JP2009013395A - Composite material powder for selective laser sintering - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite material powder, excellent in recycling property, used for the process of selective laser sintering and does not cause degradation of mechanical strength and separation of a resin powder and a filler even if used repeatedly; to provide a composite material having high bending elastic modulus, high tensile modulus and light weight compared to a molded product formed of a resin alone; and further to provide a composite material having antistatic properties and conductivity. <P>SOLUTION: The composite material, which is prepared by mixing a spherical aggregate having a true specific gravity of 0.8-2.0, a sphericity of 0.8-1.0 and an average particle diameter of 10-150 μm and a resin particle having an average particle diameter of 30-150 μm, is subjected to the process of selective laser burning. Also, when spherical carbon black is used as the aggregate, the composite material having antistatic properties and conductivity can be obtained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a composite powder as a base material for a selective laser sintering method and a molded body thereof.

  Generally, polyamide 12 powder is used as a material for selective laser sintering (see, for example, Patent Document 1). However, when a molded article is formed with the polyamide 12 alone, deformation of the molded article due to various external forces often becomes a problem because of its low elastic modulus.

  In order to solve this problem, countermeasures against deformation such as improving the elastic modulus of a molded product by mixing a fibrous filler such as glass fiber or carbon fiber with resin powder and shaping the material are taken.

  However, in the above method, there is a problem that recycling, that is, a material that has been used once but recovered in a powder state without being irradiated with a laser cannot be used again. For example, in the case of modeling only with resin powder such as polyamide 12 powder, after selective laser sintering, the powder not irradiated with laser can be collected, passed through a sieve, and used again as a substrate for selective laser sintering. When the fibrous filler is contained, it is difficult to pass through the sieve because it is caught by the mesh, and the fibrous filler and the resin powder are easily separated. As a result, it cannot be recycled and a large amount of waste is generated, which increases costs and is hardly used. Furthermore, since the fibers are distributed during modeling, there is a problem in performance that a three-dimensional uniform strength is not exhibited.

  On the other hand, there is a technique that uses a material in which a filler that passes through a sieve such as glass beads and aluminum powder and a resin powder are mixed. (For example, see Patent Document 2.)

  However, since these filler powders have a large specific gravity difference from the resin powder, when the composite material powder is impacted with a sieve or the like, the filler and the resin powder are easily separated, and the powder is not uniform. Therefore, the recycled material cannot be made into a homogeneous molded product, and is discarded. As a result, a large amount of waste is generated, resulting in high costs. Furthermore, since a molded object is heavy, it may not fully satisfy functionality.

  Further, there is a demand for a molded body having a complicated shape that cannot be molded by injection molding or extrusion molding, which are conventional molding techniques, and a selective laser sintering method capable of freely designing the shape has attracted attention. However, when a volume specific resistivity is freely adjusted and a conductive material is used from the prevention of static electricity, there are mechanical limitations and the like, and it has not yet been possible to mold freely by a selective laser sintering method. For example, many prototypes of electronic equipment are created by selective laser sintering. However, conventional selective laser sintering materials do not have antistatic properties, so there are many cases where defects occur. It was. When the copy paper transport guide parts of a copying machine are made by selective laser sintering, if nylon 12 with electrical insulation is used as the material, static electricity will be generated due to friction between the paper and the guide parts, and paper jams will occur. Wake up. As a means for solving this problem, a method of applying an antistatic coating to a guide part made of nylon 12 has been taken.

However, this method has problems such as an increase in the number of processes, repeated use of the copying machine, wear of the guide parts, and peeling of the antistatic paint. In order to solve these problems, studies have been made to add a conductive material. However, when carbon fiber is added in an amount of 30% by mass or more, fluidity is deteriorated, and when carbon black is added as a conductive filler, carbon black is added. Since the average particle size of the material is as small as several tens of nanometers, the fluidity of the material is greatly reduced. In either case, the selective laser sintering method cannot be used to form a composite material having antistatic properties. .
Japanese Patent Laid-Open No. 11-216779 Japanese National Patent Publication No. 11-509485

  An object of the present invention is to provide a composite material that is mainly used for selective laser sintering, is recyclable and low in cost, has a higher elastic modulus than a resin-only molded product, and is lightweight, and its molded product. It is in. It is another object of the present invention to provide a composite material that can be molded by a selective laser sintering method and has conductivity from antistatic.

