JP2021154737A - Powder for powder lamination molding method, powder lamination molding method and molded article - Google Patents

Abstract

To provide powder for a powder lamination molding method capable of forming a powder layer satisfactory in the addition rate of an assistant, satisfactory in the lamination formability (dispersibility) of powder and satisfactory in molding precision, namely, having uniform thickness and free from damage upon molding and producing a target molded article at high precision.SOLUTION: Powder for a powder lamination molding method comprises a thermoplastic resin and a water soluble resin, in which a hydroxyl group amount in the water soluble resin is 30 wt.% or higher and the amount of oxygen atoms in the water soluble resin comprised in particle surfaces measured by X-ray photoelectron spectroscopy measured under the following measurement conditions [1] is 0.01 to 15 atm%. Measurement conditions [1]: measurement apparatus: X-ray photoelectron spectroscopy K-Alpha (Thermo Fisher Scientific, Inc.), measurement mode: narrow mode excitation X-rays: monochromatic A| Kα(50 μm) and X-ray irradiation area size: 400×200 μm.SELECTED DRAWING: None

Description

The present invention relates to a powder for a powder additive manufacturing method containing a thermoplastic resin, a powder additive manufacturing method using the powder, and a modeled product.

In the powder additive manufacturing method, which is one of the three-dimensional modeling methods, a thin layer of a powder material such as a resin is heated to a temperature near the melting point of the resin powder using a heating means, sintered, and formed. This is a method of obtaining a three-dimensional modeled product by repeatedly forming a laminated body.
To form a thin layer of powder material, spray the powder material on a modeling table (also called a modeling stage) and smooth it with a recorder (blade or roller) (hereinafter, this operation is "applied" or "applied" or ". A powder layer having a uniform thickness (sometimes referred to as "filling"). At this time, as the heating means, a laser, an infrared lamp, a xenon lamp, a halogen lamp, or the like is used.

After irradiating the molding area of the powder layer with a heating medium such as a laser to melt-sinter the powder, the same operation is repeated to perform laminated molding. In order to improve the absorption efficiency of the heating medium after applying the powder to form the powder layer, there is also a method of applying a predetermined medium to the corresponding part of the molding.
The powder additive manufacturing method does not require the use of a mold, and various resin powders can be used as raw materials as long as they have a certain degree of heat resistance, and the resulting molded products are highly reliable, so they have been attracting attention in recent years. It is a technology that has been used.

In such a powder laminated molding method, as in Patent Document 1, good slipperiness or fluidity is imparted to the powder, and the thin layer formation in which the powder is developed into a thin layer is improved, or the powder is made into a fine powder. Attempts have been made to increase the bulk density or filling rate to impart high density and high mechanical strength to the modeled object.

Japanese Unexamined Patent Publication No. 2006-321711

On the other hand, according to the study of the present inventor, if only the slipperiness and fluidity are imparted as in Patent Document 1, the stackability (spreadability) of the powder becomes poor and the molding accuracy (formability) becomes poor. Was also found to be defective. More specifically, for example, in the powder lamination molding method, when molding powder, the average particle size of the powder particles is small, so that the contact area between the particles increases and the particles are electrostatically attracted to each other. There is a problem that the powders agglomerate with each other. When the powder is agglomerated and agglomerated, a powder layer having a uniform thickness cannot be smoothly formed on the modeling table, and the thickness may be uneven or a part where the powder does not exist (void or defective part) may be formed. .. Even if such a non-uniform powder layer is irradiated with a heating medium, a uniform molten state cannot be obtained. In addition, the modeling accuracy is also impaired, and in many cases, the desired modeled product cannot be obtained.

Moreover, as a method of avoiding the agglomeration of the powder as described above, addition of a dispersant such as silica and alumina can be mentioned. However, as a result of the study of the present inventor, when a dispersant is mixed with the resin powder and an attempt is made to increase the dispersion rate of the powder, among the dispersants mixed in the resin powder, a surplus dispersant that does not contribute to dispersibility However, it has been clarified that the properties of the modeled object are adversely affected, and the inherent properties of the resin such as heat resistance and mechanical properties are impaired.

Therefore, in the present invention, the addition rate of the auxiliary agent is good, the layered formability (spreadability) of the powder is good, and the molding accuracy (modeling property) is also good. An object of the present invention is to provide a powder for a powder additive manufacturing method, which can form a layer and can accurately produce a target modeled product.

As a result of diligent studies, the present inventors performed powder additive manufacturing using a powder for powder additive manufacturing that can directly apply an auxiliary agent such as a dispersant to the resin powder itself, thereby producing a surplus auxiliary agent in powder additive manufacturing. Therefore, the present invention is completed by finding that the auxiliary agent does not adversely affect the characteristics of the modeled object, the powder layering formability (dispersability) is good, and the modeling accuracy (modeling property) is also good. It came to. That is, the present inventor has found that these problems can be solved by using a powder for additive manufacturing method containing a specific amount of a thermoplastic resin and a water-soluble resin having a specific hydroxyl group amount. The present invention has been completed.

