JPS5933106B2 - Manufacturing method of asbestos gasket - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for producing an asbestos joint sheet cassette (asbestos-based gasket) using the mold forming method of the present invention.
The purpose is to equalize the tensile strength of each part along the periphery of the gasket, and to avoid any imperfect adhesion or bonding surfaces that would cause strong faults within the wall thickness.

Stone wire joint sheet gaskets are widely used as cylinder head gaskets, flange gaskets, and various other gaskets and packings.

In order to reduce material loss to zero or very little when manufacturing such asbestos joint sheet gaskets, the applicant has already proposed various mold manufacturing methods.

One method is to extrude an unvulcanized mixture of asbestos, latex, and solvent into a rod shape, dry it, then fill it into a product-shaped mold, pressurize it, and heat-form it (%Kasho 5L-73081).
.

However, in this case, the rod containing the solvent immediately after extrusion is very flexible and is easy to mold, adhere, and join.
The following problems arise because the extrudate is dried before preforming.

(1) The extruded product hardens and the flow of the compound becomes poor, making it more difficult to form it into a plate shape than a round bar.

(2) Even when pressurized, heated, and molded, the adhesion and joint surfaces are not completely integrated, and the mechanical strength of the product tends to decrease.

In the present invention, an extruded product extruded into a string shape (including rod shape) or a band shape from an extruder is immediately processed, that is, before the solvent evaporates, into a forming groove of a mold having a shape similar to or the same as the product shape in an open state. Fill the mold along its longitudinal direction and close the mold.
By adding a preforming process at room temperature to a soft material containing a solvent, both ends of the overlapping molded product are completely integrated in the mold, creating a fault (boundary surface) that reduces the mechanical strength of the product. ) is characterized by the fact that it does not produce larvae, and will be explained with reference to the drawings as follows.

FIG. 1 is an explanatory diagram of the extrusion process, in which an asbestos joint sheet mixture C containing asbestos, latex, and a solvent and kneaded as necessary is supplied to the hopper 11 of the extruder 1, and then passed through the rod-shaped extrusion die 12. Extrude the rod R.

A cross section of the rod R is shown in FIG. 1a. By changing the die 12 to a band-shaped extrusion die, the cross section of the rod R can be made into a band-like shape as shown in Fig. 1b.

In this case, as the extruder 1, a screw set, a ram type, or any other known extruder can be used.

In order to keep the temperature of the mixture C as low as possible, it is desirable to cool each part of the extruder 1 to prevent the solvent in the mixture C from volatilizing before extrusion.

FIG. 2 is an explanatory diagram of the process of cold-pressure forming (preforming) an extruded product into a shape approximating a product gasket. The rod R is loaded along the longitudinal direction into the gasket molding groove 21a of the female mold 21 of the gasket molding mold 2 to be constructed.
The ends r1+r2 of are overlapped.

The embodiment shown in FIG. 2 shows the case where the rod R is loaded in a single layer into the forming groove 21a, but since it is necessary to load the amount of mixture necessary to form the product gasket, the above-mentioned The thickness of the rod R is calculated in advance to match the amount required for manufacturing the gasket, and the rod R is loaded into the forming groove 21a.

Therefore, depending on the case, the rods R may be loaded twice or three times or more into the molding groove 21a, or rods of a certain length may be partially replenished and loaded.

The male mold 22 has a protrusion (not shown) that fits into the molding groove 21a, and when the mold 2 is closed, a space (filled with compound) corresponding to the product shape is formed in the molding groove 21a. The rod R loaded into the molding groove 21a is molded under pressure at room temperature using the molding die 2 shown in FIG.

Here, it is still in a soft state containing the solvent, and the overlapping part of the ends r1 and r2 of the rod R, or two or double rods R
When loaded, the spliced parts become completely mechanically connected and integrated without creating any boundary surfaces such as faults.

The obtained gasket approximation molded product is soft, and therefore it is generally difficult to take out the molded product from the gasket molding groove 21a, but it is possible to easily take out the molded product by using a jig or using a mold release agent. I can do it.

Since the gasket approximation molded product formed under pressure at room temperature contains a solvent, it is dried to volatilize the solvent.

Possible drying methods include natural leaving, forced air blowing, vacuum drying, etc., but drying using forced air blowing, vacuum drying, etc. can speed up drying.

C" in FIG. 3 is a dried gasket approximation molded product.

FIG. 4 is an explanatory diagram of the pressure and heat molding process, where 4 is a pressure and heat molding mold, 41 is a female mold, and 42 is a male mold. It has a molding groove of the same shape as in Figure 2).

The pressure-low thermoforming mold 4 may be the same as the molding mold 2.

A dried gasket approximation molded product G" is loaded into this molding groove, and pressurized and heat molded.

Heating conditions vary depending on the size of the gas get to be molded, but are usually approximately 100°C and a pressure cuff of 5 Ky/e.
rr? Heat under pressure for about 5 seconds.

Thereafter, the mold 4 is released and the gasket approximation molded product G" is taken out and vulcanized to stabilize its properties.

The vulcanization conditions at this time are usually about 135° C. for about 30 minutes, and the vulcanization means can be steam heat, electric heat, infrared, or other known vulcanization equipment.

This vulcanization may be performed within the mold 4 during the above-mentioned pressure and heating process.

