JP2003170462A - Hollow molding of thermosetting resin and method and apparatus for molding the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hollow molding made of a thermosetting resin which can be easily molded even in a thick-walled molding having good productivity in low cost without using a core and in which a fault such as a shrink or the like is seldom brought about and which has an excellent appearance. <P>SOLUTION: The method for molding the hollow molding made of the thermosetting resin having the step of molding the hollow molding by a fluid casting injection molding or fluid casting transfer molding, comprises the steps of the thermosetting resin material supply step of supplying the thermosetting resin material in the cavity of the mold for constituting the hollow molding so that the cavity is substantially completely filled, and the fluid supply step of supplying the fluid into the molten thermosetting resin material supplied to the cavity. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding technique for hollow thermosetting resin products. In particular, for example, by using gas injection injection molding technology or gas injection transfer molding technology, a molten thermosetting resin material is injected into the cavity of the mold and pressurized gas is injected to obtain a hollow thermosetting resin body. Regarding technology that can be done.

[0002]

A resin molded article having a hollow inside is well known. However, in most hollow resin molded products, the resin that is the material is thermoplastic. That is, hollow resin moldings made of thermosetting resin are very limited. This is because the characteristics of the thermosetting resin and the characteristics of the thermoplastic resin are significantly different. That is, if the technology for obtaining a hollow molded product using a thermoplastic resin is used as it is for a thermosetting resin,
It has been considered that hollow products made of thermosetting resin cannot be obtained. The reason is that gas injection injection molding and gas injection transfer molding, which have been used to obtain hollow molded articles using thermoplastic resins, cannot be adopted when hollow molded articles are obtained using thermosetting resins. A major reason that has come to be thought is that thermosetting resins are those that are melted by applying heat and are cured by applying heat.Therefore, thermosetting resin materials are gelled immediately after injection into the mold. -It is thought that the curing will start rapidly, and it is believed from the head that gas injection to obtain hollow products may not be possible.

By the way, as a method for making the inside of a thermosetting resin molded product hollow, a molding method using a core is known. For example, a low melting point metal or a resin material is used as the core material, the core is placed in a mold, and the core is melted or melted and removed after injection molding to obtain a hollow molded article. However, in this technique, since the core is used,
High cost. In particular, if the shape becomes complicated, the cost will increase rapidly. Further, the removal of the core is not easy and the productivity is poor. And, in the case of the one having a complicated shape, it is not actually performed.

There is also known a method in which a thermosetting resin-made hollow part is obtained by high-frequency welding and adhering a plurality of divided thermosetting resin molded parts and processed parts to each other.

However, the method of obtaining a hollow product by high-frequency welding / adhering a plurality of molded parts or processed parts to each other, in addition to high cost and low productivity, lowers the strength of the high-frequency welded / adhered part. At the same time, the aesthetics are greatly reduced. Furthermore, it cannot have a complicated shape.

Therefore, the problem to be solved by the present invention is to solve the above problems.

That is, the first problem to be solved by the present invention
The problem is to provide a hollow molded product made of a thermosetting resin without using a core.

A second problem to be solved by the present invention is
It is to provide a hollow molded article made of a thermosetting resin with high productivity and at a low cost.

A third problem to be solved by the present invention is
It is an object of the present invention to provide a hollow-molded product made of a thermosetting resin that can be easily molded even if it is thick, and that it is difficult for defective products such as sink marks to occur.

A fourth problem to be solved by the present invention is
A hollow molded article made of a thermosetting resin having excellent appearance is provided.

[0011]

Means for Solving the Problems The first to third problems are a method for molding a hollow product made of a thermosetting resin,
The method comprises a thermosetting resin material supplying step of supplying a thermosetting resin material into a cavity of a mold forming a hollow product, and a fluid supplying step of supplying a fluid into a molten thermosetting resin material in the cavity. This is solved by a method for molding a hollow product made of a thermosetting resin, which is characterized in that

In particular, it is a method for molding a hollow product made of a thermosetting resin by fluid injection molding or fluid injection transfer molding, in which a thermosetting resin material is supplied into the cavity of a mold forming the hollow product. A thermosetting resin hollow article molding method comprising a thermosetting resin material supplying step and a fluid supplying step of supplying a fluid into a molten thermosetting resin material in a cavity. .

A device for molding a hollow product made of a thermosetting resin, wherein a mold for molding a hollow product made of a thermosetting resin and a thermosetting resin material are supplied into the cavity of the mold. A thermosetting resin material supply means for supplying a fluid into the molten thermosetting resin material in the cavity of the mold, Solved by the device.

In particular, it is an apparatus for molding a hollow product made of a thermosetting resin by fluid injection molding or fluid injection transfer molding, which comprises a mold for molding a hollow product made of a thermosetting resin, and the mold. A thermosetting resin material supplying means for supplying a thermosetting resin material into the cavity, and a fluid supplying means for supplying a fluid into the molten thermosetting resin material in the cavity of the mold. This is solved by a thermosetting resin hollow article forming device.

A hollow article having a hollow portion made of a thermosetting resin material, which is obtained by the above-mentioned molding method or molding apparatus, is used. Will be resolved.

In particular, a hollow product made of a thermosetting resin material and having a hollow part having a hollow volume of 2 to 50% of the volume of the molded product, which is obtained by the above-mentioned molding method or molding apparatus. It is solved by a hollow product made of thermosetting resin.

In the present invention, it is preferable that the supply of the fluid into the molten thermosetting resin material in the cavity starts at a stage before the completion of the curing of the molten thermosetting resin material in the cavity. Further, it is preferable to provide a fluid supply control means so that the supply of the fluid by the fluid supply means starts at a stage before the completion of the curing of the molten thermosetting resin material in the cavity. For example, during the injection of the thermosetting resin material (in some cases, after the injection is completed) until the point where the resin viscosity inside the cavity is low even if the molten thermosetting resin material is hardened on the wall surface of the cavity Pressurized fluid is injected into the cavity of the mold from the injection port of the nozzle. Thereby, a hollow portion is easily formed in the molten thermosetting resin material inside the cavity.

In the present invention, the supply of the fluid into the molten thermosetting resin material in the cavity is preferably continued until the molten thermosetting resin material in the cavity is completely cured. Further, it is preferable to provide a fluid supply control means so that the supply of the fluid by the fluid supply means is continued until the molten thermosetting resin material in the cavity is completely cured.
When the pressure is continuously applied in this way, it becomes difficult for the molten thermosetting resin material to flow back into the fluid supply nozzle.

