JP2000000837A - Method for molding lightweight resin molded article with rising part, and lightweight resin molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve appearance, strength and rigidity of a molded article by lowering density of a rising part and making it lightweight in preparing the molded article with the rising part. SOLUTION: A molten resin is filled by injection into a mold cavity under a condition where a projecting member 4 is projected in the mold cavity 7a forming a rising part of a molded article and then, the shape of a final molded article is prepd. by retreating the projected member 4 and expanding the molten resin to lower the apparent density of this part. The rising part has a surface skin layer and inner voids or a hollow layer and appearance, strength and rigidity are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of molding a lightweight resin molded article and a lightweight resin molded article, and more particularly to a method of molding a molded article having a rising portion, particularly a rising portion at an outer peripheral portion. The present invention relates to a method for molding a lightweight resin molded product having sufficient mold transferability, a dense surface, good appearance, and a rising portion having high strength and rigidity, and a lightweight resin molded product.

[0002]

BACKGROUND ART Conventionally, thermoplastic resins and fiber-reinforced thermoplastic resins have been used for automobile parts, home appliances, office appliances,
Widely used as computer, daily necessities, furniture, construction, civil engineering members, etc. These molded products are mainly formed by injection molding in terms of productivity and the like. The feature of these molded products is that they are lighter in weight than other materials, but the industry demands further weight reduction from the viewpoint of resource saving and effective use of resin. This reduction in the weight of the resin molded article is a desirable use form from the viewpoint of increasing strength and rigidity per unit weight and effective utilization of resources. On the other hand, there is a demand for eliminating appearance defects such as prevention of sink marks and improved mold transferability in molded products.

[0003] In injection molding (including injection compression molding; the same applies hereinafter), methods for reducing the weight of a resin molded product include a method using a resin containing a foaming agent, a method of injecting a gas, and a method of using a fiber in a resin containing a fiber. There is known a method that utilizes the expandability, which is a restoring force of entanglement. All of these molding methods aim to reduce the weight by expanding the molten resin in the mold cavity. Among them, a molding method using a foaming agent-containing resin is a normal injection molding, that is, a method of injecting a resin in an amount smaller than the volume of a cavity to foam the resin. However, this molding method has a problem that a molded article having an excellent appearance cannot be obtained, for example, it is not possible to uniformly mold up to the end portion of the molded article, or a silver streak due to a foaming agent is generated on the molded article surface. As a method for solving this problem, a counter pressure method for suppressing foaming at the time of injection has been proposed, but there is a problem in economy, and a problem in which molding of a thin end portion is difficult is not solved.

[0004] On the other hand, in the gas injection (including gasification by liquid injection) molding method, similarly, after injecting a smaller amount of molten resin than the volume of a mold cavity, a gas is injected to form a hollow in a molded article. This is a molding method for forming a portion. But,
In this method, since the flow of the resin on the mold surface is intermittent, a flow mark is formed on the surface of the molded product, the mold transferability is weak, there is a problem of poor appearance, and a hollow portion is formed at a desired location. Can be difficult to do. In addition, even in the molding method utilizing the expandability of a fiber-containing resin such as glass fiber, as in a normal molding method, molding in a fixed mold cavity tends to cause poor appearance of a molded product, Also, the mold transferability at the end of the molded product may not be sufficient depending on the degree of weight reduction.

In the above-mentioned molding method for the purpose of reducing the weight of a resin molded product in injection molding, improvements have been made to solve the respective problems. For example, the molten foamable plastic composition is injected into a cavity having a volume of 10 to 95% of the volume of the intended molded article,
After forming a solidified layer in contact with the mold surface, expand the foam to the volume of the desired molded article and foam it (Japanese Unexamined Patent Publication No. Hei 8-3).
00391) has been proposed. Also, in the gas injection molding method, it is known that the cavity is expanded at the time of gas injection in order to form a large hollow portion. Further, the present applicant has proposed a method of expanding a cavity in a light-weight molding method utilizing expansion property due to entanglement of fibers by a specific fiber-containing resin (International Publication W
P97 / 29896).

That is, in these improved molding methods, a resin is injected and filled into a mold cavity smaller than the volume of the final molded product, the surface is cooled and hardened to a certain extent, and the surface transfer of the mold is completed. The purpose of the present invention is to improve the appearance of a molded product by expanding the volume of the final molded product to a lighter weight.

[0007]

However, in these improved methods, the expansion of the volume of the final molded product after the injection filling of the resin into the mold cavity generally involves the use of a mold structure, It is performed only in the mold opening / closing direction for removing the molded product. In this case, there is little problem particularly when the degree of weight reduction is low or when a simple molded product such as a plate-shaped molded product is used. However, when the shape of the molded product is a rising part,
In the case of a box-shaped product, a container-shaped product, or a cylindrical product having a rising portion on the outer periphery, it is easy to reduce the weight of the bottom portion, which is a main part of the molded product, but the weight of the rising portion is substantially reduced. Is impossible. Therefore, in such a molded product, there is naturally a limit to the weight reduction, or it is necessary to increase the wall thickness in order to secure the strength and rigidity of the rising portion. Was something.
For this reason, there is a demand for a method of molding a molded article having a rising portion which is lightweight, and has excellent appearance, strength and rigidity.

