JPH0796539A - Sealing material - Google Patents

Abstract

PURPOSE:To provide a sealing material for a mold wherein liquid molding raw materials are hard to enter the inside of a sealing groove formed in a divided surface of a mold, moreover, securing of a crushing allowance of a sealing material is possible, generation of flashes at the time of molding is controlled and the thickness of a molded product can be controlled precisely. CONSTITUTION:This material possesses a sealing material main body 22 having a thickness larger than the depth of a sealing groove 28 and a protrusion 24 formed on a seal contacting surface of the sealing material main body 22 and a hollow part 30 is formed in at least one part. A sealing material is used for sealing the parting line of a mold for molding for which liquid molding raw materials are used, for example, for injection molding. Especially, since a reactive stock solution like a norbornane monomer has ordinary viscosity of about several thousands cps or lower, it is preferable that the sealing material is used for sealing the parting line of a reactive mold for which the norbornane monomer is used as the reactive stock solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing material for sealing a divided surface of a mold, and more particularly, to a metal material for injection molding at a low pressure using a low viscosity liquid molding material. The present invention relates to a sealing material capable of excellently sealing a divided surface of a mold and suppressing burr generation.

[0002]

2. Description of the Related Art A mold used for injection molding has a mold split surface to prevent molding material from flowing out from the split surface of the mold clamped at the time of molding. A sealant may be attached. For example, as shown in FIG. 4, a seal groove 8 having a rectangular cross section is formed on one of the divided surfaces 6 and 6 of the molds 2 and 4, and a seal material 10 having a solid circular cross section is formed in the seal groove 8. There is known a structure in which the molding material is mounted and sealed so that the molding material does not flow out of the cavity through the gap between the divided surfaces 6 and 6.

Further, as shown in FIG. 5, a seal groove 8a having a rectangular cross section is formed on one of the divided surfaces 6a of the mold 2a and the mold 4a, and a rectangular solid cross section is formed in the seal groove 8a. There is also known a structure in which the sealing material 10a is attached and sealing is performed so that the molding material does not flow out of the cavity through the gap between the divided surfaces 6a.

[0004]

However, in reaction injection molding, since a low viscosity liquid molding material is used and molding is performed at a lower clamping pressure than in thermoplastic resin injection molding, the molding material is separated from the dividing surface. It easily leaks to the outside and burrs easily occur.

For example, in the seal structure of the divided surface of the mold using the seal material 10 having a solid circular cross section shown in FIG. 4, the outer diameter of the seal material 10, the width of the seal material groove, and the divided surface of the mold are smooth. Since the sealing material 10 is not uniformly crushed when the mold is clamped due to variations in degree and the like, the molding material may flow into the gap 12 of the seal groove 8 and solidify. Therefore, at the time of injection molding of the next shot, the crushing margin of the sealing material 10 is limited, the molds 2 and 4 are prevented from being completely closed, and burrs are generated in the gap between the divided surfaces 6 and 6. There is a problem such that the thickness dimension of the molded product molded in the cavity (not shown) is changed.

In the worst case, the molding material that has entered the gap 12 of the seal groove 8 solidifies together with the molding product in the cavity, and the sealing material 10 is pulled out together with the molding product when the molds 2 and 4 are opened. Therefore, there is a problem in that the sealing material 10 must be refitted at the time of injection molding of the next shot. In particular, it becomes a problem in reaction injection molding using a low-viscosity reaction liquid.

On the other hand, in the seal structure using the seal material 10a having a solid rectangular cross section shown in FIG. 5, the seal material 10a
Since there is almost no gap 12a between the seal groove 8a and the seal groove 8a, there is no inconvenience such as the molding material entering the gap 12a. However, in the seal structure having the sealing material 10a according to this conventional example, since the crushing margin of the sealing material 10a is very small, the split surfaces 6a, 6a of the molds 2a, 4a are formed.
The molds 2a, 4 should be arranged so that the mutual gap becomes the specified gap.
It is extremely difficult to combine a with each other, and therefore, it is difficult to mold the molded product formed in the cavity (not shown) in a prescribed thickness dimension.