In the present invention, the amount of thermosetting resin material supplied into the cavity is basically less than the volume of the cavity. Of course, there is no problem in exceeding this. However, if this is ignored and a large amount is supplied, the material cost will increase. That is, when a molten thermosetting resin material is injected from a resin gate into a cavity of a mold formed by closing a pair of molds using a molding method such as fluid injection molding or transfer molding, during the injection. Alternatively, after the injection is completed, the molten thermosetting resin material is cured from the wall surface of the cavity. When the viscosity of the molten resin inside the cavity is low, pressurized gas is injected into the cavity of the mold from the injection port of the gas supply nozzle that communicates with the cavity of the mold. The pressurized gas injected into the cavity is molded by maintaining the pressure of the pressurized gas until the molten thermosetting resin material is completely cured in the cavity of the mold. When the amount of injected resin is small, the molten thermosetting resin material is made to flow to the mold wall of the cavity by the pressure of the pressurized gas, and at the same time becomes a hollow shape, resulting in a hollow molded product of the thermosetting resin. can get.

However, it is preferable to supply a little more. For example, it is preferable in terms of appearance that the thermosetting resin material is supplied so that the total of the volume of the hollow portion formed and the volume of the thermosetting resin material supplied exceeds the cavity volume. Bring results. That is, when the volume of the hollow portion formed is X, the volume of the thermosetting resin material supplied is Y, and the cavity volume is Z, when Y is an amount satisfying X + Y = Z, the gas is When supplied, the molten thermosetting resin material that has started to harden will move by rubbing the cavity wall surface due to the pressure of the gas, so that the surface will have a surface roughness like sandblasting, The appearance is deteriorated. However, when the molten thermosetting resin material is supplied into the cavity to some extent as described above, for example, Y≈Z, that is, the cavity is almost completely filled with the molten thermosetting resin material. In this case, even if gas is supplied, the thermosetting resin material, which has started to harden, is not rubbed by the wall surface of the cavity and pushed into the interior of the cavity, so the surface is sandblasted. There was no deterioration in the appearance that would have been received. Therefore, heat is applied so that the total of the volume X of the hollow portion formed and the volume Y of the thermosetting resin material exceeds the cavity volume Z, particularly Y≈Z, that is, the cavity is almost completely filled with the molten thermosetting resin material. It is preferable to include a thermosetting resin material supply control means for controlling the supply amount of the curable resin material. When the cavity volume is Z, the hollow volume formed is X, and the volume of the thermosetting resin material supplied is Y, the preferable Y amount is [Z- (1/2) X] or more. Furthermore, [Z- (1
/ 3) X] or more. Particularly, it is [Z- (1/4) X] or more. The upper limit value may exceed Z, but it is meaningless if it greatly exceeds Z. On the contrary, the material cost is high. Therefore, approximately Z or less is preferable. As a result, a hollow molded article made of a thermosetting resin having a beautiful appearance, no sink mark, and no hesitation mark can be obtained.

As a method for improving the appearance,
In the case of a thermoplastic resin material, a method of raising the mold temperature to improve the mold transfer property and improving flow marks, sink marks, etc. is adopted. Since the mold temperature is 160 to 180 ° C., it is difficult to raise the temperature to eliminate the defect of the appearance. Further, a scratch mark such as unfilled peculiar to the thermosetting resin material is formed, and the appearance is poor. However, by adopting the above-mentioned method, these problems can be solved, and a hollow molded article made of a thermosetting resin having excellent appearance can be obtained.

When the resin is a thermoplastic resin, the thermoplastic resin material which has begun to solidify when the gas is supplied is the cavity of the cavity, even if Y is an amount satisfying X + Y = Z. It will not be rubbed against the wall surface, and the surface will not look bad as if it had been sandblasted. In this respect as well, the results obtained are greatly different depending on whether the material is a thermosetting resin material or a thermoplastic resin material. When a large amount of thermosetting resin material is supplied as described above, the excess amount needs to be discharged to the outside of the cavity. That is, it is necessary to provide an excess thermosetting resin material discharging means (excess thermosetting resin material discharging step) for discharging an excessive amount of the molten thermosetting resin material inside the cavity to the outside of the cavity.
A discharge valve for discharging the molten thermosetting resin material to the outside of the cavity is conceivable as the excess thermosetting resin material discharging means. The discharge valve may have a hydraulic cylinder system, an air cylinder system, a gravity core block system, or the like. The timing of operating the discharge valve is when the molten thermosetting resin material is cured from the cavity wall surface after the injection is completed and the resin viscosity inside the cavity is low, and the fluid supply nozzle pressurizes the cavity. Until the fluid is injected and the molten thermosetting resin material gels. The start of operation of the discharge valve may be linked with the molding machine or may be controlled independently.

It is also preferable to include a temperature control step (temperature control means) for controlling the temperature of the portion of the nozzle to which the fluid is supplied. As a method of controlling the temperature of the nozzle portion, for example, a mold having a space portion in the outer peripheral portion of a fluid supply nozzle for injecting a pressurized fluid into a cavity, a mold having a heat insulating member, or a jacket for a cooling member is used. It is conceivable to use a mold provided with a mechanism for circulating air, water, oil, etc. in the jacket. This can prevent the thermosetting resin material that has flowed to the tip of the fluid supply nozzle from hardening. Further, the molten thermosetting resin material can be made to flow toward the wall side of the cavity by the pressure of the pressurized fluid.

In the apparatus of the present invention, it is preferable that the fluid supply nozzle is provided in the vicinity of the resin gate port of the molten thermosetting resin material. By providing the injection port of the fluid supply nozzle in the vicinity of the resin gate port, the molten thermosetting resin material that has flowed into the cavity can be effectively filled in the cavity, and the area around the fluid supply nozzle can be filled with the flowing thermosetting resin. Can be shaped. For example, when the injection port of the fluid supply nozzle is far from the resin gate, the shaping becomes slow or difficult to be shaped, and the pressurized fluid flies around the tip of the fluid supply nozzle, and the pressurized fluid leaks. It is easy to store.

