Methods for manufacturing support materials for layered shapes, layered shapes using the same materials, and three-dimensional structures.

Abstract

A support material for layered modeling is disclosed, exhibiting excellent adhesion to various model materials; easily removable by dissolving in water when washed away; and not violating environmental regulations even when the generated waste liquid (PVA-based aqueous solution) is directly discharged and removed. The support material comprises (A) a PVA-based resin having sulfonic acid groups or their salt-containing groups and (B) a biodegradable polyester, wherein (A) the PVA-based resin having sulfonic acid groups or their salt-containing groups or (B) the biodegradable polyester has an island structure in which one of them serves as the matrix.

Description

Technical Field

[0001] This invention relates to a support material with excellent adhesion to a target shape constructed from layered structures, said support material being environmentally friendly and easily removable from the layered structure. The invention also relates to layered shapes comprising a support structure made of the support material, and a method for manufacturing a three-dimensional structure as the target shape. Background Technology

[0002] Lamination is a method of forming three-dimensional structures with a desired shape, in which a fluid material is extruded, cured to form layers, and continuously extruded fluid material is placed on previous layers and cured to build an article layer by layer. Methods for manufacturing three-dimensional structures include UV curing and thermomelting lamination. Thermomelting lamination can be implemented with simple equipment and is widely used.

[0003] In the process of creating a layered model of a three-dimensional structure, support material used to fill in the non-existent parts of the target three-dimensional structure is formed during the layering process. The support structure is only a part that is not present during the modeling of the target three-dimensional structure, and therefore needs to be removed from the layered model after modeling.

[0004] One removal method involves dissolving the support structure in a solvent, offering a simple solution that removes the support structure without damaging the target object. When using water-soluble polyvinyl alcohol (PVA) resins as the support material, water can be used as the solvent. Removal using water is both safe and environmentally friendly.

[0005] On the other hand, PVA-based resins are characterized by their rigidity, poor impact resistance, and difficulty in being melt-molded or filamentized. In order to use such PVA-based resins as support materials applicable to various shapes, they must possess both flexibility and impact resistance. To impart flexibility to PVA-based resins, it has been proposed to blend thermoplastic elastomers such as styrene-ethylene-butene-styrene block copolymers (SEBS) with PVA-based resins (e.g., disclosed via WO 2015 / 182681, WO 2018 / 061694, and JP 2019-155917 A).

[0006] The support material proposed in the aforementioned literature has an island structure in which SEBS (island component) is dispersed in a PVA-based resin (sea component) serving as a matrix. Therefore, in the waste liquid (an aqueous solution of PVA-based resin) generated after dissolving the PVA-based resin in water, the water-insoluble SEBS is dispersed in a suspension. Since the waste liquid contains non-biodegradable SEBS, it is necessary to separate the SEBS separately during waste disposal.

[0007] In recent years, from the perspective of green chemistry, JP 2018-099788A proposed using biodegradable polyesters instead of non-biodegradable SEBS. Specifically, the proposed support material for laminated molding employs a composition comprising a PVA-based resin containing 1,2-diols as side chains and a biodegradable polyester. The advantage of this support material lies in its excellent adhesion to polylactic acid (PLA)-based resins, which are widely used as materials for laminated molding.

[0008] Existing technical documents

[0009] Patent documents

[0010] [Patent Document 1] WO 2015 / 182681

[0011] [Patent Document 2] WO 2018 / 061694

[0012] [Patent Document 3] JP 2019-155917A

[0013] [Patent Document 4] JP 2018-099788A Summary of the Invention

[0014] The problem the invention aims to solve

[0015] From a green chemistry perspective, compositions for support materials, including PVA-based resins containing 1,2-diols as side chains and biodegradable polyesters, are advantageous. However, these support materials suffer from the following problems that hinder the expansion of their commercial applications:

[0016] Question 1: The support material has good adhesion to PLA resin, but low adhesion to other general-purpose resins such as ABS.

[0017] Question 2: When the support material is dissolved in water for removal, agglomerates of biodegradable polyester with low water solubility are generated. These agglomerates can adhere to the molded object or cause blockages in the waste liquid after the washing process.

[0018] Question 3: When the supporting material is melted into fine filaments, the diameter deviation of the produced filaments is relatively large.

[0019] The present invention was made in view of these circumstances. The object of the present invention is to provide a support material with excellent adhesion to modeling materials used for layering, such as not only polylactic acid (PLA), but also acrylonitrile-butadiene-styrene copolymer (ABS), polyamide (PA), ethylene glycol-modified polyethylene terephthalate (PETG), and polycarbonate (PC). Furthermore, the support material can be treated by dissolving it in water without generating problems related to agglomerates during water washing. Additionally, the waste liquid obtained as an aqueous solution of PVA-based resin after washing treatment can be discharged in compliance with environmental regulations.

[0020] Solution for solving the problem

[0021] The support material for the layered molding of the present invention includes (A) a polyvinyl alcohol resin having sulfonic acid groups or salt-containing groups thereof; and (B) a biodegradable polyester.

[0022] (A) A polyvinyl alcohol resin having a sulfonic acid group or a salt-containing group is a polyvinyl alcohol resin having a structural unit represented by the following formula (3-1), (3-2) or (3-3) as a structural unit having a sulfonic acid group or a salt-containing group.

[0023] [Chemical Formula 3]

[0024]

[0025]

[0026] In formulas (3-1), (3-2) and (3-3), M is hydrogen, alkali metal or ammonium group, and X and Y are each a linking group.

[0027] The content of the structural unit represented by formula (3-1), (3-2) or (3-3) is preferably 0.01 to 10 mol%.

[0028] Sodium acetate is preferably contained in a ratio of 0.5 to 2.0 parts by weight relative to 100 parts by weight (A) of polyvinyl alcohol resin having sulfonic acid groups or salt-containing groups thereof.

