JP5829551B2 - Method for producing pellet mixture and resin molded product - Google Patents

Description

  The present invention relates to a mixture of pellets having different shapes, and even if these pellets are shaken and air-mixed, they are in a uniformly mixed state.

  As a method for producing a thermoplastic resin composition containing a thermoplastic resin and an additive, a method of melt-kneading a master batch pellet containing a thermoplastic resin and an additive and a resin pellet is known. In this method, the resin pellets and additives of the thermoplastic resin are not integrated into the molding machine and are added to the thermoplastic resin composition in comparison with the method of kneading to produce the thermoplastic resin composition. It is excellent in that the dispersibility of the agent is improved.

  As a technique using a master batch pellet, Patent Document 1 describes a technique of mixing a master batch pellet that is a polypropylene resin composition and a dilution resin pellet made of a polypropylene resin.

  In patent document 1, it is described as a subject that a masterbatch pellet and a resin pellet are not mixed uniformly. Thus, although the technique using a masterbatch pellet is an excellent technique, it also has drawbacks.

  In the cited document 1, the said subject is solved by adjusting content etc. of the component contained in a masterbatch resin composition.

JP 2003-165847 A

  However, Cited Document 1 is a technique related to polypropylene-based materials, and the technique described in Cited Document 1 cannot be applied to materials other than polypropylene.

  In particular, when the mixture of master batch pellets and resin pellets is shaken or blown, there is a problem that the master batch pellets and resin pellets are not uniformly mixed.

  The present invention is an invention made to solve the above problems, and even if a mixture of a plurality of types of resin pellets is subjected to, for example, shaking mixing or air blowing regardless of the type of material used, these pellets An object of the present invention is to provide a pellet mixture that is uniformly mixed.

  The present inventors paid attention to the mass and shape of two types of pellets to be mixed, and conducted intensive studies to solve the above problems. As a result, when mixing the spherical resin pellets and the cylindrical resin pellets, adjusting the volume density of the cylindrical resin pellets and the bulk density of the spherical resin pellets so as to satisfy a specific relationship, The inventors have found that this can be solved, and have completed the present invention. More specifically, the present invention provides the following.

(1) A substantially spherical or substantially elliptical spherical resin pellet and a substantially cylindrical cylindrical resin pellet are mixed, and the cylindrical resin pellet is dispersed in the spherical resin pellet, A value obtained by dividing the mass of the cylindrical resin pellet by the volume of a sphere having a diameter of a rectangular diagonal line with the diameter of the circle at the bottom of the cylindrical resin pellet as one side and the height of the cylindrical resin pellet as one side. A pellet mixture in which the excluded volume density and the bulk density of the spherical resin pellet satisfy the following inequality (I).

Bulk density x 0.6 ≤ Excluded volume density ≤ Bulk density x 0.8 (I)

  (2) The pellet according to (1), wherein a mixing ratio of the spherical resin pellet and the cylindrical resin pellet is in a mass ratio (spherical resin pellet: cylindrical resin pellet) and within a range of 80: 1 to 9: 1. blend.

  (3) The spherical resin pellets are manufactured with an extruder whose pellet cutting method is an underwater cut method or a hot cut method, and the cylindrical resin pellets are manufactured with an extruder whose pellet cutting method is a strand cut method. (1) or pellet mixture as described in (2).

  (4) The cylindrical resin pellet is a masterbatch pellet containing at least one additive selected from a pigment, an inorganic filler, a stabilizer, and a resin modifier. Pellet mixture.

  (5) The spherical resin pellet is a pellet mixture as set forth in any one of (1) to (4) whose main component is polyoxymethylene.

  (6) A method for producing a resin molded product comprising a molding step of producing a molded product by melt-kneading the pellet mixture according to any one of (1) to (5).

  According to the present invention, two different types of resin pellets can be uniformly mixed regardless of the type of thermoplastic resin used.

  Hereinafter, embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment.

<Pellet mixture>
The pellet mixture of the present invention is obtained by mixing approximately spherical or approximately elliptical spherical resin pellets and approximately cylindrical columnar resin pellets.