It is also preferable that the tip of the fluid supply nozzle protrudes from the surface of the cavity by 0.5 mm or more into the cavity. By doing so, the molten thermosetting resin material is moved to the cavity wall surface by the pressure of the pressurized fluid, and is effectively hollow.
For example, if the tip of the fluid supply nozzle is not inside the molded product, it is difficult for the pressurized fluid to flow through the cavity wall surface of the mold and hollow the inside. Further, the injection port of the fluid supply nozzle preferably has a diameter of 0.05 to 5 mm. For example, if the diameter is less than 0.05 mm, the molten resin is likely to be clogged in the injection port, making it difficult to inject the pressurized fluid on the next shot. vice versa,
If the diameter exceeds 5 mm, the injection port left on the surface of the molded product becomes large, which is not preferable in appearance.

BEST MODE FOR CARRYING OUT THE INVENTION A method for molding a hollow product made of a thermosetting resin according to the present invention is a method for molding a hollow product made of a thermosetting resin. A thermosetting resin material supplying step of supplying a thermosetting resin material and a fluid supplying step of supplying a fluid into the molten thermosetting resin material in the cavity are provided. In particular, a method of molding a hollow product made of a thermosetting resin by fluid injection molding or fluid injection transfer molding, in which a thermosetting resin material for supplying a thermosetting resin material into a cavity of a mold forming the hollow product is used. It comprises a resin material supplying step and a fluid supplying step of supplying a fluid into the molten thermosetting resin material in the cavity.

A thermosetting resin hollow article molding apparatus according to the present invention is an apparatus for molding a thermosetting resin hollow article, and includes a die for molding the thermosetting resin hollow article, A thermosetting resin material supplying means for supplying a thermosetting resin material into the cavity of the mold, and a fluid supplying means for supplying a fluid into the molten thermosetting resin material in the cavity of the mold. . In particular, a device for molding a thermosetting resin hollow product by fluid injection injection molding or fluid injection transfer molding, wherein a mold for molding the thermosetting resin hollow product and a cavity for the mold are provided. A thermosetting resin material supplying means for supplying a thermosetting resin material and a fluid supplying means for supplying a fluid into the molten thermosetting resin material in the cavity of the mold are provided.

The thermosetting resin hollow article according to the present invention is a hollow article having a hollow portion formed of a thermosetting resin material, and is obtained by the above-mentioned molding method or molding apparatus. . In particular, it is a hollow product made of a thermosetting resin material and having a hollow part having a hollow part volume of 2 to 50% of the molded product volume, which is obtained by the above-mentioned molding method or molding apparatus. .

The supply of the fluid into the molten thermosetting resin material in the cavity starts at a stage before the completion of curing of the molten thermosetting resin material in the cavity. For example, during the injection of the thermosetting resin (in some cases, after the injection is completed) until the point where the resin viscosity inside the cavity is low even if the thermosetting resin is hardened on the wall of the cavity, Pressurized fluid is injected into the cavity of the mold through the mouth. Therefore, the fluid supply control means is provided so that the supply of the fluid by the fluid supply means starts at a stage before the curing of the molten thermosetting resin material supplied into the cavity is completed.

The supply (pressurization) of the fluid into the molten thermosetting resin material in the cavity is continued until the molten thermosetting resin material in the cavity is completely cured. Therefore, the fluid supply control means is provided so that the fluid supply (pressurization) by the fluid supply means is continued until the molten thermosetting resin material in the cavity is completely cured.

The amount of thermosetting resin material supplied into the cavity is basically less than the volume of the cavity. Of course, there is no problem in exceeding this.

When the molten thermosetting resin material is injected from the resin gate into the cavity of the mold formed by closing the pair of molds using a molding method such as fluid injection molding or transfer molding, The curing of the molten thermosetting resin material proceeds from the wall surface of the cavity during or after the injection. When the viscosity of the molten resin inside the cavity is low, when pressurized fluid is injected into the cavity of the mold from the injection port of the fluid supply nozzle that communicates with the cavity of the mold, the injection of the fluid supply nozzle causes the inside of the cavity of the mold to be injected. The pressurized fluid injected into the mold is molded by holding the pressure of the pressurized fluid until the molten thermosetting resin material is completely cured in the cavity of the mold. When the amount of injected resin is small, the pressure of the pressurized fluid causes the molten thermosetting resin material to flow to the mold wall of the cavity, and at the same time, it becomes hollow, resulting in a hollow molded product of thermosetting resin. can get.

The amount of thermosetting resin material supplied into the cavity is basically smaller than the volume of the cavity. When the volume of the hollow portion to be formed is X, the volume of the molten thermosetting resin material to be supplied is Y, and the cavity volume is Z, Y is supplied when the amount satisfies X + Y = Z. There is no waste in the molten thermosetting resin material. And it goes without saying that Y must be (Z-X) or more. However, when Y≈ (Z−X),
When the fluid is supplied from the fluid supply nozzle, the thermosetting resin material that has started to cure moves by rubbing the cavity wall surface due to the pressure of the fluid. For this reason, the surface has a surface roughness as if it had been subjected to sandblasting, and the appearance is deteriorated. However, Y ≧ [Z− (1 /
2) X], moreover Y ≧ [Z− (1/3) X], especially Y ≧
[Z- (1/4) X], and most preferably Y≈Z, when the fluid is supplied from the fluid supply nozzle, the thermosetting resin material that begins to cure rubs the cavity wall surface due to the pressure of the fluid. It's hard to happen. Then, a hollow molded article made of a thermosetting resin having a beautiful appearance, no sink mark, and no hesitation mark is obtained. Therefore, the molten thermosetting resin material supply control means having the above amount is provided.

When a large amount of the thermosetting resin material is supplied, the excess amount of the molten thermosetting resin material must be discharged out of the cavity as the fluid is supplied. That is, it is necessary to provide an excess thermosetting resin material discharging means (excess thermosetting resin material discharging step) for discharging an excessive amount of the molten thermosetting resin material inside the cavity to the outside of the cavity. A discharge valve for discharging the molten thermosetting resin material to the outside of the cavity is conceivable as the excess thermosetting resin material discharging means. This discharge valve is, for example, a hydraulic cylinder type,
Those having a mechanism such as an air cylinder system or a gravity core block system are conceivable. The timing of operating the discharge valve is when the molten thermosetting resin material is cured from the cavity wall surface after the injection is completed and the resin viscosity inside the cavity is low, and the fluid supply nozzle pressurizes the cavity. Until the fluid is injected and the molten thermosetting resin material gels. The start of operation of the discharge valve may be linked with the molding machine or may be controlled independently.