[0029] Furthermore, it is preferable to include (B) a biodegradable polyester in a ratio of 5 to 100 parts by weight relative to 100 parts by weight of a polyvinyl alcohol resin having sulfonic acid groups or salt-containing groups of (A).

[0030] In a preferred embodiment, (A) a polyvinyl alcohol resin having sulfonic acid groups or salt-containing groups thereof and (B) a biodegradable polyester form a phase-separated structure in which one is a matrix and the other is finely dispersed in the matrix. In a more preferred embodiment, they have an island structure in which the (B) biodegradable polyester, as an island component, is dispersed in the (A) polyvinyl alcohol resin having sulfonic acid groups or salt-containing groups thereof. In a more preferred island structure, the size of the domain of the (B) biodegradable polyester is preferably 0.05 to 2 μm.

[0031] In (B) biodegradable polyester, the ratio of aliphatic dicarboxylic acid units to dicarboxylic acid units is preferably 40 to 80 mol%.

[0032] The support material for layered molding of the present invention is suitable for use as a support material for hot-melt layered molding. In this case, the support material for layered molding is preferably in the form of filaments.

[0033] Another aspect of the invention includes a stacked structure comprising the stacked structure support material of the present invention. Another aspect of the invention includes a method for manufacturing a three-dimensional structure using the stacked structure support material.

[0034] The manufacturing method of the three-dimensional structure of the present invention includes a step of stacking and solidifying the support material and model material of the present invention in a molten state to produce a stacked model; and a step of bringing the obtained stacked model into contact with water.

[0035] The method for manufacturing the three-dimensional structure of the present invention is suitable when the model material is polylactic acid, acrylonitrile-butadiene-styrene resin, polyamide resin, polyethylene terephthalate or polycarbonate.

[0036] The effects of the invention

[0037] Because the support material for layered modeling of the present invention has excellent adhesion to various model materials and excellent water solubility, there are no insoluble aggregates in the waste liquid after washing the obtained layered model with water to remove the support structure from the layered model.

[0038] Furthermore, since the support material is biodegradable, the wastewater generated from the dissolution of the support material during water washing is easy to handle. In addition, the wastewater is environmentally friendly. Attached Figure Description

[0039] Figure 1 This is a diagram used to depict the measurement methods performed in the embodiments. Detailed Implementation

[0040] The present invention will be described in detail below, but the following are merely examples of desired embodiments.

[0041] [Supporting material for layered designs]

[0042] The support material for the layered molding of the present invention includes (A) a polyvinyl alcohol (PVA) resin having sulfonic acid groups or salt-containing groups thereon and (B) a biodegradable polyester.

[0043] (A) PVA-based resins having sulfonic acid groups or their salt-containing groups

[0044] The PVA-based resin (A) used in the support material of the present invention, which has sulfonic acid groups or salt-containing groups, exhibits excellent water solubility and melt molding properties. Furthermore, the PVA-based resin (A) has excellent compatibility with the biodegradable polyester (B), another essential component of the support material. Additionally, the support material can be provided in filament form. For laminated structures using the support material, since the support structure dissolves in water after lamination and no polyester aggregates are generated in the wastewater after washing, a washing operation can be easily performed to remove the support structure. Therefore, the treatment of wastewater after washing and removal is not troublesome, as described below.

[0045] That is, since sulfonic acid or its salts are present in the molecules of PVA-based resins having sulfonic acid groups or their salt-containing groups (A), PVA-based resins having sulfonic acid groups or their salt-containing groups (A) can exhibit compatibility with the biodegradable polyester (B) described later. If components (A) and (B) are melt-blended, they separate, but small domain-form components (A) or (B) are dispersed in the other components (B) or (A) that serve as the matrix. When the proportion of component (A) in the PVA-based resin exceeds half, an island structure is usually formed in which the PVA-based resin is the sea component and the biodegradable polyester (B) is the island component. On the other hand, in the case of unmodified PVA-based resins and PVA-based resins containing 1,2-diols as side chains, the polar groups contained in their molecules are only hydroxyl and acetyl groups, resulting in low compatibility with the biodegradable polyester (B). As a result, the size of the domain formed by the polyester resin dispersed as the island component in the PVA-based resin that serves as the sea component is 2 to 5 μm. In this respect, when they are removed by washing with water, the waste liquid contains a large amount of (B) biodegradable polyester aggregates, and the aggregates are 2 mm to 5 mm in size. After the support structure is removed, such aggregates adhere to the target model of the laminated molding and cause clogging of the filter used for waste liquid treatment. This makes waste liquid treatment difficult. In this respect, when using PVA-based resins having sulfonic acid groups or their salt-containing groups, they have good compatibility with (B) biodegradable polyesters, so (B) biodegradable polyesters can exist as domains with a size of 0.05 to 2 μm in the island structure, regardless of their phase separation. In the preferred island structure, (B) biodegradable polyesters can be finely dispersed in the matrix (sea) of (A) PVA-based resin having sulfonic acid groups or their salt-containing groups in the form of domains (islands) with a size of 0.1 to 1.0 μm, more preferably 0.1 to 0.5 μm. As a result, the PVA-based resin aqueous solution, which is the waste liquid generated by the washing process, is a homogeneous, turbid liquid, but does not contain (B) coagulations of biodegradable polyester. This means that there are no residual coagulations on the target model, and the waste liquid can be discharged during waste liquid treatment because no clogging occurs during the filtration operation. Since the dispersed polyester resin is biodegradable, the discharged waste liquid will not have a serious impact on the environment and can comply with recent microplastic regulations.