[Spherical resin pellet]
The spherical resin pellet is a resin pellet having a substantially spherical shape or a substantially elliptical spherical shape. The substantially spherical shape means a true sphere, but may be a shape that is not a perfect sphere but can approximate a true sphere (for example, a sphere having irregularities on the surface). Further, the substantially elliptical spherical shape means a spherical shape that is not a true sphere. That is, the substantially elliptical sphere includes all shapes that can be approximated to an elliptical sphere (for example, an elliptical sphere having an uneven surface). In particular, in the present invention, it is preferable that the spherical resin pellet has a spheroid shape.

  In the present invention, the relationship between the bulk density of the spherical resin pellet and the excluded volume density of the cylindrical resin pellet described later is important, and the size of the spherical resin pellet is not particularly limited. However, the size of the spherical resin pellets is preferably such that the diameter of the spherical resin pellets is 8 mm or less (the diameter refers to the diameter of a sphere in the case of a substantially spherical shape, and is the longest in the case of a substantially elliptic sphere shape). Refers to the diameter). More preferably, the diameter is 2 mm or more and 5 mm or less.

  The kind of thermoplastic resin contained in the spherical resin pellet is not particularly limited. Examples of thermoplastic resins include polyolefins such as polyethylene, polypropylene, and polystyrene; aromatic dicarboxylic acids such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate, and diols. Aromatic polyester; aliphatic polyester such as polylactic acid; polyamide resin such as nylon 46, nylon 6, nylon 66, nylon 610, nylon 612, nylon 11, nylon 12, MXD nylon; polyoxymethylene (homo or copolymer); polystyrene Polyvinyl chloride; Polyacrylonitrile; Cyclic olefin resin; (Meth) acrylic resin; Polycarbonate; AS resin; ABS resin; Polyphenylene oxide; Polyphenylene sulfide resins such as polysulfide, polyphenylene sulfide ketone, polybiphenylene sulfide, polyphenylene sulfide sulfone; polysulfone resins such as poly (ether sulfone) and poly (4,4'-bisphenol ether sulfone); polyether ketone resins; polyether ether Examples thereof include ketone resins; liquid crystalline polymers; fluororesins and the like. These thermoplastic resins can be used in combination of two or more.

  According to the present invention, the spherical resin pellets and the cylindrical resin pellets can be uniformly mixed regardless of the type of the thermoplastic resin contained in the spherical resin pellets or the cylindrical resin pellets described later. It is preferable that polyoxymethylene is a main component. Here, the main component means that polyoxymethylene is contained in the spherical resin pellet in an amount of 50% by mass or more, preferably 80% by mass or more. It is also preferred that the spherical resin pellet is made of polyoxymethylene.

The polyoxymethylene includes a polyacetal homopolymer having an oxymethylene group (—CH ₂ O—) as a structural unit and a polyacetal copolymer containing other comonomer units in addition to the oxymethylene group. In the copolymer, the comonomer unit includes an oxy C 2-6 alkylene unit (for example, an oxy C _2-4 alkylene unit such as an oxyethylene group (—CH ₂ CH ₂ O—), an oxypropylene group, an oxytetramethylene group). . The comonomer unit content is, for example, from 0.01 to 30 mol%, preferably from 0.03 to 20 mol%, more preferably from about 0.03 to 15 mol%, based on the entire polyoxymethylene resin. You can choose.

  When polyoxymethylene is a polyacetal copolymer, it may be a copolymer composed of two components, a terpolymer composed of three components, or the like. The polyacetal copolymer may be a random copolymer, a block copolymer, a graft copolymer, or the like. Moreover, polyoxymethylene may be not only linear but also a branched structure, and may have a crosslinked structure. Furthermore, the terminal of polyoxymethylene may be stabilized by, for example, esterification with carboxylic acids such as acetic acid and propionic acid, or anhydrides thereof.

  Examples of polyoxymethylene include aldehydes such as formaldehyde, paraformaldehyde, acetaldehyde, trioxane, ethylene oxide, propylene oxide, 1,3-dioxolane, 1,3-dioxane, diethylene glycol formal, 1,4-butanediol formal, and the like. It can manufacture by polymerizing the cyclic ether and cyclic formal.