That is, the present invention relates to the following <1> to <9>.
<1> On the particle surface measured by X-ray photoelectron spectroscopy measured under the following measurement condition [1], which contains a thermoplastic resin and a water-soluble resin and has a hydroxyl group content of 30 wt% or more in the water-soluble resin. A powder for a powder laminated molding method in which the amount of oxygen atoms contained in the water-soluble resin is 0.01 atm% to 15 atm%.
Measurement condition [1]:
Measuring equipment: X-ray photoelectron spectroscopy K-Alpha (Thermo Fisher Scientific)
Measurement mode: Narrow mode Excited X-ray: Monochrome Al Kα (50 μm)
X-ray irradiation area size: 400 x 200 μm
<2> The amount of oxygen atoms in the water-soluble resin contained in the particle surface, which contains a thermoplastic resin and a water-soluble resin and has a hydroxyl group content of 30 wt% or more in the water-soluble resin and is measured by organic element analysis. A powder for a powder laminated molding method in which the content is 0.01 wt% to 10 wt%.
<3> The powder for additive manufacturing method according to <1> or <2>, wherein D50 is 5 μm or more and 120 μm or less as a particle size distribution.
<4> The powder for additive manufacturing method according to any one of <1> to <3>, wherein the mode of circularity is 0.6 or more.
<5> The powder laminated molding according to any one of <1> to <4>, wherein the heat of fusion of the thermoplastic resin in the powder for the powder laminated molding method in the DSC chart is 20 J / g or more and 140 J / g or less. Legal powder.
<6> The powder for additive manufacturing method according to any one of <1> to <5>, wherein the melting point of the thermoplastic resin in the powder for additive manufacturing method is 90 ° C. or higher and 230 ° C. or lower.
<7> The powder for additive manufacturing method according to any one of <1> to <6>, wherein the weight average molecular weight of the thermoplastic resin in the powder for additive manufacturing method is 30,000 or more.
<8> A powder additive manufacturing method using the powder for the powder additive manufacturing method according to any one of <1> to <7>.
<9> A modeled product using the powder for the powder additive manufacturing method according to any one of <1> to <7>.

According to the present invention, the powder layer formation property (spreadability) is good, and the modeling accuracy (modeling property) is also good, that is, a powder layer having a uniform thickness and no defects can be formed at the time of modeling. It is possible to provide a powder for a powder additive manufacturing method capable of accurately producing the modeled product.

The best mode for carrying out the present invention will be described in detail below, but the description of the constituent elements described below is a typical example of the embodiment of the present invention, and the present invention is limited to these contents. It's not a thing.

[Powder for additive manufacturing method]
The powder for the powder laminated molding method of the present invention contains a thermoplastic resin and a water-soluble resin, has a hydroxyl group content of 30 wt% or more in the water-soluble resin, and is contained on the particle surface measured by X-ray photoelectron spectroscopy. The amount of oxygen atoms in the water-soluble resin is 0.01 atm% to 15 atm%.

<Reason why the present invention is effective>
The reason why the present invention is effective is not clear yet, but it is presumed as follows. That is, since the powder for the powder lamination molding method of the present invention is a powder containing a specific water-soluble resin, the water-soluble resin on the surface of the powder adsorbs the auxiliary agent, and the auxiliary agent is adhered more efficiently than the conventional product. Can be done. Further, it is presumed that by efficiently adhering the auxiliary agent, it is possible to improve the dispersability at the time of molding without impairing the characteristics of the thermoplastic resin contained in the powder. Further, the powder for the powder additive manufacturing method of the present invention, which has been sprayed with good sprayability, not only has the powders densely laminated with each other, but also has an auxiliary agent or the like that does not adversely affect the formability. It is presumed that the formability) will also be good.

<Composition of thermoplastic resin>
The thermoplastic resin used for the powder for the powder additive manufacturing method of the present invention can be appropriately selected according to the function to be imparted to the modeled product to be modeled.
For example, amorphous resins, crystalline resins, and thermoplastic elastomers can be mentioned. Among these, amorphous resins and crystalline resins are preferable from the viewpoint of good powder additive manufacturing. Specific examples of these are as follows.

Acrylo-nitrile resin: acrylonitrile-butadiene-styrene copolymer resin (ABS resin), methyl methacrylate-butadiene-styrene copolymer resin (MBS resin), polystyrene, polyvinyl chloride, polymethylmethacrylate, polycarbonate, modified polyphenylene ether, polyether Among these, imide and the like can be mentioned, and among these, acrylonitrile-butadiene-styrene copolymer resin (ABS resin), methyl methacrylate-butadiene-styrene copolymer resin (MBS resin), polystyrene, etc. Polyvinyl chloride, polymethylmethacrylate and polycarbonate are preferable, and acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polystyrene, polymethylmethacrylate and polycarbonate are more preferable, and acrylonitrile-butadiene-styrene copolymer resin (ABS resin) and poly. Methyl methacrylate and polycarbonate are more preferable, polymethyl methacrylate and polycarbonate are particularly preferable, and polycarbonate is most preferable.

Crystalline resin: Polyester, polyolefins such as polypropylene, polyester, polyamide, polyvinyl alcohol, polyetherketone, polyetheretherketone, polyetherketoneketone, etc. Among these, powder laminate formability is good. , Polyetherketone, polyester, polyetherketone, polyetheretherketone, polyetherketoneketone are preferable, polyolefin, polyester, polyetherketone, polyetheretherketone are more preferable, polyolefin, polyester, polyetherketone are more preferable, polyolefin, Polyester is most preferred.

Thermoplastic elastomers: olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, polyester-based thermoplastic elastomers, and mixtures thereof.
The thermoplastic resin used for the powder for additive manufacturing method of the present invention is not limited to these resins, and one type or two or more types may be contained in any combination and ratio.

<Physical characteristics of thermoplastic resin>
The amount of heat of fusion in the DSC chart of the thermoplastic resin used for the powder for the powder laminated molding method of the present invention is preferably 20 J / g or more, more preferably 30 J / g or more, from the viewpoint of heat resistance and the amount of energy required for molding. More preferably 40 J / g or more, particularly preferably 50 J / g or more, preferably 140 J / g or less, more preferably 130 J / g or less, still more preferably 120 J / g or less, particularly preferably 110 J / g or less, most preferably. Is 90 J / g or less.