[0046] (A) A PVA-based resin having a sulfonic acid group or a salt-containing group thereof comprises, as the basic structural unit of the PVA-based resin, an ethylene alcohol unit represented by the following general formula (1), an ethylene ester unit represented by the following general formula (2), and a structural unit represented by the following general formulas (3-1), (3-2), or (3-3). When the degree of saponification is less than 100%, in addition to the ethylene ester unit represented by the following general formula (2) corresponding to the unsaponified portion, it also comprises structural units represented by the following general formulas (3-1), (3-2), or (3-3), which contain a sulfonic acid group or a salt-containing group thereof in the side chain of the unit.

[0047] [Chemical Formula 1]

[0048]

[0049] [Chemical Formula 2]

[0050]

[0051] [Chemical Formula 3]

[0052]

[0053] The vinyl alcohol unit represented by formula (1) and the vinyl ester unit represented by formula (2) are both derived from vinyl ester compounds used as raw material monomers to form PVA-based resins.

[0054] Examples of vinyl ester compounds that are monomers of vinyl esters include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl neovalerate, vinyl decanoate, vinyl laurate, vinyl stearate, vinyl benzoate, and vinyl tert-carbonate. Among these, vinyl acetate is preferred due to its economic advantages.

[0055] Therefore, in equation (2), R a It is an alkyl group having 1 to 18 carbon atoms, and depends on the ethylene ester compound used as a raw material for the synthesis of PVA-based resins. a The preferred methyl group is methyl, and therefore the preferred vinyl ester unit is the vinyl acetate unit represented by the following formula (2a).

[0056] [Chemical Formula 2a]

[0057]

[0058] In formulas (3-1), (3-2), and (3-3), "-SO3M" represents hydrogen, an alkali metal, or an ammonium group. When M is hydrogen, -SO3M corresponds to a sulfonic acid group. When M is an alkali metal or ammonium, -SO3M corresponds to a salt-containing group of a sulfonic acid. R in each formula... 1 R 2 R3 R 4 R 5 and R 6 Independently, it is an alkyl group with hydrogen atoms and 1 to 4 carbon atoms. X and Y are each a linking group. Typical linking groups are alkylene groups with 1 to 4 carbon atoms, ester bonds, amide bonds, and ether bonds, etc. R c It can be hydrogen, alkyl, or a sulfonic acid group or salt-containing group of sulfonic acid represented by "-SO3M" (M represents hydrogen, alkali metal or ammonium group), or a group containing -SO3M.

[0059] The structural unit represented by formula (3-1) having a sulfonic acid group or its salt-containing group can be formed from an unsaturated monomer having a sulfonic acid or its salt (hereinafter referred to as "unsaturated monomer containing a sulfonic acid group, etc."). Examples of unsaturated monomers containing a sulfonic acid group, etc. include olefin sulfonic acid (4-1), sulfonyl (meth)acrylamide (4-2) or (4-3), and (meth)acrylate sulfonyl ester (4-4), as shown below. The linking groups X and Y are alkylene (-(CH2)n-), ester (-COO-), carbonyl (-CO-), amide, or combinations thereof, depending on the type of unsaturated monomer containing a sulfonic acid group, etc., used.

[0060] [Chemical Formula 4-1]

[0061] CH2=CH-X-SO3M (4-1)

[0062] [Chemical Formula 4-2]

[0063]

[0064] [Chemical Formula 4-3]

[0065]

[0066] [Chemical Formula 4-4]

[0067]

[0068] In equations (4-1), (4-2), (4-3), and (4-4) above, R 11 R 12 R 13 and R 14 Each is independently a hydrogen or an alkyl group having 1 to 4 carbon atoms. n is an integer from 2 to 4, and M represents a hydrogen atom, an alkali metal, or an ammonium group.

[0069] Furthermore, as an unsaturated monomer containing sulfonic acid groups, in the case of sulfonyl malates as shown below, a structural unit having sulfonic acid groups or salt-containing groups represented by formula (3-2) is formed.

[0070] [Chemical Formula 5-1]

[0071]

[0072] [Chemical Formula 5-2]

[0073]

[0074] In equations (5-1) and (5-2) above, n is an integer from 2 to 4, and M represents a hydrogen atom, an alkali metal, or an ammonium group.

[0075] Furthermore, as an unsaturated monomer containing sulfonic acid groups, the structural unit having sulfonic acid groups or salt-containing groups represented by formula (3-3) is formed using sulfoalkyl (meth)acrylamides, as shown below.

[0076] [Chemical Formula 5-3]

[0077]

[0078] In equation (5-3) above, R 15 It is an alkyl group having 1 to 4 hydrogen atoms. n is an integer from 2 to 4, and M represents a hydrogen atom, an alkali metal, or an ammonium group.

[0079] Specific examples of the aforementioned olefin sulfonic acids include olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, and methyl allyl sulfonic acid, or their salts.

[0080] In addition, specific examples of the aforementioned sulfonyl malates include sodium sulfonyl-2-ethylhexyl malate, sodium sulfonyl-2-ethylhexyl malate, sodium sulfonyl-tetrate malate, and sodium sulfonyl-eicosyl malate.

[0081] Specific examples of the aforementioned sulfonyl (methyl)acrylamides include sodium sulfonylmethacrylamide, sodium sulfonyltert-butylacrylamide, sodium sulfonyl-S-butylacrylamide, and sodium sulfonyl-tert-butylmethacrylamide.

[0082] Furthermore, specific examples of the aforementioned (meth)acrylate sulfonyl esters include sodium sulfonyl acrylate, etc. When introducing unsaturated monomers containing sulfonic acid groups, etc., via copolymerization, olefin sulfonic acids or their salts are preferred.

[0083] The saponification degree (measured according to JIS K6726 standard) of the PVA-based resin (A) having sulfonic acid groups or salt-containing groups used in this invention is preferably 75 to 99 mol%, more preferably 80 to 95 mol%, and even more preferably 85 to 90 mol%. Too low a saponification degree tends to reduce water solubility.

