JP2019098684A - Crystalline resin molded body and method for manufacturing resin molded body - Google Patents

Abstract

To provide a resin molded body maintaining a balance between practically satisfactory productivity and durability, and having an enhanced lightweight property.SOLUTION: A crystalline resin molded body formed by molding a crystalline resin composition has two or more holes. In more than half number of holes, a maximum valley depth Rv in the peripheral area within 5 mm from the edge of a hole opening is 30 μm or less, and the inner wall of the hole has a skin layer. A method for manufacturing a resin molded body includes injection molding a resin composition to mold a resin molded body. The injection molding includes the steps of: filling the resin composition into a mold, set to a mold temperature 5°C-80°C less than the melting point or the softening point of the resin composition; and forming a hole in the resin composition filled in the mold when at least a central portion of the filled up resin composition is in a molten state.SELECTED DRAWING: None

Description

  The present invention relates to a crystalline resin molded body and a method for producing a resin molded body.

Resins have advantages such as low specific gravity compared to metals, rust resistance, and excellent processability. In recent years, metal has been replaced by resin by the improvement of productivity by injection molding technology and robot technology, and it is widely used in parts such as precision instruments, home appliances, OA instruments, automobiles, industrial applications and general goods. Furthermore, with the expansion of the field of application of resin, the current situation is that the demand for maintaining the balance between productivity and durability sufficient for practical use of the resin molded product and further enhancing the lightness is increased.
Therefore, in order to improve the lightness and dimensional accuracy of the resin molded body, generally, attempts are made to provide boss holes and through holes as meat theft, and attempts are made to make the whole thin and reinforce strength with ribs. There is.

  On the other hand, attempts have been made to improve the strength of the resin itself by using a specific resin composition and to improve the reduction in thickness and weight. For example, a technique using a polyacetal resin, a polyacetal resin composition comprising a specific spindle-like calcium carbonate and a fatty acid ester (see, for example, Patent Document 1), a specific wollastonite, and a specific ester or polyoxyalkylene glycol compound A technology using a polyacetal resin composition composed of a polyolefin resin (see, for example, Patent Document 2), a technology using a polyamide resin molded article containing a thermoplastic liquid crystal resin which retains liquid crystallinity (see, for example, Patent Document 3). Etc. have been proposed.

  In addition, as a technique for improving weight reduction, strength and the like, attempts have been made to improve by using specific molding conditions and molding methods. For example, a technique (see, for example, Patent Document 4) using a hollow molded article provided with a solid portion and a hollow portion requiring strength has been proposed.

Japanese Patent Application Laid-Open No. 05-051514 WO 99/043751 Unexamined-Japanese-Patent No. 2002-241510 Japanese Patent Laid-Open No. 2000-071275

  However, in the injection-molded resin molded product having two or more holes obtained by the techniques disclosed in Patent Documents 1 to 4, the balance of productivity and durability sufficient for practical use is maintained, and lightness is achieved. There is still room for improvement in

  So, in this invention, it aims at providing the resin molded object which maintained the balance of productivity and durability sufficient for practical use, and improved lightness.

  As a result of intensive studies on the problems of the prior art described above, the present inventors have found that, in an injection-molded resin molded product having two or more holes, the surface smoothness around the opening of the hole is not more than a specified value. It has been found that the resin molded product of the present invention can solve the above-mentioned problems of the prior art, and the present invention has been completed.

  That is, the present invention is as follows.

[1]
It is a crystalline resin molded object which shape | molds a crystalline resin composition,
Have two or more holes,
The crystalline resin molded article, having a maximum valley depth Rv of 30 μm or less in a peripheral region within 5 mm from the edge of the opening of the hole and having a skin layer on the inner wall of the hole in more than half of the hole .
[2]
The crystalline resin molded article according to the above [1], wherein the crystalline resin composition contains a filler.
[3]
The crystalline resin molded article according to the above [1] or [2], wherein the crystalline resin composition contains an appearance improving agent.
[4]
The crystalline resin molded object in any one of said [1]-[3] which has a resin inflow part (gate part) of only one place.
[5]
The crystalline resin molded body according to any one of the above [1] to [4], wherein the crystalline resin composition is a polyacetal resin composition.
[6]
The crystalline resin molding according to the above [5], wherein the melt flow rate (MFR) of the polyacetal resin composition is 1.5 g / 10 minutes or more and 33.0 g / 10 minutes or less.

[7]
A method for producing a resin molded article, comprising injection molding the resin composition to form a resin molded article,
The following steps in the injection molding:
Filling the resin composition in a mold set at a mold temperature 5 ° C. to 80 ° C. lower than the melting point or softening point of the resin composition;
Forming a hole in the filled resin composition in the mold when at least a central part of the filled resin composition is in a molten state;
A method for producing a resin molded product, comprising:
[8]
The method for producing a resin molded product according to [7], wherein the resin composition is filled into the mold from a resin inflow portion (gate portion) at only one place.
[9]
The method for producing a resin molded product according to the above [7] or [8], wherein the mold temperature is 10 ° C. to 75 ° C. lower than the melting point or the softening point of the resin composition.
[10]
The method for producing a resin molded product according to any one of the above [7] to [9], wherein the holes are formed using ejector compression injection molding and / or injection compression molding as the injection molding.
[11]
The manufacturing method of the resin molding in any one of said [7]-10] which further includes the process of continuing supply of a resin composition by injection pressure after forming the said hole.

  According to the present invention, it is possible to obtain a resin molded product with improved lightness by maintaining a balance between productivity and durability sufficient for practical use.

It is a photograph which shows an example of the gear manufactured by the normal shaping | molding which used the metal mold without a meat theft as an example of the resin molding which is not based on the manufacturing method of this embodiment. It is a photograph which shows an example of the gear manufactured by the normal shaping | molding which used the metal mold | die with a meat theft as an example of the resin molding which is not based on the manufacturing method of this embodiment. It is a photograph which shows an example of the gear manufactured by performing in-mold meat theft molding as an example of the resin molding by the manufacturing method of one Embodiment of this invention. The manufacturing method of one Embodiment of this invention WHEREIN: The schematic of an example of the front-end | tip in the case of performing a meat theft by in-mold meat theft molding is shown. The manufacturing method of one Embodiment of this invention WHEREIN: The schematic diagram of another example of the front-end | tip in the case of performing meat theft by in-mold meat theft molding is shown. The manufacturing method of one Embodiment of this invention WHEREIN: The schematic diagram of another example of the front-end | tip in the case of performing meat theft by in-mold meat theft molding is shown. The manufacturing method of one Embodiment of this invention WHEREIN: The schematic diagram of another example of the front-end | tip in the case of performing meat theft by in-mold meat theft molding is shown. An example of the 3-point gate provided in the web in case the resin molding is a gear is shown. An example of the three-point gate provided in the rib part of a shaft hole periphery in case a resin molding is a gear is shown. An example of the ring-shaped film gate provided in the rib part of a shaft hole periphery in case a resin molding is a gear is shown. The schematic diagram of an example of the in-mold meat theft molding which applied ejector compression molding is shown. The schematic diagram of an example of in-mold meat theft molding which applied injection compression molding is shown. The schematic of an example of the measurement site | part around a meat theft is shown. An example of a surface roughness measurement result is shown. The other example of a surface roughness measurement result is shown. An example of the photograph of the crystalline state of the inner wall of the hole formed using in-mold meat theft molding as a meat theft using a crystalline resin is shown. An example of the photograph of the endurance tester used in the example is shown. The example of a figure of the endurance tester used in the example is shown.

Hereinafter, modes for carrying out the present invention (hereinafter, referred to as "the present embodiment") will be described in detail with reference to the drawings.
In addition, this invention is not limited to the following description, It can variously deform and implement within the range of the summary. In each drawing, the positional relationship such as upper, lower, left, and right is based on the positional relationship shown in each drawing unless otherwise specified, and the size and ratio of each component are limited to the illustrated size and ratio. Absent.

The crystalline resin molded product of the present embodiment is formed by molding the crystalline resin composition and has two or more holes, and in a hole of more than half, the largest of the peripheral region within 5 mm from the edge of the hole opening The valley depth Rv is 30 μm or less, and a skin layer is provided on the inner wall of a hole of more than half.
The method for producing a resin molded product according to the present embodiment includes the steps of: filling a resin composition in a molding die; forming a hole in the mold when at least a central portion of the filled resin composition is in a molten state; including.
The resin composition which comprises the resin molding of this embodiment, the manufacturing method of a resin molding, the resin molding, and its use application are demonstrated in order below in detail.