Further, a temperature control step (temperature control means) for controlling the temperature of the nozzle portion to which the fluid is supplied is provided. As a method of controlling the temperature of the nozzle portion, for example, a mold having a space portion in the outer peripheral portion of a fluid supply nozzle for injecting a pressurized fluid into a cavity, a mold having a heat insulating member, or a jacket for a cooling member is used. It is conceivable to use a mold provided with a mechanism for circulating air, water, oil, etc. in the jacket. This can prevent the thermosetting resin material that has flowed to the tip of the fluid supply nozzle from hardening. Further, the molten thermosetting resin material can be made to flow toward the wall side of the cavity by the pressure of the pressurized fluid. The fluid supply nozzle is provided near the resin gate port of the molten thermosetting resin material. This is because by providing the injection port of the fluid supply nozzle near the resin gate port, the molten thermosetting resin material that has flowed into the cavity can be effectively filled in the cavity, and the thermosetting property that has flowed around the fluid supply nozzle can be achieved. It can be shaped with resin. Further, the tip of the fluid supply nozzle is projected into the cavity by 0.5 mm or more from the surface of the cavity. By doing so, the molten thermosetting resin material can be moved to the cavity wall surface by the pressure of the pressurized fluid, and can be effectively made hollow. For example, when the tip of the fluid supply nozzle is not inside the molded product, the pressurized fluid flows through the cavity wall surface of the mold and cannot hollow the inside. The diameter of the injection port of the fluid supply nozzle is 0.05.
-5 mm.

A pressurized fluid injection device is used to supply the fluid from the fluid supply nozzle. The pressurized fluid injecting device injects a fluid into the molten thermosetting resin material through a jet of a fluid supply nozzle from a pipe after or during the injection of the molten thermosetting resin material, and maintains the fluid pressure for a predetermined time. It is a device that can be held. Any device can be used as long as it can compress the fluid to a high pressure, store it in the accumulator, and inject the high-pressure fluid from the pipe through the injection port of the fluid supply nozzle when the fluid is injected. The fluid supply nozzle may have a structure capable of ejecting a fluid.

The fluid may be a gas or a liquid at room temperature. In particular, it is a gas. A material that does not react with the molten thermosetting resin material at the mold temperature of injection molding or transfer molding is used. For example, inert gas such as nitrogen, carbon dioxide gas, air and the like can be mentioned. Among them, nitrogen is used.

The present invention is directed to thermosetting resins, which have been said to be troublesome as materials for hollow molded articles. Thermoplastic resins are not covered. Examples of thermosetting resins include phenolic resins, unsaturated polyester resins, diallyl phthalate resins, amino resins, epoxy resins, thermosetting polyurethane resins, and the like. Of course, in addition to these materials, wood powder, inorganic material, fiber-reinforced resin, or the like may be contained, and various additives, flame retardants, or the like may be contained. As the injection molding machine used in the present invention, an injection molding machine or an injection compression molding machine for thermosetting resin molding which is usually used can be used. A plunger type transfer molding machine can be used. Also, a hollow molding can be molded by attaching a pot injection type mold to a compression molding machine.

The details will be described below.

1 to 3 are explanatory views of a hollow molding product made of a thermosetting resin molded by gas injection injection molding or gas injection transfer molding, and FIGS. 4 to 7 are used for molding this hollow molding product. It is explanatory drawing of the apparatus (mold) which was used.

In each figure, 1 is a mold. Reference numeral 5 is a hollow molded product molded using the mold 1.

The mold 1 has a cavity 11 for forming the hollow molded product 5. Further, it has a sprue 12 communicating with the cavity 11 and a resin gate 13. And
The molten thermosetting resin material is configured to be injected into the cavity 11 via the sprue 12 and the resin gate 13 by injection molding or transfer molding.

A gas supply nozzle 2 is provided in the mold 1 at a position near the resin gate 13 and on the other side of the cavity 11 facing the resin gate 13.
Then, the gas is supplied into the cavity 11 from the injection port 22 of the gas supply nozzle 2. That is, the molten thermosetting resin material injected into the cavity 11 through the resin gate 13 is pushed to the innermost side of the cavity 11 by the gas pressure supplied from the gas supply nozzle 2. The gas supply nozzle 2 is provided. It should be noted that the tip 21 of the gas supply nozzle 2 is protruded inward so that the protrusion length into the cavity 11 is 0.5 mm or more.

A space 4 is provided in the mold 1 in the portion where the gas supply nozzle 2 is provided (see FIG. 5).
The space 4 is filled with a heat insulating member 41 made of a metal material or resin having a lower thermal conductivity than the mold material, for example, a heat-resistant plastic such as a polyamide-imide resin (FIG. 6).
reference). Alternatively, the cooling member 3 is arranged in the space 4. In addition, inside the cooling member 3, pipes 31 and 32 for passing a fluid communicating with the jacket 33 are provided. A fluid, such as air, water, or oil, flows from the pipe 31, circulates in the jacket 33, and flows out from the pipe 32 (see FIG. 7), which controls the temperature of the gas supply nozzle 2. Is to be done. That is, the space 4 or the heat insulating member 41 or the cooling member 3 causes the injection port 22 of the gas supply nozzle 2.
The temperature is controlled so that the molten thermosetting resin that flows back into the resin does not cure.

A pressurized gas injection device (not shown) is used in an injection molding machine or a transfer molding machine for molding a hollow molded article.
Is provided. The pressurized gas injection device includes a cavity 1 through a gas pressure adjusting mechanism and a gas supply nozzle 2 at the tip.
A pressurized gas is injected into 1. Then, even after a predetermined amount of gas is injected, the injection pressure can be maintained for a predetermined time (until the molten thermosetting resin is cured). Thereby, the injection port 22 of the gas supply nozzle 2
It prevents the molten thermosetting resin from flowing back.

Using the above apparatus, first, a molten thermosetting resin material is injected into the cavity 11 formed by closing the mold 1 through the sprue 12 and the resin gate 13. When the molten thermosetting resin material is being cured from the wall surface of the cavity 11 during injection of the molten thermosetting resin material or after the completion of injection, and the resin viscosity inside the cavity 11 is low (has fluidity). Then, the pressurized gas injection device is operated to inject the pressurized gas into the cavity 11 from the injection port 22 of the gas supply nozzle 2. The pressure of the pressurized gas is maintained until the molten thermosetting resin material is cured in the cavity 11.