According to the present invention, in injection molding and injection compression molding, the shape of a molding die cavity at the time of filling with a molten resin and at the time of final shaping as a final molded product is changed and enlarged to increase the volume of a rising portion. It expands and expands. That is, the present invention has excellent appearance, strength and rigidity of the rising portion, particularly the rising portion of the outer peripheral portion, and has not only a square frame shape as a cross-sectional shape of the rising portion, but also a rising portion with no limitation in its shape. An object of the present invention is to provide a molding method of a lightweight resin molded product and a lightweight resin molded product.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above-mentioned problems, and as a result, a projecting member has been protruded into a cavity at a rising portion of a mold cavity of a molded article having a rising portion, and the cavity has been melted into a narrowed cavity portion. By injecting and filling the resin and then retracting the protruding member, it has been found that the rising portion of the molded product easily expands. Moreover, the obtained molded product has good appearance due to excellent mold transferability due to injection resin pressure and injection compression force.
The present inventors have found that they are excellent in strength and rigidity and have light weight, and have completed the present invention.

That is, the present invention provides: (1) Injecting and filling a molten resin into a mold cavity with a projecting member projecting into a mold cavity portion forming a rising portion of a molded product; A method for molding a lightweight resin molded article having a rising portion in which the molten resin is expanded by retracting the resin to form a final molded article. (2) Following injection filling of the molten resin into the mold cavity, independently of the protruding member, the molten resin is expanded by retracting the mold at a portion corresponding to the thickness of the non-rise portion of the molded product, thereby expanding the molten resin. The method for producing a lightweight resin molded product having a rising portion according to the above (1) having a thickness of 1 mm. (3) The above (1) or (2), wherein the lightweight resin molded product has a rising portion at least on the outer peripheral portion of the molded product.
A method for producing a lightweight resin molded article having the rising portion according to the above. (4) The molten resin is obtained by melting a raw material containing at least a part of a resin pellet containing a fiber having a length of 2 to 100 mm, and has a fiber content of 5 to 80% by weight. (3) A method for molding a lightweight resin molded article having a rising portion according to any of (3). (5) The method for molding a lightweight resin molded article having a rising portion according to (4), wherein the fiber is glass fiber. (6) The method for molding a lightweight resin molded article having a rising portion according to the above (1), wherein the molten resin contains a foaming agent. (7) The method for molding a lightweight resin molded article having a rising portion according to the above (1), wherein a gas is injected into the molten resin in the mold cavity when the molten resin expands. (8) The outer periphery has a rising portion, and the average fiber length is 2 to 2.
A lightweight resin molded product containing 5 to 70% by weight of 20 mm glass fiber and having a porosity of 20% or more at a rising portion;
The present invention provides a lightweight resin molded product containing 0% by weight and having a porosity at a rising portion of 20% or more, and (9) the lightweight resin molded product according to (8), wherein the outer peripheral shape is not a square.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. As a molding method of the lightweight resin molded article having the rising portion of the present invention, any of an injection molding method and an injection compression molding method can be adopted. The rising portion is generally a portion that rises in the mold opening and closing direction of an injection molding machine, and the simplest shape is a cylinder, a prism, a cylinder, or a square tube. , Prisms, cylinders,
A cylinder with a base, a prism with a base, a box,
It is a container-shaped molded product. The present invention is particularly suitable for forming a box-shaped molded product having a rising portion on the outer peripheral portion. The molding die used in the molding method of the present invention has a structure in which a projecting member is provided to be able to advance and retreat in a mold cavity portion of a rising portion when forming a mold cavity at the time of injection filling of a molten resin by a mold operation. Things. Here, the protruding member can be moved forward and backward when the mold is closed or when the mold is closed and opened.

The mold cavity often has a complicated mold structure due to the functions and uses required for various molded products, and this protruding member is not necessarily provided at the rising portion at the time of injection and filling of the molten resin. It is not necessary that the shape be similar to the shape of the mold cavity, and in the cross section of the projecting member, the projecting portion that can advance and retreat under the condition that a molten resin layer is formed between the mold surface of the projecting portion and another mold surface Should be fine. Therefore, in addition to the case where the protruding member is formed over the entire area of the rising portion, the case where the protruding member is formed discontinuously may be used.

First, in the molding die, the protruding member is advanced to the die cavity portion of the concave portion forming the rising portion (in the case of the outer peripheral rising portion, the annular concave portion), so as to be interposed between other mold surfaces. A mold structure capable of forming a space in which the molten resin can be injected and filled. In other words, a molding die having a protruding member that moves forward and backward to change the cavity cross section of the rising portion is used. As a structural example of the mold, a cavity that becomes a molded product is formed by a fixed mold and a movable mold, and a concave portion corresponding to a rising portion of the molded product is configured by a combination of a movable mold, a fixed mold, and both molds. Is done. On the other hand, a mold portion protruding to reduce the cross-sectional area of the concave portion is provided fixedly to a fixed mold or a movable mold, or a structure in which the fixed mold or the movable mold is slidable within the movable mold. There is a case.