The lower limit of the melting point of the thermoplastic resin used for the powder for the powder additive manufacturing method of the present invention is not particularly limited, but from the viewpoint of the heat resistance of the obtained modeled product, it is preferably 90 ° C. or higher, preferably 100 ° C. or higher. Is more preferable, 110 ° C. or higher is more preferable, 115 ° C. or higher is further preferable, and 120 ° C. or higher is particularly preferable. The upper limit of the melting point of the thermoplastic resin used for the powder for the powder laminated molding method of the present invention is not particularly limited, but it is preferably 230 ° C. or lower from the viewpoint of the energy requirement for melting the material at the time of molding. The temperature is more preferably 200 ° C. or lower, further preferably 185 ° C. or lower, particularly preferably 170 ° C. or lower, and most preferably 155 ° C. or lower.

The lower limit of the weight average molecular weight (Mw) of the thermoplastic resin used for the powder for the additive manufacturing method of the present invention is preferably 30,000 or more, and more preferably 60,000 or more from the viewpoint of crystallinity. It is preferably 65,000 or more, more preferably 70,000 or more, and most preferably 75,000 or more. The upper limit is not particularly limited, but from the viewpoint of formability, 350,000 or less is preferable, 300,000 or less is more preferable, and 250,000 or less is further preferable.
The heat of fusion, melting point, and weight average molecular weight (Mw) of the thermoplastic resin are measured, for example, by the method described in the section of Examples described later.

The lower limit of the content of the thermoplastic resin in the powder for additive manufacturing of the present invention is not particularly limited, but from the viewpoint of formability, it is preferably 85% or more, and more preferably 90% or more. , 92% or more, more preferably 94% or more, and most preferably 95% or more. The upper limit of the content of the thermoplastic resin in the powder for additive manufacturing of the present invention is not particularly limited, but is usually preferably 99.9% or less.

<Water-soluble resin>
The water-soluble resin used in the powder for the powder lamination molding method of the present invention has a hydroxyl group content of 30 wt% or more, and the amount of oxygen atoms in the water-soluble resin contained in the particle surface measured by X-ray photoelectron spectroscopy is 0. It is 0.01 atm% to 15 atm%.

The lower limit of the amount of hydroxyl groups in the water-soluble resin used for the powder for additive manufacturing method of the present invention is 30 wt% or more, preferably 32 wt% or more, preferably 34 wt% or more from the viewpoint of stabilizing the interface between multiple components. More preferably, 36 wt% or more is further preferable, and 37 wt% or more is particularly preferable. The upper limit of the amount of hydroxyl groups contained in the water-soluble resin used for the powder for additive manufacturing method of the present invention is not particularly limited, but is preferably 50 wt% or less, preferably 48 wt% or less from the viewpoint of ensuring ease of purification. Is more preferable, 46 wt% or less is further preferable, and 44 wt% or less is particularly preferable.

The amount of hydroxyl groups in the water-soluble resin can be calculated by the 1H-NMR method (nuclear magnetic resonance method).
The water-soluble resin is not particularly limited as long as the above conditions are satisfied, and examples thereof include polyvinyl alcohols. Specific examples of polyvinyl alcohols include a copolymer of a diol having a double bond such as a butenediol / vinyl alcohol copolymer and a vinyl alcohol, a sulfonic acid group-containing vinyl alcohol copolymer, and an oxyalkylene group-containing vinyl. Examples thereof include alcohol copolymers, carboxylic acid group-containing vinyl alcohol copolymers, and acetoacetyl group-containing vinyl alcohol copolymers. Among these, because of their high hydrophilicity, there are two types such as butenediol / vinyl alcohol copolymers. A copolymer of a diol having a double bond and a vinyl alcohol, a vinyl alcohol copolymer containing a sulfonic acid group is more preferable, and a copolymer of a diol having a double bond such as a butenediol / vinyl alcohol copolymer and a vinyl alcohol is used. More preferably, among them, a butenediol / vinyl alcohol copolymer is most preferable.

The lower limit of the content of the particle surface measured by X-ray photoelectron spectroscopic analysis of oxygen atoms in the water-soluble resin used for the powder for the powder lamination molding method of the present invention is 0.01 atm% or more, and the addition rate of the auxiliary agent. From the viewpoint of the above, 0.05 atm% or more is preferable, 0.1 atm% or more is more preferable, 0.2 atm% or more is further preferable, 0.5 atm% or more is particularly preferable, and 0. Most preferably, it is 8 atm% or more. Further, the upper limit is 30 atm% or less, preferably 20 atm% or less, more preferably 15 atm% or less, further preferably 10 atm% or less, and particularly preferably 7 atm% or less from the viewpoint of formability. preferable.

The content of oxygen atoms on the particle surface in the water-soluble resin used for the powder for the powder lamination molding method of the present invention may be measured by organic element analysis.

The lower limit of the content of the particle surface measured by the organic element analysis of oxygen atoms in the water-soluble resin used for the powder for the powder lamination molding method of the present invention is 0.01 wt% or more, and the viewpoint of the addition rate of the auxiliary agent Therefore, it is preferably 0.05 wt% or more, more preferably 0.1 wt% or more, and further preferably 0.15 wt% or more. Further, the upper limit is 10 wt% or less, preferably 8 wt% or less, more preferably 5 wt% or less, further preferably 2 wt% or less, and further preferably 1 wt% or less from the viewpoint of formability. It is preferably 0.5 wt% or less, and most preferably 0.35 wt% or less.

<Auxiliary agent>
In the present invention, examples of the auxiliary agent include a dispersant, a stabilizer, and "other components" described below. Among these, it is preferable to use a dispersant or a stabilizer because it greatly affects the mechanism of action of the present invention.