[Crystalline Resin Composition Constituting Crystalline Resin Molded Body]
The crystalline resin molded product of the present embodiment is composed of a crystalline resin composition. Moreover, it is preferable that the crystalline resin molding of this embodiment contains a filler. Furthermore, it is preferable that the said crystalline resin molded object contains an appearance improving agent. In particular, the polyacetal resin composition is preferably composed, and the melt flow rate (MFR) of the polyacetal resin composition is preferably 1.5 g / 10 minutes or more and 33.0 g / 10 or less.

[resin]
The crystalline resin composition which comprises the crystalline resin molding of this embodiment contains a crystalline resin as an essential resin component.
The crystalline resin to be contained is not limited to, for example, polyolefin (polyethylene (PE), polypropylene (PP), etc.), polyacetal resin (POM), polyester (polybutylene terephthalate (PBT), polyethylene) Examples thereof include terephthalate (PET) and the like, polyamide (PA), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), liquid crystal polymer (LCP) and the like.
Among these, polyolefin, polyacetal resin, polyamide and polyester are preferable.
The content of the crystalline resin is 70% by mass to 100% by mass, preferably 75% by mass to 100% by mass, with respect to 100% by mass of the resin contained in the crystalline resin composition. More preferably, it is 80% by mass to 100% by mass.
These crystalline resins may be used alone or in combination of two or more.

The crystalline resin composition according to the present embodiment is at least one selected from a noncrystalline resin and a thermosetting resin as an optional resin component as long as the crystalline resin molded product obtained by molding has a skin layer. May be included. Specifically, the crystalline resin composition according to the present embodiment may contain an amorphous resin alone as an optional resin component or may contain a thermosetting resin alone, and the amorphous resin and the thermosetting resin. It may include a combination with a resin.
The content of these optional resin components is 0% by mass to 30% by mass, preferably 0% by mass to 25% by mass, with respect to 100% by mass of the resin contained in the crystalline resin composition. And 0% by mass to 20% by mass.

Non-crystalline resins include, but are not limited to, polyvinyl chloride (PVC), polyvinylidene chloride, polystyrene (PS), polyvinyl acetate (PVAc), polyurethane (PUR), acrylonitrile butadiene styrene resin, for example. (ABS), acrylonitrile styrene resin (AS), acrylic resin (PMMA etc.), polycarbonate (PC), modified polyphenylene ether (m-PPE), cyclic polyolefin, fluorocarbon resin (PTFE etc.), polysulfone (PSF), polyether Examples thereof include sulfone (PES), amorphous polyarylate (PAR), polyether ketone ketone (PEKK), thermoplastic polyimide (PI), and polyamide imide (PAI).
One of these noncrystalline resins may be used alone, or two or more thereof may be used in combination.

As a thermosetting resin, although it is not limited to the following, for example, phenol resin (PF), epoxy resin (EP), melamine resin (MF), urea resin (UF), unsaturated polyester resin (UP) And thermosetting polyurethane (PUR), thermosetting polyimide (PI), alkyd resin and the like.
One of these thermosetting resins may be used alone, or two or more thereof may be used in combination.

[Filling material]
Moreover, in order to improve strength, rigidity, and durability, it is preferable that the crystalline resin composition which comprises the crystalline resin molded object of this embodiment contains various fillers. Examples of the filler include, but are not limited to, inorganic and organic fillers.
As the inorganic filler, for example, metal powder (aluminum, stainless steel, nickel, silver etc.), oxide (silicon oxide / silica / glass powder / glass balloon / glass fiber, iron oxide, alumina, titanium oxide, zinc oxide etc.) ), Hydroxides (aluminum hydroxide, magnesium hydroxide, calcium hydroxide etc.), silicates (talc, mica, clay, bentonite etc.), carbonates (calcium carbonate, magnesium carbonate, hydrotalcite etc.), carbon based Substances (carbon black, graphite, carbon fiber, etc.), sulfates, boron nitride, silicon nitride, etc. may be mentioned.
Examples of the organic filler include natural products (linter, wood, rice husk, silk, leather, etc.) and synthetics (aramid, Teflon (registered trademark), viscose, synthetic cellulose, etc.).

Examples of the shape of the inorganic / organic filler include powder, scale, plate, needle, sphere, fiber, tetrapod and the like. Among them, powdery, spherical or plate-like particles having a L / D ratio of 0.2 to 5.0 are preferable, and the L / D ratio is preferably 0.3 to 3.0, in consideration of variations in physical properties. Is preferable, and 0.5 to 2.0 is particularly preferable. Here, the L / D ratio refers to the ratio of the major axis (L) to the minor axis (D) of the minor axis or the thickness.
The inorganic / organic filler may be used in combination with a known surface treatment agent in order to improve the affinity to the resin. Examples of surface treatment agents include silane coupling agents such as aminosilanes and epoxysilanes, titanate coupling agents, fatty acids (saturated fatty acids and unsaturated fatty acids), alicyclic carboxylic acids, resin acids, metal soaps, resins And the like.
3 mass% or less is preferable with respect to 100 mass% of inorganic and organic fillers, and, as for the addition amount of a surface treatment agent, 2 mass% or less is more preferable.
The inorganic and organic fillers may be used alone or in combination of two or more.

  Although content of a filler is not specifically limited, It is preferable that it is 0 mass part-40 mass parts with respect to 100 mass parts of content of resin contained in a crystalline resin composition, and 0 mass part-35 mass. It is further more preferable that it is a part, and it is more preferable that it is 0 mass part-30 mass parts. If the content of the filler is within the above range, the strength, rigidity and durability of the resin molded product can be sufficiently enhanced.

[Appearance improver]
Moreover, it is preferable that the crystalline resin composition which comprises the resin molding of this embodiment contains various appearance improving agents, in order to improve the designability. An appearance improver is a substance used for coloring, which selectively absorbs, reflects, or scatters light of a specific wavelength, or generates light of a new wavelength, to the appearance of a resin molded product. It is a substance that has the function of causing change. Examples of the appearance improver include, but are not limited to, inorganic pigments, organic pigments, dyes and the like.

  The inorganic pigment is not particularly limited, and, for example, white pigments (eg, titanium dioxide, lead white, zinc white, zinc sulfide or lithopone in three crystal forms of rutile, anatase or brookite); black pigments (eg, For example, carbon black, black iron oxide, iron manganese black or spinel black); chromium pigments such as chromium oxide, chromium oxide hydrate green, cobalt green or ultramarine green, cobalt blue, iron blue, iron blue, miloli blue, ultramarine blue Or manganese blue, ultramarine violet or cobalt or manganese violet; red iron oxide, cadmium sulfoselenide, molybde tread or ultramarine red; brown iron oxide, mixed brown, spinel phase and corundum phase or chromium oxide Yellow iron oxide, nickel titanium yellow, chromium titanium yellow, cadmium sulfide, cadmium zinc sulfide, chromium yellow, zinc yellow, alkaline earth metal chromate, napoli yellow, bismuth vanadate; effect pigments such as interference pigments; zinc silicate And fluorescent pigments such as strontium sulfide; metal powder pigments such as aluminum powder, bronze powder and copper powder; and the like.

  Other inorganic pigments are not particularly limited, and for example, pigment white 6, pigment white 7, pigment black 7, pigment black 11, pigment black 22, pigment black 27/30, pigment yellow 34, pigment yellow 35/37, Pigment Yellow 42, Pigment Yellow 53, Pigment Brown 24, Pigment Yellow 119, Pigment Yellow 184, Pigment Orange 20, Pigment Orange 75, Pigment Brown 6, Pigment Brown 29, Pigment Brown 31, Pigment Yellow 164, Pigment Red 101, Pigment Red 104, pigment red 108, pigment red 265, pigment violet 15, pigment blue 28/36, pigment blue 29, pigment green 17, pigment green 26/50 and the like.

  The organic pigment is not particularly limited. For example, aniline black, anthrapyrimidine pigment, azomethine pigment, anthraquinone pigment, monoazo pigment, monoazo pigment, diazo pigment, benzimidazolone pigment, quinacridone pigment, quinophthalone pigment, diketopyrrolopyrrole pigment, dioxazine pigment , Flavanthrone pigments, indanthrone pigments, indolinone pigments, isoindoline pigments, isoindolinone pigments, thioindigo pigments, metal complex pigments, perinone pigments, perylene pigments, pyranthrone pigments, phthalocyanine pigments, thioindigo pigments, triarylcarbonium pigments, or Metal complex pigments and the like can be mentioned.

  Other organic pigments are not particularly limited, and examples thereof include C.I. I. (Color Index) Pigment Yellow 93, C.I. I. Pigment Yellow 95, C.I. I. Pigment Yellow 138, C.I. I. Pigment Yellow 139, C.I. I. Pigment Yellow 155, C.I. I. Pigment Yellow 162, C.I. I. Pigment yellow 168, C.I. I. Pigment Yellow 180, C.I. I. Pigment Yellow 183, C.I. I. Pigment red 44, C.I. I. Pigment red 170, C.I. I. Pigment red 202, C.I. I. Pigment red 214, C.I. I. Pigment red 254, C.I. I. Pigment red 264, C.I. I. Pigment red 272, C.I. I. Pigment red 48: 2, C.I. I. Pigment red 48: 3, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment green 7, C.I. I. Pigment Blue 15: 1, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Violet 19 and the like.

