JPH1192672A - Resin composition, injection-molded product having hollow part and injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin composition capable of making the surface of a hollow part smooth, and suppressing development of large nonuniform section in the hollow part, by specifying the relationsship between the weight-average length and the content of a reinforcing material. SOLUTION: This resin composition comprises (A) a reinforcing material preferably, e.g. glass fiber) and (B) a thermoplastic resin (preferably, e.g. polyamide-based resin). When the weight-average length of the component A is expressed by L (μm) and the content of the reinforcing material in the resin composition is expressed by w (wt.%) (preferably, 5-60 wt.%), the relationship; L<=450-5 w is satisfied. It is preferable that when the average fiber diameter of the component A is expressed by D (μm), the relationship: 10D<=L is satisfied, and that when the content of the component A >=0.5 mm in length in the resin composition is expressed by W, the relationship; W<=35-0.8 w is satisfied, and further, that (c) a material for improvement of impact characteristics, e.g. styrene-ethylene-butadiene-styrene rubber is included in this composition.

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 having a hollow portion, an injection-molding method, and a resin composition. The present invention relates to an injection-molded article made of a thermoplastic resin having a hollow portion and a method of injection-molding the same, and a resin composition capable of molding such an injection-molded article.

[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, and the molten resin is injected into a space formed by the surface (hereinafter, referred to as a cavity surface of the mold) and the core that constitute the cavity of the mold, After cooling and solidifying the resin, the molded product is taken out of the mold. Thereafter, by melting the core inside the molded product, a hollow portion which is a trace of the core can be obtained inside 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.

In the gas assist molding method, a pressurized fluid is injected into the molten resin in the cavity during or after the injection of the molten resin into the cavity provided in the mold (including simultaneously with the completion of the injection). Is the way. According to such a gas assist molding method, during cooling and solidification of the resin in the cavity, the resin is pressed against the cavity surface of the mold by the pressurized fluid, and as a result, warpage or sink occurs in the obtained injection molded product. Can be effectively prevented. One type of the 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 has a short molding step and is a highly efficient molding method.

[0004]

In the gas assist molding method, a hollow portion is formed inside an injection molded product. However, at present, there are few examples in which such hollow portions are actively used. The reason is that a desired surface state of the hollow portion cannot always be stably obtained. As one of the causes, when an injection molded product is made of a so-called fiber reinforced resin containing a fiber filler (reinforcing material),
It can be mentioned that fuzzing occurs on the surface of the hollow portion. Here, the fluffing means, for example, roughness of the surface of the hollow portion caused by the tip of the fiber filler protruding from the surface of the hollow portion or floating as it is on the surface of the hollow portion. When the content of fiber filler in the raw resin is increased in order to impart higher strength to the injection molded product, fluffing usually occurs on the surface of the hollow portion.

[0005] Still another cause is that an uneven thickness portion occurs in an injection molded product. 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 that is large enough to close the hollow portion is generated on the surface of the hollow portion (see FIG. 16).

[0006] In the latter case, the amount of resin required for molding an injection-molded product greatly varies. Then, when the resin is biased to the projection-like projections, molding defects such as outgassing easily occur. Here, outgassing means
This 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 cavity surface of the mold. When such outgassing occurs, the pressurized fluid leaks out of the gap in the mold, or the resin is separated from the cavity surface of the mold. In particular, when forming a hollow portion having a high hollow ratio, if such protrusions occur irregularly, the amount of molten resin injected into the cavity is insufficient for molding an injection molded product, Outgassing occurs during the flow of the molten resin in the cavity, and an injection molded product cannot be molded.

According to the experience of the present inventors, when a so-called fiber-reinforced thermoplastic resin of a polyphenylene sulfide (PPS) or polyamide type containing a fiber filler is used,
Many phenomena have been observed in which large nodular projections (uneven portions) are formed on the surface of the hollow portion so as to close the hollow portion. 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. It has also been experienced that particularly severe fuzzing occurs on the surface of such a protrusion.

[0008] In the gas assist molding method, it is possible to form a narrow hollow portion having a considerable length inside an injection molded product. Further, it is also possible to form a hollow portion having a high hollow ratio inside the injection molded product. Thermoplastic resin containing fiber filler, especially crystalline thermoplastic resin,
In particular, it is assumed that a fluid is caused to flow through a hollow portion of an injection molded product molded by a gas-assist molding method using a polyamide-based thermoplastic resin. In this case, if gas escape does not occur, a hollow portion is formed in the injection molded product, and a low-viscosity fluid such as water can flow into the hollow portion. However, as a result of sludge and the like caused by fluffing generated on the surface of the hollow portion, it is extremely difficult to produce an injection molded product that can withstand long-term use.

In order to smooth the surface of the hollow portion, it is necessary to reduce the content of the fiber filler as much as possible. However, according to such a measure, the mechanical properties of the injection-molded product are greatly impaired, and for example, it becomes difficult to produce an injection-molded product requiring high strength.

Although it depends on the shape of the injection-molded article, the composition of the resin composition to be used, and the required smoothness of the surface of the hollow portion, it cannot be said unconditionally. For example, in the case of glass fiber, the content is about 15% by weight. %, Fluff on the surface of the hollow portion becomes noticeable. Further, even when the fiber filler is not contained, a large uneven thickness portion often occurs when a crystalline thermoplastic resin is used. Further, if the reinforcing fibers are uniformly entangled in the fiber-reinforced molten resin plasticized by the injection molding machine, the thickness of the resin wall of the molded article having a hollow portion is not uniform, or it is not uniform. A flesh occurs.

A hollow curved tube having a smooth surface and a method for producing the same are known, for example, from JP-A-6-71778. This hollow curved tube is made of a polyamide resin containing 30% by weight or less of glass fiber and having a heat deformation temperature of 423K or more and a flexural modulus of 7.8 × 10 ⁶ kPa or more. It is described that a hollow curved tube having a smooth surface in a hollow portion can be manufactured by the technique disclosed in this patent publication. However, there is no description or suggestion of a problem such as the occurrence of a bump-like protrusion (uneven portion) enough to close the hollow portion as described above, or means for solving the problem.

Alternatively, a method for producing a resin hollow tube having a hollow portion having a smooth surface is known, for example, from JP-A-8-34048. In the method disclosed in this patent publication, a resin containing reinforcing fibers and a resin containing no reinforcing fibers or a resin having a lower reinforcing fiber content are dry blended, and the resin after dry blending is brought into a molten state. After that, a pressurized fluid is injected into the resin. This method requires an extra step such as dry blending two kinds of resins (actually, two kinds of pellets) before molding. In addition, unless the mixing state of the two types of pellets after dry blending is constant for each production, the size of the injection molded product is small (that is, the ratio of the size of the injection molded product / the size of the granular material is small). In addition, the mechanical properties of the obtained injection molded product vary. Furthermore, classification may occur in a hopper of an injection molding machine due to a difference in specific gravity of pellets.

The weight-average length (L μm) of the glass fiber reinforcing material contained in the resin composition produced by the conventional extrusion method, and the weight percentage (W weight%) of the reinforcing material
Has a correlation as shown in FIG. In addition, the resin composition manufactured by the conventional extrusion method is shown in FIG.
Shown by open circles, open triangles, and open squares. The weight-average length (L μm) of the reinforcing material in the resin composition varies slightly depending on the kneading conditions for producing the resin composition, but as shown by the straight line (1) in FIG. The shorter the weight percentage of the material, the shorter it becomes.