(Dispersant)
The powder for additive manufacturing method of the present invention preferably contains a dispersant.
Dispersants include silica, alumina, aluminum silicate, colloidal silica gel, pearlite, vermiculite, calcium sulfate, talc, cement, chalk powder, clay, calcium carbonate, calcium carbonate / magnesium carbonate mixture, diatomaceous earth, silicic anhydride and the like. .. Among them, in the present invention, silica and alumina are preferable, and silica is more preferable, from the viewpoint of chemical and physical stability.

(Stabilizer)
The powder for additive manufacturing method of the present invention preferably contains a stabilizer.
Examples of the stabilizer include a phenol-based stabilizer, an amine-based stabilizer, a phosphorus-based stabilizer, and a thioether-based stabilizer. Among them, in the present invention, phosphorus-based stabilizers and phenol-based stabilizers are preferable, and phenol-based stabilizers are more preferable.

As the phenol-based stabilizer, a hindered phenol-based stabilizer is preferable, and for example, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,) 5-Di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythritol tetrakis (β-laurylthiopropionate), thiodiethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) Propionate], N, N'-hexane-1,6-diylbis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide], 2,4-dimethyl-6- (1-methylpenta) Decyl) Phenol, diethyl [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] phosphonate, 3,3', 3 ", 5,5', 5" -hexa-tert- Butyl-a, a', a "-(methicylene-2,4,6-triyl) tri-p-cresol, 4,6-bis (octylthiomethyl) -o-cresol, ethylenebis (oxyethylene) bis [ 3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate], hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,3,5 -Tris (3,5-di-tert-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 2,6-di-tert- Butyl-4- (4,6-bis (octylthio) -1,3,5-triazine-2-ylamino) phenol, 2- [1- (2-hydroxy-3,5-di-tert-pentylphenyl) ethyl ] -4,6-di-tert-pentylphenyl acrylate and the like.

Among them, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, Pentaerythritol tetrakis (β-laurylthiopropionate) is preferred.
Specific examples of such phenolic stabilizers include "Irganox 1010" and "Irganox 1076" manufactured by BASF, "Adeka Stub AO-50" and "Adeka Stub AO" manufactured by ADEKA. -60 ”,“ Adeka Stab AO-412S ”and the like.

<Other ingredients>
The powder for additive manufacturing method of the present invention may be a powder for powder additive manufacturing method containing a resin component or an additive other than the above-mentioned components. This is sometimes referred to as the powder for the additive manufacturing method of the present invention.
Other additives include crystal nucleating agents, antioxidants, color inhibitors, pigments, dyes, UV absorbers, mold release agents, lubricants, flame retardants, antistatic agents, inorganic fibers, organic fibers, inorganic particles and Organic particles are exemplified.
Examples of the flame retardant include the compounds described in paragraphs 0033 to 0040 of Japanese Patent Application Laid-Open No. 2015-205127, which are incorporated in the present specification.

<Resin composition as a precursor and its production>
The method for producing a resin composition which is a precursor of the powder for additive manufacturing method of the present invention is not particularly limited as long as it contains each component. The resin composition as a precursor can be produced by mixing each component and melt-kneading. For example, the thermoplastic resin described in the present invention, a stabilizer, and other components to be blended if necessary are premixed using various mixers such as a tumbler and a Henschel mixer, and then a Banbury mixer, a roll, a brabender, and the like. The resin composition can be produced by melt-kneading with a single-screw kneading extruder, a twin-screw kneading extruder, a kneader or the like.

It is also possible to produce a resin composition without premixing each component or by premixing only a part of the components and supplying the components to an extruder using a feeder for melt kneading.
Further, a resin composition obtained by mixing some components in advance, supplying them to an extruder, and melt-kneading the resin composition is used as a masterbatch, and the masterbatch is mixed with the remaining components again and melt-kneaded to obtain a resin. Compositions can also be produced.
The heating temperature for melt-kneading can be appropriately selected from the range of usually 150 to 300 ° C. If this heating temperature is too high, the resin may deteriorate and decomposition gas may be easily generated. Therefore, it is desirable to select a screw configuration in consideration of shear heat generation and the like. It is desirable to use stabilizers and antioxidants in order to suppress decomposition during kneading and molding in the subsequent process.

<Powder manufacturing method for additive manufacturing method>
As a powdering means for producing the powder for the powder laminated molding method of the present invention, a melt granulation in which a resin composition melted near the melting point is made into a fibrous form and then cut, or a resin material composed of the resin composition can be used. There is a method of producing resin particles by crushing or breaking by applying impact or shear, or by dispersing a resin incompatible with the matrix component in a meltable matrix component and then removing the matrix component. In order to improve the coatability of the powder in three-dimensional modeling, it is preferable that the shape of the powder is rounded, that is, the roundness is large. It is preferable to select a powder method suitable for the thermoplastic resin contained in the powder for the powder lamination molding method.
When pulverized by pulverization, it is preferable to perform a classification step after pulverization from the viewpoint of removing the stretched powder from the pulverized powder to expand the circularity.
In this case, examples of the classification method include wind power classification, sieve classification, and the like.

<Physical characteristics of powder for additive manufacturing method>
The melting point of the powder for additive manufacturing method of the present invention is not particularly limited, but from the viewpoint of heat resistance of the obtained modeled product, the lower limit is preferably 90 ° C. or higher, more preferably 100 ° C. or higher. It is more preferably 110 ° C. or higher, particularly preferably 105 ° C. or higher, and most preferably 120 ° C. or higher. The upper limit is preferably 230 ° C. or lower, more preferably 220 ° C. or lower, further preferably 215 ° C. or lower, particularly preferably 210 ° C. or lower, and 205 ° C. or lower. Is the most preferable.