The present invention has been made in view of the above circumstances, and it is difficult for the molding material to enter the seal groove formed on the divided surface of the mold, and it is possible to secure a crushing margin of the seal material. An object of the present invention is to provide a mold sealing material capable of suppressing the occurrence of burrs and molding a molded product in a prescribed thickness.

[0009]

In order to achieve the above object, a sealing material according to the present invention is formed on a sealing material body having a thickness equal to or greater than a depth of a sealing groove and a sealing surface of the sealing material body. And a hollow portion is formed in at least a part of the cross section of the sealing material body.

The sealing material according to the present invention is used for sealing a divided surface of a mold for generally known molding such as injection molding, and particularly, urethane type, urea type, nylon type,
It can be used for sealing a dividing surface of a mold for generally known reaction injection molding such as epoxy type, unsaturated polyester type, phenol type and norbornene type. Above all, the sealing material according to the present invention is suitable for sealing the divided surfaces of a reaction injection molding die that uses a norbornene-based monomer having a reaction liquid viscosity of about several thousand cps or less as a molding material.

The sealing material according to the present invention is basically composed of an elastic elastomer or foam. Elastomers are particularly preferred, as compared to foams, the material has less settling due to repeated use. Depending on the use of the sealing material, heat resistance capable of withstanding the heat of the mold and reaction heat and resistance to the liquid molding material are required.

Specifically, the sealing material is styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), nitrile butadiene rubber (NB).
R), diene rubber such as chloroprene rubber (CR),
Butyl rubber (IIR), ethylene-propylene-diene terpolymer rubber (EPDM), acrylic rubber, chlorosulfonated polyethylene rubber, olefin rubber such as fluororubber, silicone rubber, urethane rubber, polysulfide rubber, or foams thereof, Alternatively, it is made of urethane or nylon foam. Among them, the sealing material is an elastomer, particularly preferably NBR, IR or E.
It is composed of PDM, fluororubber, etc.

The sealing material according to the present invention comprises a sealing material main body and a protrusion formed on the sealing surface of the sealing material main body, and is formed by generally known extrusion molding or the like. It is preferable that the sealing material main body has a cross-sectional shape with a small gap with the sealing groove before the sealing material is crushed. This is to prevent the reaction liquid from entering the gap between the seal material and the seal groove. Since the crushing margin of the sealing material is compensated for by the hollow portion formed in the sealing material, it is theoretically unnecessary to form a gap between the sealing material and the seal groove as the crushing margin.

The cross-sectional shape of the hollow portion formed in at least a part of the cross-section of the sealing material is not particularly limited, and may be circular, suiziform, polygonal such as triangular or square, star-shaped, gourd-shaped, etc. Any shape of can be adopted. This hollow portion is formed continuously in the longitudinal direction of the sealing material.
Further, this hollow portion may be formed in a plurality. Also,
The hollow portion may be formed not only on the main body of the sealing material but also on the protruding portion.

The thickness of the main body of the sealing material according to the present invention may be equal to or larger than the depth of the seal groove, but should not be thicker than the thickness at which a desired crushing margin cannot be obtained during mold clamping. The cross-sectional shape of the protrusion formed on the sealing material according to the present invention is not particularly limited as long as it is a shape that does not get caught between the divided surfaces of the mold, and is rod-shaped protrusion, semi-circular protrusion, semi-elliptical shape. A protrusion or the like can be exemplified. The number of the protrusions is not limited to one and may be plural. Further, the protrusion is continuously formed along the longitudinal direction of the sealing material.

The thickness of the seal body is preferably determined so that the seal material is crushed in the seal groove and the divided surfaces of the die are in contact with each other when the die is clamped. If the thickness of the sealing material body is too thick with respect to the depth of the seal groove, the mold is not crushed by a predetermined amount when the mold is clamped, and the thickness dimension of the molded product is likely to be changed.

