JP7836185B2 - A method for manufacturing a molded object from thermoplastic resin using a 3D printer, and a polishing pad obtained thereby. - Google Patents

Description

This invention relates to a method for manufacturing a molded object formed from thermoplastic resin using a 3D printer, and to a polishing pad obtained thereby.

In recent years, so-called 3D printing technology has been used as a technique to create three-dimensional objects from resin materials based on three-dimensional data designs such as 3D CAD and 3D CG.
3D printers, which utilize 3D printing technology, are becoming increasingly common. For example, when using a 3D printer to create objects from thermoplastic resin, it is possible to create resin objects without using a molding machine tailored to a specific object (for example, a mold or template for molding a specific shape), as was done in the past.

One example of a 3D printing method for creating resin materials is the Fused Deposition Modeling (FDM) method, which involves heating and melting thermoplastic resin, extruding it from a nozzle, and building up the object layer by layer on a build plate.
For example, Patent Document 1 describes a material for three-dimensional molding by fused deposition modeling (FDM) comprising a specific component blended in a specific amount with a polylactic acid resin, as well as a filament, particles, or pellets for a FDM 3D printing device formed from the material, and a molded object formed from the filament, particles, or pellets.
Furthermore, Patent Document 2 describes a manufacturing method for obtaining a three-dimensional object using a 3D printer, which uses a molding material characterized by being formed as a long fiber bundle composed of multiple synthetic fibers, wherein at least some of the fibers among the multiple synthetic fibers contain a functional additive.
Another example of a 3D printing method for creating resin materials is stereolithography (SLA (Stereo Lithography Apparatus)), which involves irradiating a photocurable liquid resin with energy rays such as ultraviolet light, curing the resin layer by layer to create a three-dimensional object.
For example, Patent Document 3 describes an additive manufacturing apparatus for producing a three-dimensional object using a curable resin that hardens with radiation, the apparatus comprising a filter unit.
Other known three-dimensional fabrication methods include the inkjet method, which replaces the ink of an inkjet printer with energy-curable resin and builds up layers of cured resin while curing it with energy rays after it is ejected from the ink head.

International Publication No. 2015/037574 International Publication No. 2016/129613 Special table 2018-521888 publication

By using 3D printing technology, it becomes possible to reduce resin material loss compared to conventional methods such as extrusion molding and injection molding, resulting in benefits such as cost reduction and efficient use of resources.
On the other hand, unlike conventional methods, when using a 3D printer to create thermoplastic resins, there is a risk of foreign matter contamination. If foreign matter is present in the resulting object, it can lead to a decrease in the quality of the object, or, depending on the application, make the object unusable. However, until now, methods for removing foreign matter in thermoplastic resins created using 3D printers have not been sufficiently studied.
For example, while Patent Documents 1 and 2 mentioned above disclose thermoplastic resins suitable for 3D printing, they do not disclose how to remove foreign matter from the resin during 3D printing.
Furthermore, Patent Document 3 describes a method for molding using a curable resin that hardens upon radiation such as light, in which liquid thermosetting resin is circulated and passed through a filter to prevent the inclusion of large particles. However, this method cannot be applied to molding methods using thermoplastic resins that need to be melted by heating immediately before being extruded from the nozzle.

Therefore, the present invention aims to provide a method for manufacturing a 3D-printed object using thermoplastic resin that can prevent the inclusion of foreign matter.

This invention encompasses the following inventions.
[1] A manufacturing method for obtaining a molded object by melting a thermoplastic resin using a 3D printer, extruding it from a nozzle, and solidifying it, characterized in that the thermoplastic resin passes through a filter between the time it melts in the 3D printer and the time it is extruded from the nozzle.
[2] The method for manufacturing a molded object according to [1], wherein the filter is a metal filter.
[3] The method for manufacturing a molded product according to [1] or [2], wherein the thermoplastic resin is polyurethane.
[4] A method for manufacturing a molded object according to any one of [1] to [3], wherein the thermoplastic resin is supplied to the 3D printer in pellet form.
[5] The method for manufacturing a molded object according to [4], wherein dry nitrogen with a dew point temperature of -30°C or lower, or dry air with a dew point temperature of -30°C or lower, is supplied to the 3D printer along with pelletized thermoplastic resin.
[6] The method for manufacturing a molded object according to any one of [1] to [5], wherein the molded object is a sheet with a thickness of 1.0 to 10 mm.
[7] A method for manufacturing a molded object according to any one of [1] to [6], wherein the molded object is an abrasive layer for a polishing pad.
[8] A polishing pad having a polishing layer obtained using the method for manufacturing a molded object described in [7] above.

According to the present invention, it is possible to provide a method for manufacturing molded objects using a thermoplastic resin with a 3D printer that can prevent the inclusion of foreign matter.