The amount of heat of fusion of the powder for the powder additive manufacturing method of the present invention is not particularly limited, but from the viewpoint of heat resistance of the obtained modeled product, it is preferably 30 J / g or more, more preferably 35 J / g or more, still more preferably 40 J / g. It is g or more, particularly preferably 45 J / g or more, and most preferably 50 J / g or more. Further, it is preferably 200 J / g or less, more preferably 150 J / g or less, further preferably 120 J / g or less, particularly preferably 90 J / g or less, and most preferably 75 J / g or less.

Of the particle size distribution of the powder for the powder additive manufacturing method of the present invention, D10 in which the volume ratio occupies 10% is not particularly limited, but the uniform dispersability and dispersal rate at the time of forming the powder layer (here, the dispersal rate is It is obtained by the method described in the section of Examples described later and serves as an index of dispersability), and is usually preferably 1 μm or more, more preferably 3 μm or more, still more preferably 5 μm or more, particularly preferably. Is 7 μm or more, most preferably 10 μm or more. The upper limit of D10 is not particularly limited, but is usually preferably 50 μm or less, more preferably 40 μm or less, more preferably 30 μm or less, from the viewpoint of dispersability of the powders in the voids when the powder is applied on the modeling table. It is more preferably 25 μm or less, and particularly preferably 20 μm or less.

Of the particle size distribution of the powder for additive manufacturing method of the present invention, D50 in which the volume ratio occupies 50% is not particularly limited, but is usually preferable from the viewpoint of applying the powder to a thickness within a predetermined range at the time of modeling. Is 5 μm or more, more preferably 8 μm or more, more preferably 10 μm or more, still more preferably 12 μm or more, particularly more preferably 15 μm or more, still more preferably 17 μm or more, most 20 μm or more, and usually preferably 120 μm or less, more preferably. Is 95 μm or less, more preferably 80 μm or less, more preferably 70 μm or less, still more preferably 60 μm or less, particularly preferably 50 μm or less, and most preferably 40 μm or less.

Of the particle size distribution of the powder for additive manufacturing method of the present invention, D90 in which the volume ratio occupies 90% is not particularly limited, but is usually preferably 250 μm or less, more preferably 200 μm or less from the viewpoint of resolution at the time of modeling. , More preferably 170 μm or less, still more preferably 130 μm or less, particularly preferably 80 μm or less, and most preferably 60 μm or less. The lower limit of D90 is not particularly limited, but from the viewpoint of coating efficiency at the time of powder coating on a modeling table, it is usually preferably 10 μm or more, more preferably 15 μm or more, more preferably 20 μm or more, still more preferably. It is 25 μm or more, particularly preferably 30 μm or more, and most preferably 35 μm or more.

The particle size distribution of the powder for additive manufacturing method is measured by the method described in the section of Examples described later.
The circularity (arithmetic average value) of the powder for the powder laminated molding method of the present invention is preferably 0.60 or more, more preferably 0.65 or more, still more preferably 0.65 or more, from the viewpoint of the dispersibility or spraying rate of the powder at the time of modeling. Is 0.66 or more, particularly preferably 0.67 or more, and most preferably 0.68 or more. The upper limit of circularity (arithmetic mean) is usually preferably 1.0 or less.

The mode of the circularity of the powder for the powder laminated molding method of the present invention is preferably 0.50 or more, more preferably 0.60 or more, still more preferably 0.60 or more, from the viewpoint of the dispersibility or spraying rate of the powder at the time of modeling. It is 0.70 or more, particularly preferably 0.75 or more, and most preferably 0.8 or more. The upper limit of the circularity is usually preferably 1.0 or less, more preferably 0.99 or less, more preferably 0.98 or less, still more preferably 0.97 or less, particularly preferably 0.96 or less, most preferably. It is 0.95 or less.
The circularity of a powder is a value obtained by dividing the circumference of a circle having the same area as the projected area of the corresponding particle by the length of the contour of the particle projection diagram of the corresponding particle, and is measured by a circularity measuring device.

[Powder additive manufacturing method, modeled product]
The powder laminated molding method of the present invention is a method for producing a modeled product of the present invention using the above-mentioned powder for the powder laminated molding method of the present invention.
The powder additive manufacturing method of the present invention can be carried out according to a conventional method using an ordinary powder additive manufacturing device.

Examples of the powder laminated modeling apparatus include a modeling stage (modeling table), a thin layer forming means for forming a thin layer of powder material on the modeling stage, and heating by irradiating the formed thin layer with a laser. By doing so, the heating means for forming the modeled object layer by melting and bonding the particles of the powder material, the moving means for moving the modeling stage in the stacking direction (vertical direction), and controlling these to form a thin layer, heat, By repeatedly moving the stage, it is possible to use a powder laminating molding apparatus having a control means for laminating the shaped object layers.

For example, in the case of laser heating, this powder additive manufacturing device can be used to perform modeling through the following steps (1) to (4).
(1) Step of forming a thin layer of powder material (2) Step of selectively irradiating a preheated thin layer with laser light to form a molded product layer formed by melt-bonding powder materials, or a preliminary A melting accelerator (a component that promotes melting of the resin) and a surface decoration agent (a component that forms the outline of the layer) are selectively sprayed on the heated thin layer, and then the infrared lamp, xenon lamp, and halogen lamp are applied as a whole. In some cases, the powder material is melt-bonded to form a molded product layer.

(3) Step of lowering the modeling stage by the thickness of the formed modeling object layer (4) Steps (1) to (3) are repeated a plurality of times in this order to stack the modeling object layers.

