JP2013237185A - Method for producing molded product of organic fiber-contained thermoplastic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an organic fiber-contained thermoplastic resin capable of obtaining a molding in which fiber lumps are not suppressed from being generated especially in an end part of a molded product of an excellent appearance regardless of the shape of the molded product.SOLUTION: A method for manufacturing an organic fiber-contained thermoplastic resin includes: (1) a melting step of melting a thermoplastic resin composition containing a thermoplastic resin and an organic fiber; and (2) a filling step of supplying the melted thermoplastic resin composition into a mold cavity that is configured between a pair of molds and has a product part cavity and a non-product part cavity in partially or entire of the circumference of the product cavity and filling the melted thermoplastic resin composition.

Description

  The present invention relates to a method for producing an organic fiber-containing thermoplastic resin molding.

  A molded body made of a thermoplastic resin containing fibers is used in various fields because of its excellent rigidity. Recently, the use of organic fibers as well as inorganic fibers typified by conventional glass fibers has been studied. When producing a molded body using a thermoplastic resin containing organic fibers, the longer the length of the organic fiber used, the greater the mechanical strength of the molded body obtained, but the organic fibers become entangled in the manufacturing process of the molded body. On the other hand, a thread-like fiber lump is likely to occur. When the fiber lump is generated, the strength of the obtained molded body may vary, or the appearance of the obtained molded body may be deteriorated.

  As a method for suppressing the generation of fiber mass, Patent Document 1 discloses that a polyolefin resin containing organic fibers is melted and supplied into a mold cavity, and the mold is clamped during or after the supply. A method of manufacturing a body is described.

JP 2012-9882 A

However, for example, in the case of a molded body having a shape in which the end portion of the molded body is substantially perpendicular to the surface near the center of the molded body, the end portion of the molded body is also formed by the method described in Patent Document 1. A fiber lump may be generated.
The present invention provides a method for producing an organic fiber-containing thermoplastic resin molded article that can suppress the formation of fiber masses and can obtain a molded article having a good appearance, particularly at the end portion of the molded article, regardless of the shape of the molded article. The purpose is to provide.

That is, the present invention
(1) a melting step of melting a thermoplastic resin composition containing a thermoplastic resin and organic fibers;
(2) The thermoplastic resin composition melted in a mold cavity which is configured between a pair of molds and has a product part cavity and a non-product part cavity around a part or all of the periphery of the product part cavity. The manufacturing method of the organic fiber containing thermoplastic resin molding including the filling process which supplies and fills.

  According to the present invention, it is possible to obtain an organic fiber-containing thermoplastic resin molded article having a good appearance by suppressing the generation of fiber masses even at the end portion of the molded article, regardless of the shape of the molded article.

It is sectional drawing of a metal mold | die used for the method of this invention in the orthogonal | vertical direction with a molding surface. It is sectional drawing of the orthogonal | vertical direction with the molding surface of a metal mold | die which shows the process of the manufacturing method of this invention. It is sectional drawing of the orthogonal | vertical direction with the molding surface of a metal mold | die which shows the process of the manufacturing method of this invention. It is sectional drawing of the orthogonal | vertical direction with the molding surface of a metal mold | die which shows the process of the manufacturing method of this invention. It is sectional drawing of the orthogonal | vertical direction of the molding surface of a metal mold | die which shows the process of the manufacturing method of this invention. It is sectional drawing which shows an example of the molded object obtained by the manufacturing method of this invention. It is sectional drawing which shows another example of the molded object obtained by the manufacturing method of this invention.

  Hereinafter, preferred embodiments of a production method according to the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same part and the overlapping description is abbreviate | omitted. As shown in the drawings, the X axis and the Y axis are 90 degrees on a horizontal plane perpendicular to the molding surface of the mold. Hereinafter, the X axis and the Y axis will be described when necessary.