In FIG. 5, G is a gasket punched into a predetermined product gasket shape, and g is punching waste.

Depending on the shape of the gasket, it is possible to create a mold in the same shape as the product gasket and manufacture it without any loss.

The present invention is not limited to the embodiments described above, and the present invention can be applied by interposing a reinforcing body such as a wire mesh or a metal plate with hooks, which has substantially the same shape as the molded product, between two layers of gasket-like molded products to apply pressure. ,
If heated and molded, an asbestos joint sheet gasket containing reinforcement can be obtained.

Furthermore, by stacking and molding two or three layers of band-shaped extruded products with different compositions, gaskets with a plurality of properties can be manufactured.

Also, in the preforming process, it is possible to mold the gasket into the shape of the final product gasket, rather than creating an approximate molded product as described above.

In this case, there is no need for punching after the pressure and heating process.

Furthermore, an injection molding machine may be used as the extruder to directly mold the material into a mold.

As explained above, according to the present invention, (1) Knead asbestos, latex, and solvent.

Therefore, compared to using pelletized rubber material instead of latex, it can be kneaded in a shorter time.
The work process becomes easier.

Furthermore, since the mixture of asbestos, latex, and solvent is extruded using an extruder into a rod or band shape, asbestos fibers are oriented along the extrusion direction, and a gasket having sufficient tensile strength required for the gasket can be obtained.

Moreover, since the extruded product is loaded and molded into the molding groove of the mold along its longitudinal direction, the same strength can be obtained no matter where along the circumference of the gasket is taken.

This is clear from FIG.

FIG. 6A is an enlarged view of the cross-sectional structure of the gasket according to the present invention;
FIG. 6 is an enlarged view of the cross-sectional structure of a gasket punched from a sheet formed using a calendar roll.

(2) In the preforming process, a flexible molded product (rod R) containing a solvent is used immediately after extrusion, so the joints at both ends of the rod and the joints when two rods R are loaded are completely mechanically connected and integrated, and therefore no faults (interfaces) or the like that would cause a decrease in mechanical strength occur.

(3) In the preforming stage, a gasket approximation molded product with a shape similar to the product gasket is made in advance, so there is no or very little material loss, and any thickness and cross section can be created depending on the loading amount of the extruded product and the mold dimensions. can be manufactured.

(4) After drying following preforming, pressure is applied instead of simply heating, making it possible to obtain a product with a dense material and suitable for high pressure even when the amount of latex as a binder is small. I can do it.

In particular, a hard gasket suitable for cylinder rad gaskets etc. can be obtained.

Furthermore, by changing the pressurization and heating conditions, gaskets with different compression characteristics and flexibility can be manufactured even if they are made of the same material.

(5) By molding two or three layers of band-shaped extruded products, gaskets with multiple characteristics can be manufactured.

(6) A product can be obtained in which a reinforcing body such as a wire mesh or a metal plate with hooks is interposed.

The difference between the case where the extruded product is dried before preforming as in JP-A-51-73081 and the case where it is dried afterwards as in the present invention will be described.

(a) If dried before preforming, the extrudate will harden and the moldability of the compound will deteriorate, so even if it is molded, high surface pressure will be required during hot molding.

Therefore, only gaskets with low compressibility and poor sealing properties can be manufactured.

On the other hand, in the case of drying after preforming, gaskets having various characteristics can be easily obtained even if they are made of the same material since the extruded product is molded within its flexibility.

(b) The ends of the extruded product are compressed and bonded together, but even after compression molding after drying, the ends only appear to be stuck together, and the fibers between the ends are entangled and are not completely bonded. There is no connection, and if a gasket is used, leakage will easily occur from the end portion.

On the other hand, when the fibers are dried after preforming as in the present invention, tangles of fibers are observed at the ends, and the above-mentioned problems do not occur because the fibers are completely bonded.

(c) When the extruded product is loaded into a mold after drying, the extruded product has corners or rounded parts in its shape, and the flexibility of the extruded product is lost, so wrinkles and cracks occur in these parts, which causes problems when producing gasket products. Its sealing properties are significantly reduced.

On the other hand, even if it is loaded into the mold in a soft state containing a solvent as in the present invention, no cracks or the like will occur.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the extrusion process, and Figure 1a is A-A in Figure 1.
A sectional view, FIG. 1b is a drawing corresponding to FIG. 1a showing a modification, FIG. 2 is a perspective view for explaining the preforming process, FIG. 3 is an explanatory diagram of the drying process, and FIG. 3a is a diagram corresponding to FIG. C-C sectional view, Figure 4 is a front view of the mold used in the pressure and heat molding process, Figure 5 is
The figure is a plan view of the product gasket, and FIG. 6 is a diagram illustrating the orientation of asbestos fibers in the product gasket. 2...Gasket mold, 21a...
・Molding groove, C...mixture, R...rod (
extruded product).

Claims (1)

[Claims] 1. An unvulcanized mixture obtained by kneading asbestos, latex, and a solvent is extruded into a string or band shape using an extruder, and this is immediately molded into a mold with a shape similar to or the same as the product shape in the open state. A method for producing an asbestos-based gasket, which comprises loading the gasket into a molding groove, closing the mold, preliminarily molding the gasket at room temperature while it is soft and containing a solvent, and pressing and heating molding after drying.