Further, the weight percentage (W '% by weight) of the reinforcing material having a length of 0.5 mm or more in the reinforcing material composed of glass fibers contained in the resin composition produced by the conventional extrusion method, As shown in FIG. 2, it generally depends on the weight percentage (W weight%) of the reinforcing material. In addition, the resin composition manufactured by the conventional extrusion method is shown by a white circle, a white triangle, and a white square in FIG. The weight percentage (W '% by weight) of the reinforcing material having a length of 0.5 mm or more increases as the weight percentage (W% by weight) of the reinforcing material increases, as represented by the straight line (1) in FIG. Lower.

By the way, based on the gas-assist molding method, a resin composition (having physical properties indicated by white circles, white triangles and white squares in FIGS. 1 and 2) manufactured by the conventional extrusion method is used. When an injection molded product having a hollow portion is formed by injection molding, the surface of the hollow portion is not smooth, and it is extremely difficult to suppress the occurrence of a large uneven thickness portion in the hollow portion. As a result of the test, it became clear.

Accordingly, an object of the present invention is to provide an injection molding method based on a gas-assist molding method capable of smoothing the surface of a hollow portion and suppressing the occurrence of a large uneven thickness portion in the hollow portion. An object of the present invention is to provide an injection molded article molded by an injection molding method, and a resin composition capable of molding the injection molded article.

[0017]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the weight average length (L μm) of the reinforcing material and the weight percentage (W weight%) of the reinforcing material in the resin composition have a constant relationship. Or the content of the reinforcing material (W wt%) in the resin composition and the length in the resin composition of 0.5%
If the content (W '% by weight) of the reinforcing material of not less than mm satisfies a certain relationship, the surface of the hollow portion can be smoothed, and the occurrence of a large uneven portion in the hollow portion is suppressed. The present inventors have found out that they can do so, and have reached the present invention.

That is, the resin composition according to the first aspect of the present invention for achieving the above object is a resin composition comprising a reinforcing material and a thermoplastic resin, and has a weight average length of the reinforcing material. Is represented by L (μm) and the content of the reinforcing material in the resin composition is represented by W (% by weight), wherein the following formula (1) is satisfied, and more preferably the following formula (1 ′) is satisfied. I do.

L ≦ 450−5W (1) L ≦ 400−5W (1 ′)

The reinforcing material is an inert fibrous material added to a thermoplastic resin in order to improve mechanical properties (eg, tensile strength, bending strength, impact strength) of an injection molded product. I do.

The weight average length of the reinforcing material is 10 times the average fiber diameter.
If it is less than twice, the reinforcing effect of the reinforcing material will be small. Therefore, the ratio of weight average length / average fiber diameter (aspect ratio) after production of the resin composition is preferably 10 or more.
That is, in the resin composition according to the first embodiment of the present invention, when the average fiber diameter of the reinforcing material is D (μm), the formula (1) or the formula (1 ′) is satisfied and the following formula is satisfied. It is preferable to satisfy (2).

10D ≦ L (2)

The second object of the present invention for achieving the above object is as follows.
The resin composition according to the embodiment is a resin composition comprising a reinforcing material and a thermoplastic resin, wherein the content of the reinforcing material in the resin composition is W (% by weight), and the length in the resin composition is 0.1%. 5m
m is defined as W '(weight%),
It is characterized by satisfying the following expression (3), more preferably the following expression (3 ′).

W ′ ≦ 35−0.8 W (3) W ′ ≦ 30−0.8 W (3 ′)

The first object of the present invention for achieving the above object is as follows.
The injection molding method according to the embodiment is a resin composition comprising a reinforcing material and a thermoplastic resin, wherein the weight average length of the reinforcing material is L (μm), and the content of the reinforcing material in the resin composition is W.
(% By weight), the resin composition satisfying the following formula (1) is more preferably kneaded and plasticized to satisfy the following formula (1 ′) to obtain a molten resin. It is characterized in that a molten resin is injected and a pressurized fluid is injected into the molten resin in the cavity during or after the injection of the molten resin, thereby forming a hollow portion in the resin.

L ≦ 450−5W (1) L ≦ 400−5W (1 ′)

In the injection molding method according to the first aspect of the present invention, when the average fiber diameter of the reinforcing material is D (μm), at the same time as satisfying the expression (1) or the expression (1 ′),
It is preferable that the following expression (2) is satisfied. If the relationship of the expression (2) is not satisfied, it may be difficult to mold an injection molded product having desired mechanical properties.

10D ≦ L (2)

The second object of the present invention for achieving the above object is as follows.
The injection molding method according to the embodiment is a resin composition comprising a reinforcing material and a thermoplastic resin, wherein the content of the reinforcing material in the resin composition is W (% by weight), and the length in the resin composition is 0.1%. 5
When the content of the reinforcing material having a thickness of at least mm is represented by W ′ (% by weight), a resin composition satisfying the following formula (3), more preferably the following formula (3 ′) is kneaded and plasticized to obtain a molten resin. After that, 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. Is formed.

W ′ ≦ 35−0.8 W (3) W ′ ≦ 30−0.8 W (3 ′)

The first object of the present invention for achieving the above object is as follows.
The injection-molded article having a hollow portion according to the embodiment is a resin composition comprising a reinforcing material and a thermoplastic resin, wherein the reinforcing material has a weight average length of L (μm), and the resin composition contains the reinforcing material. When the rate is W (% by weight), the following equation (1)
More preferably, after kneading and plasticizing a resin composition satisfying the following formula (1 ′) to form a molten resin, the molten resin is injected into a cavity of a mold, and during or after injection of the molten resin. The molding is performed by injecting a pressurized fluid into the molten resin in the cavity.

L ≦ 450−5W (1) L ≦ 400−5W (1 ′)

In the injection-molded article according to the first aspect of the present invention, when the average fiber diameter of the reinforcing material is D (μm),
It is preferable to satisfy the following expression (2) while satisfying the expression (1) or the expression (1 ′). If the relationship of the expression (2) is not satisfied, it may be difficult to mold an injection molded product having desired mechanical properties.

[Expression 17] 10D ≦ L (2)

The second object of the present invention to achieve the above object.
The injection-molded article having a hollow portion according to the embodiment is a resin composition comprising a reinforcing material and a thermoplastic resin, wherein the content of the reinforcing material in the resin composition is W (% by weight), and When the content of the reinforcing material having a length of 0.5 mm or more is represented by W ′ (% by weight), a resin composition satisfying the following formula (3), more preferably the following formula (3 ′) is kneaded and plasticized. The molten resin is injected into the cavity of the mold after being formed into a molten resin, and is formed by injecting a pressurized fluid into the molten resin in the cavity during or after the injection of the molten resin. It is characterized by the following.

W ′ ≦ 35−0.8W (3) W ′ ≦ 30−0.8W (3 ′)

In the resin composition, the injection molding method or the injection molded article according to the first or second aspect of the present invention (hereinafter sometimes simply referred to as the present invention), the content W of the reinforcing material is 5 It is desirable that the content be in the range of 60 to 60% by weight, preferably 10 to 50% by weight, more preferably 20 to 40% by weight. Reinforcement content W of 5% by weight
If it is less than 50%, the effect obtained by adding the reinforcing material (for example, the effect of improving the mechanical strength of the injection molded product) becomes difficult to achieve, and the properties of the finally obtained injection molded product may not be satisfactory. There is. The upper limit of the average content of the reinforcing material depends on the type of the reinforcing material to be added, but is determined by the maximum addition rate at which the resin composition can be manufactured. In the current technology, for example, about 60% by weight is used. is there.