[0084] (A) The average degree of polymerization of the PVA-based resin having sulfonic acid groups or salt-containing groups (measured according to JIS K 6726 standard) is preferably 150 to 4000, more preferably 250 to 1000, and even more preferably 300 to 500.

[0085] A low average degree of polymerization tends to decrease melt viscosity, leading to dripping during lamination molding. Furthermore, the strength of the filamentary support material may decrease, making it prone to breakage during molding. Conversely, if the average degree of polymerization is too high, the melt viscosity increases. Filamentary support materials with high melt viscosity become difficult to supply at high rates during lamination molding. Additionally, the rate of water dissolution and removal of the support material tends to be weakened.

[0086] Furthermore, the content (modification rate) of structural units having sulfonic acid groups or their salt-containing groups in (A) PVA-based resins is preferably 0.01 to 10 mol%, more preferably 0.1 to 5 mol%, and particularly preferably 0.5 to 3 mol%. (A) PVA-based resins with excessively low modification rates will have relatively reduced charge-carrying capacity and protective colloidal properties. This leads to compromised compatibility with (B) biodegradable polyesters. Conversely, (A) PVA-based resins with excessively high modification rates may reduce the heat resistance of the supporting material. Additionally, such PVA-based resins having sulfonic acid groups or their salt-containing groups may be difficult to synthesize.

[0087] (A) PVA resins having sulfonic acid groups or their salt-containing groups can be produced by the following methods: (1) copolymerizing a vinyl ester monomer with an unsaturated monomer containing sulfonic acid groups and saponifying the resulting copolymer; (2) polymerizing a vinyl ester monomer with a compound having a functional group, such as an alcohol, aldehyde, or thiol, each having sulfonic acid groups or their salt-containing groups, in the presence of a chain transfer agent, and then saponifying the obtained polymer; (3) treating the PVA resin with bromine, iodine, etc., and then heating it with an acidic sodium sulfite aqueous solution; (4) heating the PVA resin in a concentrated sulfuric acid aqueous solution; (5) acetalizing the PVA resin having sulfonic acid groups or their salt-containing groups with an aldehyde compound or the like.

[0088] From the perspective of safety and workability during manufacturing, method (1) is preferred. This method includes copolymerizing ethylene ester monomers with unsaturated monomers containing sulfonic acid groups, etc., and saponifying the resulting polymer.

[0089] In addition to vinyl ester monomers and vinyl monomers providing oxidized olefins, other monomers can be copolymerized in PVA-based resins containing sulfonic acid groups or their salt-containing groups, which are the subject of this invention, at a proportion of less than 1 mol%. Examples of other monomers include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxyl-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, and 3,4-dihydroxy-1-butene, and their derivatives such as acylates; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and undecenoic acid, and their salts, monoesters, or dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; and acylates such as acrylamide and methacrylamide. Amines; such as olefin sulfonic acids or their salts, such as ethylene sulfonic acid, allyl sulfonic acid, and methyl allyl sulfonic acid; alkyl vinyl ethers; such as vinyl compounds, such as dimethyl allyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, and glycerol monoallyl ether; substituted vinyl acetates, such as isopropyl acetate and 1-methoxyethylene acetate, vinylidene chloride, 1,4-diacetoxy-2-butene, 1,4-dihydroxy-2-butene, and vinylene carbonate.

[0090] There are no particular restrictions on the copolymerization method of vinyl ester monomers with unsaturated monomers containing sulfonic acid groups, and other monomers optionally used as needed. Known methods such as bulk polymerization, solution polymerization, suspension polymerization, dispersion polymerization, or emulsion polymerization can be used, but solution polymerization is usually preferred.

[0091] There are no particular restrictions on the method of adding monomers for copolymerization; appropriate methods such as one-time addition, phased addition, and continuous addition can be adopted.

[0092] Typical examples of solvents used for such copolymerizations include lower alcohols such as methanol, ethanol, isopropanol, n-propanol, and butanol; and ketones such as acetone and methyl ethyl ketone. Among these, alcohols with 1 to 3 carbon atoms, especially methanol, are preferred for industrial use.

[0093] The amount of solvent used can be determined appropriately based on the degree of polymerization of the target copolymer, taking into account the chain transfer constant of the solvent. For example, when using methanol as a solvent, the amount of methanol is set in the range of 0.01 to 10 (mass ratio), preferably about 0.05 to 3 (mass ratio), based on the S (solvent) / M (polymer) ratio.

[0094] A polymerization catalyst is used during copolymerization. Examples of polymerization catalysts include known free radical polymerization catalysts such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, and lauryl peroxide, as well as low-temperature active free radical polymerization catalysts such as azodimethylpentanonitrile and azodimethoxydimethylpentanonitrile. An appropriate amount of polymerization catalyst is selected based on the desired degree of polymerization, which depends on the type of catalyst. In the case of azobisisobutyronitrile or acetyl peroxide, a suitable amount relative to the vinyl ester monomer can preferably be determined from 0.01 to 1.0 mol%, particularly from 0.02 to 0.5 mol%.

[0095] Depending on the solvent and pressure used, the reaction temperature for copolymerization can be determined from about 30°C to the boiling point, more specifically between 35°C and 150°C, and preferably between 40°C and 75°C.

[0096] The resulting copolymer is then saponified. Saponification is carried out by dissolving the copolymer in an alcohol or aqueous alcohol in the presence of an alkaline or acidic catalyst.