As a specific example, (1) a projecting member is provided in a concave portion so as to be able to advance and retreat in a state in which the mold is completely closed, and the molten resin is expanded by retreating.
This structure is advantageous in terms of molding conditions and control because the rising portion expands when the mold is completely closed.
The mold structure may be complicated. (2) The protruding member protruding from the rising portion is fixed, and when the mold is opened,
By retreating from the concave portion, the volume of the corresponding portion expands and expands. This structure is simple as a mold structure, but since the molten resin expands while opening the mold, the molding conditions and control may be somewhat difficult. Therefore, it is necessary to select an appropriate method according to the shape and size of the molded product, the type of the resin, and the like, and to perform molding.

The projecting portion inserted into the rising portion used in the present invention forms a cavity in the case of gas injection due to the receding of the projecting portion. Will expand, and the hollow portion will be buried and integrated. Because of this,
In particular, cooling of the protruding portion mold except for the base portion needs to be delayed as compared with the mold temperature of the other molding surface. The protruding portion is exposed to the high-temperature molten resin, and tends to be higher than other molding die surfaces. However, the temperature may be too low depending on the volume of the concave portion of the mold. In any case, it is preferable to provide a mold heating control unit as necessary, in order to maintain the mold protruding portion at a temperature higher than the crystallization temperature or fluidity temperature of the molding resin.

As described above, the feature of the present invention, that is, the weight reduction of the rising portion of the molded product, has been described. However, in order to secure the weight reduction, strength, and rigidity of the entire molded product, a combination with a molding method for reducing the weight of a general flat portion (bottom portion), which is a non-rise portion of the molded product, by a conventionally known method. Can be. That is, a method of adopting a mold structure in which the mold corresponding to the non-rising portion moves in the mold opening / closing direction, and after injection filling of the molten resin, retracts the moving mold to enlarge the cavity volume and expand. Can be used together.

Hereinafter, the present invention will be described in detail with reference to the drawings. Each drawing is a conceptual diagram showing an embodiment of the present invention. In each drawing, 1 is a fixed mold, 2 is a movable mold, 3 is a movable mold, 4 is a movable mold protrusion, 5 is a movable mold advance / retreat device, 6 is a sprue, 7 is a mold cavity, 8 is a mold cavity. Molded product, 9 is a fixed mold protrusion, 10 is a molded product pressing member,
Reference numeral 11 denotes a molded product pressing member operating unit, 12 denotes a molded product pressing operation member, and 13 denotes a spring.

FIGS. 1 and 2 are conceptual views of a first embodiment of the present invention. FIG. 1 shows a state before injection molding of a molten resin into a mold cavity, and FIG. 2 shows the state of the molded article after the projecting member is retracted, the volume is expanded, and the molten resin is expanded. To carry out the first embodiment, an injection mold having a specific structure is used. The injection mold is for molding a molded product in the shape of a bottomed cylindrical container, and a mold cavity is formed by the fixed mold 1, the movable mold 2, and the movable mold 3. Here, the mold cavity is used for molding the rising portion of the molded product.
It consists of a part and a 7b part that forms the bottom. The projecting member 4 of the movable mold 3 penetrating the movable mold 2
Are provided in the mold cavity 7a so as to be able to advance and retreat.
The mold part forming the bottom 7b of the movable mold is integrated with the movable mold 2 by a structure not shown. The projecting member 4 of the movable mold 3 is advanced to the portion 7a of the mold cavity 7 by the movable mold moving device 5 so as to reduce the volume of the portion 7a.

In the mold cavity 7 in this state, a molten resin (for example, a fiber-containing expandable molten resin) melted, kneaded and measured by an injection unit (not shown) is injected and filled through a sprue 6. Due to this injection filling pressure, the molten resin sufficiently spreads to the details and ends of the mold, and the mold surface including the ribs, embosses and the like is reliably transferred. Then, after the molten resin on the mold surface has cooled down to some extent, the movable mold 3 is retracted by the operation of the movable mold advance / retreat device 5, and becomes the mold shape of the final molded product shown in FIG. The molten resin expands due to the expansion of the volume, and the weight is reduced. Thereafter, after cooling, the movable mold 2 is retracted and the mold is opened to take out the molded product. The degree of weight reduction at this time can be appropriately determined by changing the volume of the mold cavity 7a and the volume of the projecting member 4 of the movable mold based on the required performance of the molded product.

FIGS. 3 and 4 are conceptual views of a second embodiment of the present invention. FIG. 3 shows a state before the molten resin is injected into the mold cavity, and FIG. The state of the molded article after retreating the member, expanding the volume, and expanding the molten resin is shown. The difference from the first embodiment is that a moving mold is not used and that the molten resin expands by opening the mold. The molding die of the second embodiment is for molding a rectangular box-shaped molded product, and a fixed mold 1 and a movable mold 2 form a mold cavity. Here, in the mold cavity, a portion 7a for molding the rising portion of the molded product is formed in the movable mold 2 as a concave portion.