In step (1), a thin layer of the powder material is formed. For example, the powder material supplied from the powder supply unit is spread flat on the modeling stage by a recorder (blade or roll). The thin layer is formed directly on the build stage or in contact with the powder material already spread or the already formed build layer.

The thickness of the thin layer can be set according to the thickness of the modeled object layer. The thickness of the thin layer can be arbitrarily set according to the accuracy of the three-dimensional model to be manufactured. The thickness of the thin layer is usually about 0.01 to 0.3 mm.
In the step (2), the laser is selectively irradiated to the position where the modeled object layer should be formed among the formed thin layers, and the powder material at the irradiated position is melt-bonded. As a result, the adjacent powder materials are melted together to form a melt-bonded body, which becomes a modeled object layer. At this time, since the powder material that has received the energy of the laser is melt-bonded to the already formed layer, adhesion between adjacent layers also occurs. The powder material that has not been irradiated with the laser is recovered as surplus powder and reused as the recovered powder.

Alternatively, instead of selectively irradiating the laser, a melting accelerator (a component that promotes melting of the resin) and a surface decoration agent (a component that forms the outline of the layer) are selectively sprayed, followed by an infrared lamp and xenon. The entire surface is irradiated with a lamp or a halogen lamp to melt-bond the powder material. As in the case of the laser, the powder material that has not been melt-bonded is recovered as surplus powder and reused as the recovered powder.

In the step (3), the modeling stage is lowered by the thickness of the modeled object layer formed in the step (2) to prepare for the next step (1).
The temperature of the modeling area during additive manufacturing is preferably a temperature about 5 to 20 ° C. lower than the melting point of the resin composition used. The modeling time varies depending on the size of the modeled product.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.

[Method for measuring physical properties of thermoplastic resin]
<Melting point / heat of fusion>
5 to 7 mg of the resin composition was weighed and packed in a sample pan to prepare a pan for measurement. Using a differential scanning calorimeter (PerkinElmer's Diamond DSC, input compensation method), the temperature was raised from 20 ° C. to 250 ° C. at a heating rate of 10 ° C./min under a nitrogen atmosphere. The DSC curve obtained in the first temperature rise measurement is analyzed, and the temperature at the apex of the endothermic peak is calculated as the melting point by using the straight line connecting the start point of the endothermic peak and the end point of the endothermic peak as the baseline. bottom. Further, the width of the endothermic peak at the midpoint of the line segment in the vertical axis direction drawn from the endothermic peak to the baseline was set as the half-value width, and the area surrounded by the endothermic peak and the extension of the baseline was calculated as the amount of heat of fusion.

<Weight average molecular weight (Mw)>
The measurement sample was dissolved in a solution of 1,1,1,3,3,3-hexafluoroisopropanol and chloroform in a 1/1 mass ratio to a concentration of 0.1% by mass. Further, it was diluted with chloroform to 0.02% by mass. The resulting solution was filtered through a 0.45 μm PTFE filter to prepare a sample for size exclusion chromatography (SEC) analysis.

The molecular weight calibration was performed by dissolving 12 types of polystyrenes having known molecular weights in chloroform. The SEC measurement was performed in the same manner as the sample.
The molecular weight calibration curve was created by plotting the elution times and Log molecular weights of 12 types of polystyrenes having known molecular weights.
The measurement conditions are as follows.

Column: TSK Gel G5000HHR + G3000HHR
(7.8 mm diameter x 300 mm lens x 2)
Temperature: 40 ° C
Mobile phase: 0.5% chloroform acetate solution Flow rate: 1.0 mL / min
Sample concentration: 0.02% by weight
Injection volume: 50 μL
Detector: UV
Detection wavelength: 254 nm
Molecular Weight Calibration Standard Sample: Monodisperse Polystyrene

[Method of measuring physical properties of water-soluble resin]
<Amount of hydroxyl groups in water-soluble resin>
It can be calculated by the 1H-NMR method (nuclear magnetic resonance method).
Measurement was performed at 80 ° C. for 1 hour using Bruker's AV400 and a mixed solvent of DMSO (dimethyl sulfoxide) -d6 and TFA (trifluoroacetic acid) as a solvent.

[Powder evaluation method for additive manufacturing method]
<Oxygen atom content in water-soluble resin>
(X-ray photoelectron spectroscopy (XPS))
The content of oxygen atoms in the water-soluble resin contained on the surface of the powder particles was measured using X-ray photoelectron spectroscopy Thermo Fisher Scientific "K Alpha". The excited X-ray is monochrome Al Kα, and the X-ray irradiation area size is 400 × 200 μm. In addition, a powder sample jig was used for the measurement.
The oxygen and carbon atoms observed in the XPS measurement are derived from the water-soluble resin remaining on the surface and the thermoplastic resin (simply called resin) that is incompatible with the water-soluble resin. Therefore, the molar ratio of the resin remaining on the surface to the water-soluble resin was calculated from the composition information and the C and O ratios obtained from the XPS measurement of the resin, and the oxygen atom of the water-soluble resin remaining on the surface was calculated from the molar ratio. The derived peak area was determined, and the amount of oxygen atoms in the water-soluble resin on the particle surface was calculated from the following formula.
Atomic weight of oxygen in the water-soluble resin on the particle surface = (peak area derived from oxygen atom of water-soluble resin) / {(peak area derived from carbon atom of water-soluble resin) + (peak area derived from carbon atom of resin) ) + (Peak area derived from oxygen atom of water-soluble resin) + (Peak area derived from oxygen atom of resin)}

(Organic elemental analysis)
The organic element analysis was carried out in CHNS mode and O mode using an elemental analyzer Vario EL cube (manufactured by Elemental).
Evaluation of Oxygen Atomic Weight in Water-Soluble Resin Contained in Particles The mass ratio of resin and residual water-soluble resin was calculated from the elemental ratio (O / C) of oxygen to carbon measured by organic elemental analysis.