[0097] Examples of alcohols include lower alcohols such as methanol, ethanol, propanol, and tert-butanol, with alcohols having 1 to 3 carbon atoms being preferred, and methanol being particularly preferred. The concentration of the copolymer in the alcohol is appropriately selected based on the viscosity of the system, but is typically selected in the range of 10 to 60% by mass. Examples of catalysts used in saponification include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide, potassium methoxide, and lithium methoxide; alkaline catalysts such as alkoxides; and acid catalysts such as sulfuric acid, chloric acid, nitric acid, methanesulfonic acid, zeolites, and cation exchange resins.

[0098] The amount of saponification catalyst used is selected based on the saponification method and the target degree of saponification. In the case of an alkaline catalyst, the amount used can be selected from 0.1 to 30 mmol relative to 1 mol of the total amount of unsaturated ethylene ester monomer and unsaturated monomers including sulfonic acid groups, preferably in the range of 2 to 15 mmol.

[0099] There is no particular limitation on the reaction temperature of the saponification reaction, but it is preferably 10 to 60°C (especially 20 to 50°C).

[0100] Thus, a PVA-based resin having sulfonic acid groups or salt-containing groups thereof can be obtained for use in the present invention (A).

[0101] When synthesizing PVA-based resins having sulfonic acid groups or their salt-containing groups by the above method, sodium acetate may be included as a byproduct.

[0102] The sodium acetate content is 0.1 parts by weight or more, preferably 0.3 parts by weight or more, more preferably 0.5 parts by weight or more, but less than 2.0 parts by weight, preferably less than 1.5 parts by weight, relative to 100 parts by weight (A) of PVA-based resin having sulfonic acid groups or their salt-containing groups. This amount of sodium acetate is preferred because the filamentous support material can slightly decompose when melted to contact the model material, thereby improving adhesion to the model (or model material). If the sodium acetate content is too low, the adhesion to the model (model material) tends to decrease. On the other hand, the thermal stability of PVA-based resins with excessive sodium acetate content is compromised. This means that during the lamination process, the portion of the support material in contact with the high-temperature model material may suffer quality damage or deterioration at a point in the resulting laminated product. In worse cases, the support material may decompose and foam during the lamination process.

[0103] (B) Biodegradable polyester

[0104] The biodegradable polyester used in this invention refers to a polyester resin that meets any one of the biodegradability requirements of ISO 14851, ISO 14855, ISO 9408, ISO 9439, ISO 10707, JIS K 6950, JIS K 6951, JIS K 6953 or JIS K 6955.

[0105] The polyester resin that satisfies biodegradability has the necessary units as aliphatic diol units represented by formula (11) and aliphatic dicarboxylic acid units represented by formula (12), and further includes aromatic dicarboxylic acid units represented by formula (13) and units derived from hydroxycarboxylic acids represented by formula (14), depending on the desired properties, such as biodegradability, mechanical properties or melt formability.

[0106] [Chemical Formula 11]

[0107]

[0108] [Chemical Formula 12]

[0109]

[0110] [Chemical Formula 13]

[0111]

[0112] [Chemical Formula 14]

[0113]

[0114] In equations (11), (12), and (14), p, q, and r are each an integer from 2 to 10, preferably from 2 to 6. In equation (13), Ar represents an aromatic ring.

[0115] The aliphatic diols of formula (11) generally have 2 or more but less than 10 carbon atoms, and examples include ethylene glycol, 1,3-propanediol, 1,4-butanediol and 1,4-cyclohexanediol. Diols with 2 or more but less than 4 carbon atoms are preferred, ethylene glycol and 1,4-butanediol are more preferred, and 1,4-butanediol is particularly preferred.

[0116] Aliphatic dicarboxylic acids of formula (12) typically have two or more but fewer than ten carbon atoms, examples of which include succinic acid, adipic acid, octanoic acid, sebacic acid, and dodecanoic acid. Adipic acid is preferred.

[0117] Examples of aromatic dicarboxylic acids of formula (13) include terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. Among these, terephthalic acid and isophthalic acid are preferred, and terephthalic acid is particularly preferred. In addition, aromatic dicarboxylic acids in which the aromatic ring is partially substituted by a sulfonate salt may also be included.

[0118] Examples of hydroxycarboxylic acids of formula (14) include 4-hydroxybutyric acid, 5-hydroxyvalerate and 6-hydroxyhexanoic acid.

[0119] The constituent units of the (B) biodegradable polyester used in this invention include aliphatic diol units, aliphatic dicarboxylic acid units, and aromatic dicarboxylic acid units. Relative to each of these units, the (B) biodegradable polyester may contain not only one type of unit but also combinations of different types of units.

[0120] In addition to the diol and dicarboxylic acid units mentioned above, (B) biodegradable polyester may further include dicarboxylic acid units with q and r less than 2, such as structural units derived from oxalic acid, malonic acid, glycolic acid, and lactic acid, as long as the biodegradability of polyester (B) is not impaired.

[0121] Specific examples of (B) biodegradable polyesters used in this invention include polyesters whose basic unit is 1,4-butanediol, such as polybutylene succinate (PBS), polybutylene adipate succinate (PBSA), polybutylene lactate succinate (PBSL), polybutylene terephthalate adipate (PBAT), and polyethylene succinate (PES).

[0122] Commercially available biodegradable polyesters can be used, such as "Ecoflex" (trade name) manufactured by BASF, which is mainly composed of a condensation polymer of adipic acid / terephthalic acid and 1,4-butanediol, and "GS-PLA" manufactured by Mitsubishi Chemical Corporation, which is mainly composed of a condensation polymer of succinic acid / 1,4-butanediol / lactic acid. Alternatively, Bionore (trade name) manufactured by Showa High Polymer Co., Ltd., Lunare (trade name) manufactured by Nippon Catalyst Co., Ltd., and [other products] manufactured by DuPont Co., Ltd. can also be used. Manufactured by Eastman Chemical Co., Ltd.