On the other hand, the fixed mold 1 is integrally provided with a fixed mold projecting member 9 so as to advance and retreat to the concave portion of the movable mold 2. A molded article pressing member 10 is provided movably so as to surround the protruding member. The molded product pressing member 10 is formed by an outer portion 10a and an inner portion 10b of the protruding member 9.
And is configured to move in conjunction with opening and closing of the fixed mold 1 and the movable mold 2. That is, the molded article pressing member 10 includes the molded article pressing member operating member 12 and the spring 13.
It is configured to be moved by the molded article pressing member operation unit 11 configured as follows. The molded article pressing member 10
When the molding die is closed, the spring 13 is pressed by the movable die 2 and compressed to fit on the die surface of the fixed die 1, and the protruding member 9 of the fixed die 1 is inserted into the concave portion of the movable die 2. Moving forward, a narrowed mold cavity 7a is formed.

The molten resin is injected and filled into the mold cavity 7 in this state in the same manner as described above, and the mold surface is reliably transferred to the surface of the molded product. Then, after the molten resin on the mold surface has cooled to some extent, the movable mold 2 is retracted, and the mold cavity is controlled to stop at a position where the mold cavity has the shape of the final molded product. The molded article 8 is separated from the fixed mold 1 together with the movable mold 2, and the molded article pressing member 10 is pressed by the movable mold 2 inside and outside of the protrusion while pressing the molded article by the repulsive force of the spring 13. Move while maintaining the state. Thus, the mold can be opened even if the molded article is not completely cooled. After the completion of cooling of the molded product, the movable mold 2 is further opened, and the molded product is taken out.

FIGS. 5 and 6 are conceptual views of a third embodiment of the present invention. FIG. 5 shows a state before injection molding of a molten resin into a mold cavity. Indicates the state of the molded article after the projecting member at the rising portion is retracted, the volume is expanded, and the molten resin is expanded. The difference from the second embodiment is to reduce the weight of the bottom of the box-shaped molded product,
The moving mold 3 shown in the first embodiment is used together. That is, before or after the opening of the molding die, the movable die 3 is retracted to expand the portion 7b corresponding to the bottom portion of the box to reduce the weight. The retreat timing of the movable mold 3 can optimize the molding conditions while specifically molding based on the overall shape of the molded product, the thickness of the bottom and rising portions, the expansion ratio, and the like.

In the above embodiment, the molten resin is injected into the mold cavity 7 through the sprue 6 and fills the cavity 7. As a result, the details of the mold surface, such as ribs and surface textures, are reliably transferred by the injection resin pressure. At the time of injection, the molten resin has expandability due to entanglement of fibers and expandability due to the inclusion of a foaming agent. In addition, it is also possible to impart expandability by injecting a gas after injection filling.

After the injection filling of the molten resin is completed, after a suitable time, when the filled resin still has fluidity, the projecting member projecting at least to the rising portion of the mold cavity 7 is moved to the mold cavity portion. Retreat from Due to the expansion of the cavity due to the retraction of the protruding member, the molten resin in the corresponding portion expands to have the shape of the final molded product 8, and after the cooling process, the mold is opened by the operation of the mold opening mechanism, and the mold is opened. The lightweight resin molded product having the portion is taken out. In addition, the molded article pressing member 10
It is also possible to employ a hydraulic cylinder or the like instead of a spring for urging.

Here, in the case where the molten resin exhibits expandability due to entanglement of fibers contained such as glass fiber and the like, and when the degree of expansion is not less than a certain level (1.5 times or more), expansion causes expansion. Continuous voids are generated inside the molten resin. In this case, a relatively low pressure (3 MPa) is utilized inside the expanded molten resin by utilizing the continuous voids.
The following gas can be injected. Due to the gas pressure of this gas injection, the molded product is pressed against the mold surface even after expansion, and the mold surface is reliably transferred even during the cooling process, and it is possible to obtain a molded product with excellent appearance. Become. The gas injected here can be cooled more quickly by discharging the gas while maintaining a pressure at which the molded product can be pressed against the mold surface. This way,
Due to the weight reduction and the formation of voids due to the expansion, it becomes a heat insulator, and cooling only by cooling from the surface of the mold makes it difficult to cool, the molding cycle becomes longer, and the disadvantage of lowering the productivity can be improved.

Although the injection molding method has been specifically described above, it is desired to prevent the flow orientation of the molten resin when the thickness of the cavity at the time of injection of the molten resin is small, or when the flowability of the molten resin is low. In some cases, injection compression molding can be employed. That is, after starting the injection of the molten resin into the mold cavity larger than the injection volume of the molten resin in advance, and preferably before the injection is completed, the movable mold is advanced to compress the molten resin, and the compression causes the molten resin to be compressed. To completely fill the mold cavity. Less than,
The cavity is enlarged according to the injection molding method, and a lightweight resin molded product having a rising portion is molded.

The thermoplastic resin used in the method of molding a lightweight resin molded article having a rising portion according to the present invention is not particularly limited, but examples thereof include polypropylene, propylene-ethylene block copolymer, and propylene-ethylene random copolymer. Polymers, polyolefin resins such as high-density polyethylene, polystyrene resins, ABS resins, polyvinyl chloride resins, polyamide resins, polyester resins, polyacetal resins, polycarbonate resins,
A polyaromatic ether or thioether resin, a polyaromatic ester resin, a polysulfone resin, an acrylate resin, or the like can be used. Here, the thermoplastic resin may be used alone, or two or more kinds may be used in combination. Among such thermoplastic resins, polypropylene, block copolymers of propylene and other olefins, random copolymers, or polypropylene-based resins such as mixtures thereof, high-density polyethylene, polyamide-based resins, polycarbonate-based resins It is particularly preferable to use a thermoplastic resin containing an acid-modified polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof, a polyolefin resin, and particularly a polypropylene resin.