Then, as shown in FIG. 4, the molten thermosetting resin material injected through the resin gate 13 flows in the cavity 11 by the pressure of the pressurized gas from the injection port 22 of the gas supply nozzle 2. Then, a hollow molded product 5 having a cross-sectional structure as shown in FIGS. still,
Reference numeral 51 denotes the outer surface of the hollow molded product 5, and 52 denotes the inner hollow portion.

FIGS. 8 to 14 show another embodiment, and FIGS. 8 to 10 are explanatory views of a hollow molded article of a thermosetting resin molded by gas injection injection molding or gas injection transfer molding, and FIG. 14 to 14 are explanatory views of the apparatus (mold) used for molding the hollow molded product.

In each figure, 1 is a mold. Reference numeral 6 is a hollow molded product molded using the mold 1.

The mold 1 has a cavity 11 for forming the hollow molded product 6. Further, it has a sprue 12 communicating with the cavity 11 and a resin gate 13. And
The molten thermosetting resin material is configured to be injected into the cavity 11 via the sprue 12 and the resin gate 13 by injection molding or transfer molding.

A gas supply nozzle 2 is provided in the mold 1 located near the resin gate 13 and on the other side of the cavity 11 facing the resin gate 13.
That is, the gas is supplied into the cavity 11 from the injection port 22 of the gas supply nozzle 2. Then, by the gas pressure supplied from the gas supply nozzle 2, the gas is injected through the resin gate 13 and the cavity 11
The gas supply nozzle 2 is provided at a position where the molten thermosetting resin material that is almost completely filled inside is pushed out of the cavity 11. The gas supply nozzle 2
Is projected to the inside so that the projection length into the cavity 11 is 0.5 mm or more.

A space is provided in the die 1 where the gas supply nozzle 2 is provided. Then, this space portion has the same configuration as that of the above embodiment.

Although not shown, a pressurized gas injection device is provided in the injection molding machine or the transfer molding machine for molding the hollow molded product, as in the above embodiment.

The major difference between the present embodiment and the above-mentioned embodiment is that the overflow cavity 14 connected to the cavity 11 can be seen from FIGS. 11 to 14.
Is configured in the mold 1. In addition, 15 is a discharge valve. That is, as shown in FIG. 13, the molten thermosetting resin material is injected from the resin gate 13 so that the inside of the cavity 11 is completely filled, and the gas is injected from the injection port 22 of the gas supply nozzle 2 almost after the injection. Is blown into the molten thermosetting resin material filling the inside of the cavity 11, and accordingly, an excessive amount of the molten thermosetting resin material is discharged into the overflow cavity 14. In this case, since the amount of the molten thermosetting resin material completely fills the inside of the cavity 11, the molten thermosetting resin material is pushed into the unfilled portion by the gas from the gas supply nozzle 2. It is rarely done. Therefore, the gas supply nozzle 2 may be provided at a position apart from the resin gate 13. Of course, it goes without saying that the nearby position is good.

Using the above apparatus, first, as shown in FIGS.
As shown in FIG. 3, the molten thermosetting resin material is injected into the cavity 11 formed by closing the mold 1 through the sprue 12 and the resin gate 13.

Then, as shown in FIG. 14, after the completion of injection of the molten thermosetting resin material and when the resin viscosity inside the cavity 11 is low (having fluidity), the pressurized gas injection device is operated. Let the injection port 22 of the gas supply nozzle 2
The pressurized gas is injected into the cavity 11. The pressure of the pressurized gas is set so that the molten thermosetting resin material is used in the cavity 11
Hold the pressure until it cures in. Then, FIG.
As shown in FIG. 8, the molten thermosetting resin material injected through the resin gate 13 is discharged into the overflow cavity 14 by the pressure of the pressurized gas from the injection port 22 of the gas supply nozzle 2, The hollow molded product 6 having a cross-sectional structure as shown in FIG. Incidentally, 61 indicates an outer surface of the hollow molded product 6, and 62 indicates an inner hollow portion.

Specific examples will be described below, but the present invention is not limited to these examples.

[0057]

EXAMPLES The injection molding machine, transfer molding machine, gas supply nozzle, injection port temperature, gas used, and hollow rate (%) used in the following examples are calculated as follows. Injection molding machine: 100N-45KS manufactured by Matsuda Mfg. Co., Ltd. Transfer molding machine: MTF50 pressurized gas injection device manufactured by Marushichi Iron Works Co., Ltd .: CP50 gas supply nozzle injection port manufactured by Mitsubishi Gas Chemical Co., Inc. : 80 to 110 ° C. Insulation around the injection port: Polyamideimide resin injection gas: Nitrogen gas hollow ratio = (weight of molded product−weight of hollow molded product / weight of molded product) × 100 [Example 1] As a molding machine Using an injection molding machine as a thermosetting resin, a phenolic resin (F250 manufactured by Fudo Co., Ltd.)
1) was used. As the mold, the mold of FIGS. 4 to 7 without the overflow cavity 14 was used. As shown in FIGS. 15 to 17, the shape of the obtained hollow molded product 6 is an elliptical cross section and is a curved handle shape, with a minimum wall thickness of 17 mm, a maximum wall thickness of 21 mm, and an extension length. The length is 220 mm. The position of the resin gate 13 communicating with the cavity 11 is P1, and the position of the tip 21 of the gas supply nozzle 2 is M1. The tip position M1 of the gas supply nozzle 2 is at a right angle of 90 ° with respect to the position P1 of the resin gate 13, and about 10 degrees from the position P1 of the resin gate 13.
It is provided at a distance of mm. The injection port of the gas supply nozzle 2 has a diameter of 0.3 mm, and the tip 21 of the gas supply nozzle 2 is provided so as to project inward from the surface of the cavity 11 by 10 mm.

Then, in the cavity 11 of the mold 1 set at 160 to 170 ° C., a resin amount of 77 g (sprue) which is 25% less than the resin amount of 103 g of the molded product 6 obtained by normal injection molding of a phenolic resin is used. And (excluding runners) is injected from position P1 of the resin gate (pressure 1
00 MPa).

