JPH10193378A - Injection molding method and injection molded product with hollow part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of an irregular thickness of a hollow part by filling pressurized fluid into molten resin during molding of a tubular part having specific weight ratio and specific sectional area with two types of thermoplastic resin composition pellets different from fiber filler content of one or mixture of glass fiber and carbon fiber of specific diameters and lengths. SOLUTION: First thermoplastic resin composition pellet A containing 10 to 70vol.% of fiber filler of one or mixture of glass fiber having mean fiber size of 3 to 23μm, and weight-average length of 10 times to length of pellet of the mean fiber size and carbon fiber having mean fiber size of 5 to 13μm, weight-average length of 10 times to length of pellet of the mean fiber size and second thermoplastic resin composition pellet B containing or not containing 5vol.% or less of fiber filler are kneaded and molten at a ratio of 1/4<=(A/B)<=20 by weight, pressurized fluid is filled in the molten resin during injection molding in a cavity 13 for molding a tubular part having a sectional area of 3 to 15cm<2> to form a hollow part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection-molded article made of a thermoplastic resin and capable of suppressing the occurrence of uneven thickness in a hollow portion, and a method of molding the same.

[0002]

2. Description of the Related Art As a method of forming a hollow portion having a high hollow ratio into a molded product, a blow molding method, a molding method using a core,
A rotational molding method, a gas assist molding method and the like are known. The blow molding method is an effective method for molding a molded article having a simple shape such as a tank or a bottle, but is generally not suitable for molding a molded article having a complicated shape. In the case of a molding method using a core, a core made of metal or resin is prepared in advance. Then, the core is disposed in the cavity of the mold, the molten resin is injected into the space formed by the mold surface of the cavity and the core, and after the resin is cooled and solidified, the molded product is taken out from the mold. . Thereafter, the core inside the molded product is melted, and a hollow portion which is a trace of the core is formed in the molded product. Since the molding method using the core requires such complicated steps, the cost of producing a molded product is high. In the rotational molding method, it is difficult to mold a molded article having a complicated shape, and moreover, since pressure is not applied to the resin during molding, the strength of the end portion of the molded article is often insufficient.

The gas assist molding method is a method of injecting a pressurized fluid into the molten resin in the cavity while the molten resin is being injected into a cavity provided in a mold or after the injection of the molten resin is completed. It is. According to such a gas assist molding method, during cooling and solidification of the resin in the cavity,
Since the resin is pressed against the mold surface of the cavity by the pressurized fluid, it is possible to effectively prevent occurrence of warpage or sink in the obtained injection molded product. One type of gas assist molding method is to inject a pressurized fluid into the molten resin while expanding the volume of the cavity during or after the injection of the molten resin into the cavity. The gas assist molding method is a highly efficient method with a short molding step.

[0004]

The gas-assist molding method is currently used mainly for preventing the occurrence of warpage and sink in an injection-molded article. However, when an injection-molded article having a large cross-sectional area and having a tubular portion having a long hollow portion is molded from a fiber-reinforced resin, the thickness of the tubular portion may become unstable. The non-uniform thickness of the tubular portion having the hollow portion (hereinafter, sometimes referred to as a hollow tubular portion) is referred to as uneven thickness in the present specification. The portion is called an uneven thickness portion. We have:
It recognizes the occurrence of two types of uneven thickness. As one aspect of such an uneven thickness portion, the thickness of the injection molded product varies in a certain range in the longitudinal direction of the injection molded product around a thin portion of the injection molded product. In this case, there can be cited an embodiment in which there is no nub-like protrusion that abnormally protrudes from the surface. As another embodiment of the uneven thickness portion, there can be cited an embodiment in which a large bulge-like projection is formed on the surface of the hollow portion so as to close the hollow portion (see FIG. 9).

When the uneven thickness portion is the latter mode, the amount of resin required for molding an injection-molded article greatly varies. Then, when the resin is biased to the projection-like projections, molding defects such as outgassing easily occur. Here, outgassing means
It refers to a phenomenon in which pressurized fluid injected into the molten resin in the cavity breaks through the molten resin and directly contacts the mold surface of the cavity. When such outgassing occurs, the pressurized fluid leaks out of the gap in the mold, or the resin is separated from the mold surface of the cavity. In particular, when a hollow portion having a high hollow ratio is formed, if such protrusions occur irregularly, the amount of resin injected into the cavity is insufficient for molding an injection molded product. Gas escape occurs during the flow of the molten resin in the inside, and a situation occurs in which an injection molded product cannot be molded. Even when the knob-shaped uneven thickness portion is small, the hollow portion may not be formed up to the end of the injection molded product due to the uneven thickness portion generated on the surface of the hollow portion. Further, when an uneven thickness portion occurs in an injection molded product requiring strength, the thickness of the hollow tubular portion becomes unstable, so that the breaking strength fluctuates, and the strength of the injection molded product cannot be guaranteed.

The case where two types of fluids having different viscosities and densities flow incompatible with each other will be considered below. Specifically, the molten resin and the pressurized fluid in the present invention correspond to a high-viscosity fluid and a low-viscosity fluid, respectively. When pressure is applied to a low-viscosity fluid by applying pressure to the low-viscosity fluid (that is, when an attempt is made to form a hollow portion in the molten resin), pressure is applied between the low-viscosity fluid and the high-viscosity fluid. If there is no difference, the flow of the high viscosity fluid does not occur. By the way, if a small flow path of a low-viscosity fluid is formed in a high-viscosity fluid, the pressure will be almost the same in a low-viscosity fluid that is easy to propagate, and the pressure for pushing the high-viscosity fluid will no longer exist. Fluid retention occurs. That is, an uneven thickness portion is generated on the surface of the hollow portion. The formation of a flow path for a low-viscosity fluid in such a high-viscosity fluid is referred to herein as a short path. Generally, in the high-viscosity fluid, the staying portion other than the shortest distance between the inlet and the outlet remains as an uneven thickness portion, and the position where the low-viscosity fluid flows serves as a gas passage.

[0007] Injection molded articles molded by a gas-assist molding method using a thermoplastic resin containing a fiber filler, in particular, a crystalline thermoplastic resin, particularly, a polyphenylene sulfide (PPS) or a polyamide-based thermoplastic resin, are resistant to injection molding. Excellent chemical properties and high strength. However, according to the experience of the present inventors, when this kind of fiber-reinforced thermoplastic resin is used, a large nub-shaped protrusion (uneven thickness portion) is formed on the surface of the hollow portion so as to close the hollow portion. Many phenomena have been observed. In particular, when a resin that rapidly solidifies from a certain temperature, such as a crystalline thermoplastic resin, is used, such a phenomenon is likely to occur. Therefore, it is extremely difficult to mold an injection-molded article having a hollow portion based on this kind of fiber-reinforced thermoplastic resin with the current technology. However, if the problem of the occurrence of the uneven thickness portion can be solved, for example, it becomes possible to commercialize an injection molded product having a hollow portion made of a fiber-reinforced thermoplastic resin having excellent chemical resistance and high strength.

A thin hollow curved tube for an oil strainer and a method for producing the same are known from JP-A-6-71778. Such a thin hollow curved tube is made of a polyamide resin containing 30% by weight or less of glass fiber, having a heat deformation temperature of 423K or more and a bending strength of 7.8 × 10 ⁶ kPa or more. It is said that by manufacturing a thin hollow curved tube using such a material, the inner surface of the hollow curved tube having high strength can be smoothed.