The acid-modified polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof improves the interfacial adhesive strength between a reinforcing material such as glass fiber and a filler and the resin, and consequently increases the physical properties of the molded product and the long-term properties. It is preferable because it contributes to the improvement of stability and promotes the impregnation of the fiber bundle with the resin. Examples of the unsaturated carboxylic acid used for the modification include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, sorbic acid, mesaconic acid, angelic acid and the like. Derivatives include acid anhydrides, esters, amides,
Examples include imides and metal salts, such as maleic anhydride, itaconic anhydride, citraconic anhydride, methyl acrylate,
Examples thereof include methyl methacrylate, ethyl acrylate, butyl acrylate, monoethyl maleate, acrylamide, maleic monoamide, maleimide, N-butylmaleimide, sodium acrylate, and sodium methacrylate. Among these, unsaturated dicarboxylic acids and derivatives thereof are preferred, and maleic anhydride is particularly preferred. As the acid-modified polyolefin resin, the addition amount of the unsaturated carboxylic acid or its derivative is
The content is preferably in the range of 0.01 to 20% by weight, preferably 0.02 to 10% by weight, and particularly preferably a maleic anhydride-modified polypropylene resin.

In the method for molding a lightweight resin molded article having a rising portion according to the present invention, in the case of a molding method utilizing expansion due to entanglement of fibers, the inclusion of fibers is essential. As the fibers, ceramic fibers: boron fiber, silicon carbide fiber, alumina fiber, silicon nitride fiber, zirconia fiber, inorganic fiber: glass fiber, carbon fiber, metal fiber:
Copper fiber, brass fiber, steel fiber, stainless fiber, aluminum fiber, aluminum alloy fiber, organic fiber: polyester fiber, polyamide fiber, aramid fiber, polyarylate fiber and the like can be exemplified. Among these, glass fibers are preferably used.

Here, as the glass fibers, glass fibers such as E-glass and S-glass having an average fiber diameter of 25 μm or less, particularly in the range of 3 to 20 μm can be preferably employed. When the diameter of the glass fiber is less than 3 μm, the glass fiber does not adapt to the resin at the time of pellet production, and it becomes difficult to impregnate the resin. On the other hand, when the diameter exceeds 20 μm, the glass fiber is liable to be cut or chipped during melt kneading.

In the present invention, when a fiber-containing resin is used as the resin raw material, for example, a pellet-shaped raw material reinforced by a pultrusion method using a thermoplastic resin and continuous fibers can be used. As a preferred example of this raw material pellet, the total length is 2 to 100 mm,
Fibers having a length equal to the total length are arranged in parallel with each other, and the fiber is a pellet containing 20 to 80% by weight or a mixture of the pellet and another resin pellet, wherein the fiber has a weight of 5 to 70% by weight. %, Preferably 10 to 60% by weight. The use of pellets in which the fibers are arranged in parallel to each other and contained 20 to 80% by weight of the total makes it difficult for the fibers to break even when plasticizing and kneading with the screw of the injection device, and to disperse the fibers. The property is also good. Thereby, the length of the fiber present in the injection molten resin can be kept relatively long, and the expansion property of the molten resin can be easily improved. In addition, the physical properties and surface appearance of the molded product are improved.

In the case where the fibers are glass fibers, pellets are produced by a pultrusion method or the like. After the glass fibers are surface-treated with a coupling agent, the glass fibers are treated with a sizing agent.
100 to 10000, preferably 150 to 5000
It is desirable to bundle them in the range of the book. The coupling agent can be appropriately selected from so-called silane coupling agents and titanium coupling agents that have been conventionally used. For example, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxy Amino silane such as silane or epoxy silane can be employed. In particular, it is preferable to employ the amino silane compound.

By adhering and impregnating the glass fibers converged with the above-mentioned converging agent with the thermoplastic resin, resin pellets containing glass fibers are produced. As a method of attaching and impregnating a thermoplastic resin to glass fibers, for example, a method of passing a fiber bundle through a molten resin and impregnating the resin with the fiber, a method of impregnating the fiber bundle through a coating die, or a method using a die A method in which the molten resin adhering around the fibers is spread and impregnated into the fiber bundle can be adopted.

Here, in order to make the fiber bundle and the resin fit well, that is, to improve the wettability, the fiber bundle is passed through a die having an uneven portion on the inner periphery and a plurality of rods alternately up and down. By pulling out through the tensioned fiber bundle, the fiber bundle is opened, the molten resin is impregnated into the fiber bundle, and further, the fiber bundle is pressed with a pressure roller. A molding method can also be adopted. If the glass fiber and the molten resin are compatible with each other and have good wettability, the molten resin can be easily impregnated into the glass fiber and the pellets can be easily manufactured. May be omitted.
Here, as a method of making the resins compatible with each other, a method of imparting polarity to the resin or grafting a functional group that reacts with the coupling agent on the surface of the glass fiber is effective. Furthermore, after treating the glass fiber bundle with a liquid material such as liquid paraffin having a boiling point equal to or higher than the melting temperature of the molten resin at the time of impregnation, a plurality of fiber bundles are introduced in a separated state into the resin impregnation section, and the A method of integrating the bundle is also preferable. According to this method, the impregnation property of the resin can be improved and high-speed pultruding can be performed.