The following description is based on an example of an embodiment of the present invention. However, the embodiments shown below are illustrative examples for embodying the technical concept of the present invention, and the present invention is not limited to the following description.
The present invention also includes embodiments in which any of the matters described herein are arbitrarily selected or combined.
In this specification, any provision deemed preferable can be selected at will, and any combination of preferred provisions is considered more preferable.
In this specification, unless otherwise specified, the notation "XX to YY" as a numerical range means "XX or greater and YY or less." For example, when the numerical range is simply stated as "10 to 90," it represents the range of 10 or greater and 90 or less.
In this specification, the lower and upper limits described in steps for numerical ranges (content of each component, values calculated from each component, and physical properties, etc.) can be combined independently. For example, from a description of the same item as "preferably 10 to 90, more preferably 30 to 60," the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to arrive at "10 to 60."
Furthermore, regarding the numerical range, for example, based on the description "preferably 10 to 90, more preferably 30 to 60," the upper limit may not be specifically defined, and only the lower limit may be defined as "10 or more" or "30 or more." Similarly, the lower limit may not be specifically defined, and only the upper limit may be defined as "90 or less" or "60 or less."
Similarly, for example, from the descriptions "preferably 10 or more, more preferably 30 or more" and "preferably 90 or less, more preferably 60 or less" for the same item, it is possible to combine the "preferred lower limit (10)" and the "more preferred upper limit (60)" to get "10 or more and 60 or less". Also, similarly, the lower limit can be specified as "10 or more" or "30 or more", and similarly, the upper limit can be specified as "90 or less" or "60 or less".

[Method of manufacturing molded objects]
One aspect of the present invention is a method for manufacturing a molded object, which involves using a 3D printer to melt a thermoplastic resin, extrude it from a nozzle, and solidify it to obtain a molded object, characterized in that the thermoplastic resin passes through a filter between the time it melts in the 3D printer and the time it is extruded from the nozzle.
Furthermore, the manufacturing method for the molded object is preferably a method that uses a 3D printer to melt a thermoplastic resin, extrude it from a nozzle, and solidify it, thereby stacking multiple layers to obtain a molded object, characterized in that the thermoplastic resin passes through a filter between the time it melts in the 3D printer and the time it is extruded from the nozzle.
The following describes the various constituent elements used in a method for manufacturing a molded object, which is one aspect of the present invention.

<3D Printer>
A 3D printer is a device that can create three-dimensional objects using 3D printing technology, which shapes raw materials in three dimensions based on a design drawing of three-dimensional data such as 3D CAD or 3D CG. The 3D printer that can be used in this invention is not particularly limited, as long as it is a device that can produce an object by melting a thermoplastic resin, extruding it from a nozzle, and solidifying it. However, it is preferable to use a 3D printer that can produce the object by a fused deposition modeling (FDM) method, which heats and melts the aforementioned thermoplastic resin, extrudes it from a nozzle, and builds the object layer by layer on a build plate.

The 3D printer may be equipped with a single nozzle or multiple nozzles. There are no particular restrictions on the nozzle as long as the effects of the present invention are not impaired. For example, a nozzle with a tip hole diameter of preferably 0.1 to 10 mm, more preferably 0.3 to 7.0 mm, and even more preferably 0.5 to 3.0 mm can be used.

Furthermore, the nozzle may extrude the molten thermoplastic resin while moving. The thermoplastic resin extruded from the nozzle is extruded, for example, in the form of a filament or a drop, and as the nozzle moves, the molten material is placed on a build plate provided below the nozzle at a position indicated in advance based on the 3D data design drawing. Then, the object is formed by placing the solidified molten material as a single layer on the build plate, or the object is formed by stacking the solidified molten material one layer at a time from the bottom to the top.
Furthermore, in one embodiment of the manufacturing method for the molded object, the molded object may be formed while the nozzle remains fixed and the molded platform on which the thermoplastic resin discharged from the nozzle is placed is moved, or the molded object may be formed while both the nozzle and the molded platform are moved.

Furthermore, the solidification of the thermoplastic resin can be carried out by methods such as cooling, light irradiation, or thermosetting, with cooling being preferred.
There are no particular restrictions on the cooling method; it may be natural cooling, or it may be a method of forced cooling such as cooling the build plate or blowing cold air onto the build object, but natural cooling is preferred.

<Filter>
The filter is not particularly limited as long as it does not impair the effects of the present invention, and for example, a filter made of metal, thermoplastic resin, or thermosetting resin can be used. Among these, a metal filter is preferred because it can be used even when the temperature of the molten thermoplastic resin is higher and because of its durability.
Examples of the aforementioned metal filters include stainless steel mesh filters.

Furthermore, from the viewpoint of more effectively preventing foreign matter from entering the molded object, the filtration accuracy of the filter is preferably 200 μm or less, more preferably 100 μm or less, even more preferably 30 μm or less, even more preferably 20 μm or less, and even more preferably 15 μm or less.
Here, the "filtration accuracy of the filter" refers to the "nominal filtration accuracy," and for example, "filtration accuracy of 15 μm or less" means that the filter can remove 95% or more of particles with a particle size of 15 μm or larger.

Furthermore, the filter can be appropriately selected from viewpoints such as the type of foreign matter to be prevented from being mixed into the molded object and productivity, and there are no particular restrictions as long as the effects of the present invention are not impaired. However, as one embodiment of the filter, for example, preferably a filter in which the vertical and horizontal mesh sizes are independently 20 to 2800 meshes each, and the vertical and horizontal wire diameters are independently 20 to 200 μm each; more preferably a filter in which the vertical and horizontal mesh sizes are independently 100 to 2500 meshes each, and the vertical and horizontal wire diameters are independently 20 to 100 μm each; can be used.