As thermoplastic resins suitable for use in the present invention, polyethylene resins, polystyrene resins, polypropylene resins, polycarbonate resins, polyacetal resins, polyamide resins, polyester resins (for example, polyethylene terephthalate resin and polybutylene terephthalate resin), Modified polyphenylene oxide resin (for example, modified polyphenylene ether resin), polyphenylene sulfide resin, acrylonitrile-butadiene-styrene copolymer resin, acrylonitrile-styrene copolymer resin, polymethyl methacrylate resin, or a mixture or polymer alloy thereof. Examples include, but are not limited to:

Further, the thermoplastic resin suitable for use in the present invention preferably comprises a crystalline thermoplastic resin or a non-crystalline thermoplastic resin. In this case, as the crystalline thermoplastic resin, a crystalline thermoplastic resin such as a polypropylene resin, a polyacetal resin, a polyester-based resin (for example, a polyethylene terephthalate resin or a polybutylene terephthalate resin), a polyamide-based resin, or a polyphenylene sulfide resin; It is preferable to use a mixture or a polymer alloy. 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 definite melting point is confirmed is a crystalline thermoplastic resin, and the resin whose definite melting point is not confirmed is an amorphous thermoplastic resin.

As the polyamide resin suitable for use in the present invention, nylon 6, nylon 66, nylon 69, nylon 610, nylon 612, nylon 12, meta-xylylenediamine alone or para-xylylenediamine 40
% By weight or less of a mixed diamine compound and a polyamide resin obtained from an α, ω-linear aliphatic dibasic acid or an aromatic dibasic acid, a linear fatty acid such as tetramethylenediamine, hexamethylenediamineoctamethylenediamine Polyamide resin obtained from an aromatic diamine and an aromatic dibasic acid,
And a mixture thereof, but are not particularly limited thereto. The polyamide resin obtained from meta-xylylenediamine and α, ω-linear aliphatic dibasic acid is hereinafter referred to as MX nylon. It is more preferable to use MX nylon, nylon 6, nylon 66, or a mixture thereof as the polyamide resin.

The reinforcing material may include at least one fiber material selected from the group consisting of glass fibers, carbon fibers, whiskers, and liquid crystal polymers. Preferably, the reinforcing material is in a defibrated state in the resin composition.
Usually, for example, 100 to 2500 reinforcing materials as raw materials before the production of the resin composition are bundled. here,
Being in the defibrated state means that the number of reinforcing materials in a bundle in the resin composition is less than 10 (for example, 2 to 3). That the reinforcing material is not in the defibrated state in the resin composition means that the number of reinforcing materials bundled in the resin composition is, for example, 10 or more. When the fibrillation of the reinforcing material in the resin composition is insufficient, although the surface smoothness of the hollow portion is excellent, the mechanical properties (for example, mechanical strength) of the injection molded article may be insufficient.

Examples of the glass fiber include glass wool, chopped glass fiber, and milled glass fiber. In addition, a milled carbon fiber can be used as the carbon fiber. Examples of the whiskers include aluminum borate whiskers, potassium titanate whiskers, basic magnesium sulfate whiskers, calcium silicate whiskers, and calcium sulfate whiskers. Further, as a liquid crystal polymer, a copolyester type of para-hydroxybenzoic acid (PHB) and polyethylene terephthalate, PHB and 6-oxy-2
-Copolyester type with naphthoic acid, ternary polyester type copolymer of PHB, terephthalic acid and p, p'-bisphenol, and the like. More specifically, it is commonly used for plastic reinforcement,
Chopped strands having an average fiber length of about 1 mm to 10 mm and converged with a surface treatment agent such as a converging agent can be used. The average fiber diameter of the reinforcing material is desirably 1 μm to 30 μm, preferably 3 μm to 24 μm, and more preferably 9 μm to 13 μm. Here, the average fiber diameter can be measured by observing the reinforcing material with a stereoscopic microscope.

Generally, in order to keep the measurement error low,
The weight average length is used as the average length of the reinforcing material. The length of the reinforcing material is measured by dissolving the resin component by immersing the resin composition or the injection molded product in a liquid that dissolves the resin component,
In the case of glass fiber, the resin component is burned at a high temperature of 600 ° C. or more, and the remaining reinforcing material can be observed and measured with a microscope or the like. Usually, a person measures the length of the reinforcement by photographing the reinforcement, or obtains the length of the reinforcement using a dedicated fiber length measuring device. In the case of the number average length, the influence of the minutely broken reinforcing material is too large, so 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 reinforcing material that are too small and crushed. If the length is smaller than twice the original diameter of the reinforcing material, the measurement becomes difficult. Therefore, for example, the reinforcing material having a length of twice or more the diameter is to be measured.

Further, as additives, various additives generally used, for example, flame retardants, stabilizers, pigments, dyes,
A release agent, a lubricant, a nucleating agent, a weather resistance improving agent and the like may be added to the resin composition. These additives can be used alone or as a mixture of two or more.

In the present invention, the resin composition may further contain an impact property improving material. Here, examples of the impact property improving material include SEBS (styrene-ethylene-butadiene-styrene) rubber, EPR (ethylene-propylene) rubber, and core-shell type rubber. The impact property improving material may be added to the thermoplastic resin in advance during the production of the resin composition, or may be added at the time of kneading the resin composition. It is desirable that the addition ratio of the impact property improving material is 5% by weight to 50% by weight, preferably 15% by weight to 35% by weight.

In the injection molding method of the present invention, the injection location of the pressurized fluid is not particularly limited, and the pressurized fluid injection section may be disposed near the resin injection section, or the pressurized fluid injection section may be formed by the resin injection section. It may be arranged away from the 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.

The volume of the molten resin to be injected into the cavity may be a volume that can mold a desired injection molded product.
It depends on the volume occupied by the hollow portion in the injection molded product. That is, the volume of the molten resin to be injected into the cavity may be a volume that completely fills the cavity or a volume that does not completely fill the cavity.

The hollow part in the injection molded article of the present invention may be a main part or a part of the injection molded article. A tubular structure (for example, a pipe) can be exemplified as an injection molded product having a hollow portion as a main portion. In this case, the hollow portion constitutes, for example, a fluid flow path. In addition, as an injection molded product in which the hollow portion is a part, an injection molded product in which the surface of the hollow portion constitutes a sliding surface, for example, the hollow portion constitutes a hole for passing an electric wire or a drive wire, An example of an injection molded product that comes into contact with and slides on the inner surface of such a hole can be exemplified.

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 mold cavity (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.

The external shape of the resin composition in the present invention can be any shape, for example, a cylindrical shape or a rugby ball shape (spheroidal shape). The external dimensions of the cylindrical resin composition can be, for example, 3 mm in diameter and 5 mm in length, but are not limited thereto.