[0123] As the (B) biodegradable polyester used in this invention, a biodegradable polyester having a percentage of 40 to 80 mol% (relative to the total dicarboxylic acid contained in the polyester), preferably 50 to 70 mol%, is preferred.

[0124] As a dicarboxylic acid unit, it can contain aliphatic dicarboxylic acid units and aromatic dicarboxylic acid units. When the percentage of aliphatic dicarboxylic acid units is set within the above range, (B) biodegradable polyester can improve mechanical strength, especially softness, tear strength and impact resistance, so biodegradable polyester in filament form is preferably used as a support material.

[0125] (B) The melt flow rate (MFR) of the biodegradable polyester, measured at 190°C and a load of 2.16 kg, is typically 1.0 g / 10 min or more, preferably 2.0 g / 10 min or more, most preferably 3.0 g / 10 min or more, but typically 6.0 g / 10 min or less, preferably 5.0 g / 10 min or less, and more preferably 4.0 g / 10 min or less. An MFR less than 1.0 g / 10 min results in insufficient fluidity in the molten state. This is not preferred because the supply rate of the support material during lamination molding does not match the molding rate from the mold material. On the other hand, an MFR greater than 6.0 g / 10 min makes it easy for the support material to drip from the orifice during lamination molding.

[0126] (B) The weight-average molecular weight of biodegradable polyester is typically between 5,000 and 50,000, preferably between 5,500 and 40,000, and particularly preferably between 6,000 and 30,000. Excessively high weight-average molecular weight results in high melt viscosity. When forming filamentary support materials through melt mixing, the extruded filamentary support materials are prone to fluctuations due to the high melt viscosity, and the wire diameter may be inconsistent. On the other hand, (B) biodegradable polyester with excessively low weight-average molecular weight is prone to leaching from the filament surface during melt mixing, and the leached polyester may remain as a water-insoluble sheath after being dissolved in water to remove the support structure from the laminated model. After removing the support structure, the remaining water-insoluble material may adhere to the model structure or cause blockage during wastewater treatment.

[0127] The content of (B) biodegradable polyester in the support material is preferably 5 to 100 parts by weight relative to 100 parts by weight of (A) PVA-based resin, more preferably 10 to 60 parts by weight, and even more preferably 20 to 50 parts by weight. If the content of (B) biodegradable polyester is too low, the filamentous support material lacks flexibility, leading to easy breakage during lamination. Furthermore, during lamination, subsequent layers of the support material are laid on top of the previous layer with relatively low adhesion. On the other hand, support materials with an excessively high proportion of (B) biodegradable polyester can impart water solubility, and such support materials are difficult to form island structures with (A) PVA-based resin having sulfonic acid groups or their salt-containing groups as the sea component. Furthermore, the islands of (B) biodegradable polyester are not finely dispersed in the sea of ​​component (A). These phenomena may cause problems related to wastewater treatment when the support material is removed by washing the resulting laminate with water.

[0128] (C) Other ingredients

[0129] (C-1) Other PVA-based resins

[0130] The support material of the present invention can include other PVA resins (i.e., PVA resins other than (A) PVA resins having sulfonic acid groups or their salt-containing groups) within a range that does not impair the compatibility between (A) the PVA-based resin and (B) the biodegradable polyester. Specifically, it comprises less than 30% by weight, preferably less than 10% by weight, of the total PVA-based resin. Other PVA resins include, for example, unmodified PVA resins or other modified PVA resins.

[0131] (C-2) packing

[0132] From the perspective of the strength of the support material, the support material of the present invention may include fillers. Preferred fillers are biodegradable. Examples of biodegradable fillers include starch, cellulose, and biodegradable plastics. The average particle size of the filler is typically 0.1 to 50 μm, more preferably 5 to 30 μm, and particularly preferably 10 to 20 μm. During the mixing operation, it may be difficult to incorporate fillers that are too small into the resin. Fillers that are too large may provide a support structure with a rough surface and insufficient strength. Furthermore, such relatively large fillers may exist in the waste liquid (PVA-based resin aqueous solution) in the form of a dispersion and therefore should be separated and removed from the waste liquid generated during the washing process.

[0133] Hereinafter, the average particle size refers to the particle size D measured by laser diffraction. 50 .

[0134] The filler content in the support material is preferably 0.3 to 40% by weight, more preferably 2 to 30% by weight, and particularly preferably 5 to 10% by weight. If the content is too low, the filler will not produce the desired effect. If the content is too high, the filler will impair the smoothness of the support structure surface and reduce the strength of the support structure.

[0135] (C-3) Other additives

[0136] The support material of the present invention may contain plasticizers; however, from the perspective of molding stability, a relatively low content of plasticizers is required. A preferred content is 20% by weight or less, particularly 10% by weight or less, more particularly 1% by weight or less, and even more particularly 0.1% by weight or less.

[0137] In addition to the above-mentioned components, known additives such as antioxidants, colorants, antistatic agents, UV absorbers, or lubricants, or other thermoplastic resins may be added as needed. When additives are included, they are preferably biodegradable so as not to impair the disposability and environmental compatibility of the support material of the present invention.

[0138] <Supporting Materials and Manufacturing Methods for Layered Molding>

[0139] The support material for layered molding of the present invention (hereinafter, sometimes simply referred to as support material) comprises (A) a PVA-based resin having sulfonic acid groups or salt-containing groups thereof and (B) a biodegradable polyester.

[0140] The support material of the present invention can be provided as a granular composition obtained by adding a predetermined amount of components, mixing them into a homogeneous mixture in a hot-melt state using a twin-screw extruder, and then granulating. Preferably, the support material is provided as a filamentous support material wound on a spool, produced by melting and mixing the granular composition of the support material using a single-screw extruder, extruding it into filaments, cooling it, and then winding the filaments onto a spool.