  The spherical resin pellet may contain components other than the thermoplastic resin. Examples of components other than the thermoplastic resin include additives such as fillers (inorganic fillers), nucleating agents, pigments, antioxidants, stabilizers, plasticizers, lubricants, mold release agents, and flame retardants. it can. For example, these other components are added to the substantially spherical resin pellet in a range of 3% by mass or less.

  The manufacturing method of a spherical resin pellet is not specifically limited. For example, the resin composition can be generally prepared by a known equipment and method as a method for preparing the resin composition. For example, the necessary components can be mixed and kneaded using a single or twin screw extruder or other melt-kneading apparatus to prepare pellets. A plurality of extruders or other melt kneaders may be used. Moreover, all the components may be charged simultaneously from the hopper, or some components may be charged from the side feed port.

  In order to produce spherical or three-dimensional pellets that can be approximated to a spherical shape, it is preferable to use an extruder whose pellet cutting method is an underwater cut method or a hot cut method.

[Cylindrical resin pellets]
The columnar resin pellet used in the present invention is a substantially columnar resin pellet. The substantially columnar shape includes not only a columnar shape but also a shape that can be approximated to a column (for example, a column having an uneven surface, a flat elliptical column, or the like). In the present invention, the size of the cylindrical resin pellet is not particularly limited, but the length of a rectangular diagonal line having a side of the diameter of the circle at the bottom of the cylindrical resin pellet and the height of the cylindrical resin pellet as one side is 8 mm or less. It is preferable that More preferably, the length of the diagonal line is 4 mm or more and 8 mm or less.

In addition, the cylindrical resin pellet used in the present invention is a volume of a sphere having the above diagonal line as a diameter, and an excluded volume density derived by dividing the mass of the cylindrical resin pellet is the following. It is necessary to have a relationship that satisfies the inequality.

Bulk density x 0.6 ≤ Excluded volume density ≤ Bulk density x 0.8 (I)

  The kind of the thermoplastic resin contained in the cylindrical resin pellet is not particularly limited as in the case of the spherical resin pellet. Usable thermoplastic resins are the same as in the case of spherical resin pellets.

  As will be described later, the cylindrical resin pellet is preferably used as a master batch pellet, not as a dilution resin pellet. When the cylindrical resin pellet is used as a master batch pellet, it is preferable that the cylindrical resin pellet contains a pigment, an inorganic filler, a stabilizer, and a resin modifier in addition to the thermoplastic resin. Hereinafter, these components will be described.

  When using cylindrical resin pellets as master batch pellets, it is preferable that the master batch pellets contain a pigment pigment because a colored molded product can be easily obtained. General pigments can be used. Non-black pigments are also included in addition to black pigments, and they may be organic pigments or inorganic pigments. For example, azo, azomethine, methine, indanthrone, anthraquinone, pyranthrone, flavanthrone, benzenethrone, phthalocyanine, quinophthalone, perylene, perinone, dioxazine, thioindigo, isoindolinone , Organic pigments such as isoindoline, pyrrole pyrrole, quinacridone, carbon black (acetylene black, lamp black, thermal black, furnace black, channel black, ketjen black, gas black, oil black, etc.), graphite, Examples thereof include black pigments such as titanium black and black iron oxide. Of these, carbon black is particularly desirable in terms of dispersibility, color developability, and cost. Also, white pigments (for example, calcium carbonate, titanium oxide, zinc oxide, zinc sulfide, etc.), yellow pigments (for example, cadmium yellow, yellow lead, titanium yellow, zinc chromate, ocher, yellow iron oxide, etc.), red pigments (for example, Red pigment, amber, red iron oxide, cadmium red, etc.), blue pigments (eg, bitumen, ultramarine blue, cobalt blue, etc.), green pigments (eg, chrome green, etc.), and the like.

  Further, the content of the pigment is not particularly limited, and may be appropriately set according to the purpose of using the pigment. For example, the content in the master batch pellet is preferably 2% by mass or more and 30% by mass or less.