In the present invention, the relationship between the weight percentage (W weight%) of the reinforcing material and the weight average length (L μm) of the reinforcing material is such that L ≦ 450-5W is satisfied, or The relationship between the content of the reinforcing material having a length of 0.5 mm or more (W '% by weight) and the weight percentage of the reinforcing material (W% by weight) satisfies W'≤35-0.8W. By using a resin composition, when an injection-molded article having a hollow portion is molded by an injection molding method, the surface of the hollow portion becomes smooth, and the occurrence of a large uneven portion in the hollow portion can be suppressed. But,
As a result of various tests, it became clear. On the other hand, the relationship between the weight percentage (W weight%) of the reinforcing material and the weight average length (L μm) of the reinforcing material, or the content of the reinforcing material having a length of 0.5 mm or more (W ′) in the resin composition. Weight%) and the weight percentage of the reinforcing material (W weight%) deviate from the above relationship, an injection molded article having a hollow portion is formed by the injection molding method using such a resin composition. In this case, the surface of the hollow portion is not smooth, and it is difficult to suppress the occurrence of a large uneven portion in the hollow portion.

That is, the weight average length (L μm) of the reinforcing material in the resin composition and the weight percentage (W weight%) of the reinforcing material are as follows:
In FIG. 1, if the relationship shown by a black circle, a black triangle, and a black square is satisfied, when an injection-molded article having a hollow portion is molded by an injection molding method, the surface of the hollow portion becomes smooth, and moreover, in the hollow portion, As a result of various tests, it was found that large uneven thickness portions can be suppressed. As described above, the weight average length (L μm) of the reinforcing material in the resin composition and the weight percentage of the reinforcing material (L μm) can smoothen the surface of the hollow portion and suppress the occurrence of a large uneven thickness portion in the hollow portion. W weight%), as shown by a straight line (2) in FIG. 1, L ≦ 450-5W, more preferably, a relationship with L ≦ 400-5W, as shown by a straight line (3) in FIG. It is in.

Alternatively, the length in the resin composition is 0.5 m
If the content (W '% by weight) of the reinforcing material and the weight percentage (W% by weight) of the reinforcing material have a relationship shown by a black circle, a black triangle, and a black square in FIG. As a result of various tests, it was found that when an injection-molded article having the following was molded by the injection molding method, the surface of the hollow portion became smooth, and the occurrence of a large uneven portion in the hollow portion could be suppressed. . As described above, the content (W ′% by weight) of the reinforcing material having a length of 0.5 mm or more in the resin composition, in which the surface of the hollow portion becomes smooth and the occurrence of a large uneven portion in the hollow portion can be suppressed. ) And the weight percentage (W weight%) of the reinforcing material are expressed by a straight line (2) in FIG. 2, and L ≦ 35−0.8 W More preferably, by a straight line (3) in FIG. And W ′ ≦ 30−0.8W.

As described above, when the weight percentage (W wt%) of the reinforcing material is set to a certain value, the weight average length (L μm) of the reinforcing material in the resin composition and the 0% .5m
It is very difficult in the prior art to control the weight percentage (W '% by weight) of the reinforcing material having a length of m or more by changing the kneading conditions, particularly in a region where the weight percentage of the reinforcing material is low. It is difficult to shorten the average weight length of the reinforcing material without deteriorating the thermoplastic resin and to reduce the ratio of 0.5 mm or more. The reinforcing material (eg, glass fiber) having a predetermined length distribution after fibrillation and pulverization is mixed with a molten resin using a batch mixer or the like, so that the weight of the reinforcing material in the resin composition is increased. Average length (Lμ
m) and controlling the weight percentage (W '% by weight) of the reinforcing material having a length of 0.5 mm or more in the reinforcing material can control the reinforcing material after defibration and pulverization having such a predetermined length distribution. It is extremely difficult to obtain and is not realistic. Also, usually
When mass-producing the resin composition, the initial length is 6 to 10 mm
Are used, and handling of the fibers after defibration and pulverization is extremely complicated.

In the present invention, a resin composition satisfying the formula (1) or the formula (3) can be produced by the following method. That is, as shown in FIG. 1, for example, the fact that the weight-average length of the reinforcing material made of glass fiber greatly depends on the addition ratio of the reinforcing material at the time of manufacturing (kneading) the resin composition is used. Weight average length (L μm) and the content of reinforcing material (W
% By weight) or the content of the reinforcing material (W% by weight) in the resin composition and the length in the resin composition of 0.5 m
It is possible to control the relationship between the content (W '% by weight) of the reinforcing material having a m or more. For example, first, a predetermined weight average length (Lμ
m) The thermoplastic resin and the reinforcing material are melt-kneaded at the reinforcing material addition ratio at which m) is obtained, and then the resin composition is melted,
Knead uniformly with the molten thermoplastic resin. This step is
It may be performed in one melting process, or after solidifying the resin composition containing the reinforcing agent with a high addition ratio to produce a granular material, melting the granular material again, and uniformly with the molten thermoplastic resin. It may be kneaded.

[0047]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

(Example 1) In Example 1, a reinforcing material made of glass fiber having specifications shown in Table 1 below was used.
A resin composition composed of a thermoplastic resin composed of nylon MXD6 resin was manufactured. The method of the prototype will be described later.

[0049]

Table 1 Reinforcement made of glass fiber Average fiber diameter (D): 13 μm Weight average length (L): 300 μm Reinforcement content (W): 30% by weight Length in resin composition 0.5 mm or more Content of reinforcing material (W '): 10% by weight

In Example 1, the average fiber diameter (D μm), the weight average length (L μm), and the content (W weight%) of the reinforcing material in the resin composition were as follows: 10D ≦ L ≦ 450-5W Satisfied with the relationship. Further, the content (W% by weight) of the reinforcing material in the resin composition and the length in the resin composition of 0.5%
With respect to the content (W '% by weight) of the reinforcing material of not less than mm, the relation of W'≤35-0.8W is satisfied.

In Example 1, an injection molding machine equipped with a mold 10 whose schematic diagram is shown in FIG. 3 was used. Except for the heating cylinder 15, the components of the injection molding machine are not shown. The mold 10 includes a fixed mold section 11 and a movable mold section 12, and when the fixed mold section 11 and the movable mold section 12 are clamped, a cavity 13 is formed. The mold 10 is provided with a resin injection part 14 opened to the cavity 13.
I am familiar with 5. Further, a pressurized fluid injection unit 16 is provided in the resin injection unit 14, and one end of the pressurized fluid injection unit 16 is opened in the resin injection unit 14. On the other hand, the other end of the pressurized fluid injection section 16 is connected to a pressurized fluid source 17.

In Example 1, the above-mentioned resin composition was supplied into a heating cylinder 15 and kneaded and plasticized in the heating cylinder 15 to obtain a molten resin.
The molten resin 20 is injected into the cavity 13 via the resin injection section 14 (see FIG. 4). After the injection of the molten resin is completed, a pressurized fluid made of nitrogen gas is pressurized into the molten resin 20 in the cavity 13. Inject from the fluid injecting section 16 (see FIG. 5),
Thus, the hollow portion 21 was formed in the resin 20A. The injection molding conditions were as shown in Table 2 below. The injection molded product having a hollow portion was a curved tube. Outer diameter of injection molded product is 20
mm. The inner diameter of the hollow portion was 16 mm, and the thickness of the injection molded product was 2 mm. Then, the obtained injection molded product is cut, and the surface roughness of the hollow portion (R _max ; unit μm)
Was measured based on JISB0601 “Definition and display of surface roughness”. Table 6 shows the measurement results. In addition, generation | occurrence | production of the uneven thickness part in the hollow part was not recognized at all.