The filter is installed between the time the thermoplastic resin melts in the 3D printer and the time it is extruded from the nozzle. Its installation location is not particularly limited, as long as it does not impair the effects of the present invention. For example, from the viewpoint of more effectively preventing the inclusion of foreign matter in the printed object, such as by removing foreign matter generated or mixed in after melting in the 3D printer, it is preferable to install the filter in the resin flow path within the nozzle.

<Thermoplastic resin>
The thermoplastic resin is not particularly limited as long as it can be melted in the 3D printer and extruded from the nozzle, but examples include: polyurethane; polyolefin resins such as copolymers polymerized from two or more selected from polyethylene, α-olefins, cyclic olefins, vinyl acetate, styrene, etc.; olefin-based thermoplastic elastomer (TPO); polyvinyl chloride; polyvinyl acetate; styrene resins such as polystyrene and acrylonitrile styrene copolymers; acrylic resins such as copolymers polymerized from one or more selected from methacrylic acid, methacrylic acid esters, acrylic acid esters, styrene, etc.; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polylactic acid, etc.; Examples include: ester-based thermoplastic elastomers; polyamides such as aliphatic polyamides, alicyclic polyamides, and aromatic polyamides; polyamide-based thermoplastic elastomers; polycarbonates; silicone-based elastomers such as silicone rubber; polylactic acid; natural rubber; diene rubbers which are copolymers of one or more selected from polybutadiene, polyisoprene, polychloroprene, or diene monomers such as butadiene, isoprene, and chloroprene, and one or more selected from vinyl monomers such as styrene, ethylene, propylene, various butenes, styrene, and acrylonitrile; alkyl acrylate rubbers (acrylic rubbers) which are copolymers with acrylic acid esters as the main monomer; fluororesins such as polytetrafluoroethylene; and fluoropolymer thermoplastic elastomers. These may be used individually or in combination of two or more.

(Thermoplastic polyurethane)
In one embodiment of the method for manufacturing the molded object, it is preferable that the thermoplastic resin is polyurethane. The polyurethane is also called thermoplastic polyurethane. Hereinafter, unless otherwise specified, the term "polyurethane" used in the method for manufacturing the molded object has the meaning of thermoplastic polyurethane.

The polyurethane is not particularly limited as long as the effects of the present invention are achieved, but for example, from the viewpoint of ease of manufacture, it is preferable that the polyurethane contains at least structural units derived from polyols, structural units derived from polyisocyanates, and structural units derived from chain extenders, and it is more preferable that it consists only of structural units derived from polyols, structural units derived from polyisocyanates, and structural units derived from chain extenders.
The total content of structural units derived from polyols, structural units derived from polyisocyanates, and structural units derived from chain extenders relative to the total structural units in the polyurethane is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass.

[Polyol]
Examples of the aforementioned polyols include polyether diols such as polyethylene glycol (PEG) and polytetramethylene ether glycol (PTMG); polyester diols; polycarbonate diols; and other polymer diols. These may be used individually or in combination of two or more.
Among these, from the viewpoint of ease of availability and excellent reactivity, one or more selected from the group consisting of polyetherdiols and polyesterdiols are preferred. When the molded material is used as the polishing layer of the polishing pad described later, it is more preferable from the viewpoint of excellent hydrophilicity to include at least one selected from the group consisting of a polyetherdiol selected from polyethylene glycol and polytetramethylene ether glycol; a polyesterdiol selected from poly(nonameethylene adipate), poly(2-methyl-1,8-octamethylene adipate), poly(2-methyl-1,8-octamethylene-co-nonameethylene adipate), and poly(methylpentane adipate); or derivatives thereof.

The number-average molecular weight of the polyol is preferably 450 to 3,000, more preferably 500 to 2,700, even more preferably 550 to 2,400, even more preferably 650 to 1,400, and even more preferably 800 to 1,200. A number-average molecular weight within this range is preferable because, when the molded object is used as a polishing layer (described later), it is easier to obtain a polishing layer with good properties such as rigidity, hardness, and hydrophilicity. Note that the number-average molecular weight of the polyol refers to the number-average molecular weight calculated based on the hydroxyl value measured in accordance with JIS K 1557-1:2007.

{polyetherdiol}
Examples of polyether diols include polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, poly(methyltetramethylene ether) glycol, and glycerin-based polyalkylene ether glycol. These may be used individually or in combination of two or more.
Among these, polyethylene glycol (PEG) and polytetramethylene ether glycol (PTMG) are preferred.

{Polyesterdiol}
Examples of polyester diols include polyester diols obtained by directly esterifying or transesterifying a low-molecular-weight diol with an ester-forming derivative such as a dicarboxylic acid or its ester or anhydride.

Examples of dicarboxylic acids include aliphatic dicarboxylic acids with 2 to 12 carbon atoms, such as oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, 2-methylsuccinic acid, 2-methyladipic acid, 3-methyladipic acid, 3-methylpentanedioic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanediic acid, and 3,7-dimethyldecanediic acid; dimerized aliphatic dicarboxylic acids (dimer acids) with 14 to 48 carbon atoms obtained by dimerizing unsaturated fatty acids obtained by fractional distillation of triglycerides, and their hydrogenated products (hydrogenated dimer acids); alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and orthophthalic acid. These may be used individually or in combination of two or more.