A resin containing reinforcing fibers and a resin containing no reinforcing fibers or a resin having a lower content of reinforcing fibers are dry blended, and the resin after dry blending is melted and fluidized. A method of manufacturing a resin hollow tube by injecting the fluid thus obtained is known from JP-A-8-34048. It is said that such a method can also smooth the inner surface of the hollow tube having high strength.

[0010] To optimize the diameter and the amount of glass fiber for smoothing the inner surface of the hollow portion of an injection-molded article molded by the gas assist molding method is disclosed in JP-A-8-4124.
No. 6 is known.

However, these patent publications disclose and suggest the occurrence of uneven thickness on the surface of the hollow portion or the technical means for suppressing the occurrence of such uneven thickness. Absent.

In the case of long fiber reinforced thermoplastic resin pellets,
For example, a glass fiber content of 60 to 80% by weight can be produced. Therefore, pellets are blended at the time of molding an injection-molded article to adjust the proportion of reinforcing fibers contained in the injection-molded article. In addition, it is common practice to use a masterbatch of a dye / pigment by blending it with pellets before putting it into a molding machine. However, it is not known to suppress the occurrence of uneven thickness portions by combining these techniques with the gas assist molding method.

In order to prevent the uneven thickness portion from being generated on the surface of the hollow portion, the content of the fiber filler is reduced as much as possible, a short fiber filler is used, a fine fiber filler having a small reinforcing effect, a fine plate-like filler, It is necessary to add spherical fillers or to use thermoplastics which do not contain fillers. However, with such a measure, it is difficult to produce an injection-molded article requiring high strength.

Accordingly, an object of the present invention is to provide an injection molding method and a hollow portion which can reliably suppress the occurrence of uneven thickness portions in a hollow portion and can form an injection molded product having high strength. An object of the present invention is to provide an injection-molded article having:

[0015]

According to a first aspect of the present invention, there is provided an injection molding method for an injection molding machine having a cross-sectional area of 3 cm ² or more and 15 cm ² or less. (A) using a mold provided with a cavity having a cavity portion for forming an injection molded article having
Glass fiber having an average fiber diameter of 3 to 23 μm and a weight average length of 10 times or more and a pellet length or less of the average fiber diameter, and an average fiber diameter of 5 to 13 μm and a weight average length of 10 times the average fiber diameter A first thermoplastic resin composition pellet containing 10% by volume or more and 70% by volume or less of a fiber filler made of any one of carbon fibers having a pellet length or less, or a mixture thereof, and (B) the fiber filler 5% by volume or less, or the second thermoplastic resin composition pellets not containing the fiber filler, in a weight ratio of ≦≦ (first thermoplastic resin composition pellets /
The second thermoplastic resin composition pellets) are blended at a ratio of ≦ 20, and after kneading and plasticizing to obtain a molten resin, the molten resin is injected into the cavity of the mold, and during injection of the molten resin,
Alternatively, after the injection is completed, a pressurized fluid is injected into the molten resin in the cavity, whereby a hollow portion is formed at least inside the resin in the cavity.

The first object of the present invention to achieve the above object.
The injection molded product according to the aspect is provided in an injection molding machine, and a mold provided with a cavity provided with a cavity portion for forming an injection molded product having a tubular portion having a cross-sectional area of 3 cm ² or more and 15 cm ² or less. (A) a glass fiber having an average fiber diameter of 3 to 23 μm, a weight average length of 10 times or more of the average fiber diameter and a pellet length or less, and an average fiber diameter of 5
To 13 μm, any one of carbon fibers having a weight average length of 10 times or more and a pellet length or less of the average fiber diameter,
Or, a first thermoplastic resin composition pellet containing 10% by volume or more and 70% by volume or less of a fiber filler composed of a mixture thereof, and (B) containing 5% by volume or less of the fiber filler or not containing the fiber filler The second thermoplastic resin composition pellets are blended in a weight ratio of 1/4 ≦ (first thermoplastic resin composition pellet / second thermoplastic resin composition pellet) ≦ 20, and the mixture is kneaded and plasticized. After the molten resin is formed into the cavity, the molten resin is injected into the cavity of the mold, and during or after the injection of the molten resin, a pressurized fluid is injected into the molten resin in the cavity. An injection-molded product having a hollow portion formed at least in the tubular portion.

In the injection molding method or the injection molded article according to the first aspect of the present invention, the weight average length of the fiber filler contained in the first and second thermoplastic resin composition pellets is at least 150 μm. The following is preferred.

In the injection molding method according to the first aspect of the present invention, the length of the cavity can be 10 cm or more. Alternatively, in the injection molded article according to the first aspect of the present invention, The length of the tubular portion can be 10 cm or more. In the cavity portion having a short length, the flow resistance of the molten resin is low, so that the uneven thickness portion is hardly generated. In a cavity portion having a length of 10 cm or more, the flow resistance of the molten resin may be large, and the uneven thickness portion is easily generated. Therefore, the length of the cavity is 10
cm or more, the injection molding method according to the first aspect of the present invention is extremely effective.

The second object of the present invention for achieving the above object is as follows.
In the injection molding method according to the embodiment, (A) a glass fiber having an average fiber diameter of 3 to 23 μm and a weight average length of 10 to 10 times the average fiber diameter and a pellet length, and an average fiber diameter of 5 to 13 μm One of carbon fibers having a weight average length of 10 times or more of the average fiber diameter and a pellet length or less, or a fiber filler made of a mixture thereof,
A first thermoplastic resin composition pellet containing 0% by volume or more and 70% by volume or less, and (B) a second thermoplastic resin composition pellet containing 5% by volume or less of the fiber filler or containing no fiber filler.
The thermoplastic resin composition pellets are blended in a weight ratio of 4 <(first thermoplastic resin composition pellets / second thermoplastic resin composition pellets) ≦ 20, kneaded and plasticized to obtain a molten resin. After the injection of the molten resin into the cavity of the mold provided in the injection molding machine, during the injection of the molten resin, or after the completion of injection, inject a pressurized fluid into the molten resin in the cavity, Thus, a hollow portion is formed in the resin.

The second object of the present invention for achieving the above object is as follows.
The injection-molded article according to the embodiment, (A) a glass fiber having an average fiber diameter of 3 to 23 μm, a weight average length of 10 to 10 times the average fiber diameter and a pellet length, and an average fiber diameter of 5
To 13 μm, any one of carbon fibers having a weight average length of 10 times or more and a pellet length or less of the average fiber diameter,
Or, a first thermoplastic resin composition pellet containing 10% by volume or more and 70% by volume or less of a fiber filler composed of a mixture thereof, and (B) containing 5% by volume or less of the fiber filler or not containing the fiber filler The second thermoplastic resin composition pellets are blended at a weight ratio of 4 <(first thermoplastic resin composition pellets / second thermoplastic resin composition pellets) ≦ 20 and kneaded and plasticized. After the molten resin is formed, the molten resin is injected into a cavity of a mold provided in an injection molding machine, and during or after the injection of the molten resin, a pressurized fluid is injected into the molten resin in the cavity. This is an injection-molded article having a hollow portion, which is formed by the above process.

In the injection molding method or the injection molded article according to the second aspect of the present invention, the weight average length of the fiber filler contained in the first and second thermoplastic resin composition pellets is 150 μm or more. The following is preferred.