Injection was completed 6 to 7 seconds after the start of injection.
10 to 15 seconds after completion of injection, nitrogen gas injection (pressure 6 MPa) was started from the gas supply nozzle 2. After maintaining the nitrogen gas pressure for 70 seconds, the injected gas was discharged, the mold was opened, and the molded product 6 was taken out.

The molded product 6 made of phenolic resin thus obtained had a front view as shown in FIG. 15 and a cross section as shown in FIGS. Incidentally, 61 is an outer surface portion, 62 is a hollow portion, the hollow ratio of the molded product 6 is about 25%, and the surface appearance is light without sink marks.

Example 2 The procedure of Example 1 was repeated. That is, a thermosetting resin (unsaturated polyester resin (FP100F of Fudo Co., Ltd.)) was applied to the cavity 11 of the mold 1 set at 160 to 170 ° C. with respect to a resin amount of 154 g of a molded product obtained by ordinary injection molding. 25% less than the resin amount of 116 g (excluding sprue and runner) is injected from the position P1 of the resin gate 13 (pressure 8).
0 MPa), the injection is completed 4 to 5 seconds after the start of injection,
Then, 10 to 15 seconds after the completion of injection, nitrogen gas is started to be injected (pressure 6 MPa) from the gas supply nozzle 2, the nitrogen gas pressure is maintained for 70 seconds, the injected gas is discharged, and the mold is opened. The molded product 6 was taken out.

The unsaturated polyester resin molded product 6 thus obtained has a front view as shown in FIG. 15 and a cross section as shown in FIGS. It was Incidentally, 61 is an outer surface portion, 62 is a hollow portion, the hollow ratio of the molded product 6 is about 25%, and the surface appearance is light without sink marks.

[Example 3] A transfer molding machine was used as a molding machine, and a phenol resin (F5700F manufactured by Fudo Co., Ltd.) was used as a thermosetting resin. As the mold, the overflow cavity 14 is not provided.
The type shown in FIG. 7 was used. The shape of the obtained hollow molded product is, as shown in FIGS. 1 to 3, a substantially rectangular parallelepiped and a width of 15 m.
m, wall thickness 15 mm, length 90 mm. The position of the resin gate 13 communicating with the cavity 11 is P,
The position of the tip 21 of the gas supply nozzle 2 is M. The tip position M of the gas supply nozzle 2 faces the position P of the resin gate 13 in a facing direction, and is approximately 8 m from the position P of the resin gate 13.
It is provided at a position separated by m. The mold temperature of the pot part for inserting the tablet necessary for injecting the resin into the mold 1 and the sprue 12 (not shown) is set to 160 ° C. The injection port of the gas supply nozzle 2 has a diameter of 0.2 mm, and the tip 21 of the gas supply nozzle 2 is provided so as to project inward by 7 mm from the surface of the cavity 11. Then, in the pot portion of the mold 1, the resin gate 13 is 33 g (excluding the sprue and runners), which is 27% less than the resin amount of 45 g of the molded product obtained by the usual molding method. Was injected (pressure 70 MPa).

Injection was completed 22 seconds after the start of injection. Two seconds after the completion of injection, nitrogen gas injection (pressure 5 MPa) was started from the gas supply nozzle 2. Nitrogen gas pressure is 120
After holding for 2 seconds, the injected gas was discharged, the mold was opened, and the molded product was taken out.

The phenol resin molded product 5 thus obtained had a perspective view as shown in FIG. 1 and a cross section as shown in FIGS. The hollow rate of the molded product was about 24%, and the surface appearance was light without sink marks.

[Example 4] The procedure of Example 3 was repeated. That is, a thermosetting resin (unsaturated polyester resin (FP100F of Fudo Co., Ltd.)) was added to the cavity 11 of the mold 1 set at 160 to 170 ° C. with respect to the resin amount of 63 g of a molded product obtained by normal injection molding. 27% less than the resin amount of 46 g (excluding sprue and runner) is injected from the resin gate (pressure 70 MPa), completed 10 seconds after the start of injection, and 5 seconds after the completion of injection. Inject nitrogen gas from (pressure 5MP
a) After starting and maintaining the nitrogen gas pressure for 120 seconds, the injected gas was discharged, the mold was opened, and the molded product was taken out.

The unsaturated polyester resin molded article 5 thus obtained has a perspective view as shown in FIG. 1 and a cross section as shown in FIGS. It was The hollow rate of the molded product 5 was about 27%, and the surface appearance was light without sink marks.

[Example 5] An injection molding machine was used as a molding machine.
A phenolic resin (F2000 manufactured by Fudou Co., Ltd.) was used as the thermosetting resin. As the mold, the mold of FIGS. 4 to 7 without the overflow cavity 14 was used. The shape of the obtained hollow molded product 7 is shown in FIG.
~ As shown in Figure 21, width 42mm, wall thickness 14mm,
A plurality of convex portions 74 are provided in a rectangular concave portion 73 having a length of 200 mm.
Is formed in a strip shape, and the unevenness is approximately 4 mm
belongs to. Resin gate 1 communicating with the cavity 11
The position of 3 is P2, and the position of the tip 21 of the gas supply nozzle 2 is M2. The tip position M2 of the gas supply nozzle 2
Is provided at a position about 15 mm away from the position P2 of the resin gate 13 in the facing direction with respect to the position P2 of the resin gate 13. The injection port of the gas supply nozzle 2 has a diameter of 0.5.
mm, and the tip 21 of the gas supply nozzle 2 is provided so as to project 6 mm inward from the surface of the cavity 11. Then, in the cavity 11 of the mold 1 set at 160 to 170 ° C., the phenol resin is 20% less than the resin amount of 176 g of the molded product 7 obtained by a normal molding method, and the resin amount of 141 g (sprue and runner content). (Except pressure) was injected from the position P2 of the resin gate 13 (pressure 100 MPa).

Injection was completed 8 seconds after the start of injection. 5 to 10 seconds after the completion of injection, nitrogen gas injection (pressure 6 MPa) was started from the tip position M2 of the gas supply nozzle 2. After maintaining the nitrogen gas pressure for 60 seconds, the injected gas was discharged, the mold was opened, and the molded product 7 was taken out.

The phenol resin molded product 7 thus obtained has a perspective view as shown in FIG. 18 and a cross section as shown in FIGS. It was In addition, 71 is an outer surface portion, 72 is a hollow portion, the hollow ratio of the molded product 7 is about 20%, and the surface appearance is light without sink marks.