In the present invention, the mold does not necessarily have to be an expensive mold having high rigidity, and is not limited to a metal mold, but may be a resin mold, a ceramic mold, wood, glass, or the like. It is possible to use simple forms that are constructed, or a combination of these. In the present invention, the term “division surface of the mold” is used in a broad sense, and is used not only in the division surface of the fixed die and the movable die, but also in the concept including the division surface of the die main body and the insert die.

The seal material according to the present invention is preferably mounted in a seal groove formed on a divided surface of the mold, in which the mold is repeatedly separated and joined for each molding. There is no burr,
This is because the detachment of the sealing material due to this is eliminated and the efficiency of the molding operation is improved. The sealing material according to the present invention,
It can also be mounted in a seal groove formed on the dividing surface of the mold body and the insert mold.

[0019]

If the sealing material according to the present invention is housed in the sealing groove formed on the dividing surface of the mold and the dividing surfaces of the molds are aligned with each other, the sealing material can be formed even if the gap between the sealing material and the sealing groove is small. Since the hollow portion is formed inside, the sealing material is crushed well. Therefore, burrs do not occur, and since the divided surface of the mold is pressed against the opposing divided surface of the mold, the thickness dimension of the molded product does not change.

[0020]

The sealing material according to the present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is a sectional view of an essential part showing a state in which a seal material according to an embodiment of the present invention is mounted in a seal groove of a mold, and FIG. 2 is a schematic view of a mold showing an example of use of the seal material according to the embodiment. Partial cross-sectional views and FIGS. 3A and 3B are cross-sectional views of a sealing material according to another embodiment of the present invention.

As shown in FIG. 1, a sealing material 20 according to an embodiment of the present invention has a hollow portion 30 in at least a part of its cross section.
As shown in FIG. 2, the sealing material main body 22 and the protrusions 24 are provided, and the sealing material main body 22 is housed in the sealing groove 28 formed in the dividing surface 27 of the mold 26. The sealing material main body 22 of this embodiment is
The cross section thereof has a rectangular shape similar to that of the seal groove 28, has an elongated shape in the longitudinal direction (the direction perpendicular to the paper surface of FIG. 1), and the thickness b of the seal material body 22 is larger than the depth d of the seal groove 28. It is large in size. The thickness b of the sealing material body 22 is determined so that the sealing material 20 is completely crushed in the sealing groove 28. The protrusion 24 is crushed into the seal groove 28 by the mold clamping. If the thickness of the sealing material main body 22 is too thick with respect to the depth b of the seal groove 28, the divided surfaces of the molds will not come into contact with each other when the molds are coupled, and the thickness dimension of the molded product will be affected.

If the thickness is too thinner than the depth of the groove 28,
The reaction liquid hardens at the upper part of the sealant body, which makes it difficult to remove the molded product from the mold, and causes uncured burrs with stickiness. Therefore, the thickness b of the sealing material body 22 is preferably about d ≦ b ≦ d + 2 mm with respect to the depth d of the sealing groove 28.

The width wa of the seal material body 22 is slightly smaller than the width wb of the seal groove 28. In this embodiment, since it is not necessary to form a crushing substitute gap between the seal material main body 22 and the seal groove 28, if the seal material 20 can be mounted in the seal groove 28, the seal material main body 22 The width wa can be set to be larger than the width wb of the seal groove 28. However, the width wa of the sealing material body 22 is 0.25 to the width wb of the seal groove 28.
It is preferably as small as 0.5 mm. This is because the work of inserting the seal material 20 into the seal groove 28 becomes easy.

A protruding portion 24 is formed on the sealing surface of the sealing material main body 22 corresponding to the side protruding from the sealing groove 28. In this embodiment, the protrusion 24 has a single rod-shaped cross section. The protrusion 24 is formed continuously along the longitudinal direction of the sealing material body 22 (the direction perpendicular to the paper surface).
The height of the protrusion 24 is set so that it does not get caught between the divided surfaces of the mold when the mold is clamped. Specifically, it is preferably about 25 to 50% of the width wa of the sealing material body 22. Also,
The width of the protrusion 24 is preferably about 20 to 60% at the root thereof with respect to the width wa of the sealing material body 22.