  When using a cylindrical resin pellet as a master batch, it is preferable that the master batch pellet contains an inorganic filler because the amount of the inorganic filler in the molded product can be easily changed. Examples of inorganic fillers include fibrous fillers, granular fillers, and plate-like fillers. Specific examples of the fibrous filler include, for example, glass fiber, asbestos fiber, silica fiber, silica / alumina fiber, alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, and stainless steel. Inorganic fibrous materials such as metallic fibrous materials such as aluminum, titanium, copper, and brass. Specific examples of the granular filler include silica, quartz powder, glass beads, milled glass fiber, glass balloon, glass powder, calcium silicate, aluminum silicate, kaolin, talc, clay, diatomaceous earth, and wollastonite. Salts, iron oxide, titanium oxide, zinc oxide, antimony trioxide, oxides of metals such as alumina, carbonates of metals such as calcium carbonate and magnesium carbonate, sulfates of metals such as calcium sulfate and barium sulfate, other ferrites, Examples thereof include silicon carbide, silicon nitride, boron nitride, and various metal powders. Specific examples of the plate-like filler include mica, glass flakes and various metal foils.

  Further, the content, size, and shape of the inorganic filler are not particularly limited, and may be set as appropriate according to the purpose of using the inorganic filler. For example, the content of the inorganic filler is preferably 2% by mass or more and 30% by mass or less in the master batch pellet.

  When using a cylindrical resin pellet as a master batch pellet, it is preferable that the master batch pellet contains a stabilizer because the amount of the stabilizer in the molded product can be easily changed. In the present invention, any known stabilizer can be used, but generally an antioxidant and a heat stabilizer are used in combination. Examples of the antioxidant include 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythrityltetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethyleneglycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], N, N'-hexamethylenebis (3 , 5-di-t-butyl-4-hydroxy-cinnamamide) and the like. Examples of the heat stabilizer include triazine compounds such as melamine and melamine-formaldehyde condensate, polyamides such as nylon 12 and nylon 6/10, hydroxides of alkali metals or alkaline earth metals, carbonates, phosphates, Examples include acetates, oxalates, higher fatty acids such as stearic acid, and higher fatty acid metal salts having substituents such as hydroxyl groups.

  Further, the content of the stabilizer is not particularly limited, and may be appropriately set according to the purpose of using the stabilizer. For example, the content of the stabilizer is preferably 2% by mass or more and 30% by mass or less in the master batch pellet.

  When using a cylindrical resin pellet as a master batch pellet, it is preferable that the master batch pellet contains a resin modifier because the amount of the resin modifier in the molded product can be easily changed. The kind of resin modifier is not specifically limited, It sets suitably according to the kind of thermoplastic resin.

  The manufacturing method of a cylindrical resin pellet is not specifically limited like the manufacturing method of a spherical resin pellet. For example, the resin composition can be generally prepared by a known equipment and method as a method for preparing the resin composition.

  In order to produce a cylindrical pellet or a three-dimensional pellet that can be approximated to a cylindrical column, it is preferable to use an extruder whose pellet cutting method is a strand cut method.

[Mixing of spherical resin pellets and cylindrical resin pellets]
In the pellet mixture of the present invention, cylindrical resin pellets are dispersed in spherical resin pellets. That is, the spherical resin pellet becomes a particle layer, and the cylindrical resin pellet is dispersed in the particle layer. The reason why such a mixed state can be realized is that in the present invention, the relationship between the bulk density of the spherical resin pellet and the excluded volume density of the cylindrical resin pellet is adjusted to a specific range.

  Usually, when comparing the bulk density of spherical resin pellets that are particle layers and the true density of cylindrical resin pellets, if the bulk density and the true density are close to a certain value, the inside of the particle layer is cylindrical. As a result of the resin pellets floating or sinking, it is considered that the spherical resin pellets and the cylindrical resin pellets are uniformly mixed. However, actually, even if the true density of the cylindrical resin pellet is adjusted based on the bulk density of the spherical resin pellet as described above, the spherical resin pellet and the cylindrical resin pellet cannot be uniformly mixed. .

  In the present invention, in consideration of the excluded volume density of the dispersed cylindrical resin pellets, the spherical resin pellets and the cylindrical resin pellets are uniformly mixed on the basis of the bulk density of the spherical resin pellets that are particle layers. When deriving the excluded volume density, as described above, consider the volume of the sphere with the diameter of the circle on the bottom of the cylindrical resin pellet as one side and the rectangular diagonal line with the height of the cylindrical resin pellet as the side. To do. This is for considering that the cylindrical resin pellet behaves as a particle having a volume larger than the actual volume when considering the cylindrical resin pellet moving in the particle layer.