[Mold]
The pair of molds used in the present invention can relatively approach and separate from each other. Both molds may be movable.
The mold shown in FIGS. 1 to 5 is a pair of molds for injection molding, and includes a fixed mold 2 and a movable mold 1. Hereinafter, the metal mold | die used for this invention is demonstrated using figures.
The movable side mold 1 and the fixed side mold 2 are disposed to face each other in the X-axis direction. From the state in which the movable mold 1 and the fixed mold 2 are not in contact, the movable mold 1 is moved toward the fixed mold 2 to bring the movable mold 1 into contact with the fixed mold 2. Thus, a mold cavity 3 is formed by these molds. The mold cavity 3 includes a product part cavity 4 corresponding to a part of a molded body that becomes a product after molding, and a non-product part cavity 5 corresponding to a part of the molded body that is removed after molding and does not become a product. The non-product part cavity 5 may be provided over the entire periphery of the product part cavity 4 or may be provided only in a part of the periphery. The shape and size of the non-product part cavity 5 are not particularly limited, but if it is too small, the fiber mass is not sufficiently discharged and the appearance is deteriorated.If it is too large, the appearance is improved but the material is wasted. It is preferable that the minimum size that can discharge the fiber mass is used. The cavity clearance at the boundary between the product part cavity 4 and the non-product part cavity 5 is preferably smaller than the product part thickness of the molded body so that the non-product part can be easily removed from the molded body after molding.

The movable mold 1 reciprocates in the X-axis direction by a mold opening / closing mechanism (not shown). The mold cavity 3 is reduced by moving the movable mold 1 toward the fixed mold 2 from the state in which the fixed mold 2 and the movable mold 1 are in contact with each other as shown in FIG. . The cavity clearance is the distance between the molding surface of the fixed mold 2 and the molding surface of the movable mold 1 facing the molding surface. The cavity clearance is variable by moving the movable mold.
In FIG. 1, the stationary mold 2 and the movable mold 1 are closed. When the stationary mold 2 and the movable mold 1 are closed, a mold cavity 3 formed by these molds is composed of a product part cavity 4 and a non-product part cavity 5. The shape corresponds to the shape of the desired product part molded body.

  The stationary mold 2 is provided with a gate portion 6 for supplying a molten thermoplastic resin composition (hereinafter also simply referred to as “molten resin”) to the mold cavity 3. It is connected to the molten resin supply passage 7. An opening / closing mechanism such as a valve pin 8 that can block the passage is provided at the tip of the molten resin supply passage 7. The valve pin 8 can reciprocate in the X-axis direction. When the molten resin 9 is supplied, the valve pin 8 is retracted to secure a flow path of the molten resin 9, and after the supply of the molten resin 9 is completed, the valve pin 8 is advanced to melt. The flow path of the resin 9 can be blocked. The valve pin 8 is driven by a drive source (not shown) such as hydraulic pressure, pneumatic pressure, and electric power. When using a mold having two or more gate portions 6 each having a valve pin 8, the timing of supplying molten resin from each gate portion 6 to the mold cavity 3 can be freely controlled by controlling the operation of each valve pin. can do.

The area of the gate portion 6 at the outlet of the gate portion 6 is preferably 7 mm ² or more and 50 mm ² or less. When the area is within the above range, when the molten resin is supplied into the mold cavity, cutting of the organic fibers contained in the molten resin is prevented, and the molded body is taken out after being taken out. It is easy to cut and remove the gate part from the product part.

  The installation location and number of the gate portions 6 are appropriately determined depending on the shape and size of the molded body to be manufactured. In this example, the mold is disposed so as to be movable in the X-axis direction, but the mold may be disposed so as to be movable in the Y-axis direction.

[Method for producing molded article]
A method for producing an organic fiber-containing thermoplastic resin molding using such a mold will be described.
The method of the present invention includes (1) a melting step of melting a thermoplastic resin composition containing a thermoplastic resin and organic fibers, and (2) a product part cavity formed between a pair of molds, and the product A filling step of supplying and filling the molten thermoplastic resin composition into a mold cavity having a non-product part cavity around a part of or around the part cavity.