In the present embodiment, the hollow portion 30 formed in the cross section of the seal material body 22 has a circular cross section and is formed continuously along the longitudinal direction of the seal material body 22. The size of the hollow portion 30 is determined according to the crushing margin of the sealing material 20 within a range where the sealing material has a restoring force, and is not particularly limited, but its cross-sectional area is equal to that of the sealing material main body 22. About 10 to 60% is preferable.

The sealing material body 22 having the hollow portion 30 and the protrusion 24 are integrally formed by, for example, extrusion molding. The sealing material 20 composed of the sealing material body 22 and the protrusions 24 is made of an elastic material,
For example, it is made of an elastomer such as NBR.

As shown in FIG. 2, for example, the sealing material 20 according to the present embodiment is formed on one of the divided surfaces 27 and 29 of the molds 26 and 31 (the divided surface 27 in FIG. 2). It is mounted in the seal groove 28. Of the molds 26 and 31,
For example, one die 26 is a fixed die and the other die 3
Reference numeral 1 denotes a movable type, and both of them are configured to be movable (closed) and separated (released).

The seal groove 28 is formed so as to surround the cavity formed between the convex mold 34 and the concave mold 32. The molding material is injected into the cavity through an injection port 36 formed in one of the molds 26. For example, as general molding conditions for reaction injection molding in the case of bulk polymerization of a norbornene-based monomer with a metathesis catalyst system, the reaction stock solution temperature is 20 to 80 ° C, the mold temperature is 20 to 150 ° C, and the mold clamping pressure is 0.1-10kg / cm
^{At 2} , the reaction time is in the range of 10 seconds to approximately 10 minutes.
The viscosity of the reaction stock solution is about 5 cps to several thousand cps.

In such molding, matting,
A reinforcing material such as cloth-woven glass fiber, aramid fiber, carbon fiber, etc. is installed in advance in the mold, and the reaction liquid is supplied into the mold to polymerize to produce a reinforced polymer (molded product). be able to.

Further, various plastic / rubber antioxidants, fillers such as carbon black, talc and calcium carbonate, pigments, colorants, foaming agents, flame retardants, sliding agents,
Styrene-butadiene copolymer (SBR), styrene-
Butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SI
The properties of the obtained polymer can be modified by blending various additives such as an elastomer such as S), a dicyclopentadiene-based thermopolymerized resin and a hydrogenated product thereof.

The additives are usually mixed in advance with either one or both of the reaction solutions. Molds 26 and 3 shown in FIG.
When the divided surfaces 27 and 29 of No. 1 are aligned, the mold is clamped, and the reaction injection molding as described above is performed, in the process, the reaction stock solution filled in the cavity is divided into the divided surfaces 27 and 29.
Since it is sealed by the sealing material 20, it does not flow out between the divided surfaces 27 and 29 to the outside, and the reaction liquid does not harden in the sealing groove. Therefore, burrs do not occur in the molded product obtained in the cavity, and the molding operation can be performed efficiently.

The present invention is not limited to the above-mentioned embodiments, but can be variously modified within the scope of the present invention. For example, as shown in FIGS. 3A and 3B, the cross-sectional shape of the sealing material can be variously modified. In the sealing material 20a of the embodiment shown in FIG. 3A, the cross-sectional shape of the hollow portion 30a formed in the cross section of the sealing material main body 22a is the same rectangular shape as that of the sealing material main body 22a. Further, the shape of the protrusion 24a is semicircular.

In the sealing material 20b shown in FIG. 3 (B), the sealing material main body 22b has a circular cross section, and
The shape of the hollow portion 30b is also circular. Also, the protrusion 2
The shape of 4b is a semi-elliptical shape. These sealing materials 20a and 20b can also be used in the same manner as the sealing materials of the above-described embodiments, and have the same operational effects.