The fiber filler used in the present invention is made of glass fiber or carbon fiber, or a mixture thereof, and is sold, for example, as a long fiber reinforced type.
A fiber filler whose residual fiber length in the pellet is equal to the pellet length can be used. In this case, the pellet length is 3 mm or more, and the maximum length is a length that can be supplied from the hopper of the injection molding machine. Although it depends on the size of the injection molding machine, the maximum length may be about 30 mm. Alternatively, chopped strands which are generally used for reinforcing plastics and have a mean fiber length of about 1 mm to about 10 mm and which have been subjected to convergence treatment with a surface treatment agent such as a sizing agent can also be used. Further, when a long fiber reinforced type is used, the same roving can be used.
The average fiber diameter is 3 to 23 μm, more preferably 6 to 13 μm for glass fiber, and 5 to 13 μm for carbon fiber. Here, the average fiber diameter is
It can be measured by observing the fiber filler with a stereoscopic microscope.

The lower limit of the proportion of the fiber filler contained in the first thermoplastic resin composition pellets is 10% by volume.
When the proportion of the fiber filler is less than 10% by volume, the reinforcing effect of the fiber filler is reduced, and the strength of the finally obtained injection molded article may be reduced. The upper limit is defined by the maximum addition rate at which the first thermoplastic resin composition pellet can be produced, and is 70% by volume in the current technology. First
Although it depends on the thermoplastic resin constituting the thermoplastic resin composition pellets and the pellet production apparatus, for example, M
In the case of X nylon and glass fiber, it is possible to produce up to a content of 65% by weight (about 47% by volume). In the case of the pultrusion method for producing long fiber reinforced pellets, the content can be set to 65% by weight or more, and a type of 80% by weight (about 65% by volume) can be found.

Except for the long fiber reinforced type, the fiber length in the pellet depends on the method for producing the pellet. If the fiber filler is broken and becomes too short during the production of the pellet, the reinforcing effect of the fiber filler is reduced, and the addition of the fiber filler becomes meaningless. Therefore, it is desirable to adopt a pellet production method in which the thermoplastic resin and the fiber filler are not kneaded too strongly during the production of the pellet and the fiber length is maintained. That is, it is preferable to produce pellets by a side-feed method or the like in which the kneading is not so strengthened and the dispersion is favorable, but pellets produced by a single screw extruder can also be used.

In the injection molding method or the injection molded article of the present invention, when the weight average length is less than 10 times the average fiber diameter, the reinforcing effect of the fiber filler is reduced. Therefore,
The ratio of weight average length / average fiber diameter (aspect ratio) after pellet production is required to be 10 or more. For example, when chopped strand glass fibers having an average fiber diameter of 13 μm are used as the fiber filler, the weight average length after pellet production may be reduced to about 150 μm. The larger the ratio of weight average length / average fiber diameter, the better. In the case of the long fiber reinforced type, the ratio of weight average length / average fiber diameter expressed by pellet length / average fiber diameter is as ^{high as} 103 orders. In a compound of a composite material, a weight average length is generally used as a fiber length in order to keep measurement errors low.

The second thermoplastic resin composition pellets include:
Injection molding, wherein the same type of fiber filler as that contained in the first thermoplastic resin composition pellets described above is not contained, or, if contained, is 5% by volume or less. It is required so as not to generate uneven thickness on the surface of the hollow part of the product. In the second thermoplastic resin composition pellets, an inorganic filler that does not cause uneven thickness on the surface of the hollow portion, for example, a fine fibrous filler,
The microplate-like filler or the powder filler can be contained in an amount of 40% by volume or less, preferably 25% by volume or less. Note that the addition of such an inorganic filler is not essential. Although such an inorganic filler has little contribution to improving the strength of the injection molded product, it can contribute to the improvement of the thermal deformation temperature, the elastic modulus, and the like of the injection molded product. Therefore, such an inorganic filler may be added in consideration of the performance and use required for the injection molded product.
In addition, even if these inorganic fillers are less likely to generate uneven thickness portions on the surface of the hollow portion, if they exceed 40% by volume,
In some cases, an uneven thickness portion is formed on the surface of the hollow portion of the injection molded product.

As the inorganic filler that can be added to the second thermoplastic resin composition pellet, a known inorganic filler can be used. The form of the inorganic filler may be any form such as fibrous, plate-like, needle-like, spherical, and powdery. In the case of the fibrous or needle-like inorganic filler, the average fiber diameter is 2 μm.
m or a material having a weight average length of 150 μm or less is desirably used. When the average fiber diameter exceeds 2 μm and the weight average length exceeds 150 μm, if the amount of the inorganic filler added increases, uneven thickness may occur on the surface of the hollow portion of the injection molded product. In the case of a plate-like inorganic filler, the average diameter is preferably 50 μm or less.
If the average diameter exceeds 50 μm, it may cause uneven thickness on the surface of the hollow part of the injection molded product. In the case of a spherical or powdered inorganic filler, the average diameter is preferably 100 μm or less. Specific examples of the inorganic filler include glass wool, milled glass fiber, milled carbon fiber, talc, fine mica, fine glass flake, wollastonite, potassium titanate, magnesium sulfate, sepiolite, zonolite, aluminum borate, glass Examples include beads, balloons, calcium carbonate, silica, kaolin, clay, titanium oxide, barium sulfate, zinc oxide, and magnesium hydroxide. These inorganic fillers can be used alone or as a mixture of two or more. In addition, these inorganic fillers, in some cases,
It may be added to the first thermoplastic resin composition pellet.

The length of the fiber filler may be measured by immersing the thermoplastic resin composition pellet or the injection molded product in a liquid in which the resin component is dissolved to dissolve the resin component, or, in the case of glass fiber, to 600 ° C. or more. By burning the resin component at a high temperature, the remaining fiber filler can be measured by observing with a microscope or the like. Usually, a person measures the length by photographing the fiber filler, or obtains the length of the fiber filler using a dedicated fiber length measuring device. Since the number average length has too great an effect of the finely broken fibers, it is necessary to adopt the weight average length. In the measurement of the weight average length, the measurement is performed by excluding the fragments of the fiber filler that are too small and crushed. If the length is smaller than twice the original diameter of the fiber filler, the measurement becomes difficult. Therefore, for example, a fiber filler having a length equal to or more than twice the diameter is measured.

As the resin components constituting the first and second thermoplastic resin composition pellets used in the present invention, polyethylene resin, polystyrene resin, polypropylene resin,
Polycarbonate resin, polyacetal resin, polyamide resin, polyester resin (for example, polyethylene terephthalate resin or polybutylene terephthalate resin), modified polyphenylene oxide resin (for example, modified polyphenylene ether resin), polyphenylene sulfide resin, acrylonitrile-butadiene-styrene Examples thereof include, but are not limited to, a polymer resin, an acrylonitrile-styrene copolymer resin, a polymethyl methacrylate resin, a mixture thereof, and a polymer alloy.

Further, as resin components constituting the first and second thermoplastic resin composition pellets used in the present invention, polypropylene resin, polyacetal resin, polyester resin (for example, polyethylene terephthalate resin or polybutylene terephthalate resin) ), A crystalline thermoplastic resin such as a polyamide resin or a polyphenylene sulfide resin, or a mixture or a polymer alloy thereof. Here, whether or not the thermoplastic resin is a crystalline thermoplastic resin is generally determined by whether or not a clear melting point (a temperature at which a sharp endotherm is detected) is confirmed by a differential scanning calorimetry (DSC) method. You. The resin whose clear melting point is confirmed is a crystalline thermoplastic resin.