By cutting the resin-impregnated strand or the like along the longitudinal direction of the fiber by the above-described method, a resin pellet containing a long fiber having the same length as the entire length of the pellet can be obtained. . At this time, as resin pellets,
The fiber bundle is made into strands, and the cross-sectional shape is not limited to a resin-containing long fiber bundle whose cross-sectional shape is substantially circular, but a resin in a sheet shape, tape shape or band shape by arranging the fibers flat. The long fiber bundle may be cut into a predetermined length.

In the method of molding a lightweight resin molded article having a rising portion according to the present invention, when foaming is used, a molding material containing, for example, about 0.1 to 5% by weight of a foaming agent is used. Here, the type of the foaming agent is not limited as long as it decomposes by heat to generate gas. For example, oxalic acid derivatives, azo compounds, hydrazine derivatives, semicarbazides, azide compounds, nitroso compounds, triazoles, ureas and related compounds, nitrites, hydrides, carbonates, bicarbonates and the like can be employed. More specifically, azodicarbonamide (ADCA), benzenesulfohydrazide, N, N-dinitropentamethylenetetramine, terephthalazide,
Etc. can be adopted. Further, a physical foaming agent such as butane, propane, and water may be used.

Next, when a gas injection molding method is employed as a method for molding a lightweight resin molded article having a rising portion according to the present invention, it is usually preferable to use a gas injection nozzle provided on a cavity wall to supply nitrogen or the like. Injects an inert gas into the molten resin in the cavity. As an injection point,
The top of the cavity recess is preferred. Injection of gas is generally performed after retraction of the protrusion has begun. In addition, in the present invention, unlike a general gas injection molding method, gas injection is performed while retracting the protruding portion, so that the inside of the cavity is relatively low in pressure, and the pressure of the gas to be injected is
Usually, a low gas pressure of 20 MPa or less, especially 3 Mpa or less, is sufficient.

In order to form the lightweight resin molded article having a rising portion according to the present invention, an antioxidant, an ultraviolet absorber, an antistatic agent, a weathering agent, a light stabilizer, Additives such as colorants and nucleating agents, and fillers such as short glass fibers and talc can also be added. In the method of molding a lightweight resin molded article having a rising portion according to the present invention, the molten resin is injected into a mold cavity corresponding to the narrowed rising portion, or is injected and compressed to fill the mold cavity with the molten resin. Then, the movable mold moving in the mold opening / closing direction or the protrusion relatively retracted by opening the mold is retracted. Here, the timing of starting the retreat of the protruding portion after the injection of the molten resin is appropriately determined according to the shape, thickness, size, temperature of the mold, and the like of the molded product.
However, on the surface of the molded product, the mold transfer is completed, and conversely, the molten resin expands due to the retreat of the protruding portion. Therefore, it is important to secure the expansion. Therefore, it is desirable to select molding conditions such that the cooling of the molten resin in the expanded portion is somewhat delayed from the other portions.

The object of the method for molding a lightweight resin molded article having a rising portion according to the present invention is to make the mold cavity at the rising portion smaller than the shape and volume of the final molded product, and to inject and fill a molten resin. The goal is to reach the ends and details of the mold cavity. In this way, it is possible to ensure the transfer of fine ribs and grain on the surface of the mold and to obtain a molded product having excellent appearance. Further, by this, the molded product surface forms a dense structure while the final molded product is light in weight, and in this regard, the molded product has excellent appearance, strength, and rigidity.

As described above, in the molding method of the present invention, the use of a fiber-containing raw material resin, the use of a foaming agent-containing resin, the use of a normal resin other than these, and the use of gas injection are independently used. In addition to the case, the case where two or more kinds are combined and molded is naturally included. In addition, when injecting a gas, the injected gas is maintained at a certain pressure (ensure shapeability) during the cooling process of the molded product.
It is preferable to circulate the gas while exhausting the gas to the outside. As a result, while being a lightweight resin molded product, the inside of the molded product is uniformly cooled by the flowing gas, and the cooling efficiency,
The molding cycle can be improved.

The lightweight resin molded article molded by the method for molding a lightweight resin molded article having a rising portion according to the present invention includes a tubular or box-shaped lightweight resin molded article having a rising portion. It can be suitably molded by adopting a molding method. Among them, a glass fiber having a rising portion on the outer periphery and an average fiber length of 2 to 20 mm
60% by weight, average porosity at rising part is 20%
As described above, it is a lightweight resin molded product having preferably 25% or more, and in particular, a lightweight resin molded product whose outer peripheral shape is not square can be easily molded. The present invention has an excellent advantage that the cross-sectional shape of the rising portion can be freely selected, such as a circle, a corner, or a combination. In order to satisfy weight reduction, strength, and rigidity, it is preferable that the general part other than the rising part also has a porosity equal to or higher than that. In addition, in the molding method of the lightweight resin molded product having a rising portion and the lightweight resin molded product of the present invention, if necessary, a resin sheet,
A skin-integrated lightweight resin molded product can also be obtained by setting a skin material such as an Eratosuma sheet, a foam sheet, a woven fabric, and a nonwoven fabric in a mold cavity in advance.