[Example 6] The procedure of Example 5 was repeated. That is, a thermosetting resin (unsaturated polyester resin (FP100F of Fudo Co., Ltd.)) was added to the cavity 11 of the mold 1 set at 160 to 170 ° C. to a resin amount of 242 g of a molded product 7 obtained by normal injection molding. 20% against
A small amount of resin of 194 g (excluding sprue and runner) is injected from the position P2 of the resin gate 13 (pressure 8).
0 MPa), the injection is completed 5 seconds after the injection is started, and 10 to 15 seconds after the injection is completed, nitrogen gas is injected (pressure 6 MPa) from the tip position M2 of the gas supply nozzle 2 and the nitrogen gas pressure is 60 seconds. After the holding, the injected gas was discharged, the mold was opened, and the molded product 7 was taken out.

The unsaturated polyester resin molded product 7 thus obtained has a perspective view as shown in FIG. 18 and a cross section as shown in FIGS. Met. In addition, 71 is an outer surface portion, 72 is a hollow portion, the hollow ratio of the molded product 7 is about 20%, and the surface appearance is light without sink marks.

[Embodiment 7] An injection molding machine is used as a molding machine.
A phenolic resin (F2501 manufactured by Fudo Co., Ltd.) was used as the thermosetting resin. As the mold, the mold of FIGS. 11 to 14 provided with the overflow cavity 14 was used. The shape of the obtained hollow molded article is shown in FIG.
As shown in FIG. 10, the hollow molded product 6 thus obtained has an elliptical cross section and a curved handle shape, with a minimum wall thickness of 17 mm, a maximum wall thickness of 21 mm, and an extension length of 2 mm.
It is 20 mm. The position of the resin gate 13 communicating with the cavity 11 is P1, and the position of the tip 21 of the gas supply nozzle 2 is M1. The tip position M1 of the gas supply nozzle 2 is provided at a right angle of 90 ° with respect to the position P1 of the resin gate 13, and is provided at a distance of about 10 mm from the position P1 of the resin gate 13. The injection port of the gas supply nozzle 2 has a diameter of 0.3 mm, and the tip 21 of the gas supply nozzle 2 is provided so as to project inward from the surface of the cavity 11 by 10 mm.

Then, in the cavity 11 of the mold 1 set at 160 to 170 ° C., an amount of phenolic resin corresponding to the entire volume of the cavity 11 is placed at the resin gate position P1.
Was injected (pressure 100 MPa).

Injection was completed 6 to 7 seconds after the start of injection.
5 to 30 seconds after the completion of injection, nitrogen gas injection (pressure 6 MPa) was started from the gas supply nozzle 2. Then, with the injection of nitrogen gas, when the injection gas pressure becomes a constant value,
This is detected by the sensor. Then, the discharge valve 15 is automatically opened by the output signal of the sensor, and the excessive amount of the molten resin inside the cavity 11 is discharged to the overflow cavity 14 side. Then, the nitrogen gas pressure was maintained for 70 seconds under the conditions, the injected gas was discharged, the mold was opened, and the molded product 6 was taken out.

The phenol resin molded product 6 thus obtained had a front view as shown in FIG. 8 and a cross section as shown in FIGS. Incidentally, 61 is an outer surface portion, and 62 is a hollow portion.
The hollow ratio was about 25%, and the surface appearance was light without sink marks. Particularly, in the case of the present example, the whitening stains generated by rubbing on the surface, which were observed in the hollow molded article of Example 1, were not recognized, and the appearance was excellent.

[Embodiment 8] The same process as in Embodiment 7 was carried out. That is, in the cavity 11 of the mold 1 set to 160 to 170 ° C., a thermosetting resin (unsaturated polyester resin (FP100F of Fudo Co., Ltd.)) in an amount corresponding to the entire volume of the cavity 11 is provided in the resin gate 13. Injection was performed from the position P1 (pressure 80 MPa). Injection was completed 4 to 5 seconds after the start of injection, and nitrogen gas injection (pressure 6 MPa) was started from the gas supply nozzle 2 5 to 30 seconds after the completion of injection.
Then, when the injection gas pressure reaches a constant value due to the injection of nitrogen gas, this is detected by the sensor, and the discharge valve 15 is automatically opened by the output signal of the sensor to melt the excess amount inside the cavity 11. The resin was discharged to the overflow cavity 14 side. Then, the nitrogen gas pressure was maintained for 70 seconds under the conditions, the injected gas was discharged, the mold was opened, and the molded product 6 was taken out.

The unsaturated polyester resin molded product 6 thus obtained has a front view as shown in FIG. 8 and a cross section as shown in FIGS. It was Incidentally, 61 is an outer surface portion, 62 is a hollow portion,
The hollow ratio of the molded product 6 was about 30%, and the surface appearance was light without sink marks. In particular, in the case of the present example, the whitening stain produced by rubbing on the surface, which was observed in the hollow molded article of Example 2, was not recognized, and the appearance was excellent.

[Example 9] The same process as in Example 7 was carried out. That is, a thermosetting resin (diallyl phthalate resin (D2200F of Fudo Co., Ltd.)) in an amount corresponding to the total volume of the cavity 11 is placed in the cavity 11 of the mold 1 set at 160 to 170 ° C. at the position of the resin gate 13. Injection was performed from P1 (pressure 80 MPa). Injection was completed 4 to 5 seconds after the start of injection, and nitrogen gas injection (pressure 6 MPa) was started from the gas supply nozzle 2 5 to 30 seconds after the completion of injection.
Then, when the injection gas pressure reaches a constant value due to the injection of nitrogen gas, this is detected by the sensor, and the discharge valve 15 is automatically opened by the output signal of the sensor to melt the excess amount inside the cavity 11. The resin was discharged to the overflow cavity 14 side. Then, the nitrogen gas pressure was maintained for 70 seconds under the conditions, the injected gas was discharged, the mold was opened, and the molded product 6 was taken out.

The molded product 6 made of diallyl phthalate resin thus obtained has a front view as shown in FIG. 8 and a cross section as shown in FIGS. . Incidentally, 61 is an outer surface portion, 62 is a hollow portion,
The hollow ratio of the molded product 6 was about 35%, and the surface appearance was light without sink marks. Particularly, in the case of the present example, the whitening stains generated by rubbing on the surface, which were observed in the hollow molded articles of Examples 1 and 2, were not recognized, and the appearance was excellent.