[0053]

Table 2 Melting temperature of resin composition (heating cylinder temperature): 270 ° C Injection speed of molten resin: 10 mm / sec Pressure of pressurized fluid: 5 MPa Mold temperature: 100 ° C

(Example 2) In Example 2, a reinforcing material made of glass fiber having the specifications shown in Table 3 below was used.
A resin composition composed of a polycarbonate resin and a thermoplastic resin was prototyped.

[0055]

Table 3 Reinforcement composed of glass fiber Average fiber diameter (D): 13 μm Weight average length (L): 350 μm Reinforcement content (W): 20% by weight Length in resin composition 0.5 mm or more Content of reinforcing material (W '): 16% by weight

Also in Example 2, the average fiber diameter (D μm), the weight average length (L μm) of the reinforcing material and the content (W wt%) of the reinforcing material in the resin composition were as follows: 10D ≦ L ≦ 450-5W Satisfied with the relationship. Further, the content (W% by weight) of the reinforcing material in the resin composition and the length in the resin composition of 0.5%
With respect to the content (W '% by weight) of the reinforcing material of not less than mm, the relation of W'≤35-0.8W is satisfied.

Then, using the same injection molding machine and mold as in Example 1, injection molding was performed under the same conditions as in Example 1 to obtain an injection molded product. Then, by cutting the injection-molded article obtained was measured surface roughness R _max of the hollow portion. Table 6 shows the measurement results. In addition, generation | occurrence | production of the uneven thickness part in the hollow part was not recognized at all.

(Comparative Example 1) In Comparative Example 1, a reinforcing material made of glass fiber having the data shown in Table 4 below (the same as the glass fiber used in Example 1) was used.
A resin composition composed of a thermoplastic resin composed of nylon MXD6 resin was used. The resin composition is commercially available from Mitsubishi Gas Chemical Company as Reny 1002H.

[0059]

Table 4 Reinforcement made of glass fiber Average fiber diameter (D): 13 μm Weight average length (L): 360 μm Reinforcement content (W): 30% by weight Length in resin composition 0.5 mm or more Content of reinforcing material (W '): 22% by weight

In Comparative Example 1, the weight average length (L μm) of the reinforcing material and the content (W wt%) of the reinforcing material in the resin composition do not satisfy the relationship of L ≦ 450−5W. Further, the content (W weight%) of the reinforcing material in the resin composition and the length in the resin composition of 0.1% were used.
The content of the reinforcing material of 5 mm or more (W '% by weight) does not satisfy the relationship of W'≤35-0.8W.

Using the same injection molding machine and mold as in Example 1, injection molding was carried out under the same conditions as in Example 1 to obtain an injection molded product. Then, by cutting the injection-molded article obtained was measured surface roughness R _max of the hollow portion. Table 6 shows the measurement results. Note that occurrence of uneven thickness portions was observed in the hollow portions.

(Comparative Example 2) In Comparative Example 2, a reinforcing material composed of glass fibers having the specifications shown in Table 5 below (the same as the glass fibers used in Example 2) was used.
A resin composition composed of a polycarbonate resin was used. This resin composition is commercially available from Mitsubishi Gas Chemical Company as Iupilon GS-2020M.

[0063]

Table 5 Reinforcement made of glass fiber Average fiber diameter (D): 13 μm Weight average length (L): 450 μm Reinforcement content (W): 20% by weight Length in resin composition 0.5 mm or more Content of reinforcing material (W '): 40% by weight

Also in Comparative Example 2, the weight average length (L μm) of the reinforcing material and the content (W wt%) of the reinforcing material in the resin composition do not satisfy the relationship of L ≦ 450−5W. Further, the content (W weight%) of the reinforcing material in the resin composition and the length in the resin composition of 0.1% were used.
The content of the reinforcing material of 5 mm or more (W '% by weight) does not satisfy the relationship of W'≤35-0.8W.

Then, using the same injection molding machine and mold as in Example 1, injection molding was carried out under the same conditions as in Example 1 (however, the melting temperature of the resin composition was changed to 290 ° C.). I got The outer diameter of the injection molded product was 20 mm. Then, the obtained injection-molded product is cut, and the surface roughness R of the hollow portion is obtained.
_{The max} was measured. Table 6 shows the measurement results. Note that occurrence of uneven thickness portions was observed in the hollow portions.

[0066]

Table 6 Glass fiber Weight average length Content Inner surface roughness Content (W) (L) (W ′) R _max unit Weight% μm Weight% μm Example 1 30 300 10 89 Example 2 20 350 16 100 Comparative Example 1 30 360 22 451 Comparative Example 2 20 450 40 380

As is apparent from Table 6, when the resin composition satisfies the relationship of the formula (1) or (3), the conventional resin composition containing glass fibers can be used as a raw material for injection molding. An injection-molded article having much better surface smoothness in the hollow portion than in the case of using it could be obtained.

The outline of the method for producing the resin composition used in Example 1 will be described below. The kneading state in the production of the resin composition was changed by changing the screw shape of the twin-screw extruder.

The resin composition used in Example 1 is shown in FIG. 6A as a schematic partial cross-sectional view, and as shown in FIG. It can be manufactured based on a step of kneading a resin and a reinforcing material, and a step of kneading a kneaded product of the thermoplastic resin and the reinforcing material and a molten thermoplastic resin. That is, using a twin-screw extruder with a screw diameter of 55 mm and a schematic partial cross-sectional view of which is shown in FIG. 6 (A), using nylon MXD6 and glass fiber (see Example 1 for specifications) as raw materials, The resin composition (pellet) used in Example 1 was manufactured under the conditions shown in Table 7 below. That is, nylon MXD6 which is a thermoplastic resin is supplied to the twin-screw extruder from the upstream side of the twin-screw extruder, and melted and kneaded in the twin-screw extruder. The kneading state at this time is a strong kneading state (normal kneading state of thermoplastic resin). And
A reinforcing material made of glass fiber is added in the middle stream of the twin-screw extruder based on the side feed method, and the molten thermoplastic resin and the reinforcing material are kneaded. The kneading state at this time is a medium kneading state. Thus, a kneaded product of the thermoplastic resin and the reinforcing material can be obtained in the middle stream of the twin-screw extruder. Further, on the downstream side of the twin-screw extruder, a thermoplastic resin made of nylon MXD6 is supplied to the twin-screw extruder based on a side feed method, and the supplied and melted thermoplastic resin and the kneaded material are kneaded. The kneading state at this time is set to a weak kneading state so that the reinforcing material is not damaged by the kneading.
Finally, the strand discharged from the twin-screw extruder is cut into a desired length to obtain a resin composition (pellet). In FIGS. 6, 7 and 15, the elliptical mark on the twin-screw extruder indicates a place where various materials are supplied to the twin-screw extruder by the side feed method. 6, 7 and 1
In 5, a screw part with a diagonal line is a part that mainly conveys the material, and a screw part shown in a ring shape is a part that mainly kneads the material.

[0070]

[Table 7]

The resin composition thus produced is the same as the resin composition produced by the conventional extrusion method, when the content W (% by weight) of the reinforcing material in the resin composition is the same. Weight average length of reinforcement in composition (Lμm)
Or the value of the content (W '% by weight) of the reinforcing material having a length of 0.5 mm or more in the resin composition is larger than these values in the resin composition manufactured by the conventional extrusion method. It was a low value. As a result, when an injection-molded article is molded by the injection molding method using such a resin composition, the surface of the hollow part of the obtained injection-molded article becomes smooth, and the occurrence of a large uneven thickness part in the hollow part is reduced. Can be suppressed.