  As a result of intensive studies, the present inventors have found that a composite material that can achieve the above object can be obtained by mixing a specific spherical aggregate and a resin powder. The present invention has been made based on the above findings, and provides a composite material used for selective laser sintering in which a spherical aggregate having a true specific gravity close to that of a resin is mixed with a resin powder. Furthermore, this invention provides the composite material which has electroconductivity from electrostatic prevention by using spherical carbon as an aggregate of a composite material.

  The composite powder containing the spherical aggregate can pass through a sieve during recycling. Further, since the specific gravity is close to that of the resin powder, the spherical carbon and the resin powder can be recovered while being uniformly mixed during recycling. As a result, it is possible to form the recycled material by selective laser sintering five or more times while maintaining the same mechanical strength.

  Furthermore, a molded article having excellent mechanical strength can be obtained by using a spherical aggregate. In particular, the tensile elastic modulus, bending elastic modulus, and bending strength are remarkably improved.

  Further, the volume specific resistivity can be adjusted by using spherical carbon which is a conductive material as the aggregate constituting the composite material powder of the present invention and changing the amount of addition. Therefore, a molded product obtained by adding spherical carbon as an aggregate and shaped by a selective laser sintering method can be widely used in fields where static electricity prevention and conductivity are required.

The composite material powder of the present invention and the production method thereof will be described in detail below. The spherical aggregate constituting the composite material powder of the present invention is a spherical aggregate having a true specific gravity of 0.8 to 2.0 g / cm ³ and an average particle size of 10 to 150 μm and having no melting point, and further a spherical thermosetting resin. It is a cured product and spherical carbon. Examples of the spherical thermosetting resin dropping product include a spherical cured product of a phenol resin, and a phenol and an aldehyde are condensed in an aqueous medium in the presence of a condensation reaction catalyst and an emulsifying dispersant under high temperature and high pressure. Can be obtained. Specifically, the HF type manufactured by Gunei Chemical Industry Co., Ltd. is preferable. As the spherical carbon, for example, a spherical thermosetting cured product can be obtained by carbonizing at 400 to 1000 ° C. in a nitrogen atmosphere, and specifically, the GC type manufactured by Gunei Chemical Industry Co., Ltd. is preferable. By mixing these aggregates with resin powder having adhesive ability, a material for selective laser sintering having high strength and high elastic modulus can be obtained. These aggregates do not melt at high temperatures and do not have a melting point. In addition, this spherical aggregate has a true specific gravity of 0.8 to 2.0 g / cm ^{3, which} is lighter than glass powder, ceramic powder, and metal powder, which have a higher melting point than nylon, and is close to resin powder. The spherical aggregate and the resin powder are not separated by the impact of the sieve. Therefore, it has a great industrial merit that the environmental load due to disposal can be reduced and at the same time the production cost can be reduced. In addition, when spherical carbon, which is a conductive material, is used as the spherical aggregate, it is possible to adjust the volume resistivity in the range required for electrical conductivity prevention and conductivity by changing the amount of addition, which is selective. It can be easily molded by laser sintering.

  About the average particle diameter of the spherical aggregate which comprises the composite material powder of this invention, Preferably it is 10-150 micrometers, More preferably, it is 40-60 micrometers. When the average particle size is 10 μm or less, it is difficult to lay the material during modeling, and when the average particle size is 150 μm or more, a finely shaped shaped product cannot be obtained.