  The dye is not particularly limited, and examples thereof include disperse dyes and oil dyes used for resins.

Among the above-mentioned, particularly preferred as the appearance improving agent contained in the resin molded product of the present embodiment are inorganic pigments, particularly metal powder pigments, which are highly effective.
The said appearance improving agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the appearance improving agent is not particularly limited, but is preferably 0 parts by mass to 15 parts by mass with respect to 100 parts by mass of the resin contained in the crystalline resin composition, and 0 parts by mass to 12 parts by mass. It is further more preferable that it is a mass part, and it is more preferable that it is 0 mass part-10 mass parts. If the content of the appearance improving agent is within the above range, the effects described later can be sufficiently exhibited.

  Some appearance improvers have poor dispersibility, and due to the combination of the appearance improver and the resin, compounding concentration, molding conditions, etc., color unevenness may be observed in visual appearance observation. Therefore, in order to uniformly distribute the appearance improving agent in the resin composition, a dispersion aid may be further blended. Alternatively, a colorant concentrate (masterbatch) obtained by mixing a high concentration of an appearance modifier with a polymeric carrier or the like may be used. Further, in order to enhance the stability of the resin composition at the time of coloring, a heat stabilizer or the like may be contained in the appearance improving agent.

  Since the crystalline resin molded product of the present embodiment contains an appearance improving agent, it is possible not only to obtain a resin molded product having improved productivity and durability but also to improve the lightness, as well as color. There are cases where it is possible to obtain a resin molded product in which the appearance such as unevenness or flow mark is improved.

[Other additives]
The crystalline resin molded product according to the present embodiment is not limited to the following as other additives, but, for example, an antioxidant, a stabilizer, a weather (light) agent, a lubricant / releasing agent, a conductive agent An agent, an antistatic agent, etc. may be included.
The other additives may be used alone or in combination of two or more.

  The total content of the other additives is not particularly limited, but is preferably 0.01 parts by mass to 10 parts by mass with respect to 100 parts by mass of the resin contained in the crystalline resin composition, and 0 The content is further preferably 0.55 parts by mass to 8 parts by mass, and more preferably 0.1 parts by mass to 5 parts by mass.

[Polyacetal resin composition]
In particular, when the crystalline resin molded article of the present embodiment is used for a mechanical component or a design component, the crystalline resin composition is a polyacetal resin composition from the viewpoint of its chemical characteristics, mechanical characteristics, dimensional stability, etc. Is preferred.
The polyacetal resin composition which concerns on this embodiment contains polyacetal resin as an essential resin component. The polyacetal resin may be a homopolymer, a copolymer, or a combination thereof.
The content of the polyacetal resin is 70% by mass to 100% by mass, preferably 75% by mass to 100% by mass, with respect to 100% by mass of the resin contained in the polyacetal resin composition, and 80% by mass. More preferably, it is% to 100% by mass.

The polyacetal resin composition according to the present embodiment may be made of other crystalline resin, non-crystalline resin, and thermosetting resin as an optional resin component as long as the crystalline resin molded body obtained by molding has a skin layer. It may include one or more selected. Specifically, the polyacetal resin composition according to the present embodiment may contain another crystalline resin alone as an optional resin component, or may contain an amorphous resin alone, or a thermosetting resin alone. And other crystalline resin and non-crystalline resin, combination of other crystalline resin and thermosetting resin, combination of non-crystalline resin and thermosetting resin, or other crystalline resin A non-crystalline resin and a thermosetting resin may be included.
The content of these optional resin components is 0% by mass to 30% by mass, preferably 0% by mass to 25% by mass, with respect to 100% by mass of the resin contained in the polyacetal resin composition. More preferably, it is 0% by mass to 20% by mass.

As the other crystalline resin, among the specific examples of the crystalline resin described above, any one may be used alone, or two or more may be used in combination, except for the polyacetal resin.
As a non-crystalline resin, any one of the specific examples of the non-crystalline resin described above may be used alone, or two or more types may be used in combination.
As the thermosetting resin, any one of the specific examples of the thermosetting resin described above may be used alone, or two or more may be used in combination.

When the crystalline resin composition which comprises the crystalline resin molding of this embodiment is a polyacetal resin composition, the melt flow rate (MFR) of the said polyacetal resin composition is 1.5 g / 10 minutes or more and 33 g / 10. It is preferable that it is a minute or less, more preferably 1.6 g / 10 minutes or more and 32 g / 10 minutes or less, and still more preferably 1.7 g / 10 minutes or more and 20 g / 10 minutes or less.
The melt flow rate of this polyacetal resin composition is measured in accordance with ISO 1133 (condition D, temperature 190 ° C.).
The melt flow rate polyacetal resin composition of the above-mentioned range can be obtained by balancing the polymerization catalyst of the polyacetal resin and the chain transfer agent, or adjusting the addition amount of the various additives.
When the resin composition constituting the resin molded product of the present embodiment is a polyacetal resin composition, the balance between productivity and durability sufficient for practical use is maintained by setting the above preferable melt flow rate, and lightness is achieved. It shows a tendency that can be enhanced.

  As the crystalline resin composition according to the present embodiment, a crystalline resin molded body may be used. For example, flakes obtained by pulverizing the already produced crystalline resin molding may be used as a crystalline resin composition, and a part of the flakes may be added to the newly obtained crystalline resin composition. You may use it.

  The crystalline resin molded product of the present embodiment tends to maintain a balance between productivity and durability sufficient for practical use and to be able to enhance lightweight by using the above-described preferable crystalline resin composition.

[Method for producing resin molded product]
The method for producing a resin molded product of the present embodiment includes in-mold meat theft molding. The in-mold meat theft molding refers to a molding method which performs a lightening process in which holes are formed before the resin composition filled in the mold is completely solidified during injection molding. More specifically, in injection molding, the step of filling the resin composition in a mold set to a mold temperature lower by 5 ° C. to 80 ° C. than the melting point or the softening point of the resin composition, and at least Forming a hole in the mold when the central portion is in a molten state. Thereby, in a hole having two or more holes and having a half or more hole, the maximum valley depth Rv of the peripheral region within 5 mm from the edge of the hole opening is 30 μm or less, and the resin has a skin layer on the inner wall of the hole It shows a tendency to obtain a molded body. Moreover, in the manufacturing method of this embodiment, it is preferable to fill a resin composition from the resin inflow part (gate part) of only one place. Further, in the manufacturing method of the present embodiment, it is preferable to form the holes by using ejector compression injection molding and / or injection compression molding as injection molding. In the manufacturing method of this embodiment, it is preferable to further include the step of continuing the supply of the resin composition by injection pressure after forming the holes.

  The manufacturing method of the present embodiment includes injection molding of the resin composition to form a resin molded body. As an injection molding method, for example, usual injection molding (normal molding), ejector compression molding, injection compression molding, decoration molding, multicolor molding, gas assist injection molding, foam injection molding, low pressure molding, ultra thin wall injection molding It can be molded by any of injection molding methods such as (super high speed injection molding), in-mold composite molding (insert molding, outsert molding), hot runner molding and the like, and some may be combined. In particular, from the viewpoint of productivity, it is preferable to use a combination of ejector compression molding, injection compression molding, and hot runner molding.

FIG. 1 shows an example of a normally molded gear in which a resin molded body uses a mold having no meat theft except an axial hole.
Further, FIG. 2 shows an example of a gear by normal molding in which holes are formed in the resin molded body in addition to the axial holes from the start of injection molding, that is, a mold having a thickness of 30%.

Here, as injection molding technology, normal molding which is a manufacturing method of the gear shown in FIG. 1 and FIG. 2 will be described.
The normal molding is a general injection molding, in which a resin heated to a temperature to be softened is pressed into a mold under an injection pressure and filled in a mold to obtain a molded body. An injection molding machine is used for injection molding, which has an injection unit and a mold clamping unit. In the injection unit, the resin supplied from the hopper is heated and melted, and the amount of resin necessary for the molded body is measured and injected. At this time, the molten resin having exited the injection unit tip (nozzle) enters the mold from the sprue, passes through the runner gate, and is filled in the cavity, that is, the cavity formed in the shape of the molded body. The filling is controlled by the injection pressure (holding pressure) after controlling the injection speed, and the inside of the cavity is filled with the resin. In the mold clamping unit, the mold is closed with a mold clamping force higher than the injection pressure using a mold capable of temperature control, the molten resin filled in this state is cooled, the molten resin is solidified, and the mold is opened. After that, the molded body is ejected (ejector), and the molded body is taken out of the mold. In this way, it is possible to obtain a molded body in the shape of a cavity of a mold.