On the other hand, using a twin-screw extruder with a screw diameter of 55 mm, a schematic partial cross-sectional view of which is shown in FIG. 15, using nylon MXD6 and glass fiber (refer to Example 1 for specifications), Under the conditions shown in Table 8, the resin composition (pellet) used in Comparative Example 1 was produced. That is, 2
Nylon MX which is a thermoplastic resin from the upstream side of the screw extruder
D6 is supplied to a twin-screw extruder, and melted and kneaded in the twin-screw extruder. The kneading state at this time is a strong kneading state (normal kneading state of thermoplastic resin). Then, in the middle of the twin-screw extruder, a reinforcing material made of glass fiber is added to the melted and kneaded thermoplastic resin based on the side feed method, and the thermoplastic resin and the reinforcing material are kneaded. The kneading state at this time was set so that the reinforcing material was dispersed as uniformly as possible in the resin composition. Finally, the strand discharged from the twin-screw extruder is cut into a desired length to obtain a resin composition (pellet).

[0073]

[Table 8] Upstream supply amount of nylon MXD6: 70 kg / h Downstream glass fiber supply amount: 30 kg / h Barrel temperature: 290 degrees Screw rotation speed: 50 rpm

The microscopic structure of the resin composition thus manufactured is such that the glass fibers are sufficiently defibrated in the resin composition and the distribution of the reinforcing material in the resin composition is uniform. I was Under the conditions shown in Table 8, in the middle stream of the twin-screw extruder, a reinforcing material made of glass fiber was added to the melted and kneaded thermoplastic resin based on the side feed method, and the thermoplastic resin and the reinforcing material were mixed. When kneading, when the kneading state was weakened, the distribution of the reinforcing material in the resin composition became uneven, but the glass fibers were not sufficiently defibrated in the resin composition. When injection molding is performed using such a resin composition, it is possible to obtain an injection molded article having excellent surface smoothness of the hollow portion, but the glass fibers are not sufficiently defibrated in the resin composition. The mechanical properties (for example, mechanical strength) of the obtained injection molded article become insufficient.

Although the present invention has been described based on the preferred embodiments, the present invention is not limited to these embodiments. The various conditions described in the examples are exemplifications, and may be appropriately changed depending on the resin composition (pellet) to be used, the shape and structure of the injection molded product to be injection molded, the shape and structure of the hollow portion, and the like. be able to. 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.

The method for producing the resin composition is not limited to the method shown in FIGS. 6A and 8A. FIG. 6B is a schematic partial cross-sectional view, and FIG. 8B is a conceptual diagram illustrating an example in which the thermoplastic resin and the reinforcing material are extruded from the upstream side of the twin-screw extruder. And melted and kneaded in a twin screw extruder. The kneading state at this time is a medium kneading state (a kneading state weaker than the kneading state of a normal thermoplastic resin). In this way, the molten thermoplastic resin and the reinforcing material are kneaded in the upstream to middle flow of the twin-screw extruder, and a kneaded product of the thermoplastic resin and the reinforcing material can be obtained. Then, a thermoplastic resin made of nylon MXD6 is supplied on the downstream side of the twin-screw extruder based on the side feed method, and the supplied and melted thermoplastic resin and the kneaded material are kneaded. The kneading state at this time is set to a weak kneading state so that the reinforcing material is not damaged by the kneading. Finally, the strand discharged from the twin-screw extruder is cut into a desired length to obtain a resin composition (pellet).

In the example shown in FIG. 7A, which is a schematic partial sectional view, two twin-screw extruders are used, and a thermoplastic resin is supplied from the upstream side of the first twin-screw extruder. Melt and knead in a first twin screw extruder. The kneading state at this time is a strong kneading state (normal kneading state of thermoplastic resin). Then, a reinforcing material made of glass fiber is added in the middle stream of the first twin-screw extruder based on the side-feed method, and the molten thermoplastic resin and the reinforcing material are kneaded. The kneading state at this time is a medium kneading state. Thus, a kneaded product of the thermoplastic resin and the reinforcing material can be obtained in the middle stream of the twin-screw extruder. Further, the kneaded material is supplied upstream of the second twin-screw extruder, and is melted and kneaded in the second twin-screw extruder. The kneading state at this time is a strong kneading state (normal kneading state of thermoplastic resin). Then, a thermoplastic resin is added in the middle stream of the second twin-screw extruder based on the side feed method and kneaded. The kneading state at this time is a medium kneading state. Finally, the strand discharged from the second twin-screw extruder is cut into a desired length to obtain a resin composition (pellet).

In the example shown in FIG. 7B, which is a schematic partial sectional view, two twin-screw extruders are used, and a thermoplastic resin, a reinforcing material, and the like are arranged from the upstream side of the first twin-screw extruder. And melted and kneaded in a first twin-screw extruder. The kneading state at this time is a strong kneading state (normal kneading state of thermoplastic resin). Further, the kneaded material is supplied upstream of the second twin-screw extruder, and at the same time, the thermoplastic resin is supplied upstream of the second twin-screw extruder. Then, these are melted and kneaded in a second twin-screw extruder. The kneading state at this time is a strong kneading state (normal kneading state of thermoplastic resin). Finally, the strand discharged from the second twin-screw extruder is cut into a desired length to obtain a resin composition (pellet).

Alternatively, as shown in the conceptual diagram of FIG. 8C, a kneaded product obtained by kneading a thermoplastic resin and a reinforcing material which have been melted in advance is mixed with the kneaded product from the upstream side of the twin-screw extruder. It may be supplied to a screw extruder. In this case, the kneading state in the upstream to middle flow of the twin-screw extruder is a weak kneading state. Alternatively, a resin composition can be produced by a step of melting a thermoplastic resin, and a step of melting and kneading a melt of the thermoplastic resin and a kneaded product of the thermoplastic resin and a reinforcing material. That is, as shown in the conceptual diagram of FIG. 8D, the thermoplastic resin is supplied to the twin-screw extruder from the upstream side of the twin-screw extruder. In this case, the kneading state on the upstream side of the twin-screw extruder is a weak kneading state. And the thermoplastic resin and the reinforcing material are melted in advance, and the kneaded material obtained by kneading is
It is supplied to the twin screw extruder from the middle stream of the twin screw extruder based on the side feed method. In this case, the kneading state on the upstream side of the twin-screw extruder is a strong kneading state (normal kneading state). The kneading state on the downstream side is a weak kneading state.

Further, as a modification of the method for producing the resin composition shown in FIG. 8A, as shown in FIG.
Using a main extruder and a sub-extruder, which are twin-screw extruders, a thermoplastic resin is supplied to the main extruder from the upstream side of the main extruder, and melted and kneaded in the main extruder. The kneading state at this time is a strong kneading state (normal kneading state of thermoplastic resin). Then, the reinforcing material is added in the middle stream of the main extruder based on the side feed method, and the thermoplastic resin and the reinforcing material are kneaded. The kneading state at this time is a medium kneading state. Thus, a kneaded product of the thermoplastic resin and the reinforcing material can be obtained in the middle stream of the main extruder. Further, in the sub-extruder, the thermoplastic resin is supplied to the sub-extruder from the upstream side, melted, and weakly kneaded. Then, the kneaded material in the main extruder and the molten thermoplastic resin from the sub-extruder are kneaded at the head portion (downstream side) of the main extruder to produce a strand.