The melting process will be described. In the melting step, it is preferable to use a melting device provided with a screw. In the melting step, the screw in the melting device is preferably a deep groove and a small compression ratio in order to suppress breakage of the organic fibers.
In order to suppress the breakage of the organic fiber in the melting step, the screw rotation speed and the back pressure are lowered, or the temperature when the thermoplastic resin composition containing the thermoplastic resin and the organic fiber is melted is lowered. It is preferable. Here, “melting” is synonymous with “plasticization” and means that the thermoplastic resin composition is softened to a moldable state by heating and mechanical operation.
Specifically, when the temperature at which the thermoplastic resin composition is melted is equal to or higher than the melting point of the thermoplastic resin in the thermoplastic resin composition and the melting point of the organic fiber is Tm (° C.), (Tm-30 It is preferable that it is below ℃. As described above, the upper limit temperature when the thermoplastic resin composition is melted is set to a temperature of (Tm-30) ° C. or lower, so that the thermoplastic resin composition is melted in the melting apparatus. When supplying the thermoplastic resin composition into the mold cavity, cutting of the organic fibers can be prevented.

Next, the filling process will be described. In the filling step, the molten thermoplastic resin composition is configured between a pair of molds and has a product part cavity and a non-product part cavity around a part or all of the periphery of the product part cavity. It is a process of filling inside.
The mold temperature when the molten resin is supplied into the mold cavity is preferably 10 ° C to 100 ° C.
° C, more preferably 30 ° C to 80 ° C.

As a first aspect of the filling step, when the cavity clearance when supplying the molten resin is a clearance in which the volume of the molten resin to be supplied and the volume of the mold cavity are the same, the molten resin 2 is started (FIG. 2), and the product cavity and the non-product cavity are filled in the mold cavity with the cavity clearance fixed (FIG. 3).
This first aspect is effective when the fiber length of the organic fiber to be used is short or when the thickness of the molded body is thick. Specifically, the fiber length of the organic fiber is preferably 5 times or less of the thickness of the molded body, and more preferably 4 times or less. The thickness of the molded body is preferably 0.2 times or more, and more preferably 0.3 times or more the fiber length of the organic fiber to be used.

As a second aspect of the filling step, when the cavity clearance when the molten resin is supplied is a clearance in which the volume of the mold cavity is larger than the volume of the molten resin to be supplied, the molten resin (FIG. 4), and while supplying the molten resin or after the completion of the supply, the mold is clamped to fill the product cavity and the non-product cavity in the mold cavity (FIG. 3). When the cavity clearance at the time of supplying the molten resin is too large, the supply trace of the molten resin is conspicuous, and therefore it is usually preferably 30 mm or less.
When performing mold clamping after completion of the supply of the molten resin, it is preferable to perform mold clamping immediately after the completion of the supply. The degree of compression by mold clamping is determined by the volume of molten resin supplied into the cavity, the cavity clearance when the molten resin supply is completed, and the cavity clearance when mold clamping is completed. Is usually indicated by the movement distance of the movable mold 1 in the X-axis direction shown in FIG. 4, preferably a movement distance of 0.5 mm or more, and more preferably 1.0 mm or more. The mold clamping speed when clamping the mold is preferably 1 mm / second or more and 30 mm / second or less. Within the above range, the mold cavity can be filled before the supplied molten resin is cooled, so that the shearing force applied to the molten resin does not increase and fiber mass is generated. Hard to do.
In the second aspect, there is no limitation on the fiber length of the organic fiber to be used and the thickness of the molded body, but this is particularly effective when the fiber length of the organic fiber is long or the molded body is thin.