Examples of low molecular weight diols include aliphatic diols such as ethylene glycol, 1,3-propanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; and alicyclic diols such as cyclohexanedimethanol and cyclohexanediol. These may be used individually or in combination of two or more. Among these, diols with 6 to 12 carbon atoms are preferred, diols with 8 to 10 carbon atoms are more preferred, and diols with 9 carbon atoms are even more preferred.

{Polycarbonate diol}
Examples of polycarbonate diols include those obtained by the reaction of a low-molecular-weight diol with a carbonate compound. Examples of low-molecular-weight diols used to produce polycarbonate diols include those exemplified above.
Examples of carbonate compounds used to produce polycarbonate diols include dialkyl carbonates, alkylene carbonates, diaryl carbonates, and the like.
Examples of dialkyl carbonates include dimethyl carbonate and diethyl carbonate, while examples of alkylene carbonates include ethylene carbonate, and examples of diaryl carbonates include diphenyl carbonate.

[Polyisocyanate]
The aforementioned polyisocyanate is not particularly limited as long as it is a polyisocyanate used in the production of ordinary thermoplastic polyurethanes, for example, ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, dodecamethylene diisocyanate, isophorone diisocyanate, isopropylidene bis(4-cyclohexyl isocyanate), cyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethyl caproate, bis(2-isocyanatoethyl) fumarate, bis(2-isocyanatoethyl) carbonate, 2-isocyanatoethyl-2,6-diisocyana Aliphatic or alicyclic diisocyanates such as tohexanoates, cyclohexylene diisocyanates, methylcyclohexylene diisocyanates, bis(2-isocyanatoethyl)-4-cyclohexene; 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 2,4-tollylene diisocyanate, 2,6-tollylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate Aromatic diisocyanates such as annetes, m-xylylene diisocyanate, p-xylylene diisocyanate, 1,5-naphthylene diisocyanate, 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, chlorophenylene-2,4-diisocyanate, and tetramethylxylylene diisocyanate can be used. These may be used individually or in combination of two or more.
Among these, when the molded object is used as the polishing layer of the polishing pad described later, 4,4'-diphenylmethane diisocyanate (MDI) is preferred from the viewpoint of improving the wear resistance of the resulting polishing layer.

[Chain extender]
As the chain extender, any of the chain extenders conventionally used in the manufacture of ordinary polyurethanes may be used. Specifically, it is preferable to use low molecular weight compounds with a molecular weight of 300 or less that have two or more active hydrogen atoms in the molecule that can react with an isocyanate group. Examples include ethylene glycol, diethylene glycol (DEG), 1,2-propanediol, 1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol (BD), 1,5-pentanediol (PD), neopentyl glycol, 1,6-hexanediol, 2,5-dimethyl-2,5-hexanediol, 3-methyl-1,5-pentanediol (MPD), 1,4-bis(β-hydroxyethoxy)benzene, and 1,4-cyclohexanediol. Diols such as cyclohexanedimethanol (1,4-cyclohexanedimethanol, etc.), bis(β-hydroxyethyl) terephthalate, 1,9-nonanediol (ND), m-xylylene glycol, p-xylylene glycol, triethylene glycol, etc.; ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 3-methylpentamethylenediamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 1,2-diaminopropane, 1,3-diaminopropane, hydra Zin, xylylenediamine, isophoronediamine, piperazine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, tolylenediamine, xylenediamine, adipic acid dihydrazide, isophthalic acid dihydrazide, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylsulfone, 3,4-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 4,4'-methylene-bis(2-chloroaniline), 3,3'-dimethyl Tyl-4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl sulfide, 2,6-diaminotoluene, 2,4-diaminochlorobenzene, 1,2-diaminoanthraquinone, 1,4-diaminoanthraquinone, 3,3'-diaminobenzophenone, 3,4-diaminobenzophenone, 4,4'-diaminobenzophenone, 4,4'-diaminobibenzyl, 2,2'-diamino-1,1'-binaphthalene, Examples include 1,n-bis(4-aminophenoxy)alkanes (where n is 3 to 10), such as 1,3-bis(4-aminophenoxy)alkanes, 1,4-bis(4-aminophenoxy)alkanes, and 1,5-bis(4-aminophenoxy)alkanes; 1,2-bis[2-(4-aminophenoxy)ethoxy]ethane; 9,9-bis(4-aminophenyl)fluorene; and diamines such as 4,4'-diaminobenzanilide. These may be used individually or in combination of two or more.
Among these, at least one selected from the group consisting of 1,3-propanediol, 1,4-butanediol (BD), neopentyl glycol, 1,5-pentanediol (PD), and 1,6-hexanediol and cyclohexanedimethanol is preferred.

The blending ratios of the monomer polyol, polyisocyanate, and chain extender components used in the polymerization of the polyurethane are appropriately selected considering the desired physical properties such as abrasion resistance. For example, from the viewpoint of superior mechanical strength, abrasion resistance, productivity, and storage stability of the polyurethane, a ratio of 0.80 to 1.30 moles of isocyanate groups in the polyisocyanate per mole of active hydrogen atoms in the polyol and chain extender is preferred, more preferably 0.85 to 1.20 moles, even more preferably 0.90 to 1.10 moles, and even more preferably 0.95 to 1.05 moles. A ratio of 0.80 or higher tends to improve the mechanical strength and abrasion resistance of the molded product formed from the polyurethane, while a ratio of 1.30 moles or lower tends to improve the productivity and storage stability of the polyurethane, thus being preferable.