On the other hand, FIG. 3 shows an example of a gear manufactured using the method for manufacturing a resin molded product of the present embodiment. The surface property of the resin molding by in-mold thickness theft molding as shown in FIG. 3 tends to be improved as compared with the resin molding in which weight reduction is achieved using a mold having a thickness theft as shown in FIG. Show.
Hereinafter, the manufacturing method of the present embodiment will be described more specifically.

The resin composition used for the manufacturing method of this embodiment contains resin as an essential component.
The resin contained in the resin composition is not limited to crystalline resin, and non-crystalline resin may be used. For example, a thermoplastic resin or a thermosetting resin can be used.

  Examples of the thermoplastic resin include, but are not limited to, polyolefin (PE, PP), polyvinyl chloride (PVC), polyvinylidene chloride, polystyrene (PS), polyvinyl acetate (PVAc), polyurethane (for example) PUR), acrylonitrile butadiene styrene resin (ABS), acrylonitrile nitrile resin (AS), acrylic resin (PMMA etc.), polyamide (PA), polyacetal resin (POM), polycarbonate (PC), modified polyphenylene ether (m-PPE) , Polyester (PET, PBT, etc.), cyclic polyolefin, polyphenylene sulfide (PPS), fluorocarbon resin (PTFE, etc.), polysulfone (PSF), polyether sulfone (PES), amorphous polyarylate (PAR), liquid crystal polymer (LCP), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), thermoplastic polyimide (PI), polyamideimide (PAI), and the like.

As a thermosetting resin, although it is not limited to the following, for example, phenol resin (PF), epoxy resin (EP), melamine resin (MF), urea resin (UF), unsaturated polyester resin (UP) And thermosetting polyurethane (PUR), thermosetting polyimide (PI), alkyd resin and the like.
Although content of a thermosetting resin is not specifically limited, It is 0 mass%-30 mass% with respect to 100 mass% of resin contained in a resin composition, It is preferable that it is 0 mass%-25 mass%. And 0% by mass to 20% by mass.

The resin composition used in the manufacturing method of the present embodiment may contain, as optional components, fillers, appearance improvers, other additives, and the like. The filler, the appearance improving agent, and the other additives are not particularly limited, and, for example, those of the type described above for the crystalline resin composition may be used at the above-mentioned content.
Moreover, you may use the crystalline resin composition mentioned above, for example, a polyacetal resin composition etc., as a resin composition used for the manufacturing method of this embodiment.

In the manufacturing method of the present embodiment, the resin composition is molded by setting the mold temperature at the time of injection molding to a temperature 5 ° C. to 80 ° C. lower than the melting point of the resin composition (the softening point for a resin composition without a melting point). . The mold temperature is preferably 10 ° C. to 75 ° C. lower than the melting point or softening point of the resin composition, and more preferably 15 ° C. to 70 ° C. lower.
The melting point or softening point of the resin composition constituting the resin molded product is in accordance with ISO 11357 using a differential scanning calorimeter (DSC: for example, Parkin Elmer company / DSC-2C, NETZSCH company / DSC350, etc.) Ask.
Conventionally, in an attempt to improve the productivity, the mold temperature has been made close to normal temperature, solidification has been quickened, and the gate seal time has tended to be shortened in the molding cycle until the resin molded product is taken out. On the other hand, in consideration of the surface properties of the resin molded product, it is effective to set the temperature to near the melting point or the softening point.
Therefore, in the manufacturing method of the present embodiment, a resin molded product with a balance of productivity and durability sufficient for practical use maintained and the lightness enhanced by molding the resin composition with the mold temperature as the preferable range. Show a tendency to get Depending on the type of resin contained in the resin composition, heat and cool control of the mold may be used in combination with the mold temperature range as the upper limit.

  The manufacturing method of the present embodiment includes the step of forming a hole in the filled resin composition when at least the central part of the filled resin composition is in a molten state. Specifically, at least 80% by mass of a resin composition of at least 80% by mass is filled in a mold with 100% by mass of a resin molded product (hereinafter also referred to as “final formed body”) as a final product. It is preferable to perform in-mold thickness theft forming in the resin composition to form a hole in the mold when the central part is still in a molten state, more preferably 90% by mass or more, and 95% by mass or more Is more preferred. Here, "when at least the central portion of the resin composition is still in the molten state" is a state in which the resin composition filled in the mold is not gate-sealed, and holes are formed in the resin composition in the mold. It does not form a crack when it is formed, and refers to a state in which it is difficult to form a hole due to overload. On the other hand, when the solidification of the resin proceeds at the central portion of the resin composition, cracking occurs at the time of formation of the hole, or overloading occurs at the time of formation of the hole, and formation of the hole becomes difficult.

2. Description of the Related Art Conventionally, there is a manufacturing method (for example, the gear in FIG. 2) in which the above-described normal molding is performed using a mold having a meat theft beforehand. In this conventional manufacturing method, since the resin composition is filled so as to go around the dead part (protruding part) of the mold, a junction of the resin compositions is generated, and this junction is the surface of the resin molded body It causes an increase in roughness (maximum valley depth Rv) and a decrease in durability. Furthermore, when the resin composition contains a filler having a large aspect ratio, the orientation of the filler is disturbed at the junction of the resin compositions, and the tendency of the surface roughness increase and the durability decrease becomes more remarkable.
On the other hand, in the manufacturing method of the present embodiment, more than half of the resin composition filled in the mold is injected after injection of the resin composition into the mold proceeds to a certain extent. By performing in-mold meat stealing to form a hole, it is possible to provide a resin composition excellent in surface smoothness and durability without generating a junction between the resin compositions described above.

In the manufacturing method of the present embodiment, the holes may be formed by compressing and removing the filled resin composition in the thickness direction in the mold using a known power.
Also, the formation of the holes may be performed in one step, or may be performed in multiple steps depending on the number of holes to be formed.

Although not particularly limited, in the manufacturing method of the present embodiment, it is preferable to form the holes by using ejector compression injection molding and / or injection compression molding as injection molding. Specifically, as injection molding, either ejector compression injection molding or injection compression molding may be performed, or both of them may be used in combination.
For example, the hole may be formed in one step or multiple steps using only one of ejector compression injection molding and injection compression molding, and it may be formed in one step or multiple steps using ejector compression injection molding and injection compression molding in combination. You may form a hole

FIG. 11 shows, as an example of the present embodiment, an example of a molding image in which the inside of the mold is stolen by using a horizontal injection molding machine, using ejector compression molding, and devising the timing of compression. The mold shown in FIG. 11 is a two-piece mold composed of a female mold (also referred to as “cavity plate”) and a male mold (also referred to as “core plate”), and the right side is a female mold It is fixed and the left side is movable in male form.
In the ejector compression molding in the manufacturing method of the present embodiment, for example, as shown in (1), the resin composition is filled in a hollow portion (also referred to as a “cavity portion”) inside a completely closed mold; As shown in 2), before the cavity portion is completely filled, a hole-forming ejector pin provided in a male mold is protruded in the direction of the arrow to form a hole in the resin composition. Next, as shown in (3), after the resin composition is completely filled in the cavity by pressure holding, the ejector pin is returned as shown in (4).
In the present specification, the ejector pin is an example of a part that protrudes into a closed mold to form a hole, and any part having the same function may have any name, shape, arrangement position, etc. Absent. Also, the ejector pin may be provided in either the male or female mold, or may be provided in both the male and female mold.
The mold may be a mold in which the female mold is movable and the male mold is fixed.

FIG. 12 shows, as another example of the present embodiment, an example of a molded image in which mold internal thickness theft is performed using a horizontal injection molding machine, using injection compression molding, and devising the timing of compression. The mold shown in FIG. 12 is also a two-piece mold composed of a female mold (also referred to as “cavity plate”) and a male mold (also referred to as “core plate”), and the right side is a female mold It is fixed and the left side is movable in male form.
In the injection compression molding in the manufacturing method of the present embodiment, for example, as shown in (1), the resin composition is filled in the cavity part of a semi-closed mold which is not completely closed, as shown in (2) Then, while moving the male mold in the female mold direction and performing mold clamping, holes are formed in the resin composition in the cavity with the male mold projecting portion (the meat theft portion). Next, as shown in (3), after the resin composition is completely filled in the cavity by solidification or the like and solidified, as shown in (4), the male mold is returned and the mold is opened, and the resin molded body Take out.
The mold may be a mold in which the female mold is movable and the male mold is fixed.
Moreover, the protrusion part which forms a hole in a resin composition may be equipped with any one of male type and female type, and may be equipped with both male type and female type.