As a third aspect of the filling process, the cavity clearance is closed until the volume of the molten resin to be supplied and the volume of the mold cavity are approximately the same, and then the molten resin is put into the mold cavity while increasing the cavity clearance. Then, while supplying the molten resin or after the supply is completed, the mold is clamped to fill the product part and the non-product part in the cavity of the mold. The cavity clearance can be expanded by moving the movable side mold away from the fixed side mold mechanically using the mold clamping device of the injection molding machine, or by using the mold clamping. The method of enlarging the cavity clearance with the molten resin supply pressure is set so that the mold clamping force of the device is set slightly low so that the movable mold is moved away from the fixed mold by the molten resin supply pressure. It is done.
When the movable side mold is moved mechanically to increase the cavity clearance, the speed of the movable side mold is preferably 0.5 mm / second or more and 20 mm / second or less. Within this range, the molding cycle does not become long. In addition, since the molten resin supplied into the cavity expands with an increase in the cavity clearance, appearance defects such as uneven gloss are unlikely to occur on the surface of the obtained molded body. The speed at which the cavity clearance is enlarged may be reduced or increased in the middle.
The timing for stopping the expansion of the cavity clearance may be after supplying the entire amount of the molten resin to be supplied or during the supply of the molten resin to be supplied.
In this third aspect, there is no limitation on the fiber length of the organic fiber and the thickness of the molded body used in the same manner as in the second aspect, but particularly when the fiber length of the organic fiber is long or the thickness of the molded body is thin. It is effective in the case.

  After the molten resin filled in the product cavity and the non-product cavity in the cavity is thus cooled, the movable mold 1 is moved away from the fixed mold 2 to contain organic fibers. The thermoplastic resin molding (FIG. 6) is taken out. Then, the non-product part 11 is removed from the obtained molded body to obtain a product part molded body.

Next, another aspect of the present invention will be described. The molten thermoplastic resin composition obtained by the melting step described above may contain a foaming agent. The foaming agent may be a chemical foaming agent or a physical foaming agent, and a chemical foaming agent and a physical foaming agent may be used in combination. When a chemical foaming agent is used, a masterbatch containing a chemical foaming agent at a high concentration is prepared, and a thermoplastic resin composition containing a thermoplastic resin and an organic fiber and the masterbatch are mixed in advance, and a screw is provided. It is preferably supplied to a melting apparatus to be in a molten state. When a physical foaming agent is used, a thermoplastic resin composition containing a thermoplastic resin and organic fibers is supplied to the melting device from upstream of the melting device, and a physical foaming agent is supplied to the melting device from the middle of the melting device. Thus, it is preferable to uniformly mix the molten thermoplastic resin composition and the physical foaming agent.
After the molten thermoplastic resin composition containing the foaming agent thus obtained is filled into the product part cavity and the non-product part cavity in the mold cavity, the mold is opened by a predetermined amount and the thermoplastic resin composition Make things foam.
FIG. 5 is a schematic cross-sectional view showing a state in which the movable mold 1 is opened by a predetermined amount in the direction opposite to the fixed mold 2 to enlarge the volume of the mold cavity 3 and the mold is opened by a predetermined amount. . The timing for opening the movable mold 1 is preferably set to a time when the unsolidified portion of the molten thermoplastic resin composition containing the foaming agent reaches a temperature suitable for forming cells of the foamed layer. When this temperature is too high, coarse cells are likely to be formed due to the foaming pressure of the foaming agent dissolved in the thermoplastic resin, and the physical properties may be deteriorated. On the other hand, if this temperature is too low, the melt viscosity of the thermoplastic resin is lowered and the desired expansion ratio cannot be obtained. By setting the temperature of the unsolidified part to an appropriate temperature, it is possible to obtain a desired foaming ratio while preventing deterioration of physical properties due to the coarse cell. The temperature of the unsolidified portion is also referred to as a time from when the fiber-containing thermoplastic resin is filled in the mold cavity until the volume of the mold cavity is increased after the mold clamping is completed (hereinafter also referred to as “delay time”). ) Can be adjusted by controlling.