As polyamide resins suitable for use in the present invention, nylon 6, nylon 66, nylon 69, nylon 610, nylon 612, nylon 11, nylon 12, meta-xylylenediamine alone or 40% by weight of para-xylylenediamine A mixed diamine compound with the following,
Polyamide resin obtained from α, ω-linear aliphatic dibasic acid or aromatic dibasic acid, tetramethylene diamine, linear aliphatic diamine such as hexamethylene diamine octamethylene diamine and aromatic dibasic acid Examples of the obtained polyamide resin and a mixture thereof are not limited to these. A polyamide resin obtained from meta-xylylenediamine and α, ω-linear aliphatic dibasic acid is called MX nylon. It is more preferable to use MX nylon, nylon 6, nylon 66, or a mixture thereof as the polyamide resin.

In the injection molding method or the injection molded product according to the first or second aspect of the present invention, the first and / or
Alternatively, based on the resin component excluding the filler constituting the second thermoplastic resin composition pellet, at least 30% by weight of the resin component is a crystalline thermoplastic resin, so that the injection molded article has high strength and high chemical resistance. It is desirable in giving properties and the like. Further, it is more preferable that the crystalline thermoplastic resin is a polyamide resin, and in this case, the polyamide resin is MX
It is even more preferable to use a nylon resin.

In the injection molding method or the injection molded article according to the first aspect of the present invention, the mixing ratio of the first thermoplastic resin composition pellets and the second thermoplastic resin composition pellets is expressed by weight ratio, 1/4 ≦ (first thermoplastic resin composition pellet / second thermoplastic resin composition pellet) ≦ 2
0. When the blending ratio of the first thermoplastic resin composition pellets exceeds this range (that is, the blending weight ratio is 2).
If it exceeds 0), as in the case where the first thermoplastic resin composition pellet is used alone, an uneven thickness portion is generated on the surface of the hollow portion. On the other hand, when the blending ratio of the second thermoplastic resin composition pellets is larger than this range (that is, when the blending weight ratio is less than 1/4), the amount of the fiber filler contained in the injection molded article decreases. Excessively, the reinforcing effect of the fiber filler is reduced, and the strength of the injection molded product may be reduced.

In the injection molding method or the injection molded article according to the second aspect of the present invention, the blending ratio of the first thermoplastic resin composition pellets and the second thermoplastic resin composition pellets is expressed by weight ratio: 1/4 ≦ (first thermoplastic resin composition pellet / second thermoplastic resin composition pellet) ≦ 2
0, preferably 4 <(first thermoplastic resin composition pellet / second thermoplastic resin composition pellet) ≦ 20. When the blending ratio of the first thermoplastic resin composition pellets exceeds this range (that is, when the blending weight ratio exceeds 20), the same as when the first thermoplastic resin composition pellets are used alone. Then, an uneven thickness portion is generated on the surface of the hollow portion. On the other hand, when the blending ratio of the second thermoplastic resin composition pellets exceeds this range,
Furthermore, depending on the shape of the injection molded article, if (first thermoplastic resin composition pellet / second thermoplastic resin composition pellet) ≦ 4, the amount of fiber filler contained in the injection molded article Is too small, the reinforcing effect of the fiber filler is reduced, and the strength of the injection molded article may be reduced.

The first thermoplastic resin composition pellets and the second
The step of kneading and plasticizing the thermoplastic resin composition pellets into a molten resin can be performed, for example, in a heating cylinder provided in an injection molding machine. The total content of the fiber filler in the injection molded article is 2 to 67% by volume, preferably 5 to 40% by volume (in the case of glass fiber, 10 to 60% by volume).
%, More preferably 16 to 35% by volume (30 to 55% by weight in the case of glass fiber).

The resin component of the first thermoplastic resin composition pellets and the resin component of the second thermoplastic resin composition pellets are not necessarily required to be the same, and the resin exemplified above or a mixture thereof is used as a main component. If so, any combination may be used. For example, the main resin component of the first thermoplastic resin composition pellet is MX nylon, the main resin component of the second thermoplastic resin composition pellet is nylon 6, or the first thermoplastic resin The main resin component of the composition pellets is a polyamide resin, and the main resin component of the second thermoplastic resin composition pellets is a modified polyethylene resin or polypropylene resin compatible with the polyamide resin. Can be.

The first thermoplastic resin composition pellets and / or
Or, to the second thermoplastic resin composition pellets, various commonly used additives such as a flame retardant, a stabilizer, a pigment, a dye, a mold release agent, a lubricant, a nucleating agent, and a weather resistance improver are appropriately added. can do.

[0038] The first thermoplastic resin composition pellets
It can also be composed of a mixture (mixture) of different types of pellets. Also, the second thermoplastic resin composition pellets,
It can also be composed of a mixture (blended product) of two types of pellets. That is, existing thermoplastic resin composition pellets, if appropriate, the desired thermoplastic resin composition pellets can be obtained by combining a plurality, or, for example, additives, pigments, when the release agent is added in the form of pellets In such cases, by appropriately mixing two or more types of materials,
An appropriate blend of the first and / or second thermoplastic resin composition pellets can be obtained. In some cases, a powdery additive, pigment, release agent, or a masterbatch thereof may be mixed with the pellet.

The method for producing the first thermoplastic resin composition pellets and the second thermoplastic resin composition pellets used in the present invention may be any known method. For example, pellets can be produced by a method in which a resin component is melted and kneaded with a fiber filler using an ordinary vented extruder or a device similar thereto. The long fiber reinforced pellets can be produced by a known pellet production method, for example, a pultrusion method.

The injection molding method carried out in the present invention is a method generally called a gas assist molding method, in which a pressurized fluid is injected into a molten resin at the time of injection molding to improve the appearance (such as sink marks and warpage). (Improvement).
Then, there is a method generally called a simple press molding method, but it is not particularly limited to this method.
The method of injecting the pressurized fluid after completely filling the cavity with the molten resin in advance is called the full shot method, and the method of injecting the pressurized fluid without completely filling the cavity with the molten resin is called the short shot method. Although called, the invention encompasses these two methods. The volume of the molten resin injected into the cavity may be a volume that can mold a desired injection molded product, and depends on the volume occupied by the hollow portion and the like.

In the present invention, a pressurized fluid is injected into the molten resin in the cavity during or after the injection of the molten resin into the cavity of the mold (including simultaneously with the completion of the injection). When the mold is composed of a fixed mold part and a movable mold part, the fixed mold part and the movable mold part are fixed so that the volume of the cavity remains unchanged from the start of the injection of the molten resin to the completion of the injection of the pressurized fluid. The holding of the mold part may be continued. Alternatively, the volume of the cavity may be increased by moving the movable mold part before, during, or after the injection of the molten resin into the cavity. Also in this case, the injection of the pressurized fluid may be started during or after the injection of the molten resin into the cavity. Further, a movable plug can be provided in the cavity, and the volume of the cavity can be increased by moving the plug.