As described in detail above, the method of molding a lightweight resin molded article having a rising portion according to the present invention is conventionally
It can be applied to the molding of a molded article having a rising portion as a molded article, for which it was difficult to reduce the weight, and has a good balance of density, strength, and rigidity, and has excellent mold transferability. In particular,
Even in the case of a molded product having a rising portion at the outer peripheral portion of the molded product, for example, a box-shaped molded product, the density of the side wall portion can be adjusted substantially arbitrarily, and the object of weight reduction is achieved. Therefore, it can be applied to various molded products that emphasize appearance, and the application field is expected to be expanded. By these features, as described above, automobile parts, home appliances,
It expands its application fields as various molded articles such as office equipment, computers, furniture, architecture, and civil engineering. In particular, it is expected to be applied to molded articles such as boxes, cylinders, and housings, which have been difficult in the past.

[0044]

Next, the effects of the present invention will be described based on specific examples, but the present invention is not limited to these examples. Example 1 Glass fiber reinforced polypropylene pellets in which glass fibers (13 μm) are arranged in parallel and whose content is 70% by weight and length is 15 mm (glass fiber length = 15 mm, containing 3% by weight of maleic anhydride-modified polypropylene) ) 45% by weight and melt index (MI: 230 ° C, 2.16k)
g load) 30 g / 10 min polypropylene pellet 5
To 5 parts by weight of 100 parts by weight, 0.3 parts by weight of a foaming agent (Eiwa Kasei Co., Ltd., polysulene E115: containing 10% by weight of a foaming agent) was added and dry-blended to obtain a raw material for molding. The injection molding machine has a mold clamping force of 850 t and a compression ratio of 1.9.
And a molding device provided with a movable mold moving device (compression unit) that allows the moving mold 3 to advance and retreat in the fixed mold 1 and the movable mold 2. The molded product cavity is for producing a molded product having a cylindrical shape with a bottom. Initial cavity 7 at the start of injection has an outer diameter of 300 mm, a height of 50 mm, a bottom thickness of 4 mm, and a thickness of a rising portion:
12 mm, thickness of the protruding portion: 4 mm. (See FIGS. 1 and 2).

As shown in FIG. 1, the mold was clamped, and the resin corresponding to the initial mold cavity 7 was melt-plasticized (resin temperature: 250 ° C.), measured and injected and filled. Thereafter, the movable mold was retracted, and the protruding member was retracted from the cavity. The rising portion of the molded product expanded about 1.5 times, the average porosity was about 30%, and the average fiber length measured by a microscope after incineration was 5.1 mm. The surface of the molded article had a skin layer formed thereon, had no silver streaks or sink marks, and exhibited a good surface.

Example 2 Glass fiber reinforced polypropylene pellets (glass fiber length = 12 mm) 70 in which glass fibers (13 μm) are arranged in parallel, the content is 60% by weight, and the length is 12 mm
% By weight and melt index (MI: 230 ° C., 2.1
30 wt% of polypropylene pellets having a load of 6 kg / 30 min / 10 g were dry blended to obtain a raw material for molding.
The injection molding machine includes a screw having a mold clamping force of 850 t and a compression ratio of 1.9, and includes a fixed mold 1 and a movable mold 2. The fixed mold 1 has a molded article pressing member 10 and an operation thereof. A molding device having a part was used. The molded article cavity is for producing a box-shaped molded article. Initial cavity 7 at the start of injection is 250 × 250 × 40 mm high, bottom thickness: 4 m
m, thickness of rising part: 8 mm, thickness of protruding part: 4 m
m. (See FIGS. 3 and 4). Except for the root of the protrusion of the fixed mold, the heating was controlled by a heater so as to reach 130 ° C.

As shown in FIG. 3, the mold was clamped, and the resin corresponding to the initial mold cavity 7 was melt-plasticized (resin temperature: 250 ° C.), measured, and injection-filled. After the filling is completed, the surface of the molded product is cooled to a certain extent.
Was controlled to start retreating to the mold opening / closing mechanism and stop at the position where the tip of the protruding member comes to the top of the rising portion of the molded product. Thereafter, the cooling was completed, the mold was opened, and the molded product was taken out. The rising portion of the molded product expanded about 2.0 times, had an average porosity of about 48%, and had an average fiber length of 5.1 mm. The surface of the molded article had a skin layer formed thereon, had no silver streaks or sink marks, and exhibited a good surface.

Example 3 Glass fiber reinforced polypropylene pellets in which glass fibers (13 μm) are arranged in parallel, whose content is 40% by weight, and whose length is 10 mm (glass fiber length = 10 mm, maleic anhydride-modified polypropylene is 2 (% By weight). The injection molding machine has a mold clamping force: 850 t, a compression ratio:
A moving mold advance / retreat device (e.g., a compression unit, which includes a compression unit and has a molded article pressing member), which has a screw of 1.9 and allows the moving mold 3 to advance and retreat in the fixed mold 1 and the movable mold 2. 10
And a molding device having an operation unit for the above. The molded article cavity is for producing a box-shaped molded article. Initial cavity 7 at the start of injection is 250 × 250 × 50 mm
Height, bottom thickness: 4mm, thickness of rising part: 10m
m, thickness of the protruding portion: 6 mm. (See FIGS. 4 and 6).