  The spherical aggregate constituting the composite material of the present invention has a true spherical shape, preferably a sphericity of 0.7 to 1.0, more preferably a sphericity of 0.95 to 1.0. Here, the sphericity is an index for measuring the sphericity of a particle by (the diameter of a circle equal to the projected area of the particle) / (the diameter of the smallest circle circumscribing the projected image of the particle). The closer to, the closer to a true sphere. When the spherical aggregate has a sphericity of 0.7 or less, the powder cannot be uniformly dispersed during molding and cannot be molded. Moreover, since it is spherical, it has the merit that the mechanical strength of the molded product is isotropic. In the case of a fibrous filler, since anisotropy occurs in the mechanical strength of the molded product, the finished molded product has a large variation in strength depending on the part.

  Further, the content of the spherical aggregate in the composite material is preferably 10% by mass to 80% by mass, and more preferably 20% by mass to 60% by mass. When the content of the spherical aggregate is 10% by mass or less, the elastic modulus is hardly improved, and when it is more than 90% by mass, a molding defect occurs.

In particular, when spherical carbon is used as the composite material, the volume resistivity is 10 ⁶ Ω · cm or more and 10 ¹⁰ Ω · cm or less when the content of the spherical carbon in the composite material is 35% by mass or more and less than 55% by mass. It has antistatic effect. On the other hand, when the content of spherical carbon is 55% by mass or more and 80% by mass or less, the volume resistivity is 10 ¹ Ω · cm or more and less than 10 ⁶ Ω · cm. Applicable to parts. When the content of the spherical carbon is 10% by mass or more and less than 35% by mass, the volume resistivity exceeds 10 ¹⁰ Ω · cm and cannot be used for the above applications.

  The resin powder constituting the composite material powder of the present invention may be either a thermoplastic resin or a thermosetting resin, preferably polyamide, polystyrene, polybutylene terephthalate, polyacetal, polypropylene, polyethylene, polyaryletherketone, phenol resin, An epoxy resin, a melamine resin, more preferably a polyamide, may be used as a mixture of two or more. The sphericity of the powder resin is preferably 0.6 to 1.0. The average particle size of the powder resin is preferably 30 to 150 μm.

  The spherical aggregate constituting the composite material of the present invention can be surface treated with a coupling agent or the like. By performing the surface treatment, adhesion between the spherical aggregate and the resin is improved during molding. Preferably, the surface treatment is a silane coupling agent, a titanate coupling agent, or an aluminum coupling agent. Examples of the silane coupling agent include γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-aminopropyltriethoxysilane, N, N-bis [3- (tri Methoxysilyl) propyl] amine, N, N-bis [3- (trimethoxysilyl) propyl] ethylenediamine, N, N-bis [3- (trimethoxysilyl) propyl] methacrylamide, N-glycidyl-N, N- Bis [3- (trimethoxysilyl) propyl] amine, γ-aminopropyltetraethoxydisilooxane, N, N-bis [3- (methyldimethoxysilyl) propyl] amine, N, N-bis [3- (methyl Dimethoxysilyl) propyl] ethylenediamine, N, N-bis [3- (methyldimethoxysilyl) Propyl] methacrylamide, N-glycidyl-N, N-bis [3- (methyldimethoxysilyl) propyl] amine and the like, and titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl trioctanoyl titanate, Isopropyldimethacrylisostearoyl titanate, isopropylisostearoyldiacryl titanate, isopropyltris (dioctylpyrophosphate) titanate, tetraoctylbis (ditridecylphosphite) titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis ( Ditridecyl) phosphite titanate, bis (dioctylpyrophosphate) oxyacetate titanate, bis (dioctylpyrophosphate) ethylene titanate Examples of aluminates include acetoalkoxy aluminum diisopropylate, diisopropoxy aluminum ethyl acetoacetate, diisopropoxy aluminum alkyl acetoacetate, isopropoxy aluminum alkyl acetoacetate mono (dioctyl phosphate), diisopropoxy Examples thereof include aluminum monomethacrylate, aluminum-2-ethylhexanoate oxide trimer, aluminum stearate oxide trimer, and alkyl acetoacetate aluminum oxide trimer. Further, the addition amount is preferably 0.05 to 0.1% by mass, and two or more kinds may be mixed and used.