  The combined use of the ejector compression injection molding and the injection compression molding is not particularly limited. For example, as shown in FIG. 12 (1), the resin composition is filled in a state in which the mold having the projecting portion is semi-closed, The embodiment in which the ejector pin shown in FIG. 11 (2) is ejected before the mold clamping in FIG. 12 (2) and the ejector pin shown in FIG. 11 (2) at the same time while the mold clamping in FIG. And the like.

Also, the tip of the part or part forming the hole by compressing and removing the filled resin composition, such as the ejector pin and the projecting part (the meat theft part) mentioned above, is butted as shown in FIG. Although a shape may be used, a tip shape may be devised. For example, as shown in FIGS. 4 to 6, asperities that form holes may be provided.
The mold shape of the part (receiving part) positioned in the direction in which the part or part forming the hole projects is the same as that of the tip as shown in FIGS. 4 to 6, as shown in FIG. Alternatively, the receiving portion may be temporarily inserted into the inside.

In the resin molded product, the surface on which the holes are formed is not particularly limited, and examples thereof include flat surfaces, curved surfaces, cut-off portions, and tapered portions.
Cavities (discarded cavities) other than the final molded product may be attached to the formation of the holes in the mold. After releasing the mold, the dumping cavity may be removed by an impact at the time of mold opening, or may be removed mechanically by using a three-piece mold or by providing a dumping resin in the dumping cavity to the mold. .
By utilizing the above-mentioned molding method, the surface properties of the resin molded product are improved, and a balance between productivity and durability sufficient for practical use can be maintained, and a tendency to be able to increase the lightness is exhibited.

  In the manufacturing method of this embodiment, it is preferable that the resin inflow portion (gate portion) to the mold product portion at the time of injection molding be one place. Here, the resin inflow portion is a portion where the resin composition injected and melted from the injection molding machine nozzle passes through the sprue and the runner and enters the mold product portion (product cavity / mold cavity of the resin molded body). It means that. Although the type of the resin inflow portion is not limited to the following, for example, direct gate, side gate, pin gate, film gate, sleeve gate, valve gate and the like can be mentioned. The term “tub gate”, “fan gate” or the like also refers to the inlet portion where the resin composition flows into the mold product portion. In particular, pin gates, film gates, ring gates, sleeve gates and the like are preferable. Furthermore, it is preferable to use a mold structure in which the gate is automatically cut off when the mold is opened.

The image example of the gate design in case a resin molding is a gear is shown to FIGS.
8 shows the case where the gate of the gear is provided with three gates so as to shorten the flow length of the resin, FIG. 9 shows the case where the three points are provided at the rib portion around the shaft hole, FIG. When the ring-shaped film gate provided in the part is provided, the flow path at the time of filling the resin can be further simplified in FIG. That is, in the resin molded product of the present embodiment, the surface property of the resin molded product is improved by bringing the resin inflow portion (gate portion) close to one point or by making it one point, and the productivity and durability sufficient for practical use It shows a tendency to maintain the balance of sexuality and increase the lightness.
Moreover, as for the position of the gate, if the molded body to be manufactured has a point-symmetrical shape, it is preferable that the shape closer to the center of the molded body is good because the surface property of the molded body is good.

In the manufacturing method of the present embodiment, after forming the holes, it is preferable to continue the supply of the resin composition by injection pressure. The holes are formed, and the remaining resin composition is filled and shaped by injection pressure. At this time, the maximum injection pressure is set, injection molding is performed at a primary pressure below this, and after forming a hole in the mold, 70% or more of the primary pressure or depending on the shape of the resin molding or the shape of the gate It is preferable to complete the filling of the resin composition at the above pressure to obtain a resin molded product. In the conventional injection molding, pressure is applied to fill the molten resin in the mold to some extent, and the pressure is lowered to 60% or less from the maximum injection pressure during holding pressure, and the pressure is maintained for a while to deform or crack the gate. The filling was often completed while suppressing the
Therefore, in the manufacturing method of the present embodiment, it is preferable to obtain the resin molded body with a high filling pressure even at the time of holding pressure in order to improve the mold transfer of the resin molded body while confirming that burrs are not generated. In the manufacturing method of the present embodiment, by performing injection molding under the above conditions, a balance between productivity and durability sufficient for practical use can be maintained, and a tendency can be obtained to obtain a resin molded product with enhanced lightness. .

  Moreover, when the manufacturing method of this embodiment uses ejector compression molding and / or injection compression molding, it is preferable to fill a resin composition using the nozzle which has a shut-off mechanism. In ejector compression molding and / or injection compression molding, the pressure in the mold may exceed the injection pressure when the resin composition is filled and enters the compression step. In such a case, shutoff is performed to prevent backflow of the resin composition. It is preferred to use a nozzle having a mechanism or a mold of the same mechanism. In some cases, 100% by mass or more of the resin composition of the final molded body is pre-filled. Moreover, when it exceeds 100 mass%, it is necessary to provide a cavity part (discarded cavity part) other than the shape of the required final molded body. The resin molded product manufactured by the manufacturing method of the present embodiment can apply a higher pressure to the molten resin by using these mechanisms, and therefore, maintains a balance of productivity and durability sufficient for practical use. Show a tendency to be able to increase the lightness.

[Crystalline resin molding]
The crystalline resin molded product according to the present embodiment has two or more holes, and the maximum valley depth Rv of the peripheral region within 5 mm from the edge of the opening at the opening of the hole of more than half is 30 μm or less It has a skin layer on the inner wall of the extra hole. Moreover, it is preferable that the said resin molding has a resin inflow part (gate part) of only one place.
In the case of two or more holes, the combination of the above techniques tends to provide better effects.

  Hereinafter, the crystalline resin molded product of the present embodiment will be more specifically described.

The crystalline resin molded product of the present embodiment has two or more holes in order to increase the lightness and dimensional accuracy or to impart another function by meat theft.
The holes in the present embodiment may be through holes (for example, shaft holes) or non-through holes (for example, boss holes), and two or more of the resin moldings of the present embodiment have The holes may be all through holes, all non-through holes, or a combination of through holes and non-through holes.
The holes in the present embodiment include holes for achieving the functions originally possessed by the crystalline resin molded body, as well as holes unrelated to the functions. More specifically, it includes a hole for joining to another part such as a shaft hole and the like, and also a hole for weight reduction and the like such as a meat theft hole and the like.
The three-dimensional shape (three-dimensional shape) inside the hole (dent) is not particularly limited, and may be a cylindrical shape, a rectangular shape, or any other three-dimensional shape. When the hole is a non-through hole, the bottom of the hole may have any planar shape (two-dimensional shape).

Moreover, the opening in this embodiment means the entrance part of a hole which exists on the surface of a crystalline resin molding.
When the hole in the present embodiment is a non-through hole, the longest depth from the opening to the bottom of the hole is 0.5 mm or more. Here, the longest depth is the longest distance among the distances obtained by measuring the depth of the recess in the vertical direction from the plane in contact with the edge of the opening at any two or more points.
In addition, the opening of the hole has a closed shape on the surface of the resin molded body. Thus, for example, notches in gear teeth etc. are excluded from the holes.
The shape (two-dimensional shape) of the opening is not particularly limited, and may be circular, rectangular, ring-shaped, or any other shape.

The resin molded product of the present embodiment has a maximum valley depth Rv of 30 μm or less in the surface smoothness of the peripheral region within 5 mm from the edge of the opening of the hole for a hole of more than half.
Here, the peripheral area within 5 mm from the edge of the opening of the hole means a peripheral area surrounded by a distance of 5 mm outward from the edge of the opening of the hole.

  In the surrounding area within 5 mm from the edge of the opening of one hole, the maximum valley depth Rv is measured on the same plane as much as possible with respect to the opening. For example, in the gear as shown in FIG. 2, when the opening of one hole is in the web, the measurement position is selected in the peripheral region of the opening on the web surface. If the hole is an axial hole, the measurement position is selected in the peripheral area on the rib surface located around the opening of the axial hole.

More than half of the holes in the resin molded product of the present embodiment means two if the number of holes is two, and three or more if the number is four. For example, in the case of a gear as shown in FIG. 2, there are 18 holes in the web and 19 in the axial hole, so more than half, ie, 10 or more holes in this embodiment are conditions of surface smoothness. Meet the
If the holes are non-through holes, measure the maximum valley depth Rv in the surrounding area within 5 mm from the edge for all hole openings.
When the hole is a through hole, the maximum valley depth Rv in the peripheral region within 5 mm from the edge may be measured for any one of the two openings.