  Specifically, when a chemical foaming agent is used as the foaming agent, the delay time is preferably 0.1 seconds to 5 seconds, but is appropriately adjusted depending on the type of thermoplastic resin used and the cylinder temperature setting of the injection machine. The When a physical foaming agent is used as the foaming agent, the delay time is adjusted so that the maximum temperature of the unsolidified part is not less than (crystallization temperature −15 ° C.) and not more than (crystallization temperature + 15 ° C.) of the thermoplastic resin used. It is preferable to do.

  The amount of opening the movable side mold 1 may be an amount that provides a desired expansion ratio, but is preferably 0.5 to 5 times the clearance of the mold cavity when the mold is clamped. More preferably, it is double. By making the amount of opening the movable mold 1 more than 0.5 times the clearance of the mold cavity when the mold is clamped, a large weight reduction effect can be expected. Moreover, by making the opening amount of the movable side mold 1 not more than 5 times the clearance of the mold cavity when the mold is clamped, the foam cell is prevented from becoming coarse and the strength of the resulting foam molded article is good. It can be.

  After enlarging the volume of the mold cavity 3, the organic fiber-containing thermoplastic resin molding that is a foam is then cooled. During this cooling, the mold cavity clearance may be narrowed by a predetermined amount, and cooling may be performed while applying a compressive force to the molded body that is the foam. After the cooling is completed in this way, the movable mold 1 is moved away from the fixed mold 2 and the organic fiber-containing thermoplastic resin molded body (FIG. 7) is taken out. Then, the non-product part 11 is removed from the obtained molded body to obtain a product part molded body.

<Thermoplastic resin>
Examples of the thermoplastic resin used in the present invention include polypropylene, polyethylene, acrylic, acrylonitrile-styrene-butadiene block copolymers, polyamides such as polystyrene and nylon, polyvinyl chloride, polycarbonate, styrene-butadiene block copolymers, etc. And thermoplastic elastomers such as EPM and EPDM, mixtures thereof, polymer alloys using these, and the like, and polypropylene is particularly preferable.

<Organic fiber>
Examples of the organic fiber used in the present invention include polyethylene fiber, polypropylene fiber, aramid fiber, polyester fiber, vinylon fiber, cotton, hemp, silk, bamboo and the like. You may use the fiber which provided the metal layer on the surface of these fibers, and provided electroconductivity. The method for providing the metal layer on the surface of the fiber may be appropriately selected according to the fiber to be used, and examples thereof include methods such as vapor deposition, plating, sputtering, and ion plating. The metal constituting the metal layer is preferably copper.
These organic fibers may be used alone or in combination of two or more. Among these, polyester fibers and vinylon fibers are preferable, and organic fibers made of polyalkylene terephthalate and / or polyalkylene naphthalene dicarboxylate are more preferable.

<Organic fiber-containing thermoplastic resin>
As a method for obtaining the thermoplastic resin composition containing the thermoplastic resin and the organic fiber described above, the thermoplastic resin and the organic fiber are mixed in advance, the mixture is melt-kneaded, and pelletized, or the organic fiber Although a method of pelletizing by a pultrusion method in which a fiber bundle is impregnated with a thermoplastic resin is mentioned, it is preferable to obtain a thermoplastic resin composition pellet by a pultrusion method. Moreover, you may blend the thermoplastic resin composition pellet obtained by the pultrusion method, and the thermoplastic resin composition pellet obtained by the melt-kneading method.

  The content of the organic fiber in the thermoplastic resin composition is preferably 5 to 70% by mass and more preferably 15 to 60% by mass from the viewpoint of mechanical strength and appearance of the molded body (however, The total of the thermoplastic resin and organic fiber contained in the thermoplastic resin composition is 100% by mass).

  Thermoplastic resin compositions include, for example, antioxidants, heat stabilizers, neutralizers, UV absorbers and other stabilizers, bubble inhibitors, flame retardants, flame retardant aids, dispersants, antistatic agents, lubricants. Anti-blocking agents such as silica, colorants such as dyes and pigments, plasticizers, nucleating agents, crystallization accelerators and the like may be added as optional components.