[0081]

EFFECTS OF THE INVENTION A hollow molded article made of a thermosetting resin can be obtained without using a core. In particular, a hollow molded product made of a thermosetting resin can be obtained with good productivity and at a low cost. Furthermore,
It is possible to obtain a hollow-molded product made of a thermosetting resin, which can be easily molded even if it is thick and complicated and in which defective products such as sink marks hardly occur. Moreover, a hollow molded article made of a thermosetting resin having excellent appearance can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view of a hollow molded article of a thermosetting resin obtained by carrying out the present invention.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a sectional view taken along line BB in FIG.

FIG. 4 is an explanatory view of a mold for molding a hollow molded article of the thermosetting resin of the present invention.

FIG. 5 is an explanatory view of a gas supply nozzle portion in a mold for molding a hollow molded article of the thermosetting resin of the present invention.

FIG. 6 is an explanatory view of a gas supply nozzle portion of a mold for molding a hollow molded article of the thermosetting resin of the present invention.

FIG. 7 is an explanatory view of a gas supply nozzle portion in a mold for molding a hollow molding product of the thermosetting resin of the present invention.

FIG. 8 is a front view of a hollow molded product of a thermosetting resin obtained by carrying out the present invention.

9 is a sectional view taken along line AA in FIG.

10 is a sectional view taken along line BB in FIG.

FIG. 11 is an explanatory view of a mold for molding a hollow molded article of the thermosetting resin of the present invention.

12 is an explanatory diagram of molding steps using the mold of FIG. 11.

FIG. 13 is an explanatory view of molding steps using the mold of FIG.

FIG. 14 is an explanatory view of molding steps using the mold of FIG.

FIG. 15 is a front view of a hollow molded article of thermosetting resin obtained by carrying out the present invention.

16 is a sectional view taken along the line CC in FIG.

FIG. 17 is a sectional view taken along the line DD in FIG.

FIG. 18 is a perspective view of a hollow molded article of thermosetting resin obtained by carrying out the present invention.

FIG. 19 is a sectional view taken along line EE in FIG.

20 is a sectional view taken along line HH in FIG.

FIG. 21 is a sectional view taken along line FF in FIG.

[Explanation of symbols]

1 mold 2 gas supply nozzle 11 cavities 13 resin gate 14 Overflow cavity 15 Release valve

Claims (15)

[Claims] 1. A method of molding a hollow product made of a thermosetting resin, comprising a thermosetting resin material supplying step of supplying a thermosetting resin material into a cavity of a mold forming the hollow product, and a cavity. And a fluid supplying step of supplying a fluid into the molten thermosetting resin material therein. 2. A method for molding a hollow product made of a thermosetting resin by fluid injection molding or fluid injection transfer molding, wherein a thermosetting resin material is supplied into a cavity of a mold forming the hollow product. A method for molding a thermosetting resin hollow article, comprising: a thermosetting resin material supplying step; and a fluid supplying step of supplying a fluid into the molten thermosetting resin material in the cavity. 3. The method according to claim 1, wherein the supply of the fluid into the molten thermosetting resin material in the cavity starts at a stage before the completion of curing of the molten thermosetting resin material in the cavity. Item 2
A method for molding a hollow product made of a thermosetting resin. 4. The supply of fluid into the molten thermosetting resin material in the cavity is continued until the molten thermosetting resin material in the cavity is completely cured. A method for molding a hollow product made of any thermosetting resin. 5. The thermosetting resin hollow article according to claim 1, wherein the amount of the thermosetting resin material supplied into the cavity is less than the volume of the cavity. Molding method. 6. In the thermosetting resin material supplying step, the thermosetting resin material is supplied so that the total of the volume of the hollow portion formed and the volume of the thermosetting resin material supplied exceeds the cavity volume. The invention further comprises an excess thermosetting resin material discharging step in which an excess amount of the molten thermosetting resin material in the cavity is discharged to the outside of the cavity. Molding method for hollow thermosetting resin products. 7. The method according to claim 1, further comprising a temperature control step of controlling the temperature of a portion of the nozzle to which the fluid is supplied, so that the molten thermosetting resin material which is about to flow back into the nozzle is not cured. A method for molding a hollow thermosetting resin product according to any one of claims 1 to 6. 8. An apparatus for molding a hollow product made of a thermosetting resin, which comprises a mold for molding a hollow product made of a thermosetting resin, and a thermosetting resin material supplied into the cavity of the mold. And a fluid supply means for supplying a fluid into the molten thermosetting resin material in the cavity of the mold, for molding a thermosetting resin hollow article. apparatus. 9. The heat according to claim 8, further comprising a fluid supply control means so that the supply of the fluid by the fluid supply means starts at a stage before the completion of the curing of the molten thermosetting resin material in the cavity. Molding equipment for hollow products made of curable resin. 10. The fluid supply control means is further provided so that the fluid supply by the fluid supply means is continued until the molten thermosetting resin material in the cavity is completely cured. Molding equipment for hollow products made of thermosetting resin. 11. Thermosetting resin material supply control means for controlling the supply amount of the thermosetting resin material so that the total of the volume of the hollow portion formed and the volume of the thermosetting resin material exceeds the cavity volume, and a cavity. An excess thermosetting resin material discharging means for discharging an excess amount of the molten thermosetting resin material inside the cavity is further provided, and the thermosetting resin according to any one of claims 8 to 10. Molding equipment for hollow products. 12. A temperature control means for controlling the temperature of a portion of a nozzle to which a fluid is supplied, further comprising a temperature control means for preventing a molten thermosetting resin material which is about to flow back into the nozzle from being cured. A molding apparatus for hollow thermosetting resin according to any one of claims 8 to 11. 13. The molding apparatus for hollow thermosetting resin according to claim 8, wherein the fluid supply nozzle is provided in the vicinity of the resin gate of the thermosetting resin material. 14. The thermosetting resin hollow article molding apparatus according to claim 8, wherein the tip of the fluid supply nozzle projects from the surface of the cavity into the cavity by 0.5 mm or more. 15. A hollow article having a hollow portion formed by using a thermosetting resin material, which is obtained by the method for molding a hollow article made of a thermosetting resin according to any one of claims 1 to 7. A hollow product made of a thermosetting resin, which is characterized in that