  If necessary, the composite material of the present invention may contain auxiliary agents such as antistatic agents and lubricants. By adding an antistatic agent and a lubricant, the fluidity of the powder is improved and molding becomes easier. As antistatic agents and lubricants, surfactants, silicone resins, and metal soaps are preferable. Further, the addition amount is preferably 0.05 to 0.1% by mass, and two or more kinds may be mixed and used.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limited at all by these Examples.

[Example 1]
40 parts by mass of a spherical phenol resin cured product having a true specific gravity of 1.25 g / cm ³ , a sphericity of 0.95 and an average particle size of 45 μm, and 60 parts by mass of a spherical polyamide 12 having a sphericity of 0.9 (average particle size of 50 μm) A modeling test was performed with a laser sintering machine (EOSINT P360 manufactured by EOS) using a sample mixed for 5 minutes with a mixer.

[Example 2]
60 parts by weight of a spherical phenol resin cured product having a true specific gravity of 1.25 g / cm ³ , a sphericity of 0.95 and an average particle size of 45 μm, and 40 parts by weight of a spherical polyamide 12 having a sphericity of 0.9 (average particle size of 50 μm) A modeling test was performed with a laser sintering machine (EOSINT P360 manufactured by EOS) using a sample mixed for 5 minutes with a mixer.

[Example 3]
True specific gravity 1.35 g / cm ³ , sphericity 0.95, spherical carbon 40 parts by weight with an average particle size 45 μm, spherical polyamide 12 with a sphericity 0.9 (average particle size 50 μm) 60 parts by weight 5 A modeling test was conducted with a laser sintering machine (EOSINT P360 manufactured by EOS) using the sample mixed for a minute.

[Example 4]
True specific gravity 1.35 g / cm ³ , sphericity 0.95, 20 parts by weight of spherical carbon having an average particle diameter of 45 μm, and 80 parts by weight of spherical polyamide 12 having a sphericity of 0.9 (average particle diameter of 50 μm) are 5 with a screw mixer. A modeling test was conducted with a laser sintering machine (EOSINT P360 manufactured by EOS) using the sample mixed for a minute.

[Example 5]
True specific gravity 1.35 g / cm ³ , sphericity 0.95, spherical carbon 40 parts by weight with an average particle size 55 μm, spherical polyamide 12 with a sphericity 0.9 (average particle size 50 μm) 60 parts by weight 5 A modeling test was conducted with a laser sintering machine (EOSINT P360 manufactured by EOS) using the sample mixed for a minute.

[Example 6]
True specific gravity 1.35 g / cm ³ , sphericity 0.85, 40 parts by weight of spherical carbon having an average particle diameter of 45 μm, and 60 parts by weight of spherical polyamide 12 having a sphericity of 0.9 (average particle diameter of 50 μm) are 5 with a screw mixer. A modeling test was conducted with a laser sintering machine (EOSINT P360 manufactured by EOS) using the sample mixed for a minute.

[Example 7]
True specific gravity 1.35 g / cm ³ , sphericity 0.95, 40 parts by weight of spherical carbon having an average particle diameter of 45 μm, and 60 parts by weight of spherical polyamide 12 having a sphericity of 0.9 (average particle diameter of 40 μm) are 5 with a screw mixer. A modeling test was conducted with a laser sintering machine (EOSINT P360 manufactured by EOS) using the sample mixed for a minute.

[Example 8]
50 parts by weight of spherical carbon having a true specific gravity of 1.35 g / cm ³ , a sphericity of 0.95, an average particle diameter of 45 μm, and a spherical polyamide 12 having an sphericity of 0.9 (average particle diameter of 50 μm) was 5 with a screw mixer. A modeling test was conducted with a laser sintering machine (EOSINT P360 manufactured by EOS) using the sample mixed for a minute.