The mass ratio of polyol, polyisocyanate, and chain extender is preferably 10/90 to 50/50, more preferably 15/85 to 45/55, and even more preferably 20/80 to 40/60, in the ratio of [amount of polyol / (total amount of polyisocyanate and chain extender)].

[Method for manufacturing polyurethane]
The polyurethane is obtained by polymerization using the aforementioned raw materials by a known prepolymerization method or a one-shot method of urethane formation. More specifically, this can be achieved by a method of producing the polyurethane by melt polymerization using a single-screw or multi-screw extruder while mixing the aforementioned components in predetermined ratios in substantially the absence of a solvent (continuous melt polymerization method); or by polymerization using a prepolymerization method in the presence of a solvent.

The nitrogen content derived from the isocyanate groups of the polyurethane polyisocyanate is preferably 4.0 to 8.0% by mass, more preferably 4.5 to 7.5% by mass, and even more preferably 5.0 to 7.0% by mass.
The nitrogen content ratio is defined as "(mass ratio of structural units derived from polyisocyanate contained in thermoplastic polyurethane) × ((total mass of nitrogen atoms present in the isocyanate group contained in one polyisocyanate molecule) / (mass of one polyisocyanate molecule)) × 100," and can also be measured, for example, by the method described below.
First, the total nitrogen content is calculated using elemental analysis under the following conditions.
• Equipment: PerkinElmer 2400 Series II fully automated elemental analyzer (with autosampler as standard) C/H/N/S/O analyzer • Electric furnace temperature: 975°C
Sample quantity: 2 mg
• Combustion aid: None • Sample container: Tin foil (has combustion-enhancing effect, one sheet used)
• Standard material for calibration curve creation: Sulfanilamide Next, nitrogen atoms derived from polyisocyanate and nitrogen atoms derived from the chain extender are detected by NMR measurement under the following conditions.
• Equipment: JEOL Lambda 500 nuclear magnetic resonance spectrometer
Measurement conditions: Resonance frequency; 1H 500MHz / Probe; TH5FG2
• Solvent: DMSO-d6 Concentration: 5 wt%/vol
・Measurement temperature: 80℃
- Total count: 64s
Then, the nitrogen content derived from the isocyanate groups of the polyisocyanate is calculated from the results of elemental analysis and NMR.

<Other additives>
The thermoplastic resin may optionally contain additives such as crosslinking agents, softeners, tackifiers, antioxidants, foaming agents, processing aids, adhesion enhancers, crystal nucleating agents, heat stabilizers, weather stabilizers, antistatic agents, colorants, lubricants, flame retardants, mold release agents, thickeners, antioxidants, and conductive agents.
If the thermoplastic resin contains other additives, the proportion of the additives in the thermoplastic resin is not particularly limited, but is preferably 50% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less.

Furthermore, there are no particular restrictions on the form in which the thermoplastic resin is supplied to the 3D printer, but examples include powder, pellet, and strand forms. In one embodiment of the molding method, it is preferable to supply the thermoplastic resin to the 3D printer in pellet form.

Furthermore, when supplying the thermoplastic resin to the 3D printer, it is preferable to supply dry nitrogen with a dew point temperature of -30°C or lower, or dry air with a dew point temperature of -30°C or lower, along with the pelletized thermoplastic resin. Supplying the pelletized thermoplastic resin using this method is preferable from the viewpoint of further reducing molding defects and deterioration of the physical properties of the molded object due to foaming, void formation, discoloration, decomposition, etc., caused by moisture absorption of the thermoplastic resin in the 3D printer, and from the viewpoint of more effectively preventing the inclusion of foreign matter in the molded object, such as by suppressing the generation of foreign matter due to resin degradation. From this viewpoint, the dew point temperatures of the dry nitrogen and dry air are, more preferably, -40°C or lower, and even more preferably -50°C or lower, respectively.
Furthermore, from a similar viewpoint, it is desirable to further reduce the moisture content in the thermoplastic resin, and it is preferable to dehumidify and dry the thermoplastic resin before supplying it to the 3D printer.

<Shaped object obtained by the above manufacturing method>
The molded object obtained by the above manufacturing method (hereinafter also simply referred to as "molded object") is not particularly limited as long as it is a molded object made of thermoplastic resin.
Examples of the aforementioned molded object include a sheet, a three-dimensional molded object, a three-dimensional molded object with a hollow structure, and among these, a sheet is preferred.
The thickness of the sheet can be set appropriately depending on the application of the sheet, but one embodiment of the sheet is preferably 0.5 to 15 mm, more preferably 1.0 to 10 mm, and even more preferably 1.5 to 5.0 mm.

The sheet obtained by the above manufacturing method has no particular limitations on its use, but it is preferably used as an abrasive layer for a polishing pad, as described later. In other words, it is preferable that the molded object is an abrasive layer for a polishing pad.