  The maximum valley depth Rv of the surface smoothness of the peripheral region of the opening is the “maximum valley depth Rv of the roughness curve” defined in JIS B 0601: 2013. For the evaluation, a contact-type surface roughness meter (for example, “Surfcom Series” manufactured by Tokyo Seimitsu Co., Ltd., “Surftest Series” manufactured by Mittoyo Co., Ltd., etc.) or a laser microscope type non-contact type surface roughness A scale (for example, "VR series" manufactured by Keyence Corporation, "Opterix Series" manufactured by Lasertec Corporation, etc.) can be used. Roughness curve determined from the obtained cross-sectional curve by measuring the surface roughness at any position with the same distance from the edge within the peripheral region within 5 mm from the edge of the opening with these surface roughness testers The maximum valley depth Rv is 30 μm or less, preferably 16 μm or less, more preferably 10 μm or less, and still more preferably 4 μm or less. The lower limit of the maximum valley depth Rv is 0 μm.

FIG. 13 shows an example of the measurement site around the meat theft of the resin molded body.
One hole was selected from the left drawing of FIG. 13 and the maximum valley depth Rv of the surrounding area within 5 mm from the edge of the opening of the hole was measured as shown in the right drawing of FIG. Open hexagons indicate measurement sites when the probe (probe) of the surface roughness meter moves linearly. The vertical distance from the apex of the hexagon to the edge of the opening of the hole is less than 5 mm.
Moreover, the measurement example about two sides shown by the white arrow in FIG. 13 right figure is shown in FIG.14 and FIG.15.
FIG. 14 is a roughness curve obtained by measuring the upper left oblique side of the hexagon in FIG. 13 right figure. In this measurement portion, since streaky flow marks are included, a large valley of 30 μm or more corresponding to the flow mark portion is recognized in the roughness curve.
On the other hand, FIG. 15 is the roughness curve which measured the upper side part of the hexagon of FIG. 13 right figure. Since the measurement portion does not include the flow mark, the roughness curve has no noticeable valley.

  Also, in the case of a hole formed by using a mold having a meat theft in advance, such as the shaft hole of the gear shown in FIG. 1 or the shaft hole or the meat theft hole of the gear shown in FIG. Since the resin composition is filled so as to wrap around the (protrusion part), the junction of the resin compositions occurs around the hole, and the maximum valley depth Rv of the area around the opening of the hole exceeds 30 μm. Increase. Furthermore, when the resin composition contains a filler with a large aspect ratio, the orientation of the filler is disturbed at the junction of the resin compositions, so the tendency of increase in maximum valley depth Rv and decrease in durability is more remarkable. Become.

On the other hand, as in the gear shown in FIG. 3, the resin composition is formed around the meat theft hole by performing in-mold thickness stealing to form a hole of more than half in the resin composition filled in the mold in the middle of the injection molding. The maximum valley depth Rv of the peripheral region of the opening of the hole can be set to 30 μm or less without generating a junction between the objects.
That is, in the crystalline resin molded product of the present embodiment, the hole having the maximum valley depth Rv of 30 μm or less in the peripheral region within 5 mm from the edge of the opening was previously formed using a mold having a thickness theft. It can be said that it is not a hole but a hole formed by in-mold meat theft or a hole formed by post-processing.

  As described above, by setting the maximum valley depth Rv of the peripheral region within 5 mm from the opening of the resin molded product to be in the above range, the resin molded product of the present embodiment has a balance of productivity and durability sufficient for practical use. Can be maintained and lightened.

  The surface state in which the opening of the hole of the crystalline resin molded body is present may be glossy or may be subjected to various embossing, and the state is the whole or a part of the crystalline resin molded body It does not matter. And when a crystalline resin molding has an embossed part, a level | step-difference part, etc. by design or functional provision, this influence is substantially eliminated and it carries out. Therefore, a roughness curve in which the undulation is removed at a cutoff of 0.2 to 1.2 from the cross-sectional curve is used, or the level portion is measured separately for the high and low portions.

Moreover, the crystalline resin molded product of the present embodiment has a skin layer on the inner wall of the half or more holes. The skin layer refers to a portion formed by suppressing the growth of the resin crystal by the molten resin contained in the resin composition being brought into contact with the mold and quenched when injection molding is performed. .
The result of having observed the crystal state of the cross section of the hole formed in FIG. 16 using in-die meat theft molding as a meat theft by 50 times with a polarization microscope is shown. The skin layer is observed with a thickness of about 10 μm to several hundreds of μm as a layer bordered on the surface layer portion of the inner wall of the hole touched to the mold as shown in FIG.

  The skin layer can be confirmed by observing the crystal state of the cross section of the hole with a polarizing microscope as described above. In addition, the skin layer has a lower melting point or a lower density than the portion where the resin crystal has grown (for example, the central portion of the slowly cooled molded body) by suppressing the crystal growth of the resin. Therefore, it can also be confirmed by measuring these.

In the prior art, after obtaining a resin molded product by injection molding, there are cases where a meat theft hole for weight reduction is provided by mechanical post-processing or the like, but the inner wall of the hole generally provided by a post-processed product However, since there is no contact between the molten resin and the mold, no skin layer formed by melting and quenching of the resin can be seen.
That is, in the crystalline resin molded product, the hole having the skin layer on the inner wall is not a hole provided by post processing or the like, but a hole formed by in-mold meat theft or a mold having the thickness theft beforehand. It can be said that the hole is formed.

  That is, in the crystalline resin molded product according to the present embodiment, the maximum valley depth Rv of the peripheral region within 5 mm from the edge of the opening is 30 μm or less, and more than half of the holes have a skin layer on the inner wall, It can be said that it is a hole formed by in-die meat theft.

  The crystalline resin molded product of the present embodiment has no trace by machining, and the burr tends to be reduced. Furthermore, since the post-processed product is provided with a hole after obtaining a resin molded product on which ordinary injection molding has been performed, productivity is reduced as compared with one injection molding.

  Moreover, it is preferable that the crystalline resin molding of this embodiment has a resin inflow part (gate part) of only one place. When the resin inflow portion (gate portion) is only at one place, the surface property of the crystalline resin molded product is improved, and a balance between productivity and durability sufficient for practical use can be maintained, and lightness can be enhanced. Show a trend.

  Moreover, in the crystalline resin molded product of the present embodiment, when the thickness of the thinnest portion is 0.5 mm or more, the effect of enhancing the lightness of the present invention tends to be more exhibited. Furthermore, the thickness of the thinnest portion is more preferably 0.8 mm or more, and particularly preferably 1.0 mm or more. When the thickness of the thinnest part of the resin molded product is the above, the crystalline resin molded product of the present embodiment tends to maintain a balance between productivity and durability sufficient for practical use, and can enhance lightness. Indicates

  The crystalline resin molded article according to the present embodiment is not particularly limited, but in the method for producing a resin molded article described above, the crystalline resin composition described above is used as the resin composition, and more than half of the holes are cut by internal thickness theft. By forming, it can manufacture suitably.

〔Use applications〕
The resin molded product according to the present embodiment, when used for mechanical parts and / or design parts, maintains a balance between productivity and durability sufficient for practical use, and has the effect of showing a tendency of being able to enhance lightness. It is expressed.

  Examples of mechanical components in which the resin molded body of the present embodiment is used include components with mechanical motion, components for transmitting and converting motion, components for joining, and the like. The parts that involve mechanical movement and the parts that transmit and convert movement are parts that emit their functions by rotational movement or linear movement, and the shape is not limited. The movement here includes rotational movement, forward / reverse movement, intermittent rotational movement, linear movement, continuous movement, intermittent movement, reciprocating movement, or a combination of these, and the like. The parts to be joined include parts having a fitting mechanism that utilizes a reaction force generated by deformation of part or all of the parts. The resin molded product of the present embodiment may be the entire mechanical component or may be a part of the mechanical component.

  Design parts in which the resin molded product according to the present embodiment is used mainly refer to parts equipped and used outside the product and parts installed in places visible from the outside, but parts according to this also Color and flow marks affect the quality of parts and products or include parts that are being tested for these. The resin molded product of the present embodiment may be all or part of a design part.

  As mechanical parts and / or design parts in which the resin molded body of the present embodiment is used, vehicle parts (for example, parts such as railways and automobiles), electric / electronic parts (for example, OA equipment or music / video, information equipment, Parts provided in communication equipment etc.) Industrial parts (eg parts provided in FA equipment etc. such as transport and assembly and their peripheral parts), parts of medical equipment, health appliances and beauty equipment, furniture and design interior equipment and housing Parts such as equipment and accessories, household goods (parts such as clothes, shoes, hats and other clothing items, cosmetics, parts such as toys, stationery and sporting goods) may be mentioned.

  Hereinafter, the present invention will be described by way of examples and comparative examples, but the present embodiment is not limited to the following examples.

  In Examples and Comparative Examples, polyacetal resin used for mechanical parts and design parts was used as a resin composition constituting a resin molded body. The polyacetal resin composition used for evaluation, the method for producing a resin molded product, the basic evaluation of the resin molded product, and the performance evaluation of the resin molded product will be sequentially described below.