As shown in FIG. 5, the mold was clamped, and the resin corresponding to the initial mold cavity 7 was melt-plasticized (resin temperature: 250 ° C.), measured and injected and filled. After the filling of the molten resin was completed, the movable mold 3 was retracted to a position where the thickness of the bottom became 10 mm. Then, the movable mold 2 was controlled to start retreating by the mold opening / closing mechanism and stop at a position where the tip of the protruding member comes to the top of the rising portion of the molded product. Thereafter, the cooling was completed, the mold was opened, and the molded product was taken out. The rising part of the molded product expanded about 2.5 times, the average porosity was about 58%, and the bottom part also expanded about 2.5 times. The average fiber length was 6.2 mm. The surface of the molded article had a skin layer formed thereon, had no silver streaks or sink marks, and exhibited a good surface.

[0050]

According to the present invention, after the molten resin is injected and filled, and the mold surface is reliably transferred, the projecting member projecting to the rising portion is retracted to increase the cavity volume of the rising portion. Therefore, the rising portion, which is difficult to inflate and reduce in weight, can be easily reduced in weight, and the purpose of reducing the weight of the molded article as a whole is further achieved. In particular, expansion of the rising portion of a molded product having a rising portion at the outer peripheral portion of the molded product, such as a box-shaped molded product, is reliably achieved, and strength and rigidity are ensured along with a good appearance. Moreover,
There are no restrictions on the cross-sectional shape of the rising part, circular, polygonal,
It consists of these combinations and is not limited to a square. Therefore, it is possible to easily mold a molded article with a particularly high weight reduction, the degree of freedom of design is widened, and the application field is expected to be greatly expanded.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a first embodiment of the present invention, showing a state before injection of a molten resin.

FIG. 2 is a conceptual diagram showing the first embodiment of the present invention, showing a state after the protrusion of the rising portion is retracted, the volume is expanded, and the molten resin is expanded.

FIG. 3 is a conceptual diagram showing a second embodiment of the present invention, showing a state before molten resin injection.

FIG. 4 is a conceptual diagram showing a second embodiment of the present invention, showing a state in which a protruding portion of a rising portion is retracted, a volume is expanded, and a molten resin is expanded.

FIG. 5 is a conceptual diagram showing a third embodiment of the present invention, showing a state before molten resin injection.

FIG. 6 is a conceptual diagram showing a third embodiment of the present invention, showing a state after the protrusion of the rising portion is retracted, the volume is expanded, and the molten resin is expanded.

[Explanation of symbols]

 1: Fixed mold 2: Movable mold 3: Moving mold 4: Moving mold projecting member 5: Moving mold advance / retreat device 6: Sprue 7: Mold cavity 8: Molded product 9: Fixed mold projecting member 10: Molded product pressing member 11: Molded product pressing member operating unit 12: Molded product pressing member operating member 13: Spring

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F202 AA03 AA13 AA15 AB02 AB25 AG20 AH56 AH81 CA11 CB01 CK19 CK52 CK75 4F206 AA03 AA13 AA15 AB02 AB25 AG20 AH56 AH81 JA07 JM05 JN22 JN25 JN27 JQ81

Claims (9)

[Claims] A mold resin is injected and filled into a mold cavity in a state where a projecting member is projected into a mold cavity portion forming a rising portion of a molded product, and then the projecting member is retracted to melt the molten resin. A method for molding a lightweight resin molded article having a rising portion that expands into a final molded article shape. 2. Injection filling of a molten resin into a mold cavity is performed independently of the protruding member by retreating a mold at a portion corresponding to a thickness of a non-rising portion of a molded product, thereby expanding the molten resin to a final state. 2. The method for producing a lightweight resin molded article having a rising portion according to claim 1, wherein the molded article has a thickness. 3. A light-weight resin molded product having a rising portion at least on an outer peripheral portion of the molded product.
A method for producing a lightweight resin molded article having the rising portion according to the above. 4. A molten resin obtained by melting a raw material containing at least a part of resin pellets containing fibers having a length of 2 to 100 mm, and having a fiber content of 5 to 80% by weight.
The method for molding a lightweight resin molded article having a rising portion according to any one of claims 1 to 3. 5. The method according to claim 4, wherein the fibers are glass fibers. 6. The method according to claim 1, wherein the molten resin contains a foaming agent. 7. The method for molding a lightweight resin molded article having a rising portion according to claim 1, wherein a gas is injected into the molten resin in the mold cavity when the molten resin expands. 8. A glass fiber having a rising portion on an outer peripheral portion and having an average fiber length of 2 to 20 mm, containing 5 to 70% by weight,
A lightweight resin molded product having a porosity of 20% or more at the rising portion. 9. The lightweight resin molded article according to claim 8, wherein the outer peripheral shape is not a square.