Furthermore, when the molded object obtained by the above manufacturing method is used, for example, as an abrasive layer in a polishing pad described later, it is preferable that it substantially contains no fillers such as inorganic fillers having a higher hardness than the molded object formed from the thermoplastic resin used, in order to better prevent the occurrence of scratches. "Substantially containing no fillers" means that the content of the fillers is 1.0% by mass or less, preferably 0.1% by mass or less, more preferably 0.01% by mass or less, even more preferably 0.005% by mass or less, and even more preferably 0.0001% by mass or less, based on 100% by mass of the total amount of the molded object.

[Polishing pad]
A polishing pad according to one aspect of the present invention has a polishing layer obtained using the method for manufacturing the molded object according to one aspect of the present invention.
The abrasive layer of the abrasive pad may be made from the sheet obtained by the manufacturing method as is, or from a sheet obtained by the manufacturing method that has been further processed into a desired abrasive layer shape using one or more methods selected from the group consisting of cutting, machining, grinding, and punching.

Furthermore, the polishing layer is more preferably formed using polyurethane as the thermoplastic resin, and may be either a foamed or non-foamed polyurethane, but a non-foamed polyurethane is even more preferable. When the polishing layer is a non-foamed polyurethane, the polishing uniformity of the polishing pad having the polishing layer is further improved, and variations due to foam distribution and defects caused by aggregates within the foam can be further suppressed, thereby making it easier to achieve stable polishing with less fluctuation in polishing characteristics.

Furthermore, the density of the polishing layer formed using the thermoplastic polyurethane for polishing is preferably 0.75 g/ ^cm³ or more, more preferably 0.85 g/ ^cm³ or more, even more preferably 1.0 g/ ^cm³ or more, and even more preferably 1.1 g/ ^cm³ or more. When the density is above the lower limit, the polishing layer will have appropriate flexibility. In addition, the polishing layer formed using thermoplastic polyurethane for polishing is preferable if it is formed using non-foamed thermoplastic polyurethane for polishing, as it has superior polishing stability due to its higher rigidity and material homogeneity.

The shape of the polishing layer is not particularly limited, but for example, when viewed from above, it may be a circular shape. The shape of the polishing layer may be designed in advance using 3D data when fabricating the object using the manufacturing method described above, and then fabricated directly using a 3D printer, or, as described above, the object obtained by the manufacturing method may be further prepared as appropriate by one or more processes selected from the group consisting of cutting, machining, grinding, and punching.

The thickness of the polishing layer is not particularly limited, but is preferably 0.5 to 5.0 mm, more preferably 1.0 to 3.0 mm, and even more preferably 1.2 to 2.5 mm. A polishing layer thickness within this range is preferable from the viewpoint of improving productivity and handling, as well as the stability of polishing performance.

Furthermore, it is preferable that grooves or holes, or other recesses, are formed on the polishing surface of the polishing layer in predetermined patterns such as concentric circles, grids, spirals, or radials. Such recesses help to uniformly and sufficiently supply slurry to the polishing surface, facilitate the removal of polishing debris that causes polishing scratches, and prevent wafer damage due to the adsorption of the polishing layer. For example, when forming grooves in a concentric or spiral pattern, the spacing (pitch) between grooves is preferably 1.0 to 50 mm, more preferably 1.5 to 30 mm, and even more preferably 2.0 to 15 mm. The groove width is preferably 0.1 to 3.0 mm, more preferably 0.2 to 2.0 mm. The groove depth is less than the thickness of the polishing layer, preferably 0.2 to 1.8 mm, and more preferably 0.4 to 1.5 mm. The cross-sectional shape of the groove can be appropriately selected depending on the purpose, for example, a rectangle, trapezoid, triangle, or semicircle.

The recesses on the polished surface may, for example, be pre-designed using 3D data during the manufacturing process of the molded object and directly fabricated during the 3D printing process. Alternatively, they may be formed on the molded object obtained by the manufacturing process using the aforementioned method, by methods such as grinding, laser processing, transfer using a mold, or stamping with a heated mold.

The hardness of the abrasive layer is preferably 45 or higher, more preferably 50 or higher, even more preferably 55 or higher, and preferably 90 or lower, more preferably 85 or lower, and even more preferably 80 or lower, as measured according to JIS K 7311:1995.

The polishing pad may consist solely of a polishing layer obtained using the manufacturing method for a molded object according to one aspect of the present invention, or it may be a laminate in which a cushioning layer is laminated on the side of the polishing layer that is not the polishing surface.

Preferably, the cushion layer has a hardness lower than that of the polishing layer. When the hardness of the cushion layer is lower than that of the polishing layer, the hard polishing layer follows local irregularities on the surface to be polished, and the cushion layer follows warping and undulation of the entire substrate to be polished. This is preferable because it enables polishing with a better balance between global flatness (a state in which large periodic irregularities on the wafer substrate are reduced) and local flatness (a state in which local irregularities are reduced).
Furthermore, the thickness of the cushion layer is not particularly limited, but is preferably, for example, 0.3 to 5.0 mm.