Hereinafter, the present invention will be described in more detail with reference to more specific examples of the present invention, but the present invention is not limited to these examples. In addition,
Parts and percentages are by weight unless otherwise specified. Example 1 Phenolic antioxidant (trade name: Irganox 101)
0, manufactured by Ciba-Geigy Co., Ltd., containing 2% of a monomer mixture (ie, dicyclopentadiene (DCP) 90%).
And 10% methyltetracyclododecene) in two containers, one containing 100 parts of the monomer mixture of diethylaluminum cloyd (DEAC) at 0.
4 parts, 0.15 parts of n-propanol, 0.36 parts of silicon tetrachloride, and 6 parts of a styrene-isoprene-styrene block copolymer (Kreton 1170, manufactured by Shell Co.) were added (solution A). On the other hand, 0.3 part of tri (tridecyl) ammonium molybdate was added to 100 parts of the monomer mixture (solution B).

Liquids A and B were respectively sent to a power mixer by a gear pump so that the volume ratio was 1: 1, and then, into a cavity of a mold formed by a convex mold and a concave mold, Injection was performed at a mold temperature of 70 ° C., and a reaction was performed for 3 minutes in the mold device. As molds, molds 26 and 31 as shown in FIG. 2 were used. Dividing surface 27 of mold 26
The width wb (see FIG. 1) of the seal groove 28 formed in 1 is 1
It was 0.0 mm. The depth d of the seal groove 28 is 9.0 mm
Met. The sealing material 20 mounted in the sealing groove 28
1 has a cross-sectional shape as shown in FIG. 1, the width wa of the sealing material main body 22 is 9.5 mm, and the thickness b is 9.
It was 5 mm. The cross section of the hollow portion 30 is circular,
Its inner diameter was 5 mm. The height and width of the protrusion 24 were 3.5 mm and 4.0 mm, respectively. The sealing material 20 was formed by extrusion molding using NBR as a raw material.

A series of operations was performed under a nitrogen atmosphere. The viscosities of liquids A and B are 300 cp.
s, 300 cps. Burr was hardly formed on the molded product obtained after the injection molding, and the molding could be performed efficiently. In addition, there was no variation in the thickness dimension of the molded product, and the dimensional accuracy was good.

Comparative Example 1 Reaction injection molding was performed in the same manner as in Example 1 except that the sealing material 10 shown in FIG. Figure 4
The cross-sectional outer diameter of the sealing material 10 shown in is 10.0 mm.
NBR packing was used.

The obtained molded product had many burrs and the post-processing was complicated.

[0039]

As described above, if the sealing material according to the present invention is used to seal the mold, the liquid forming raw material enters the gap between the sealing groove and the sealing material and solidifies. Can be effectively prevented. Further, the crushing margin of the sealing material can be secured well, and the sealing action is good. Further, since the dividing surfaces of the mold can be brought into contact with each other while the sealing action is good,
The occurrence of burrs during molding can be suppressed, and the thickness of the molded product can be controlled well.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing a state in which a seal material according to an embodiment of the present invention is mounted in a seal groove of a mold.

FIG. 2 is a cross-sectional view of a main part of a mold showing a usage example of the sealing material according to the embodiment.

3A and 3B are cross-sectional views of a sealing material according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view of essential parts showing a state in which a sealing material according to a conventional example is mounted in a seal groove of a mold.

FIG. 5 is a cross-sectional view of essential parts showing a state in which a sealing material according to another conventional example is mounted in a seal groove of a mold.

[Explanation of symbols]

 20, 20a, 20b ... Sealing material 22, 22a, 22b ... Sealing material main body 24, 24a, 24b ... Projection part 26, 31 ... Mold 27, 29 ... Dividing surface 28 ... Seal groove 30, 30a, 30b ... Hollow part

Claims (1)

[Claims] 1. A seal material, which is housed in a seal groove formed in a divided surface of a mold to seal the divided surface of the mold, the seal having a thickness equal to or greater than a depth of the seal groove. A sealing material having a material body and a protrusion formed on a sealing surface of the sealing material body, wherein a hollow portion is formed in at least a part of a cross section of the sealing material body.