In the injection molding method of the present invention, there is basically no particular restriction on the injection location of the pressurized fluid, and the pressurized fluid injection section may be arranged near the resin injection section, The injection section may be arranged apart from the resin injection section, or a pressurized fluid injection section may be arranged inside the resin injection section. Further, the number of pressurized fluid injection sections is not particularly limited. When a plurality of pressurized fluid injection portions are provided, resin partition walls can be generated inside the injection molded product, and hollow portions forming a plurality of fluid flow paths and the like are formed in the injection molded product. It becomes possible.
The pressurized fluid is desirably a gaseous or liquid at normal temperature and normal pressure and does not react or mix with the molten resin during molding. Specific examples include nitrogen gas, air, carbon dioxide gas, helium, water and the like, and an inert gas such as nitrogen and helium is preferable.

In the injection-molded article according to the first aspect of the present invention, the outer cross-sectional shape of the tubular portion can be an irregular shape. Here, the irregular shape refers to a shape that is not circular,
It refers to a square, a rectangle, a polygon, a trapezoid, a shape having corners, or a shape formed by an outline having an inconstant curvature. In addition, examples of the injection molded product include an automobile roof rail and an automobile kangaroo bumper. That is, the injection molding method according to the first aspect of the present invention can be applied to, for example, a roof rail of an automobile having a modified cross-sectional shape, a pipe-shaped kangaroo bumper attached to a so-called leisure vehicle (RV) vehicle as a bumper, and the like.
This is extremely effective for hollowing out an injection molded article having a tubular portion. The roof rail for automobiles is formed by integrally molding a rail body and legs provided at both ends of the rail body, and the longitudinal direction of the rail body substantially coincides with the vertical direction of the mold. So that the cavity is provided in the mold,
A resin injection part is provided in the mold so that the molten thermoplastic resin is injected into the lower part of the cavity, and a pressurized fluid injection part is formed so that a pressurized fluid is injected into the thermoplastic resin from the lower part of the cavity. Preferably, it is arranged in a mold.

When the outer cross-sectional shape of the hollow tubular portion of the injection molded article is circular, and when the cross-sectional area is less than 3 cm ² , the formed hollow portion is narrow at first and it is easy to make the hollow tubular portion the same thickness. It is. However, when the cross-sectional area is 3 cm ² or more, the thickness of the hollow tubular portion tends to fluctuate due to the occurrence of the uneven thickness portion. In addition, when the external cross-sectional shape of the hollow tubular portion of the injection molded product is irregular, if the cross-sectional area is 3 cm ² or more, the flow path of the pressurized fluid in the molten resin is biased, and the uneven thickness portion is easily generated. In addition, it is difficult to ensure the uniformity of the thickness of the hollow tubular portion. In the injection molding method or the injection molded product according to the first aspect of the present invention, the used 2
By defining the fiber filler in the two types of thermoplastic resin composition pellets and defining the blending weight ratio of the two types of thermoplastic resin composition pellets, the cross-sectional area is 3c.
It is possible to reliably prevent the occurrence of the uneven thickness portion on the surface of the hollow portion formed in the hollow tubular portion of m ² or more. The cross-sectional area here is not the cross-sectional area of the hollow part formed in the injection molded product. On the other hand, when the cross-sectional area exceeds 15 cm ² ,
It becomes difficult for the pressurized fluid to uniformly push the molten resin toward the cavity surface of the mold, causing a short path, and easily causing uneven thickness portions. For example, even if the hollow tubular portion of the injection molded article has a circular outer cross-sectional shape, a short path is likely to occur due to an increase in the cross-sectional area, and an uneven thickness portion is generated.
ADVANTAGE OF THE INVENTION According to this invention, the limit of the cross-sectional area which the uneven thickness part produces in a hollow tubular part can be expanded.

In the injection molding method or the injection molded product according to the second aspect of the present invention, the fiber filler in the two types of thermoplastic resin composition pellets to be used is defined,
Moreover, by defining the blending weight ratio of the two types of thermoplastic resin composition pellets, it is possible to reliably prevent the occurrence of uneven thickness portions on the surface of the hollow portion.

[0046]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings based on embodiments (hereinafter abbreviated as embodiments) of the invention and examples.

FIG. 1 is a schematic sectional view of an example of an injection molding machine suitable for carrying out the present invention. A mold 10 for molding an injection molded product includes a fixed mold section 11 and a movable mold section 12. A cavity 13 is provided in the fixed mold part 11 and the movable mold part 12. Also, the mold 10
Is provided with a resin injection section 14 composed of a gate section, and the resin injection section 14 is open to the cavity 13. The other end of the resin injection section 14 communicates with the heating cylinder 15.
For example, a pressurized fluid composed of high-pressure nitrogen gas is supplied to the cavity 13.
A pressurized fluid injection section 16 for injecting the molten resin injected into the inside is provided in the resin injection section 14. The pressurized fluid injection unit 16 is connected to a pressurized fluid source 17 via a pipe.

In practicing the present invention, the fixed mold 11
And the movable mold part 12 are clamped, and the first thermoplastic resin composition pellets and the second thermoplastic resin composition pellets are blended (mixed) at a predetermined weight ratio. Then, the compounded product of the first thermoplastic resin composition pellets and the second thermoplastic resin composition pellets is put into a hopper (not shown) provided in the heating cylinder 15. Heating cylinder 15
Within, the compound is kneaded and plasticized to become a molten resin. Thereafter, the molten resin 20 is injected from the heating cylinder 15 into the cavity 13 of the mold 10 via the resin injection unit 14. This state is shown in the schematic sectional view of FIG. 2 and 3, only the mold portion is shown. Depending on the desired injection molded product and the structure and shape of the hollow portion, during injection of the molten resin or after completion of the injection, the cavity 13
A pressurized fluid is injected into the molten resin 20 through the pressurized fluid injection unit 16, thereby forming a hollow portion 21 in the resin.
This state is shown in FIG. Until the resin in the cavity is cooled and solidified, the inside of the hollow portion 21 is continuously pressurized by the pressurized fluid. After the resin in the cavity is cooled and solidified, the pressurized fluid in the hollow portion 21 is released to the outside via the pressurized fluid injection unit 16. Thereafter, the mold is opened, and the injection molded product is taken out of the mold. Finally, if necessary, the injection molded product can be cut or cut at appropriate portions (for example, both ends) to produce, for example, a pipe-shaped injection molded product.

[0049]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to perform injection molding, a mold having a cylindrical cavity having a length of 200 mm and a diameter of 30 mm (referred to as a mold-1) is used in a mold and an injection molding machine shown in FIG.
Injection molding was performed using a mold (referred to as mold-2) having an inclined cavity whose perspective view is shown in FIG. In mold-1, the cross-sectional area is about 7.1 cm.
An injection molded product (pipe-shaped injection molded product) having ^two tubular portions is formed. That is, in the mold 1, the cavity for forming an injection molded article having a tubular portion having a cross-sectional area of 3 cm ² or more and 15 cm ² or less is the cavity itself. On the other hand, the mold-2 has an inclined portion, and as shown in FIG. 4 (B), the external sectional area of the injection molded product at the position indicated by the symbol A is about 9 cm ² , and the external sectional shape is It is trapezoidal. The outer cross-sectional area of the injection molded product at the position indicated by the symbol B is about 22 cm ² . In the mold-2, the cavity portion for forming an injection molded product having a tubular portion having a cross-sectional area of 3 cm ² or more and 15 cm ² or less is a region indicated by the symbols C to D.