Examples of materials used as the cushioning layer include composites made by impregnating nonwoven fabric with polyurethane (for example, "Suba400" manufactured by Nitta Haas Co., Ltd.); rubbers such as natural rubber, nitrile rubber, polybutadiene rubber, and silicone rubber; thermoplastic elastomers such as polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, and fluorine-based thermoplastic elastomers; foamed plastics; and polyurethane.
Among these, polyurethane having a foamed structure is particularly preferred because it easily provides the desired flexibility for use as a cushioning layer.
Furthermore, the polyurethane mentioned in the description of the cushioning layer includes both thermoplastic polyurethane and thermosetting polyurethane.

The polishing layer and the cushioning layer may be laminated together, for example, using double-sided tape, or they may be laminated together via an adhesive layer. Furthermore, when forming the polishing layer using the manufacturing method of the molded object, the entire or a portion of the polishing layer may be laminated directly onto the cushioning layer or another intermediate layer (e.g., an adhesive layer).

Since the polishing pad has a polishing layer obtained using the method for manufacturing the molded object, it can effectively prevent the incorporation of foreign matter into the polishing layer. Therefore, by using a polishing pad having a polishing layer obtained using the method for manufacturing the molded object, it is possible to effectively prevent the occurrence of polishing scratches caused by the incorporation of inorganic foreign matter.
Therefore, it can be suitably used as a polishing pad for polishing the surface of a semiconductor wafer, for example, and can be more suitably used as a polishing pad for polishing the surface of a semiconductor wafer by a CMP (Chemical Mechanical Polishing (Planarization)) polishing method. CMP is a method of polishing an object to be polished with high precision using a polishing pad while supplying a slurry containing abrasive particles and a reaction solution to the surface of the object to be polished, and is known as a suitable method for polishing various semiconductor materials such as silicon wafers.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited in any way by these examples.

[Manufacturing Example 1]
Polytetramethylene ether glycol [abbreviation: PTMG], 1,4-butanediol [abbreviation: BD], and 4,4'-diphenylmethane diisocyanate [abbreviation: MDI], all with a number-average molecular weight of 850, were used in a ratio of PTMG:BD:MDI = 32.5:15.6:51.9 (mass ratio). These were continuously supplied to a coaxially rotating twin-screw extruder using a metering pump, and continuous melt polymerization was carried out to produce thermoplastic polyurethane. The molten polymerized thermoplastic polyurethane was then continuously extruded into water in strand form, and shredded with a pelletizer to obtain thermoplastic polyurethane pellets. These pellets were dehumidified and dried at 70°C for 20 hours, and then sealed in moisture-proof bags.

[Manufacturing Example 2]
To 100 parts by mass of thermoplastic polyurethane pellets obtained in Production Example 1, 0.01 parts by mass of heavy calcium carbonate (untreated surface, median diameter 25 μm), produced by physically crushing and classifying limestone, was added as a model for impurities, and the mixture was dry-blended to obtain pellets of thermoplastic polyurethane composition. Then, after dehumidifying and drying at 70°C for 20 hours, the mixture was sealed in a moisture-proof bag.

[Manufacturing Example 3]
To 100 parts by mass of the thermoplastic polyurethane pellets obtained in Production Example 1, 0.02 parts by mass of spherical silica (untreated surface, median diameter 40 μm), which was formed by melting pulverized silica powder in a high-temperature flame, was added as a model for impurities, and the mixture was dry-blended to obtain pellets of a thermoplastic polyurethane composition. Then, after dehumidifying and drying at 70°C for 20 hours, the pellets were sealed in a moisture-proof bag.

[Reference example 1]
A fused deposition modeling (FDM) 3D printer (nozzle tip hole diameter 1 mm) was used to supply thermoplastic polyurethane pellets obtained in Production Example 1 along with dry air with a dew point temperature of -60°C, yielding a 3 mm thick, 20 cm square sheet. The calcium and silicon atom content in the obtained sheet was analyzed using the method described later, and both were below the limit of quantification.

[Example 1]
A stainless steel wire mesh (twill weave, 270 vertical mesh, 2000 horizontal mesh, 40 μm vertical wire diameter, 28 μm horizontal wire diameter) with a filtration accuracy of 10 μm was attached to the resin flow path in the nozzle (1 mm tip hole diameter) of the aforementioned fused deposition modeling (FDM) 3D printer. Pellets of the thermoplastic polyurethane composition obtained in Production Example 2 were supplied along with dry air with a dew point of -60°C to obtain a 3 mm thick, 20 cm square sheet. The calcium and silicon atom content in the obtained sheet was analyzed using the method described later, but both were below the limit of quantification.