[Polyacetal resin composition (P)]
As raw materials for preparing the polyacetal resin composition (P), the following (A) polyacetal resin, (B) filler or pigment, and (C) other additives were used.

((A) Polyacetal resin)
(Polymerization process)
A jacketed self-cleaning type twin-screw paddle type continuous mixing reactor (screw diameter 3 inches, length to diameter ratio (L / D) = 10) through which a heat medium can be passed was adjusted to 80.degree. 3750 g / hr of trioxane as the main monomer and about 1.33 g / hr of 1,3-dioxolane as the comonomer were continuously fed to the continuous mixing reactor so that the oxyethylene group was 1.35 mol% with respect to the oxymethylene group. . Moreover, the chain transfer agent (methylal) was adjusted so that the resin composition of the melt flow rate (MFR) shown in Table 1 could be obtained in the range of 1 to 20 g / hr, and was continuously fed to the continuous mixing reactor. . A 1 mass% cyclohexane solution of boron trifluoride di-n-butyl etherate as a polymerization catalyst was added to the continuous mixing reactor so that the catalyst was 2.0 × 10 ⁻⁵ mol with respect to 1 mol of trioxane. The polymerization was carried out to obtain polymerized flakes.
(Terminal stabilization process)
The obtained polymerized flakes were pulverized, and then the pulverized product was charged into a 1% by mass aqueous solution of triethylamine and stirred for 1 hour to deactivate the polymerization catalyst. Thereafter, an aqueous triethylamine solution containing the polymerized flakes was filtered by a centrifuge and dried at 120 ° C. for 3 hours under nitrogen to obtain a dried polymer.
Next, terminal stabilization was carried out as follows using the obtained dried polymer. The obtained dry polymer is added to the front part of a vented screw type twin screw extruder (manufactured by Plastic Engineering Research Institute, Inc., BT-30, L / D = 44, setting temperature 200 ° C., rotation speed 80 rpm) Furthermore, 0.5 parts by mass of water was added to 100 parts by mass of the dry polymer, and the pressure reduction was performed while stabilizing the polymer end, to obtain a stabilized polyacetal resin (A).
(Granulation process)
The resulting stabilized polyacetal resin (A) was dried for 12 hours after confirming that the product temperature was 100 ° C. or higher in a gear oven (set at 105 ° C.) under a nitrogen atmosphere.
As the other additives, the following (C1) and (C2) were mixed in a Henschel mixer for 1 minute at 2: 1. A screw type twin screw extruder with a vacuum vent (manufactured by Plastic Engineering Laboratory, Inc., BT, so that the obtained mixture is 0.4 parts by mass with respect to 100 parts by mass of the stabilized polyacetal resin (A) -30, L / D = 44, L: Distance from the material feed port to the discharge port of twin screw extruder, D: Inner diameter of twin screw extruder), screw rotation speed is 100 rpm, 22 amps or less from die It melt-kneaded so that molten resin temperature might be 205 +/- 2 degreeC, and the pellet of polyacetal resin as shown in Table 1 containing (C) other additives was obtained.
The operation was performed so as to avoid the mixing of oxygen from raw material feeding to polyacetal resin pellet collection.

((B) filler or pigment)
(B) The following (B1)-(B3) were used as a filler or a pigment.
(B1): Boron nitride made by Denki Kagaku Kogyo Denka boron nitride (SP-2 average particle size 5 μm / filler)
(B2): Carbon black Denka black (inorganic pigment / black pigment) manufactured by Denki Kagaku Kogyo Co., Ltd.
(B3): Aluminum Silbeads (registered trademark) M050-AP (inorganic pigment / metal powder pigment) manufactured by Asahi Kasei Metals Corporation

((C) Other additives)
(C) The following (C1) and (C2) were used as other additives.
(C1): Antioxidant / Irganox 245 (Ciba Specialty Chemicals Co., Ltd.)
(C2): heat stabilizer / H-3 (manufactured by Asahi Kasei Finechem Co., Ltd.)

<Production of Polyacetal Resin Composition (P)>
The manufacturing process of the polyacetal resin composition (P) used for the Example and the comparative example is demonstrated. After mixing the pellet of polyacetal resin containing the above (C) other additives and (B) filler or pigment in the ratio of Table 1, a vented screw type twin screw extruder (manufactured by Plastics Industrial Research Institute, Inc.) The mixture is melt-kneaded at 24 amps using BT-30, L / D = 44, preset temperature = 200 ° C., rotation speed = 100 rpm) to obtain a pellet-like sample of polyacetal resin composition (P). The
In addition, the resin composition P1 was manufactured only from the pellet of polyacetal resin (A) containing (C) other additives, and did not mix the (B) filler or the pigment.
Resin compositions P2 to P4 are obtained by adjusting the addition amount of a chain transfer agent (methylal) at the time of polymerization of polyacetal resin (A), and have different melt flow rates from resin composition P1 (C) and other additives It manufactured using only the pellet of polyacetal resin (A) containing, (B) filler or the pigment was not mixed.
For resin compositions P5 to P7, pellets of polyacetal resin (A) containing the same (C) other additives as used in resin composition P1 are mixed with (B) filler or pigment shown in Table 1 Manufactured.
The melting point of the obtained pellet was determined in accordance with ISO 11357 using a differential scanning calorimeter (manufactured by NETZSCH / DSC 350). All polyacetal resin compositions had melting points between 165-166 ° C.

[Method for producing resin molded product]
The resin molded product is produced using an injection molding machine (FANUC Roboshot (registered trademark) i50B type, manufactured by FANUC CO., LTD.) Using the polyacetal resin composition (P) at a cylinder temperature of 200 ° C. and a maximum injection pressure of 500 kgf. / Cm ² , and the mold temperature was set at the set temperature shown in Table 1. As the pressure holding time and the cooling time, it was carried out while confirming that the resin composition was sufficiently charged up to 30 seconds and no burr was generated.
The shape of the resin molding used, the injection molding method, and the mold gate design will be described below. Table 1 below shows the shape of the molded product, the manufacturing method (molding method / mold temperature), and the gate design when manufacturing each resin molded product of [Example] and [Comparative Example].
(Shape of molded body)
Shape of molded body A: Spur gear as shown in FIG. 1 (element: module m = 0.8, number of teeth Z = 50, tooth thickness b = 5 mm, web thickness = 2 mm, shaft hole diameter = 8 mm, shaft Rib around the hole = 2 mm)
Shape of molded body B: Spur gear having a shape as shown in FIG. 2 (sheet: module m = 0.8, number of teeth Z = 50, tooth thickness b = 5 mm, web thickness = 2 mm, shaft Hole diameter = 8 mm, shaft hole peripheral rib = 2 mm, diameter 3 mm × 14 locations and diameter 2.5 mm × 4 locations in a round shape)
(Injection molding method)
Molding method A-1: Normal molding using a mold without meat theft (injection, injection pressure 95% of the pressure, cooling)
Molding method A-2: Normal molding using a mold with meat theft (injection, injection pressure 95% of the pressure, cooling)
Forming method B ... as shown in Fig. 11: In-mold meat theft forming (Ejector compression molding: injection · 98% by weight filled with the theft performed by the ejector pin · retention pressure 95% of the injection pressure · cooling)
(Mold gate design)
Gate A: 1.2Φ × 3 pin gate gates B at a position 20 mm in diameter from the center of gear shaft hole as shown in FIG. 8 A position 10 mm in diameter from the center of gear shaft hole as shown in FIG. 1.2Φ × 3 pin gate gates C at the center of the rib section of the bearing ... Ring-shaped 0.5 mm film at the position of 10 mm in diameter (center of the rib section of the bearing) from the center of the gear shaft hole as shown in FIG. Gate

[Fundamental evaluation of resin moldings]
As a basic evaluation of the obtained resin molded product, the surface property of the resin molded product, the melt flow rate of the resin composition constituting the resin molded product, and the presence or absence of the skin layer at the opening were evaluated as follows.

(Evaluation of surface properties of resin molded products Maximum valley depth Rv)
The surface properties of the resin molded product were evaluated by measuring the maximum valley depth Rv of the peripheral region within 5 mm from the edge of the hole opening as shown in FIG. For measurement of Rv, a contact-type surface roughness tester (Surfcom, manufactured by Tokyo Seimitsu Co., Ltd.) was used. The measurements were carried out for 10 holes, and the maximum value among the obtained 10 Rv measurements is shown in Table 1 below as the measurement result.

(Evaluation of Melt Flow Rate of Resin Composition Constituting Resin Molded MFR)
In the measurement of the melt flow rate of the resin composition which comprises a resin molding, the flakes obtained by grind | pulverizing the obtained polyacetal resin molding were used. The flakes were dried at 80 ° C. for 2 hours in a gear oven (GPH-102, manufactured by Espec Corporation). The melt flow rate of the polyacetal resin composition was measured in accordance with ISO 1133 (condition D, temperature 190 ° C.) using the dried flakes using a melt indexer (F-W01 manufactured by Toyo Seiki Co., Ltd.). The obtained results are shown in Table 1.