As a modification of the method for producing the resin composition shown in FIG. 8B, as shown in FIG.
Using a main extruder and a sub-extruder, which are screw extruders, the main extruder supplies the thermoplastic resin and the reinforcing material to the main extruder from the upstream side of the main extruder, and melts and kneads in the main extruder. I do. The kneading state at this time is a medium kneading state. In this way, the molten thermoplastic resin and the reinforcing material are kneaded in the upstream to middle flow of the main extruder, and a kneaded product of the thermoplastic resin and the reinforcing material can be obtained. Furthermore, in the sub-extruder,
The thermoplastic resin is supplied to the sub-extruder from the upstream side, melted,
Apply weak kneading. Then, the kneaded material in the main extruder and the molten thermoplastic resin from the sub-extruder are kneaded at the head portion (downstream side) of the main extruder to produce a strand.

Alternatively, as a modification of the method for producing the resin composition shown in FIG. 8C, as shown in FIG. 10A, a main extruder and a sub-extruder which are twin-screw extruders are used. Using, in the main extruder, from the upstream side of the main extruder, kneaded material obtained by kneading the thermoplastic resin and the reinforcing material previously melted is supplied to the main extruder, melted in the main extruder, Knead. The kneading state at this time is a weak kneading state. Thus, a kneaded product of the thermoplastic resin and the reinforcing material can be obtained in the upstream to middle streams of the main extruder. Further, in the sub-extruder, the thermoplastic resin is supplied to the sub-extruder from the upstream side, melted, and weakly kneaded. Then, the kneaded material in the main extruder and the molten thermoplastic resin from the sub-extruder are kneaded at the head portion (downstream side) of the main extruder to produce a strand.

Further, as a modification of the method for manufacturing the resin composition shown in FIG. 8D, as shown in FIG. 10B, a main extruder and a sub-extruder which are twin-screw extruders are used. In the main extruder, a thermoplastic resin is supplied to the main extruder from the upstream side of the main extruder, and is melted and kneaded in the main extruder. The kneading state at this time is a strong kneading state. In this way, a molten thermoplastic resin (melt) can be obtained in the upstream to middle streams of the main extruder. Furthermore, in the sub-extruder,
A kneaded product obtained by previously melting and kneading the thermoplastic resin and the reinforcing material is supplied to the sub-extruder from the upstream side, melted, and weakly kneaded. And at the head (downstream side) of the main extruder,
The melt in the main extruder and the melted kneaded material from the sub-extruder are kneaded to produce a strand.

11A and 11B and FIGS. 12A and 12B show a method of manufacturing a resin composition as shown in conceptual views in FIGS. 9A, 9B and 9 B, respectively. The difference from the method for producing the resin composition described with reference to FIGS. 10A and 10B is that the strand from the sub-extruder is added to the strand from the main extruder before the strand cools. (Specifically, close contact). That is, FIG.
In the method for producing a resin composition shown in conceptual views in (A), (B) of FIG. 1, and (A) of FIG. 12, a step of kneading a molten thermoplastic resin and a reinforcing material, A step of adding a thermoplastic resin to the kneaded material of the reinforcing material. In the method for producing a resin composition shown in the conceptual view of FIG. 12B, a step of melting a thermoplastic resin and adding a kneaded product of a thermoplastic resin and a reinforcing material to a melt of the thermoplastic resin. The step of performing

FIGS. 13 (A), (B) and FIGS. 14 (A) and (B) show a conceptual drawing of the resin composition, respectively. FIG. 12 is a modification of the method for producing a resin composition shown in conceptual views in FIGS. FIGS. 13A, 13B and 14A show a method for producing a resin composition whose conceptual views are shown in FIGS. 11A, 11B and 12A, respectively. The difference from the method for producing a resin composition showing a conceptual diagram is that a strand from an extruder, which is a kneaded product of a thermoplastic resin and a reinforcing material, is immersed in a molten thermoplastic resin stored in a hot bath and heated. The point is that a thermoplastic resin is added to a strand from an extruder which is a kneaded product of a thermoplastic resin and a reinforcing material. On the other hand, the difference between the method for producing the resin composition shown in the conceptual diagram in FIG. 14B and the method for producing the resin composition shown in the conceptual diagram in FIG. The extruder is immersed in the kneaded product of the molten thermoplastic resin and the reinforcing material stored in the hot bath, and the kneaded product is added to the extruder strand that is a molten thermoplastic resin. On the point.

Alternatively, as a modification of the method for producing the resin composition shown in the conceptual view of FIG.
After supplying the thermoplastic resin and the reinforcing material to the granulator, sufficiently melting and kneading, then adding the thermoplastic resin, further melting,
The resin composition can also be manufactured by kneading. Alternatively, as a modification of the method for producing the resin composition shown in the conceptual diagram of FIG. 8C, a kneaded product obtained by kneading a thermoplastic resin and a reinforcing material that have been melted in advance is supplied to a granulator. After sufficient melting and kneading, a thermoplastic resin is added, and further melting and kneading are performed to produce a resin composition. Further, as a modification of the method for producing the resin composition shown in the conceptual view of FIG. 8D, a thermoplastic resin is supplied to the granulator using a granulator and sufficiently melted and kneaded. Thereafter, a kneaded product of a thermoplastic resin and a reinforcing material is added to the melt, followed by further melting and kneading to produce a resin composition.

In the method for producing a resin composition described above, other additives (for example, a flame retardant or a release agent) may be contained in the thermoplastic resin in advance. On the other hand, the reinforcing material may contain other additives (for example, a flame retardant or a release agent) in advance, and furthermore, the reinforcing material may contain a small amount of thermoplastic resin in advance. Good. During the production of the resin composition, the thermoplastic resin to be melted and kneaded first and the thermoplastic resin to be added later may be the same thermoplastic resin, or may be the same type of thermoplastic resin, or May be a different kind of thermoplastic resin. For example, a method and a position of supplying the raw materials to the extruder may be appropriately selected, and a vent (exhaust) is also an example.

[0088]

According to the present invention, it is possible to obtain a good injection-molded article having little fluff on the surface of the hollow portion, excellent surface smoothness of the hollow portion, and no abnormal uneven thickness portion in the hollow portion. Thus, even when a fluid flows through the hollow portion, for example, high long-term reliability can be obtained, and even when the hollow portion forms a sliding surface, the component can slide with low friction. Will be possible.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a weight average length of a reinforcing material and a weight percentage (% by weight) of the reinforcing material.

FIG. 2 shows the relationship between the weight percentage (% by weight) of a reinforcing material having a size of 0.5 mm or more in a glass fiber reinforcing material contained in a resin composition and the weight percentage (% by weight) of a reinforcing material. It is a graph.

FIG. 3 is a schematic view of an injection molding machine provided with a mold suitable for carrying out the present invention, showing a state in which the mold is clamped.

FIG. 4 is a schematic sectional view of a mold or the like showing a state where molten resin is injected into a cavity of the mold via a resin injection section.

FIG. 5 is a schematic cross-sectional view of a mold and the like showing a state in which a pressurized fluid is injected into a cavity of the mold via a pressurized fluid injection unit.

FIG. 6 is a view schematically showing a step of manufacturing a resin composition (pellet) used in Example 1 using a twin-screw extruder.

FIG. 7 is a conceptual diagram of a process for producing a resin composition (pellet) used in the present invention.