[Example 2]
A stainless steel mesh with a filtration accuracy of 15 μm (twill weave, 200 vertical mesh, 2000 horizontal mesh, 50 μm vertical wire diameter, 28 μm horizontal wire diameter) was attached to the resin flow path in the nozzle (tip hole diameter 2 mm) of a fused deposition modeling (FDM) 3D printer. Pellets of the thermoplastic polyurethane composition obtained in Production Example 3 were supplied along with dry air with a dew point of -60°C to obtain a 2 mm thick, 40 cm square sheet. The calcium and silicon atom content in the obtained sheet was analyzed using the method described later, but both were below the limit of quantification.
The obtained sheet was cut into a disc with a diameter of 38 cm and a thickness of 1.5 mm to create an abrasive layer, and spiral grooves with a width of 0.5 mm, a depth of 0.8 mm, and a pitch of 3.5 mm were formed on the surface that would be used for abrasives. Next, double-sided tape (Sekisui Chemical Co., Ltd.'s "#5605HG") was attached to the back side, which is the side opposite to the abrasive surface, to manufacture an abrasive pad.
The obtained polishing pad was mounted on a polishing device "MAT-BC15" manufactured by M.A.T. Corporation. Then, using a diamond dresser (diamond grit #100, base diameter 19 cm) manufactured by Allied Material Corporation, the surface of the polishing pad was conditioned for 60 minutes while flowing pure water at a rate of 150 mL/min under the conditions of a dresser rotation speed of 140 rpm, a polishing pad rotation speed of 100 rpm, and a dresser load of 5 N. Next, a solution was prepared by mixing 100 parts by mass of polishing slurry "PL7105" manufactured by Fujimi Incorporated with 200 parts by mass of pure water and 10 parts by mass of 30% hydrogen peroxide solution. Then, under the conditions of a platen rotation speed of 100 rpm, a head rotation speed of 99 rpm, and a polishing pressure of 30 kPa, a 100 mm diameter silicon wafer with an initial copper film thickness of 1500 nm on its surface was polished for 60 seconds while supplying polishing slurry to the polishing surface of the polishing pad at a rate of 100 mL/min. The polished surface of the wafer was observed at 100 random locations using a laser microscope "VKX-200" manufactured by Keyence Corporation with an objective lens magnification of 1000x to check for the presence or absence of scratches. As a result, no scratches were found.

[Comparative Example 1]
In Example 1, a sheet with a thickness of 3 mm and a square length of 20 cm was obtained in the same manner as in Example 1, except that a wire mesh was not attached inside the nozzle of the 3D printer. The calcium and silicon atom content in the obtained sheet was analyzed using the method described later, and it was found that it contained 34 ppm (μg/g) of calcium atoms. The silicon atom content was below the limit of quantification.

[Comparative Example 2]
In Example 2, a sheet with a thickness of 2 mm and a square of 40 cm was obtained in the same manner as in Example 2, except that a wire mesh was not attached inside the nozzle of the 3D printer. The calcium and silicon atom content in the obtained sheet was analyzed using the method described later. The results showed that the calcium atom content was below the limit of quantification, but the silicon atom content was 82 ppm (μg/g).
The obtained sheet was processed in the same manner as in Example 2 to manufacture a polishing pad, and polishing was performed in the same manner as in Example 2. The polished wafer was observed at 100 random locations using a KEYENCE VKX-200 laser microscope with an objective lens magnification of 1000x to check for scratches, and multiple scratches were found.

<Calcium and silicon atom content in the sheet>
After cutting the sheets obtained in the examples and comparative examples, the samples were decomposed by adding nitric acid and sulfuric acid and heating. Using this decomposition solution, the calcium atom content was measured by ICP mass spectrometry, and the silicon atom content was measured by flameless atomic absorption spectrometry. The detection limits were 1 ppm (μg/g) for calcium and 10 ppm (μg/g) for silicon.

As can be seen from the comparison between Example 1 and Comparative Example 1, and between Example 2 and Comparative Example 2, in Examples 1 and 2, where the material was passed through a wire mesh filter before being extruded from the nozzle during 3D printing, no foreign matter was found in the resulting printed object. Furthermore, from the comparison between Example 2 and Comparative Example 2, it can be seen that the polished layer obtained from a sheet printed using a filter in a 3D printer did not contain any foreign matter that would cause scratches during polishing.

By using the aforementioned manufacturing method for molded objects, it is possible to effectively prevent the inclusion of foreign matter in molded objects made from thermoplastic resin using a 3D printer. Therefore, it can be suitably used, in particular, when preventing the inclusion of foreign matter in molded objects, such as when manufacturing polishing layers for polishing pads used in the manufacture of semiconductor devices. For example, by using a polishing pad having a polishing layer obtained using the aforementioned manufacturing method, it is possible to effectively prevent the occurrence of polishing scratches caused by the inclusion of inorganic foreign matter.

Claims (6)

In a manufacturing method for obtaining a molded object by melting a thermoplastic resin using a 3D printer, extruding it from a nozzle, and allowing it to solidify, the manufacturing method is characterized in that the thermoplastic resin passes through a filter between the time it melts in the 3D printer and the time it is extruded from the nozzle.
The filtration accuracy of the aforementioned filter is 15 μm or less.
The aforementioned molded object is characterized in that it is an abrasive layer for a polishing pad.
A method for manufacturing molded objects. The method for manufacturing a molded object according to claim 1, wherein the filter is a metal filter. The method for manufacturing a molded object according to claim 1 or 2, wherein the thermoplastic resin is polyurethane. A method for manufacturing a molded object according to any one of claims 1 to 3, wherein the thermoplastic resin is supplied to the 3D printer in pellet form. A method for manufacturing a molded object according to claim 4, wherein dry nitrogen with a dew point temperature of -30°C or lower, or dry air with a dew point temperature of -30°C or lower, is supplied to the 3D printer along with pelletized thermoplastic resin. The method for manufacturing a molded object according to any one of claims 1 to 5, wherein the molded object is a sheet with a thickness of 1.0 to 10 mm.