<Thermal characteristics>
(Chemical value of melting, melting point)
The heat of fusion and melting point of the powder for additive manufacturing method were measured by the same method as in the case of the above-mentioned thermoplastic resin.

<Particle size distribution>
5 g of the powder was weighed, and the particle size distribution of the powder was measured with a particle size distribution measuring device (Microtech, MT3300). Of the detected particle size distributions, the particle sizes D10, D50, and D90 located at the powder frequency distributions of 10%, 50%, and 90% were determined, respectively.

<Mode of circularity>
The circularity was measured using LA-960 (manufactured by HORIBA, Ltd.). Weigh 3 to 5 g of powder, measure the projected area and contour length (perimeter) from the projection drawing of the particles using a circularity measuring device (Sysmex, FPIA-3000S), and measure the circularity by the following formula. Calculated. This was calculated for 80 particles, and the average value of the values was taken as the circularity of the powder.
Circularity = (perimeter of a circle having the same area as the projected area of the particle) / (length of the outline of the projection drawing of the particle)
Regarding the mode value of the circularity, the value having the largest ratio among all the particles measured when calculating the circularity was defined as the mode value of the circularity of the powder.

<Auxiliary agent addition rate>
The addition rate of the auxiliary agent contained in the particle surface of the powder was measured using X-ray photoelectron spectroscopy Thermo Fisher Scientific "K Alpha". The excited X-ray is monochrome Al Kα, and the X-ray irradiation area size is 400 × 200 μm. In addition, a powder sample jig was used for the measurement.
From the peak area of all elements measured by X-ray photoelectron spectroscopy of the powder for the powder laminated molding method, the ratio of the following specific elemental components X contained in the powder for the powder laminated molding method is calculated and contained on the powder surface. The content rate (atom%) of the element component X was determined.
Element component X: One or more selected from the group consisting of Si, Al, Fe, Ca, Mg

<Spray rate>
After placing 1 g of powder in the recess of a table having a recess of 20 mm × 20 mm in size and 0.2 mm in depth, the powder in the recess is smoothed by rolling a roller on the table at a speed of 3 mm / sec. Then, the volume of the powder filled in the recess was calculated from the weight and specific gravity of the powder filled in the recess, the volume ratio of the filled powder to the volume of the recess was obtained, and this was calculated as the spraying rate of the powder. And said.
The spray rate was measured at room temperature and a melting point of −20 ° C. The melting point means the melting point of the thermoplastic resin.

[Evaluation method of formability]
<Making a modeled object>
Using the powder bed melt-bonding printer Lisa Pro (Sinterit), set the modeling table temperature and pitch, prepare a 1BA type tensile test piece conforming to JIS K7161 and use it as a test piece for altitude difference / appearance measurement. bottom.

<Altitude difference>
The altitude difference of the obtained sintered sample test piece was measured using a microscope (HiROX, DIGITAL MICROSCOPE KH-8700). The altitude difference means the difference between the maximum altitude and the minimum altitude in the entire prepared test piece. The smaller the altitude difference is, the better the formability is, and it is preferably 100 μm or less, more preferably 50 μm or less.

<Appearance>
As the appearance of the obtained sintered sample,
〇: Sample that reproduces the shape of the set modeling data Δ: Sample that deviates from the shape of the modeling data.

[Example 1]
As a water-soluble resin, BVOH (butenediol / vinyl alcohol copolymer, methanol, water-soluble resin synthesized from methyl acetate, amount of hydroxyl groups: 37.8%) pellets, and as a thermoplastic resin, PP (Nippon Polypro Co., Ltd.) Ltd. trade name Novatec FY6H) (heat of fusion: 101J / g, melting point: 169 ° C., a weight average molecular weight ^{(Mw): 3.35 × 10 5} ) pellets in advance 7: after blended at a ratio of 3, biaxial It was put into the main hopper of the kneading extruder.

The mixed resin was melt-kneaded under the conditions of a discharge rate of 3 kg / h, a cylinder temperature of 190 ° C., and a screw rotation speed of 50 rpm.
It was extruded by an extruder, and the obtained melt-kneaded product was cut with a pelletizer or the like and pelletized.
The obtained strand was put into water (or hot water at 50 ° C.) so as to have a concentration of 20 wt%, and BVOH was dissolved while stirring under the condition of 200 rpm / 30 min.

The obtained solution is filtered by suction filtration, and the solid content (PP) is collected. The collected solid content is put into water (or warm water) again, and the mixture is stirred so as to wash the BVOH adhering to the solid content. At this time, the sprayability improving aid (nanosilica) is mixed with 0.5% of the solid content. This solution is filtered again by suction filtration to obtain a solid content. This washing step was repeated 6 times, and the solid content produced was 80 ° C./ovn. After drying with, if necessary, classification (sieving) was performed, and the mixture was classified into an appropriate particle size to obtain a PP powder to which nanosilica was attached.
In this way, a powder for additive manufacturing was obtained.
For the obtained powder, the content of the water-soluble resin, the thermal characteristics, the particle size distribution, the mode of circularity, the addition rate of the auxiliary agent, and the spraying rate were measured.
Furthermore, a 1BA type tensile test piece conforming to JIS K7161 was prepared from the obtained powder using a powder bed melt-bonding printer Lisa Pro (Sinterit) under the conditions of a modeling table temperature of 150 ° C. and a pitch of 0.125 mm. As a test piece for measuring altitude difference and appearance, the formability was evaluated and the results are shown in Table 1.