Eliminating close to the bulk density value based on the bulk density value of the spherical resin pellets, considering that the cylindrical resin pellet particles have the volume of the sphere when moving in the spherical resin pellet particle layer By using columnar resin pellets having a volume density, spherical resin pellets and columnar resin pellets can be uniformly mixed. Specifically, an inequality of the following formula (I) is established between the excluded volume density and the bulk density.

Bulk density x 0.6 ≤ Excluded volume density ≤ Bulk density x 0.8 (I)

  The method of adjusting the bulk density when the above inequality is not satisfied is not particularly limited. For example, the bulk density can be increased by reducing the diameter of the spherical resin pellet, and conversely, the diameter of the spherical resin pellet can be increased. The bulk density can be reduced by increasing the density.

  In addition, the method of adjusting the excluded volume density is not particularly limited when the above inequality is not satisfied, but the excluded volume density is reduced by, for example, increasing the columnar resin pellet height (increasing the strand length). can do. On the other hand, the volume density excluded can be increased by, for example, a method of shortening the height of the cylindrical resin pellet (shortening the strand length).

  In the present invention, the mixing ratio of these resin pellets is not particularly limited, but is preferably in the range of 80: 1 to 9: 1 in terms of mass ratio (spherical resin pellet: columnar resin pellet). It is preferable that the content of the cylindrical resin pellet is 1/80 or more in the above mass ratio because of uniform dispersibility at the time of melt mixing, and that the content is 1/9 or less in the above mass ratio is low in cost. It is preferable from the viewpoint of suppression. A more preferable mass ratio is 1:15 to 1:60.

  The mixing method of the spherical resin pellets and the cylindrical resin pellets is not particularly limited, but is preferably a mixing method in which the cylindrical resin pellets are dispersed in the particle layer of the spherical resin pellets while vibrating. Regardless of the mixing method, since the cylindrical resin pellets are dispersed in the particle layer while moving, the cylindrical resin pellets are treated as particles having a volume larger than the actual volume, and the bulk density of the spherical resin pellets If the above excluded volume density is adjusted based on the above, uniform mixing of spherical resin pellets and cylindrical resin pellets can be realized. However, if the preferable mixing method is adopted, the volume of the particles in which the cylindrical resin pellets behave is close to the excluded volume density, and the spherical resin pellets and the cylindrical resin pellets can be mixed more easily.

  Examples of the mixing method in which the cylindrical resin pellets are dispersed in the particle layer of the spherical resin pellets while being vibrated include shaking mixing and air mixing. Shaking mixing is a method of mixing spherical resin pellets and cylindrical resin pellets by applying vibration. Mixing by air sending is a method in which spherical resin pellets and cylindrical resin pellets are mixed by moving spherical resin pellets or cylindrical resin pellets in flowing gas (for example, air).

  As described above, the spherical resin pellet preferably has a diameter of 8 mm or less (the diameter indicates the diameter of a sphere in the case of a substantially spherical shape, and the longest diameter in the case of an elliptic sphere). And it is preferable that the diagonal of the rectangle which makes the diameter of the circle | round | yen of the bottom face of a cylindrical resin pellet one side, and makes the height of a cylindrical resin pellet one side is 8 mm or less. When spherical resin pellets and cylindrical resin pellets of the size described above are used, the pellets in the mixture easily move during mixing even under normal stirring and vibration conditions. As a result, the spherical resin pellets and the cylindrical resin pellets are mixed. It becomes easy to do.

  Also, as described above, if polyoxymethylene is used as the thermoplastic resin contained in the spherical resin pellets or cylindrical resin pellets, the slipperiness between the pellets is good, which is preferable because the pellets in the mixture easily move during mixing. .

<Resin molded product>
The method for producing a resin molded product of the present invention is a method for producing a resin molded product using the above pellet mixture as a raw material. In the pellet mixture of the present invention, cylindrical resin pellets and spherical resin pellets are sufficiently mixed, and as a result, the quality of the produced resin molded product is also stabilized.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not limited to these Examples.

<Material>
Spherical polyoxymethylene resin pellet 1 (spherical resin pellet 1): “Duracon M90-44” manufactured by Polyplastics Co., Ltd.
Spherical polyoxymethylene resin pellet 2 (spherical resin pellet 2): “Iupital F20-03” manufactured by Mitsubishi Engineering Plastics Co., Ltd.