  Thermoplastic resin compositions include glass fibers, alumina fibers, carbon fibers, glass flakes, mica, glass powder, glass beads, talc, clay, alumina, carbon black, wall snite, etc. Granular and whisker-like inorganic compounds may be blended.

<Foaming agent>
When the molten thermoplastic resin composition obtained by the melting step contains a foaming agent, a chemical foaming agent or a physical foaming agent can be used as the foaming agent. In the case of a chemical foaming agent, the addition amount of the foaming agent is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the thermoplastic resin. In the case of a physical foaming agent, the addition amount of the foaming agent is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the thermoplastic resin.

  Examples of the chemical foaming agent include inorganic chemical foaming agents and organic chemical foaming agents. Examples of the inorganic chemical foaming agent include hydrogen carbonates such as sodium hydrogen carbonate, ammonium carbonate, and the like. Examples of the organic chemical foaming agent include polycarboxylic acid, azo compound, sulfone hydrazide compound, nitroso compound, p-toluenesulfonyl semicarbazide, isocyanate compound and the like. Examples of the polycarboxylic acid include citric acid, oxalic acid, fumaric acid, phthalic acid and the like.

  Examples of the physical foaming agent include inert gases such as nitrogen, carbon dioxide, argon, neon, and helium, and volatile organic compounds other than chlorofluorocarbons such as butane and pentane. Of these, carbon dioxide, nitrogen, or a mixture thereof is preferably used. These may be used alone or in combination of two or more. The physical foaming agent and the chemical foaming agent may be used in combination. In this case, the amount of the chemical foaming agent added is, as described above, 0.1 to 10 parts by mass with respect to 100 parts by mass of the thermoplastic resin. Preferably, it is 0.2-8 mass parts.

  When using a physical foaming agent, it is preferable that it is a supercritical state, and the method of inject | pouring a physical foaming agent in the nozzle or cylinder of an injection molding apparatus in a melting process is mentioned. Since it is easy to uniformly mix the molten resin and the physical foaming agent, a method of injecting the physical foaming agent into the cylinder in which the thermoplastic resin composition containing the thermoplastic resin and the organic fiber is melted is preferable.

[Use of molded body]
Applications of the molded body obtained by the method of the present invention include automobile interior parts and exterior parts, parts for engine rooms, parts for trunk rooms, motorcycle parts, furniture and electrical parts, and building materials. The molded product obtained by the method of the present invention is particularly useful as an automotive part.

1: Movable mold 2: Fixed mold 3: Mold cavity 4: Product part cavity 5: Non-product part cavity 6: Gate part 7: Molten resin supply passage 8: Valve pin 9: Molten resin 10: Molded body Product part 11: Non-product part of the molded product

Claims (4)

(1) a melting step of melting a thermoplastic resin composition containing a thermoplastic resin and organic fibers;
(2) The thermoplastic resin composition melted in a mold cavity which is configured between a pair of molds and has a product part cavity and a non-product part cavity around a part or all of the periphery of the product part cavity. The manufacturing method of the organic fiber containing thermoplastic resin molding including the filling process which supplies and fills. In the filling step, the molten thermoplastic resin composition is supplied into the mold cavity, and then the mold is clamped to form a product part cavity and a non-product part cavity in the mold cavity. The manufacturing method of the organic fiber containing thermoplastic resin molding of Claim 1 with which it fills. The method for producing an organic fiber-containing thermoplastic resin molded article according to claim 1 or 2, wherein the molten thermoplastic resin composition contains a foaming agent. The manufacturing method of the organic fiber containing thermoplastic resin molding of Claim 3 including the foaming process which opens the said metal mold | die in the direction opposite to a mold clamping direction after the said filling process, and foams the said thermoplastic resin composition.

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