When the mold 1 is used, the outer shape of the cut surface perpendicular to the axial direction of the injection molded product is circular. Therefore, the thickness of the hollow tubular portion was measured with calipers at four positions every 90 degrees from the thickest portion. Also,
When the mold-2 was used, since the outer shape of the cut surface at the position indicated by the symbol A was trapezoidal, the thickness of the hollow tubular portion almost at the center of each side was measured with calipers. With respect to the hollow tubular portion at the position indicated by the symbol B, the cut surface was observed to check whether or not the uneven thickness portion was generated in the hollow portion.

In the injection molding, the molten resin was injected under the following conditions. The temperature of the injection molding machine was set to 250 ° C. only in Comparative Example 3. After a lapse of 0.6 seconds from the end of the injection of the molten resin, a pressurized fluid made of nitrogen gas was injected into the molten resin 20 in the cavity 13 at an initial pressure of about 100 kgf / cm ² . Here, the molten resin 2 to be injected into the cavity 13 is formed so that the hollow portion 21 is formed inside the resin in the cavity 13.
The amount of 0 was adjusted. After the injection of the pressurized fluid, the pressure of the pressurized fluid is maintained for 60 seconds, and after the resin in the cavity 13 is cooled and solidified, the pressurized fluid is released into the atmosphere to open the mold, and the injection is performed. The molding was removed from the mold. Molding machine cylinder setting temperature: 270 ° C Mold setting temperature: 130 ° C

[Production of prototype 1] MX nylon (Lenny 600 manufactured by Mitsubishi Engineering-Plastics Corporation)
2) 93% by weight of glass fiber chopped strand 0
7% by weight of 3MA409C (manufactured by Asahi Fiberglass Co., Ltd.) was mixed with a tumbler for 30 seconds. And
Vent type 40mmφ single screw extruder V set to 260 ° C
The mixture was extruded using S-40 (manufactured by Tanabe Plastic Co., Ltd.) and pelletized, and then overnight at 80 ° C.
Was dried with a hot air dryer to produce Prototype 1. The measured values of the average fiber diameter and the weight average length of the glass fibers in the pellet are shown in Table 1 below.

[Production of prototype 2] Similarly, 70% by weight of MX nylon (Renny 6002), 15% by weight of glass fiber 03MA409C, and 15% by weight of carbon fiber diamond lead K223NW (manufactured by Mitsubishi Chemical Corporation) were used. , 3
The mixture was mixed with a tumbler for 0 seconds. Then, the mixture was extruded using a vented 40 mmφ single screw extruder VS-40 set to 260 ° C., and pelletized.
The product was dried with a hot air dryer at 0 ° C. to produce a prototype 2.
The measured values of the average fiber diameter and the weight average length of the glass fiber and the carbon fiber in the pellet are shown in Table 1 below.

[0054]

Table 1 Glass fiber average fiber diameter in prototype 1 (pellet): 13 μm Weight average length: 450 μm Glass fiber average fiber diameter in prototype 2 (pellet): 13 μm Weight average length: 300 μm prototype 2 (pellet) Carbon fiber average fiber diameter: 8 μm Weight average length: 300 μm

The specifications of the first and second thermoplastic resin composition pellets used in each Example and Comparative Example are shown in Table 2 below.
Shown in

[0056]

[Table 2]

(Examples 1 to 7 and Comparative Examples 1 to 3)
Table 3 shows the compositions of the first and second thermoplastic resin composition pellets, the blending weight ratio, and the total content (% by weight) of the fiber filler in each of the examples and comparative examples. In Table 3, A / B
Represents the blending weight ratio of (first thermoplastic resin composition pellet) / (second thermoplastic resin composition pellet). Tables 4 and 5 show the measurement results of the uneven thickness portion when the mold 1 and the mold 2 were used. The first and second thermoplastic resin composition pellets were mixed in a plastic bag and then charged into a hopper of an injection molding machine. The amount of molten resin injected into the cavity was varied for each test in accordance with the occurrence of uneven thickness portions.

[0058]

[Table 3]

[0059]

[Table 4]

[0060]

[Table 5]

From the results shown in Tables 4 and 5, in the injection molding method or the injection molded product according to the first embodiment of the present invention, the fiber filler in the two types of thermoplastic resin composition pellets to be used is specified. In addition, by defining the blending weight ratio of the two types of thermoplastic resin composition pellets, an uneven thickness portion is generated on the surface of the hollow portion formed in the hollow tubular portion having a cross-sectional area of 3 cm ² or more and 15 cm ² or less. It can be seen that can be reliably prevented. The cross-sectional area of the hollow tubular portion at the position indicated by the symbol B of the mold-2 is about 22 cm.
^{In the} hollow tubular portion having such a large cross-sectional area, occurrence of the uneven thickness portion cannot be prevented. Further, in Comparative Example 3, since the second thermoplastic resin composition pellets containing no fiber filler were used, no uneven thickness portion was generated on the surface of the hollow portion. The strength does not satisfy the required strength.

In Comparative Example 1, injection molding was carried out using a mold having a rod-shaped cavity having a length of 400 mm (referred to as mold 3) whose cross section is shown in FIG. went. By using such a mold-3, an injection molded article having a tubular portion having a cross-sectional area of about 1.5 cm ² is formed. When the mold 3 was used in Comparative Example 1, no uneven thickness portion was found on the inner surface of the hollow tubular portion. This is because the external cross-sectional area of the hollow tubular part is 3 cm ²
This is because the uneven thickness portion is unlikely to be generated on the inner surface of the hollow tubular portion having such a small cross-sectional area.

(Embodiment 8) Embodiment 8 relates to an automobile roof rail for carrying or decorating various kinds of luggage such as surfboards and skis. This automotive roof rail has a hollow portion 43, a rail main body portion 41,
The legs 42 provided at both ends of the rail main body 41 are integrally formed. FIG. 7A is a schematic cross-sectional view of the automobile roof rail 40. FIG. 7B is a schematic bottom view of the roof rail 40 for an automobile. A uniform hollow portion 43 is formed inside the roof rail 40 for an automobile, more specifically, inside the entire rail main body 41 and inside a part of the leg 42. A hollow portion 43A communicating with the hollow portion 43 is also formed inside the third leg portion 42A formed integrally with the rail main portion at the center of the rail main portion 41. The third leg is 1
The number may be one or more, or may not be provided.

In a mold for molding the roof rail 40 for an automobile, a cavity is provided in the mold so that the longitudinal direction of the rail main body 41 substantially coincides with the vertical direction of the mold. A resin injection part is provided in the mold so that the thermoplastic resin is injected, and a pressurized fluid injection part is provided in the mold so that the pressurized fluid is injected into the thermoplastic resin from the lower part of the cavity. Is preferred. With this configuration of the mold, it is possible to suppress the draw-down phenomenon in which the thermoplastic resin drips under its own weight when the molten thermoplastic resin is injected into the cavity, and it is possible to suppress the uniformity when the pressurized fluid is injected. It becomes possible to obtain a hollow part.

FIG. 5 is a schematic sectional view of the mold used in the eighth embodiment. The mold 30 includes a fixed mold part 31 and a movable mold part 32. Then, a cavity 33 for molding a roof rail for automobiles, a resin injection portion (resin gate portion) 34 for injecting the molten thermoplastic resin into the cavity, and a thermoplastic resin injected into the cavity 33 are added. And a pressurized fluid injection section 36 for injecting a pressurized fluid. The cavity 33 is formed when the fixed mold part 31 and the movable mold part 32 are clamped. In the figure, reference numeral 38 is a runner on the parting surface. The pressurized fluid injection unit 36 includes, for example,
It may be a well-known gas injection nozzle provided with a check valve (not shown) at the tip. The other end of the pressurized fluid injection unit 36 is connected to a pressurized fluid source (not shown) by a pipe (not shown). The distal end of the pressurized fluid injection unit 36 can be moved in the left-right direction in FIG.