[0141] Specifically, a granular support material composition is melt-blended using a twin-screw extruder and extruded through a single-hole or multi-hole drawing die of a single-screw extruder in the form of filaments with a diameter of 1.5 to 3.0 mm. The extruded filament support material is cured by air cooling and then wound onto a reel for market delivery. Such filament support materials are convenient because they can be fed from the head along with the target model material for lamination molding. The filament support material needs to have sufficient flexibility and toughness to maintain the reel winding operation and sufficient rigidity to be delivered to the head without delay during lamination molding. The support material of the present invention meets these requirements.

[0142] Therefore, the support material produced as described above, comprising (A) a PVA-based resin having sulfonic acid groups or their salt-containing groups and (B) a biodegradable polyester, has a phase-separated structure in which one component is finely dispersed in a matrix composed of the other components. Preferably, the support material has an island structure in which (A) the PVA-based resin having sulfonic acid groups or their salt-containing groups is present as a sea component and (B) the biodegradable polyester is finely dispersed as an island component. The size of the domains composed of (B) the biodegradable polyester is in the range of about 0.05 to 2 μm, preferably 0.1 to 1.0 μm, more preferably 0.1 to 0.5 μm. Under the following conditions, more than 90% of the domains are within the above-mentioned range in a 0.01 mm × 0.01 mm field of view observed by SEM (electron microscopy).

[0143] Device: JSM-6060LA (manufactured by JEOL Ltd.)

[0144] Accelerating voltage: 5kV

[0145] Spot size: 30

[0146] Stage angle: 0 degrees

[0147] Observe the image: Secondary electron image

[0148] Pretreatment: Etched with chloroform (60℃ × 2 hours), then vacuum dried for 24 hours.

[0149] [Manufacturing methods for layered shapes and three-dimensional structures]

[0150] The layered model of the present invention is obtained in the manufacture of a target model body, which is a three-dimensional structure (model material) having a desired shape. A support structure made of the support material of the present invention is integrally formed with the model structure (target model body) in the layered model body.

[0151] The method for manufacturing a three-dimensional structure according to the present invention is a method for forming a target model of a three-dimensional structure having a desired shape by means of a layered molding process in which the support material of the present invention is used. The method includes a step of layering and solidifying a support material and a model material for the target model in a molten state to produce a layered model; and a step of contacting the layered model with water.

[0152] The model material for which the support material of the present invention can be applied is a thermoplastic resin that can be melt-formed and resin compositions thereof. For example, polylactic acid (PLA), acrylonitrile-butadiene-styrene copolymer (ABS), polyamide (PA), polycarbonate (PC), polyethylene terephthalate (PET), glycol-modified polyethylene terephthalate (PETG), polyhydroxyalkanoates (PHA), wood-filled composites, metal-filled composites, carbon fiber-filled composites, polyvinyl butyral (PVB), thermoplastic elastomers (TPE), thermoplastic polyurethanes (TPU), polyolefins, polypropylene (PP), acrylonitrile-styrene acrylate (ASA), polyacrylate, polymethyl methacrylate, polystyrene (PS), polyoxymethylene (POM), and mixtures thereof can be used.

[0153] The support material of the present invention is particularly excellent as a support material for PLA, ABS, PA, PETG and PC due to its excellent adhesion to these materials.

[0154] The equipment used in the method for manufacturing the three-dimensional structure of the present invention can be a stacked modeling device equipped with multiple nozzles for independently extruding molten mold material and molten support material. Stacked modeling devices include dual-head FDM 3D printers, such as the Creator manufactured by FlashForge, the Eagleed manufactured by Rays Enterprises, the MBot Grid II manufactured by 3D Systems, the NJB-200W manufactured by Ninjabot, and the EVO manufactured by Airwolf.

[0155] In the case of a stacking modeling printer, the model material, composed of the aforementioned constituent materials, is typically provided in the form of strands or filaments and wound onto a spool like a support material. The strands or filaments of the model material and the support material are supplied to different heads of the stacking modeling equipment, where they are then heated and melted at their nozzle heads, and placed on the print bed to form a layered structure.

[0156] The materials are melted at their respective heads, typically at temperatures of 150 to 300°C, and extruded under pressures of 200 to 1000 psi. The stacking spacing is typically 100 to 350 μm.

[0157] The melt-extruded support material and model material are cooled and solidified, and then the melt-extruded support material and model material are placed on top of the previous layers of solidified support material and model material. The resulting structure or laminated model includes a target model made of model material.

[0158] The process of bringing the laminated structure into contact with water involves removing the supporting structure from the laminated structure, which consists of the target structure and the supporting structure, by means of water. This removal process can be carried out by immersing the laminated structure in water or warm water, or by washing the laminated structure with running water. To shorten the immersion time for dissolving the supporting structure, the water can be agitated or exposed to ultrasound. The water used in the removal process can preferably have a temperature of about 25 to 80°C. The amount of water or warm water used for dissolution is about 10 to 10,000 times the weight of the supporting structure.

[0159] Even complex three-dimensional structures with overhangs (target shapes) can be obtained by removing the supporting structures from the stacked shapes.

[0160] In the waste liquid (PVA-based resin aqueous solution) generated by washing the laminated model with water, the water-insoluble component or (B) biodegradable polyester is finely dispersed as a dispersion. However, the waste liquid (PVA-based resin aqueous solution) generated by the water washing removal process is likely a suspension in which (B) biodegradable polyester is dispersed in the form of particles with an average particle size of 0.1 to 5 μm, preferably 0.2 to 2 μm. Therefore, the waste liquid (drainage) can be treated directly without some special separation treatment. Since the waste liquid can be discharged, a relatively large amount of water (warm water) can be used for removal treatment, for example, by washing with running water.

[0161] Example

[0162] The present invention will be described in more detail below with reference to embodiments, but the invention is not limited to the following embodiments, as long as they do not deviate from the spirit of the invention. In the embodiments, "part" means weight basis.