FIG. 8 is a conceptual diagram of a process for producing a resin composition (pellet) used in the present invention.

FIG. 9 is a conceptual diagram of a process for producing a resin composition (pellet) used in the present invention.

FIG. 10 shows a resin composition (pellet) used in the present invention.
It is a key map of the process of manufacturing.

FIG. 11 shows a resin composition (pellet) used in the present invention.
It is a key map of the process of manufacturing.

FIG. 12 shows a resin composition (pellet) used in the present invention.
It is a key map of the process of manufacturing.

FIG. 13 shows a resin composition (pellet) used in the present invention.
It is a key map of the process of manufacturing.

FIG. 14 shows a resin composition (pellet) used in the present invention.
It is a key map of the process of manufacturing.

FIG. 15 is a view schematically showing a step of manufacturing a granular material (pellet) used in Comparative Example 1 using a twin-screw extruder.

FIG. 16 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]

 REFERENCE SIGNS LIST 10 mold 11 fixed mold part 12 movable mold part 13 cavity 14 resin injection part (resin gate part) 15 heating cylinder 16 pressurized fluid injection part 17 pressurized fluid source 20 molten resin 20A resin 21 hollow part

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 51/04 C08L 51/04 77/00 77/00 101/12 101/12 // B29K 9:06 77:00 105: 12 B29L 22: 00

Claims (30)

[Claims] 1. A resin composition comprising a reinforcing material and a thermoplastic resin, wherein the weight average length of the reinforcing material is L (μm), and the content of the reinforcing material in the resin composition is W (% by weight). A resin composition satisfying the following formula (1). L = 450-5W (1) 2. The resin composition according to claim 1, wherein when the average fiber diameter of the reinforcing material is D (μm), the following formula (2) is satisfied. ## EQU2 ## 10D ≦ L (2) 3. A resin composition comprising a reinforcing material and a thermoplastic resin, wherein the content of the reinforcing material in the resin composition is W
(% By weight), and when the content of the reinforcing material having a length of 0.5 mm or more in the resin composition is W ′ (% by weight), the following formula (3) is satisfied. . ## EQU3 ## W '≦ 35−0.8W (3) 4. The method according to claim 1, wherein the content W of the reinforcing material is 5 to 60% by weight.
Item 14. The resin composition according to Item. 5. The method according to claim 1, wherein the thermoplastic resin is made of a crystalline thermoplastic resin.
Item 14. The resin composition according to Item. 6. The resin composition according to claim 5, wherein the thermoplastic resin is a polyamide resin. 7. The resin composition according to claim 1, wherein the thermoplastic resin comprises an amorphous thermoplastic resin. 8. The material according to claim 1, wherein the reinforcing material is at least one fiber material selected from the group consisting of glass fibers, carbon fibers, whiskers and liquid crystal polymers. Item 14. The resin composition according to Item. 9. The resin composition according to claim 1, further comprising an impact property improving material. 10. The resin composition according to claim 9, wherein the impact property improving material is styrene-ethylene-butadiene-styrene rubber, ethylene-propylene rubber or core-shell type rubber. 11. A resin composition comprising a reinforcing material and a thermoplastic resin, wherein the weight average length of the reinforcing material is L (μm), and the content of the reinforcing material in the resin composition is W (% by weight). Then, after kneading and plasticizing a resin composition satisfying the following formula (1) to obtain a molten resin, the molten resin is injected into a cavity of a mold, and during or after the injection of the molten resin, An injection molding method characterized by injecting a pressurized fluid into a molten resin in a cavity, thereby forming a hollow portion in the resin. L = 450-5W (1) 12. The injection molding method according to claim 11, wherein when the average fiber diameter of the reinforcing material is D (μm), the following formula (2) is satisfied. 10D ≦ L (2) 13. A resin composition comprising a reinforcing material and a thermoplastic resin, wherein the content of the reinforcing material in the resin composition is W
(% By weight), when the content of the reinforcing material having a length of 0.5 mm or more in the resin composition is W ′ (% by weight), the resin composition satisfying the following formula (3) is kneaded and plasticized. After the molten resin, the molten resin is injected into the mold cavity,
During or after the injection of the molten resin, a pressurized fluid is injected into the molten resin in the cavity, thereby forming a hollow portion in the resin. (6) W ′ ≦ 35−0.8W (3) 14. The injection molding method according to claim 11, wherein the content W of the reinforcing material is 5 to 60% by weight. 15. The injection molding method according to claim 11, wherein the thermoplastic resin is made of a crystalline thermoplastic resin. 16. The injection molding method according to claim 15, wherein the thermoplastic resin is a polyamide resin. 17. The injection molding method according to claim 11, wherein the thermoplastic resin is made of an amorphous thermoplastic resin. 18. The reinforcing material according to claim 1, wherein the reinforcing material is at least one fiber material selected from the group consisting of glass fibers, carbon fibers, whiskers, and liquid crystal polymers.
The injection molding method according to any one of claims 1 to 17. 19. The resin composition according to claim 11, further comprising an impact property improving material.
The injection molding method according to any one of the above. 20. The injection molding method according to claim 19, wherein the impact property improving material is styrene-ethylene-butadiene-styrene rubber, ethylene-propylene rubber or core-shell type rubber. 21. A resin composition comprising a reinforcing material and a thermoplastic resin, wherein the weight average length of the reinforcing material is L (μm), and the content of the reinforcing material in the resin composition is W (% by weight). Then, after kneading and plasticizing a resin composition satisfying the following formula (1) to obtain a molten resin, the molten resin is injected into a cavity of a mold, and during or after the injection of the molten resin, An injection-molded article having a hollow portion, which is formed by injecting a pressurized fluid into a molten resin in a cavity. L = 450-5W (1) 22. The injection-molded article according to claim 21, wherein the following formula (2) is satisfied when the average fiber diameter of the reinforcing material is D (μm). 10D ≦ L (2) 23. A resin composition comprising a reinforcing material and a thermoplastic resin, wherein the content of the reinforcing material in the resin composition is W
(% By weight), when the content of the reinforcing material having a length of 0.5 mm or more in the resin composition is W ′ (% by weight), the resin composition satisfying the following formula (3) is kneaded and plasticized. After the molten resin, the molten resin is injected into the mold cavity,
An injection-molded article having a hollow portion, which is formed by injecting a pressurized fluid into the molten resin in the cavity during or after the injection of the molten resin. ## EQU9 ## W '≦ 35-0.8W (3) 24. The injection molded article according to claim 21, wherein the content W of the reinforcing material is 5 to 60% by weight. 25. The injection-molded article according to claim 21, wherein the thermoplastic resin is made of a crystalline thermoplastic resin. 26. The injection molded article according to claim 25, wherein the thermoplastic resin is a polyamide resin. 27. The injection molded article according to claim 21, wherein the thermoplastic resin is made of an amorphous thermoplastic resin. 28. The reinforcement according to claim 2, wherein the reinforcement is at least one fiber material selected from the group consisting of glass fibers, carbon fibers, whiskers and liquid crystal polymers.
The injection molded article according to any one of claims 1 to 27. 29. The resin composition according to claim 21, further comprising an impact property improving material.
The injection-molded article according to any one of the above. 30. The injection-molded article according to claim 29, wherein the impact property improving material is styrene-ethylene-butadiene-styrene rubber, ethylene-propylene rubber or core-shell type rubber.