[Example 9]
The true specific gravity is 1.35 g / cm ³ , the sphericity is 0.95, the spherical carbon having an average particle size of 45 μm is 60 parts by mass, and the spherical polyamide having a sphericity of 0.9 is 12 (average particle size is 50 μm). A modeling test was conducted with a laser sintering machine (EOSINT P360 manufactured by EOS) using the sample mixed for a minute.

[Example 10]
True specific gravity 1.35 g / cm ³ , sphericity 0.95, spherical carbon 70 parts by mass with an average particle size of 45 μm, spherical polyamide 12 (average particle size 50 μm) 30 parts by mass with a screw mixer 5 A modeling test was conducted with a laser sintering machine (EOSINT P360 manufactured by EOS) using the sample mixed for a minute.

[Comparative Example 1]
A modeling test was conducted with a laser sintering machine (EOSINT P360 manufactured by EOS) using spherical polyamide 12 powder having an sphericity of 0.9 (average particle size 50 μm).

[Comparative Example 2]
Laser sintering machine using a sample prepared by mixing 30 parts by weight of PITCH fibrous carbon (average fiber length 1 mm) and 70 parts by weight of spherical polyamide 12 (average particle size 50 μm) with a sphericity of 0.9 with a screw mixer for 5 minutes A modeling test was performed with EOSINT P360 manufactured by EOS.

[Comparative Example 3]
A sample obtained by mixing 30 parts by weight of glass beads (average particle size 40 μm) with a true specific gravity of 2.50 g / cm ³ and 70 parts by weight of spherical polyamide 12 (average particle size 50 μm) with a sphericity of 0.9 with a screw mixer for 5 minutes. Using this, a modeling test was conducted with a laser sintering machine (EOSINT P360 manufactured by EOS).

[Comparative Example 4]
5 parts by weight of a true specific gravity of 1.35 g / cm ³ , sphericity of 0.95, 8 parts by weight of spherical carbon having an average particle diameter of 45 μm, and 92 parts by weight of spherical polyamide 12 having a sphericity of 0.9 (average particle diameter of 50 μm) are mixed with a screw mixer. A modeling test was conducted with a laser sintering machine (EOSINT P360 manufactured by EOS) using the sample mixed for a minute.

[Comparative Example 5]
40 parts by mass of spherical carbon having a true specific gravity of 1.35 g / cm ³ (sphericity 0.65, average particle size 45 μm) and 60 parts by mass of spherical polyamide 12 having a sphericity of 0.9 (average particle size 50 μm) are screw-type mixers Using the sample L mixed for 5 minutes, a molding test was performed with a laser sintering machine (EOSINT P360 manufactured by EOS). However, the powder could not be uniformly dispersed and could not be molded.

[Comparative Example 6]
Laser sintering machine (manufactured by EOS Co., Ltd.) using a material in which 30 parts by mass of carbon black having an average particle diameter of 40 nm and 70 parts by mass of spherical polyamide 12 having an sphericity of 0.9 (average particle diameter of 50 μm) were mixed for 5 minutes with a screw mixer. A modeling test was performed at EOSINT P360). However, the material could not be spread uniformly and could not be molded.

  The blending ratios of Examples 1 to 10 and Comparative Examples 1 to 6 are shown in Table 1, and the resulting molded article was measured for tensile strength, tensile elastic modulus, bending strength, bending elastic modulus, and density. It was shown to. In addition, for Examples 3, 4, 8 to 10 and Comparative Examples 1 and 2, volume resistivity was also measured. Here, the tensile strength and tensile modulus are JIS K 7162, the bending strength and flexural modulus are JIS K 7171, the density is ISO 1183, and the volume resistivity is JIS K 6911 or JIS K. 7194. In addition, about bending strength, a bending elastic modulus, tensile strength, and a tensile elastic modulus, it is the average of the measured value of a X-axis direction and a Y-axis direction.