[Example 2]
Except that the mixing ratio of BVOH and PP was set to 6: 4, the mixed resin was set to a discharge rate of 5 kg / h, melt-kneaded under the conditions of a cylinder temperature of 210 ° C. and a screw rotation speed of 100 rpm, and the cleaning process was performed 5 times. , A powder was prepared in the same manner as in Example 1. Further, a modeled object was produced by the same method as in Example 1.

[Example 3]
The PP Japan Polypropylene Corporation, trade name WINTEC WFX4M pellets (heat of fusion: 65 J / g, melting point: 124 ° C., a weight average molecular weight ^{(Mw): 2.30 × 10 5} ) changed to and the washing step three times Except for the above, a powder was prepared in the same manner as in Example 2. Further, a modeled object was produced under the same conditions as in Example 1 except that the modeling table temperature was changed to 105 ° C., and the formability was evaluated.

[Example 4]
BVOH pellets and PC (polycarbonate) Mitsubishi Gas Chemical Company, Inc. trade name Iupiron H4000) pellets (glass transition temperature: 141 ° C., weight average molecular weight (Mw): 3.54 × 10 ⁴ ) at a ratio of 7: 3 in advance. After blending, it was kneaded with brabender.
The obtained resin composition was put into water (or hot water at 50 ° C.) so as to have a concentration of 20 wt%, and BVOH was dissolved while stirring under the conditions of 200 rpm / 30 min to obtain a powder by the same method as in Example 3.

[Comparative Example 1]
In Example 1, a powder for additive manufacturing method was obtained in the same manner as in Example 1 except that the production method was changed to the freeze pulverization method.
The method of freeze crushing is as follows.
Since it is generally difficult to pulverize a granular resin at room temperature, the PP raw material is first precooled with liquid nitrogen to freeze the raw material. The frozen raw material is quantitatively transported from the screw feeder to the mill portion, and the frozen raw material is crushed in the mill portion. A frozen finely pulverized product is obtained by pulverizing the resin by utilizing the low temperature brittleness of the resin. The crushed particles are collected in a cyclone by a blower. If necessary, it was classified (sieved) and classified into an appropriate particle size to obtain a powder for additive manufacturing method.
For this powder, a modeled product was prepared in the same manner as in Example 1, evaluated, and the results are shown in Table 1.

[Comparative Example 2]
In Example 1, the cleaning step was performed three times, and the dispersability improving aid (nanosilica) was not mixed during the cleaning step, and after obtaining a dry solid content, the nanosilica was adjusted to 0.5% of the solid content. A powder for additive manufacturing was obtained in the same manner as in Example 1 except that a PP powder to which nanosilica was attached was obtained by dry blending.
Further, a modeled object was produced by the same method as in Example 1, and the formability was evaluated.

[Comparative Example 3]
In Example 3, powder for additive manufacturing method was obtained in the same manner as in Example 3 except that the number of times of filtration was one.

As is clear from the above results, since the powder for additive manufacturing method of the present invention contains a predetermined amount of a water-soluble resin having a specific hydroxyl group amount, a high addition rate is obtained when an auxiliary agent is added after powdering. It can be realized. Further, since the powder for the powder laminated molding method of the present invention has the most frequent values of particle size distribution and circularity within a predetermined range, the accuracy of the thickness of the powder layer at the time of powder application in the molding area and the recess of the molding table. The dispersion rate of the powder on the powder is improved, and the uniformity when melting with a laser, an infrared lamp, a xenon lamp, a halogen lamp, or the like is improved. As a result, the target three-dimensional modeled product can be manufactured with good formability and accuracy.

Claims (9)

Contains thermoplastic and water-soluble resins
The amount of hydroxyl groups in the water-soluble resin is 30 wt% or more, and the amount of hydroxyl groups is 30 wt% or more.
Powder for powder lamination molding method in which the amount of oxygen atoms in the water-soluble resin contained in the particle surface measured by X-ray photoelectron spectroscopy measured under the following measurement condition [1] is 0.01 atm% to 15 atm%. ..
Measurement condition [1]:
Measuring equipment: X-ray photoelectron spectroscopy K-Alpha (Thermo Fisher Scientific)
Measurement mode: Narrow mode Excited X-ray: Monochrome Al Kα (50 μm)
X-ray irradiation area size: 400 x 200 μm Contains thermoplastic and water-soluble resins
The amount of hydroxyl groups in the water-soluble resin is 30 wt% or more, and the amount of hydroxyl groups is 30 wt% or more.
A powder for a powder laminated molding method in which the amount of oxygen atoms contained in the water-soluble resin contained in the particle surface is 0.01 wt% to 10 wt% as measured by organic elemental analysis. The powder for additive manufacturing method according to claim 1 or 2, wherein D50 is 5 μm or more and 120 μm or less as a particle size distribution. The powder for additive manufacturing method according to any one of claims 1 to 3, wherein the mode of circularity is 0.6 or more. The powder for the powder laminated molding method according to any one of claims 1 to 4, wherein the amount of heat of melting of the thermoplastic resin in the powder for the powder laminated molding method in the DSC chart is 20 J / g or more and 140 J / g or less. The powder for additive manufacturing method according to any one of claims 1 to 5, wherein the melting point of the thermoplastic resin in the powder for additive manufacturing method is 90 ° C. or higher and 230 ° C. or lower. The powder for additive manufacturing method according to any one of claims 1 to 6, wherein the weight average molecular weight of the thermoplastic resin in the powder for additive manufacturing method is 30,000 or more. A powder additive manufacturing method using the powder for the powder additive manufacturing method according to any one of claims 1 to 7. A modeled product using the powder for the powder additive manufacturing method according to any one of claims 1 to 7.