(Presence or absence of a skin layer on the inner wall of the hole of the resin molding)
The presence or absence of the skin layer on the inner wall of the hole of more than half of the resin molded product was determined by observing the crystallinity of the cross section of the hole of the resin molded product with a polarizing microscope, as shown in FIG. The observation of crystallinity of the cross section of the hole is performed by cutting a slice perpendicularly to the opening using a microtome (RM2245 manufactured by LEICA), and this is subjected to a magnification of 50 to 100 times with a polarization microscope (DM4000B manufactured by LEICA) The presence or absence of the skin layer on the inner wall of the hole was evaluated. The results are shown in Table 1 below.

[Performance evaluation of resin molded product]
With respect to the resin molded product obtained as described above, the productivity of the resin molded product, the durability of the resin molded product (gear durability), and the lightness of the resin molded product (mass of the molded product) were evaluated as follows.
The evaluation results are shown in Table 1 below.

(Evaluation of productivity of resin moldings)
The evaluation of the productivity of the resin molded product is compared with the time taken from the input of the resin composition which is the raw material to the molding machine of the following reference example 1 to the acquisition of the molded product of the final shape, Specified. Productivity evaluation was performed according to the following evaluation criteria.
Evaluation criteria ◎: Very good compared to Reference Example 1 (time reduction is 10% or more)
○: better than Reference Example 1 (time reduction is 5% or more and less than 10%)
◇: When compared to Reference Example 1, when the level is equivalent (50 seconds) (time reduction is less than 5% or extension is less than 10% / 47.5 to 55 seconds)
Fair: Compared to Reference Example 1, when decreased (time extension is 10% or more and less than 20%)
X: In the case of a large decrease compared to Reference Example 1 (time extension is 20% or more and less than 80%)

(Evaluation of the durability of resin moldings)
In order to evaluate the durability of the resin molded product, a gear durability test was performed. A gear endurance tester that can adjust the distance between the shafts as shown in FIG. 17 for the test, and a suitable motor for driving according to the test conditions, a power absorption type (electromagnetic clutch / brake) gear endurance tester that applies torque The evaluation was performed using a high torque gear endurance tester NS-1 (manufactured by Nakagawa Seisakusho). As shown in the schematic diagram of Fig. 18, the testing machine has a spur metal gear (A) (module: 0.8, Z: 48 mm, tooth width: 10 mm) via the drive motor (a1) and shaft (a2). It is installed and can be operated at any rotational speed. The metal gear (A) and the test gear (B) are engaged with each other at a gear radius of 0.02 mm as an inter-shaft. The test gear (B) is connected to the power absorbing device (b1) via the shaft (b2) and has a structure capable of giving an arbitrary load torque. The test was performed in a constant temperature room at a temperature of 23 ° C. and a humidity of 50%.
The durability of the resin molded product was measured by measuring the life time when rotating at 477 rpm with a torque of 25 kgfcm (the time until the motor can not transmit power because the teeth can be broken and so on), and Evaluated on the basis of Evaluation was performed by n = 3 and made the average value the evaluation value.
AAA: very good (compared to Reference Example 1) (lifetime is over 170%)
AA: very good compared to Reference Example 1 (lifetime 150% or more and less than 170%)
A: Better than Reference Example 1 (lifetime 130% or more and less than 150%)
B: Slightly better than the reference example 1 (lifetime 110% or more and less than 130%)
C: When the level was equivalent (51 hours) to that of Reference Example 1 (life time is 80% or more and less than 110%)
D: Compared to Reference Example 1, when decreased (lifetime less than 80%)

(Evaluation of the lightness (weight of molded body) of resin molded body)
The evaluation of the lightness of the resin molded body was performed by measuring the mass of the resin molded body (the reference example 4 is the mass of a processed product after the opening is provided by machining in addition to the shaft hole). The resulting resin molded product was conditioned for 48 hours in a thermostatic chamber at 23 ° C. and 50% humidity, then weighed, and evaluated according to the following criteria. Evaluation was performed by n = 3 and made the average value the evaluation value.
◎: better than Reference Example 1 (mass less than 95% of Reference Example 1)
◇: Compared to Reference Example 1 (5.08 g), in the same case (mass is 95% or more and less than 105% of Reference Example 1)
X: When it is lower than Reference Example 1 (The mass is 105% or more of Reference Example 1)

The symbols *, ** and *** in Table 1 mean the following.
*: The shape of the molded body is A, and the opening is one axial hole, so the valley depth at the periphery of the axial hole is not measured. Since the opening of the shaft hole was usually formed, the skin layer was confirmed.
**: After the injection molding was carried out, an opening was provided in the post-processing, and it took much more time to obtain a molded product of the final shape as compared to Reference Example 1.
***: Mold release defects from the mold of the molded article frequently occurred, making it difficult to obtain a stable sample.

[Examples 1 to 6, Comparative Examples 1 to 5, Reference Examples 1 to 4]
The performance evaluations of the resin molded products obtained in Examples 1 to 6 and Comparative Examples 1 to 5 and Reference Examples 1 to 4 are shown in Table 1. From this, by setting the maximum valley depth Rv specified by the present application, the resin molded product can maintain the balance of productivity and durability sufficient for practical use, and can enhance the lightness. Moreover, the resin molded object obtained by the manufacturing method prescribed | regulated by this application can maintain the balance of productivity and durability sufficient practically, and can improve lightweightness.
Although the lightness is not enhanced because Reference Examples 1 to 4 are evaluation results of the resin molded product having only the axial hole portion, the tendency that the durability can be enhanced by the kind of the gate is shown. Reference Example 4 is a post-processed product in which the resin molded body having no holes at two or more places obtained in Reference Example 3 is machined into two or more holes. Although this can maintain durability and increase lightness, it can not maintain productivity sufficient for practical use.

[Examples 5, 7 and 9]
The performance evaluations of the resin moldings obtained in Examples 5 and 7 to 9 are shown in Table 1. From this, when the resin composition is a polyacetal resin, by setting it as a preferable melt flow rate (MFR) of the present application, a balance between productivity and durability sufficient for practical use can be maintained, and a tendency to be able to enhance lightweight can be exhibited. .

[Examples 10 to 12 and Comparative Examples 6 to 8]
The performance evaluations of the resin molded products obtained in Examples 10 to 12 and Comparative Examples 6 to 8 are shown in Table 1. From this, even when the resin composition contains a filler or a pigment, a balance between productivity and durability sufficient for practical use can be maintained, and the lightweight can be enhanced.

(A1) ... Drive motor (a2) ... Bearing support (a3) ... Rotation meter (b1) ... Bearing support (b2) ... Power absorbing device (b3) ... Torque Gauge (A) · · · Metal gear (B) · · · Test gear

Claims (11)

It is a crystalline resin molded object which shape | molds a crystalline resin composition,
Have two or more holes,
The crystalline resin molded article, having a maximum valley depth Rv of 30 μm or less in a peripheral region within 5 mm from the edge of the opening of the hole and having a skin layer on the inner wall of the hole in more than half of the hole .   The crystalline resin molding according to claim 1, wherein the crystalline resin composition contains a filler.   The crystalline resin molding according to claim 1, wherein the crystalline resin composition contains an appearance improving agent.   The crystalline resin molding according to any one of claims 1 to 3, which has a resin inflow portion (gate portion) at only one place.   The crystalline resin molding according to any one of claims 1 to 4, wherein the crystalline resin composition is a polyacetal resin composition.   The crystalline resin molding according to claim 5, wherein the melt flow rate (MFR) of the polyacetal resin composition is 1.5 g / 10 minutes or more and 33.0 g / 10 minutes or less. A method for producing a resin molded article, comprising injection molding the resin composition to form a resin molded article,
The following steps in the injection molding:
Filling the resin composition in a mold set at a mold temperature 5 ° C. to 80 ° C. lower than the melting point or softening point of the resin composition;
Forming a hole in the filled resin composition in the mold when at least a central part of the filled resin composition is in a molten state;
A method for producing a resin molded product, comprising:   The manufacturing method of the resin molding of Claim 7 with which the said resin composition is filled in the said metal mold from the resin inflow part (gate part) of only one place.   The method for producing a resin molded product according to claim 7 or 8, wherein the mold temperature is 10 ° C to 75 ° C lower than the melting point or the softening point of the resin composition.   The manufacturing method of the resin molding of any one of Claims 7-9 which forms a hole using an ejector compression injection molding and / or injection compression molding as said injection molding.   The manufacturing method of the resin molding of any one of Claims 7-10 which further include the process of continuing supply of a resin composition by injection pressure after forming the said hole.