  Table 3 shows the measured values of Example 3 and Comparative Example 2 in the respective axial directions of tensile strength, tensile elastic modulus, bending strength, and bending elastic modulus.

  As is apparent from Table 2, when Examples 1 to 7 of the present invention are compared with Comparative Example 1, the bending strength and the elastic modulus are remarkably improved as compared with the case of using polyamide alone, and the comparison using glass beads is performed. Compared to Example 3, it was found that the same effects were obtained in both elastic modulus and strength. Further, in Comparative Example 4 containing 8% by mass of spherical carbon, which is outside the scope of the present invention, the mechanical strength was not different from the case where the polyamide of Comparative Example 1 was used alone, and the addition effect was not obtained. Further, from Tables 2 and 3, the present invention has almost the same mechanical strength in the X-axis direction and the Y-axis direction. On the other hand, in Comparative Example 2 in which a fibrous filler is used, all three directions have different mechanical strengths. I understood. Furthermore, from Table 2, it was found that in Examples 3, 4, and 8 to 10 in which the addition amount of the spherical carbon as the conductive material was changed, the volume resistivity also changed depending on the addition amount. That is, when the amount of spherical carbon added is large, the volume resistivity decreases, and when the amount of spherical carbon added is small, the volume resistivity increases. Further, even when the amount of spherical carbon added in Example 10 is 70% by mass, molding by selective laser sintering is possible, whereas in Comparative Example 6, when carbon black is used as the conductive material, Even if the amount added was 30% by mass, molding by selective laser sintering was impossible.

  Next, a recyclability test was performed on Examples 1 to 10 and Comparative Examples 1 to 4 that were moldable.

[Recyclability test]
After the completion of laser molding, the composite powder not irradiated with laser was collected and passed through a sieve having an opening of 250 μm to obtain a recycled material. A new composite material having the same composition as the recycled material was mixed at a mass ratio of 1: 1 using a screw mixer, and a modeling test was conducted in the same manner as in the example. The same material as above was used, and the recyclability test was conducted five times. Table 4 shows the bending strength transition and recyclability.

  As shown in Table 4, the composite powder of the present invention was repeated five times with the same material as in Comparative Example 1 used alone with polyamide and Comparative Example 4 containing 8% by mass outside the scope of the present invention. Even if it is used, it is a composite material that is excellent in recyclability and does not cause defects such as a decrease in mechanical strength and a decrease in density. Moreover, in the comparative example 2 which used the carbon fiber as a filler, when performing the reproduction | regeneration operation through a sieve, the carbon fiber was caught on the sieve and was not recyclable. Furthermore, in Comparative Example 3 using glass beads as the filler, the specific gravity was greatly reduced at the first stage of recycling, and as a result of analysis, it was found that the glass was separated and dropped out.

  From the above results, the molded product obtained by the present invention has higher mechanical strength compared to the case where polyamide is used alone, has mechanical strength comparable to other aggregates, and can be recycled. I found out I could get something. In addition, composite powders using spherical carbon as an aggregate can be easily molded by selective laser sintering, so the amount of spherical carbon added can be freely changed, preventing static electricity from conducting applications It was possible to obtain a volume resistivity corresponding to.

Recyclability test method

Claims (5)

Spherical aggregate having a true specific gravity of 0.8 to 2.0 g / cm ³ , an average particle size of 10 to 150 μm, and a mean particle size of 30 to 150 μm, which are used for selective laser sintering (SLS) A composite material powder comprising a resin powder as an essential component.   2. The composite material powder according to claim 1, comprising 10 to 80% by mass of a spherical aggregate having a sphericity of 0.7 to 1.0.   3. The composite material powder according to claim 1, wherein the spherical aggregate contains at least one of a spherical thermosetting resin cured product and a spherical carbon.   4. The composite material powder according to claim 1, which contains a resin powder having a sphericity of 0.6 to 1.0.   A method for producing a molded body by selectively laser sintering the composite material powder according to claim 1.

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