  The mass per spherical resin pellet 1 was 15.8 mg (the mass per one is an average value calculated from the mass of 100 spherical resin pellets 1).

  Moreover, after putting this spherical resin pellet 1 into a 50 mL graduated cylinder and applying a vibration to the graduated cylinder so that the spherical resin pellet was densely packed, the bulk density of the spherical resin pellet 1 was measured. The bulk density of the spherical resin pellet 1 was 0.82 g / mL.

  Moreover, the bulk density of the spherical resin pellet 2 was measured by the same method as the measurement of the bulk density of the spherical resin pellet 1. The bulk density of the spherical resin pellet 2 was 0.87 g / mL. Further, the mass per spherical resin pellet 2 was 11.6 mg (the mass per one is an average value calculated from the mass of 100 spherical resin pellets 2).

[Manufacture of cylindrical resin pellet 1]
The raw material consisting of 90 parts by weight of spherical resin pellets 1 and 10 parts by weight of pigment is charged into an extruder having a cutting method of strand cut method (“TEX30α” manufactured by Nippon Steel Works). Produced a cylindrical resin pellet 1 having a bottom circle diameter of 2.4 mm (height and diameter were calculated by measuring the height and diameter of ten cylindrical resin pellets 1. Average value). Moreover, the mass per one cylindrical resin pellet 1 was 18.4 mg (the mass per one is an average value calculated from the mass of 100 cylindrical resin pellets 1). The length of the diagonal line of the rectangle with the height as one side and the diameter as one side is 4.00 mm, and the excluded volume density is 0.549 g / mL. Further, the bulk density of the cylindrical resin pellet 1 was measured by the same method as the measurement of the bulk density of the spherical resin pellet 1. The bulk density was 0.77 g / mL.

  Cylindrical polyoxymethylene resin pellet 2 (cylindrical resin pellet 2) composed of a material containing a pigment pigment: “Duracon M90-07 K30682” manufactured by Polyplastics Co., Ltd.

  When the pellet shape and bulk density of the cylindrical resin pellet 2 were measured in the same manner as in the case of the cylindrical resin pellet 1, the bulk density was 0.89 g / mL, the height was 3.3 mm, and the diameter of the bottom circle was 2. It was 2 mm (height and diameter are average values calculated by measuring the height and diameter of ten cylindrical resin pellets 2). Moreover, the mass per one cylindrical resin pellet 2 was 16.8 mg (the mass per one is an average value calculated from the mass of 100 cylindrical resin pellets 2). Moreover, the length of the diagonal of the rectangle which makes the said height one side and the said diameter is one side is 3.97 mm, and the excluded volume density is 0.514 g / mL.

Information on the spherical resin pellets and cylindrical resin pellets is summarized in Table 1 below.

<Example 1>
The pellets shown in Table 2 were put into a 50 mL graduated cylinder at the rate shown in Table 2 for 50 mL, mixed with an electric vibrator for 30 seconds, and the pellets in the graduated cylinder were mixed for 30 seconds with fine vibration. A mixture was prepared. Table 1 also shows the bulk density of the spherical resin pellets, the calculation result of the above bulk density × 0.8, and the calculation result of the above bulk density × 0.6.

[Evaluation of dispersibility]
The dispersibility was evaluated by the following method. The evaluation criteria are the following two stages, and the evaluation results are shown in Table 2.
“◯”: When the ratio of the cylindrical master batch pellet to the spherical pellet contained in the upper 25 mL of the graduated cylinder is 0.6 to 25 by mass ratio and does not exceed this, “X”: contained in the upper 25 mL of the graduated cylinder When the ratio of columnar master batch pellets and spherical pellets exceeds 0.6: 25 by mass ratio

[Manufacture and evaluation of resin molded products]
A resin molded product (70 mm × 50 mm × 3 mm) was produced from the pellet mixture of Example 1 under the following molding conditions.
(Molding condition)
Molding machine: Japan Steel Works J75E-P
Molding conditions: cylinder temperature (° C) nozzle (200 ° C) -C1 (200 ° C) -C2 (190 ° C) -C3 (180 ° C)
Injection pressure: 60 (MPa)
Injection speed: 1.0 (m / min)
Mold temperature: 60 (℃)

