component to be incinerated during firing as a binder before firing is molded into the low melting point ceramic powder. The fired body is composed of a fired body fired at a calcination temperature, and the fired body has the high melting point ceramic powder as an aggregate, the low melting point ceramic powder is sintered, and a binding material that connects the high melting point ceramic powder. What is claimed is: 1. A mold with air permeability, characterized in that the mold has a skeleton as follows, and the skeleton provides a porous structure as a whole. (2) The fired body is configured to have a laminated structure of a mold surface thin layer forming the mold surface of the mold and a back reinforcing layer located on the back side of the mold surface thin layer, and the mold surface thin layer is 2. The air-permeable mold according to claim 1, wherein the fine-grained ceramic powder with a high melting point is used, and the back reinforcing layer uses the coarse-grained ceramic powder with a high melting point. (3) The mold having air permeability according to claim 1, wherein the fired body is fired in an oxidizing atmosphere.