As shown in FIG. 5, the cavity 33 is provided in the mold 30 such that the longitudinal direction of the rail main body substantially matches the vertical direction of the mold 30. The resin injection section 34 is disposed in the mold 30 so as to inject the molten thermoplastic resin into a lower portion (lower end portion) of the cavity 33. Further, the pressurized fluid injection unit 36 is provided in the mold 30 so as to inject the pressurized fluid into the thermoplastic resin from the lower portion (lower end portion) of the cavity 33. The resin injection unit 3
The position at which the mold 4 is disposed in the mold 30 is exactly
It is not necessary that the molten thermoplastic resin be injected into the lower part of the cavity 3. The point is that most of the molten thermoplastic resin fills the cavity 33 from the bottom to the top of the cavity 33. It is sufficient that 34 is provided in the mold 30. Further, the position where the pressurized fluid injection part 36 is disposed in the mold 30 may not be a position where the pressurized fluid is injected strictly from the lower part of the cavity 33 into the thermoplastic resin.
In short, it is sufficient that the pressurized fluid injection part 36 is provided in the mold 30 so that most of the pressurized fluid flows upward from below the cavity 33. The cavity 33 has a shape in which a rail body 41 of a roof rail 40 for an automobile and legs 42 provided at both ends of the rail body 41 are integrally formed. 41 has a shape in which a leg 42 </ b> A is formed integrally with the rail body 41 at the center.

In Example 8, as the first and second thermoplastic resin composition pellets, the same pellets as in Example 2 were used in the same mixing ratio. Then, the compounded product of the first thermoplastic resin composition pellets and the second thermoplastic resin composition pellets is charged into a hopper (not shown) provided in a heating cylinder. In the heating cylinder, the compound is kneaded and plasticized to form a molten resin. The thermoplastic resin melted and plasticized at a resin temperature of 270 ° C. in an injection cylinder of an injection molding machine is subjected to a resin injection section (resin gate section) 34 via a runner 38 under the following injection conditions. From the cavity 33. The injection amount of the molten thermoplastic resin was set so as to completely fill the cavity 33.
After the mold 30 is clamped, the hydraulic cylinder 35 is operated to move the distal end of the pressurized fluid injection unit 36 in the left-hand direction in FIG. Keep in close contact.

Injection conditions Injection pressure: 1200 kgf / cm ² Mold temperature: 130 ° C.

About 7 seconds after the start of injection of the molten thermoplastic resin, a pressure of 100 kgf / cm ^{2 is} applied from the pressurized fluid injection section 36 into the thermoplastic resin injected into the cavity 33.
Of pressurized fluid (nitrogen gas) was injected. This state is shown in FIG. In the drawings, reference numeral 20 denotes a cavity 33.
The reference numeral 21 denotes a hollow portion. After three minutes have elapsed from the start of the injection of the molten thermoplastic resin into the cavity 33, the distal end of the pressurized fluid injection part 36 is moved by operating the hydraulic cylinder 35 as shown in FIG.
Of the pressurized fluid injection unit 36 and the mold were released, and the pressurized fluid in the hollow portion 21 was released to the atmosphere. After that, a molded automobile roof rail was taken out of the mold.

The roof rails for automobiles were good with no trace of resin flow. In addition, no sink marks occurred in the thick part of the roof rail for automobiles, no warpage was observed on the entire roof rail for automobiles, and no generation of burrs was observed. When the roof rail for automobiles was cut and the internal state was examined, a hollow portion was clearly formed in the thick portion, the thickness was uniform, and the occurrence of an uneven portion was not recognized at all. The weight of the automobile roof rail was about 1.7 kg.

FIG. 8A shows a schematic cross-sectional view along the longitudinal direction of an automobile roof rail, FIG. 8B shows a schematic bottom view, and FIG. As shown in an end view along line CC in FIG. 8A, a third leg 42B formed continuously with the legs 42 provided at both ends of the rail body 41 is provided. Alternatively, the rail body 41 may be provided integrally with the rail body 41. Also in this case, the number of the third leg may be one or plural. Further, as shown in FIG. 8D, a projection 44 is provided on the side surfaces of the legs 42 and 42B as shown in an end view similar to the line CC of FIG. 8A. Can also. In this embodiment, by providing a groove for engaging with the third leg 42B below the projection 44 on the roof of the automobile, the roof rail for the automobile can be securely mounted on the roof of the automobile. Becomes It is also possible to attach bolts, brackets, moldings, and the like, which are used for attaching to the vehicle body or the roof, to the legs. The surface of the automobile roof rail may be unpainted, or may be subjected to painting, plating, or hard coating as needed. The hollow portion is preferably formed in all parts of the rail main body and a part of the legs provided at both ends of the rail main body, but is not limited thereto. Part and one of the legs provided at both ends of the rail body, one part of the rail body and one part of the legs provided at both ends of the rail body, only the entire rail body, It may be formed only on a part of the rail main body.

Although the present invention has been described based on the embodiments and the preferred embodiments, the present invention is not limited to these. The structure of the mold described in the embodiment of the invention, the various conditions described in the examples are examples, and the thermoplastic resin composition pellets to be used, the shape and structure of the injection molded product to be molded, the hollow portion Can be changed as appropriate depending on the shape, structure, etc. In addition, the external shape and the structure of the hollow portion of the injection molded product are examples, and may be appropriately designed according to the specifications and performance required for the injection molded product.

[0073]

According to the present invention, it is possible to reliably suppress the occurrence of uneven thickness in a hollow portion, and to form an injection molded product having high strength and excellent appearance characteristics. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an outline of an injection molding machine suitable for carrying out the present invention.

FIG. 2 is a schematic cross-sectional view of a mold and the like for explaining a molding process of an injection molded product.

FIG. 3 is a schematic cross-sectional view of a mold and the like for describing a molding step of an injection-molded product, following FIG. 2;

FIG. 4 is a perspective view of a cavity of a mold-1 used in Examples and Comparative Examples, a schematic view of a cut surface when the cavity is cut at a position indicated by a symbol A, and Comparative Example 1. It is typical sectional drawing of the cavity of used mold-3.

FIG. 5 is a schematic cross-sectional view of a mold suitable for molding an automotive roof rail having a hollow portion according to the present invention.

6 is a schematic cross-sectional view showing a state in which a molten thermoplastic resin is injected into a cavity of the mold shown in FIG. 5, and then a pressurized fluid is injected.

FIG. 7 is a schematic sectional view and a bottom view of an automobile roof rail which is an injection-molded article having a hollow portion according to the present invention.

FIG. 8 is a schematic sectional view, a bottom view, and an end view showing a deformation of a roof rail for a vehicle having a hollow portion according to the present invention.

FIG. 9 is a schematic cross-sectional view of an injection-molded product, showing a state in which a knob-shaped protrusion is formed on the surface of a hollow portion.