The color unevenness of the resin molded product was visually evaluated. The evaluation criteria are the following two stages, and the evaluation results are shown in Table 2.
“○”: When the color unevenness of the molded product cannot be specified “X”: When the color unevenness of the molded product is recognized

<Example 2>
A pellet mixture was produced in the same manner as in Example 1 except that the raw materials used were changed to the materials shown in Table 2. The dispersibility of the pellet mixture of Example 2 was evaluated by the above method, and the evaluation results are shown in Table 2. Moreover, using the pellet mixture of Example 2, a resin molded product was produced in the same manner as in Example 1, and the uneven color of the resin molded product was evaluated. The evaluation results are shown in Table 2.

<Example 3>
A pellet mixture was produced in the same manner as in Example 1 except that the raw materials used were changed to the materials shown in Table 2. The dispersibility of the pellet mixture of Example 3 was evaluated by the above method, and the evaluation results are shown in Table 2. Moreover, using the pellet mixture of Example 3, a resin molded product was produced in the same manner as in Example 1, and the uneven color of the resin molded product was evaluated. The evaluation results are shown in Table 2.

<Comparative Example 1>
A pellet mixture was produced in the same manner as in Example 1 except that the raw materials used were changed to the materials shown in Table 2. The dispersibility of the pellet mixture of Comparative Example 1 was evaluated by the above method, and the evaluation results are shown in Table 2. Moreover, the resin molded product was manufactured by the method similar to the case of Example 1 using the pellet mixture of the comparative example 1, and the color unevenness of the resin molded product was evaluated. The evaluation results are shown in Table 2.

  As apparent from the results in Table 2, it was confirmed that different types of pellets were uniformly mixed by adjusting the relationship between the bulk density of the spherical resin pellets and the excluded volume density of the cylindrical resin pellets.

Claims (6)

A spherical resin pellet having a substantially spherical shape or a substantially elliptical spherical shape; and
A substantially cylindrical cylindrical resin pellet, and
In the spherical resin pellets, the cylindrical resin pellets are dispersed,
A value obtained by dividing the mass of the cylindrical resin pellet by the volume of a sphere having a diameter of a rectangular diagonal line with the diameter of the circle at the bottom of the cylindrical resin pellet as one side and the height of the cylindrical resin pellet as one side. Is the volume density excluded,
A pellet mixture in which the excluded volume density and the bulk density of the spherical resin pellet satisfy the following inequality (I).

Bulk density x 0.6 ≤ Excluded volume density ≤ Bulk density x 0.8 (I)
  2. The pellet mixture according to claim 1, wherein a mixing ratio of the spherical resin pellets to the cylindrical resin pellets is in a mass ratio (spherical resin pellets: cylindrical resin pellets) in a range of 80: 1 to 9: 1. The pellet mixture according to claim 1 or 2, wherein the cylindrical resin pellet is a master batch pellet containing at least one additive selected from a pigment, an inorganic filler, a stabilizer, and a resin modifier. The pellet mixture according to any one of claims 1 to 3 , wherein the spherical resin pellet is mainly composed of polyoxymethylene. In extruder A down Zehnder water cut system or hot cut method, to produce a substantially spherical shape or a substantially elliptical spherical shape of the spherical resin pellets,
An extruder of the scan Portland cut method, to produce a substantially columnar cylindrical resin pellets,
Mixing the spherical resin pellets and the cylindrical resin pellets to produce a pellet mixture,
The pellet mixture is a volume of a sphere having a diameter of a rectangular diagonal line with the diameter of the circle at the bottom of the cylindrical resin pellet as one side and the height of the cylindrical resin pellet as a side, A manufacturing method of a pellet mixture in which the excluded volume density and the bulk density of the spherical resin pellet satisfy the following inequality (I) when a value obtained by dividing mass is defined as an excluded volume density.
Bulk density x 0.6 ≤ Excluded volume density ≤ Bulk density x 0.8 (I) The manufacturing method of the resin molded product which has a shaping | molding process of melt-kneading the pellet mixture in any one of Claim 1 to 4 and manufacturing a molded product.