[Explanation of symbols]

 10, 30 Mold 11, 31 Fixed mold part 12, 32 Movable mold part 13, 33 Cavity 14, 34 Resin injection part (resin gate part) 15 Heating cylinder 16, 36 Pressurized fluid injection part 17 Pressurized fluid source Reference Signs List 20 molten resin 21 hollow part 35 hydraulic cylinder 38 runner 40 roof rail for automobile 41 rail body part 42 leg 42A, 42B third leg 43, 43A hollow part 44 protrusion

Continuing from the front page (72) Inventor Noriyoshi Watanabe 5-6-1 Higashi-Hachiman, Hiratsuka-shi, Kanagawa Prefecture Mitsubishi Engineering Plastics Co., Ltd. Technology Center

Claims (19)

[Claims] 1. An injection molding machine having a sectional area of 3 cm ²
A mold provided with a cavity having a cavity for forming an injection molded article having a tubular portion of not less than 15 cm ² is used. (A) Average fiber diameter is 3 to 23 μm and weight average length is average fiber Glass fiber whose diameter is 10 times or more and a pellet length or less, and any one of a carbon fiber whose average fiber diameter is 5 to 13 μm and whose weight average length is 10 times or more and a pellet length or less, or A first thermoplastic resin composition pellet containing 10% by volume or more and 70% by volume or less of a fiber filler composed of these mixtures; and (B) a first thermoplastic resin composition pellet containing 5% by volume or less of the fiber filler or containing no fiber filler. 2 of the thermoplastic resin composition pellets in a weight ratio of 1/4 ≦ (first thermoplastic resin composition pellet / second thermoplastic resin composition pellet) ≦ 20. After compounding, kneading and plasticizing to form a molten resin, the molten resin is injected into the cavity of the mold, and during or after the injection of the molten resin, a pressurized fluid is injected into the molten resin in the cavity. Injection molding, whereby a hollow portion is formed at least inside the resin in the cavity portion. 2. The fiber filler contained in the first and / or second thermoplastic resin composition pellets has a weight average length of 15
The injection molding method according to claim 1, wherein the length is not less than 0 µm and not more than a pellet length. 3. The injection molding method according to claim 1, wherein the length of the cavity is at least 10 cm. (A) a glass fiber having an average fiber diameter of 3 to 23 μm, a weight average length of 10 times or more of the average fiber diameter and a pellet length, and an average fiber diameter of 5 to 13 μm;
A first thermoplastic resin composition containing at least 10% by volume and not more than 70% by volume of a carbon filler having a weight average length of at least 10 times the average fiber diameter and not more than the pellet length, or a fiber filler made of a mixture thereof; Product pellets and (B) a second thermoplastic resin composition pellet containing 5% by volume or less of the fiber filler or not containing the fiber filler in a weight ratio of 4 <(first thermoplastic resin composition Product pellet / second thermoplastic resin composition pellet)
≦ 20, and after kneading and plasticizing to form a molten resin, the molten resin is injected into a cavity of a mold provided in an injection molding machine, during injection of the molten resin, or after completion of injection, Inject the pressurized fluid into the molten resin in the cavity,
Thus, an injection molding method characterized by forming a hollow portion in a resin. 5. The weight average length of the fiber filler contained in the first and second thermoplastic resin composition pellets is 150 μm.
The pellet length is not more than the length.
3. The injection molding method according to 1. 6. The resin composition according to claim 1, wherein at least 30% by weight of the resin component is a crystalline thermoplastic resin, excluding the fiber filler constituting the first and second thermoplastic resin composition pellets. The injection molding method according to any one of claims 1 to 5. 7. The injection molding method according to claim 6, wherein the crystalline thermoplastic resin is a polyamide resin. 8. The injection molding method according to claim 7, wherein the polyamide resin is MX nylon resin. 9. An injection molding machine having a sectional area of 3 cm ²
A mold provided with a cavity having a cavity for forming an injection molded article having a tubular portion of not less than 15 cm ² is used. (A) Average fiber diameter is 3 to 23 μm and weight average length is average fiber Glass fiber whose diameter is 10 times or more and a pellet length or less, and any one of a carbon fiber whose average fiber diameter is 5 to 13 μm and whose weight average length is 10 times or more and a pellet length or less, or A first thermoplastic resin composition pellet containing 10% by volume or more and 70% by volume or less of a fiber filler composed of these mixtures; and (B) a first thermoplastic resin composition pellet containing 5% by volume or less of the fiber filler or containing no fiber filler. 2 of the thermoplastic resin composition pellets in a weight ratio of 1/4 ≦ (first thermoplastic resin composition pellet / second thermoplastic resin composition pellet) ≦ 20. After compounding, kneading and plasticizing to form a molten resin, the molten resin is injected into the cavity of the mold, and during or after the injection of the molten resin, the pressurized fluid is injected into the molten resin in the cavity. An injection-molded article having a hollow portion formed at least in the tubular portion. 10. The weight average length of the fiber filler contained in the first and second thermoplastic resin composition pellets is 150 μm.
The injection-molded article according to claim 9, wherein the length is not less than m and not more than a pellet length. 11. The injection-molded article according to claim 9, wherein the length of the tubular portion is 10 cm or more. (A) a glass fiber having an average fiber diameter of 3 to 23 μm and a weight average length of at least 10 times the average fiber diameter and a pellet length, and an average fiber diameter of 5 to 13 μm.
m, a carbon filler having a weight average length of 10 times or more of the average fiber diameter and a pellet length or less, or a fiber filler composed of a mixture thereof in an amount of 10% by volume or more.
A first thermoplastic resin composition pellet containing 0% by volume or less,
And (B) a second thermoplastic resin composition pellet containing 5% by volume or less of the fiber filler or not containing the fiber filler in a weight ratio of 4 <(first thermoplastic resin composition pellet / The second thermoplastic resin composition (pellet) is blended at a ratio of ≦ 20, kneaded and plasticized to form a molten resin, and then the molten resin is injected into a cavity of a mold provided in an injection molding machine, and the molten resin is injected. An injection-molded article having a hollow portion formed by injecting a pressurized fluid into a molten resin in a cavity during or after injection of a resin. 13. The weight average length of the fiber filler contained in the first and second thermoplastic resin composition pellets is 150 μm.
The injection-molded product according to claim 12, wherein the length is not less than m and not more than a pellet length. 14. A resin composition according to claim 1, wherein 30% by weight or more of the resin component is a crystalline thermoplastic resin, based on the resin component excluding the filler constituting the first and / or second thermoplastic resin composition pellets. The injection-molded article according to any one of claims 9 to 13, wherein 15. The injection molded article according to claim 14, wherein the crystalline thermoplastic resin is a polyamide resin. 16. The injection molded article according to claim 15, wherein the polyamide resin is an MX nylon resin. 17. The tubular part according to claim 9, wherein the outer cross-sectional shape is an irregular shape.
Injection molded article according to the item. 18. The injection-molded article according to claim 9, wherein the injection-molded article is an automobile roof rail. 19. A roof rail for an automobile, wherein a rail main body and legs provided at both ends of the rail main body are integrally formed, and a longitudinal direction of the rail main body is perpendicular to a vertical direction of a mold. A cavity is provided in the mold so as to substantially coincide with the mold, and a resin injection portion is provided in the mold so that the molten thermoplastic resin is injected into the lower portion of the cavity. The injection-molded article according to claim 18, wherein a pressurized fluid injection portion is provided in the mold so as to be injected into the inside.