[0163] [Measurement and Evaluation Methods]

[0164] 1. Characteristics of modified PVA resins

[0165] (1) Degree of saponification

[0166] The degree of saponification was determined by analyzing the amount of alkali required for the hydrolysis of residual vinyl acetate units. In the case of PVA-based resins modified with side-chain 1,2-diol, the degree of saponification was determined by analyzing the amount of alkali required for the hydrolysis of residual vinyl acetate units and 3,4-diacetoxy-1-butene structural units.

[0167] (2) Degree of aggregation

[0168] The degree of polymerization is expressed as number-average degree of polymerization. The number-average degree of polymerization is calculated based on the viscosity (mPa·s) of a 4% aqueous solution at 20°C, as measured according to JIS K6726 standard.

[0169] (3) Modification rate

[0170] The amount of modifying groups (structural units having sulfonic acid groups or their salt-containing groups, or groups containing 1,2-diol side chains) is determined by... 1 Calculation of the integral value of H-NMR (300MHz proton NMR, d6-DMSO solution, tetramethylsilane as internal standard, 50℃).

[0171] 2. Characteristics of the supporting material

[0172] (1)(B) Domain size of biodegradable polyester

[0173] The prepared support material was observed by SEM (0.01 mm × 0.01 mm field of view) under the following conditions, and the domain size of (B) biodegradable polyester domain (PBAT domain) was measured.

[0174] Device: JSM-6060LA (manufactured by JEOL Ltd.)

[0175] Accelerating voltage: 5kV

[0176] Spot size: 30

[0177] Tabletop angle: 0 degrees

[0178] Observe the image: Secondary electron image

[0179] Pretreatment: Etched with chloroform (60℃ × 2 hours), then vacuum dried for 24 hours.

[0180] (2) Deviation in wire diameter fluctuation (wire diameter stability)

[0181] Regarding the diameter, the prepared filamentary support material (diameter 2.85 mm) was measured at 15 points at 1 m intervals along its length, and the deviation from the predetermined diameter of 2.85 mm was calculated. The smaller the deviation, the more stable the diameter of the filamentary support material.

[0182] 3. Adhesion to model materials

[0183] As modeling materials, polylactic acid (PLA), ABS resin (ABS), polyamide (PA), ethylene glycol-modified polyethylene terephthalate (PETG), or polycarbonate (PC) were used to evaluate the adhesion of the filamentous support material to these modeling materials as follows.

[0184] The aforementioned support material and the four model materials were placed in the nozzle head of an FDM dual-head 3D printer (an EVO manufactured by Airwolf3D) to form a shape as shown above. Figure 1 The layered structure shown. In Figure 1 In this process, the supporting structure 1 is made of supporting material, and the L-shaped model structure 2 is made of model material. The produced layered model is observed in its final form. Furthermore, to evaluate the adhesion of each surface, the layered model is separated into the supporting structure and the model structure by hand peeling along the α-face or β-face. The α-face is the surface of the model material layered on top of the model made of supporting material, and the β-face is the surface of the supporting material layered on top of the model made of model material.

[0185] Evaluate adhesion according to criteria A, B, or C below. If separation by peeling is easily done by hand, it is difficult to perform layering at a relatively high speed.

[0186] A: Layering is possible, and the resulting layered shapes cannot be separated by hand.

[0187] B: Layering is possible, but the resulting layered shapes can be easily separated by hand.

[0188] C: Layering shapes is difficult and will fail.

[0189] 4. Water washing removes toxicity.

[0190] (1) Water solubility (complete dissolution time)

[0191] 5g of granules, each 2mm in length, obtained by cutting the support material, were placed into a 90-mesh wire mesh cage. The wire mesh cage was then immersed in a 500ml hot water bath at 40°C with stirring (300rpm). The time until the granules in the wire mesh cage were no longer visible due to dissolution was measured. This time is called the complete dissolution time (unit: minutes). The shorter the complete dissolution time, the better the water solubility.

[0192] (2) Formation of condensates

[0193] If, even after 2 hours, coagulations remain on the wire mesh used for the water solubility test as insoluble substances, the test result is evaluated as coagulation formation. If no coagulations are clearly identifiable on the wire mesh, the test result is evaluated as no coagulation formation.

[0194] [Manufacturing of Modified PVA-Based Resins]

[0195] (1) A PVA-based resin 1 having sulfonic acid groups or salt-containing groups (hereinafter referred to as "sulfonic acid modified PVA-based resin 1")

[0196] In a reactor equipped with a reflux condenser, a dropping funnel, and a stirrer, 1000 parts by weight of vinyl acetate, 422 parts by weight of methanol, and 62 parts by weight (corresponding to 3.7 mol% of vinyl acetate and 0.26% chlorine content) of sodium allyl sulfonate, and 0.072 mol% (relative to the amount of vinyl acetate charged) of azobisisobutyronitrile (AIBN) were charged. Polymerization was carried out while stirring, and the mixture was heated and refluxed under nitrogen blowing.

[0197] During polymerization, azobisisobutyronitrile (AIB) was added four times at 0.072 mol% (relative to the amount of vinyl acetate charged). When the polymerization rate of vinyl acetate reached 96.4%, the polymerization was terminated by adding 0.1 parts by weight of m-dinitrobenzene. Subsequently, unreacted vinyl acetate monomers were removed from the reaction system by blowing methanol vapor to obtain a methanol solution of the copolymer.

[0198] The resulting methanol solution containing the copolymer was diluted with methanol to adjust the concentration to 55% and then loaded into a mixer. While maintaining the solution temperature at 35°C, a methanol solution of sodium hydroxide (sodium concentration 2%) was added at a ratio of 8 mmol / L relative to 1 mol of vinyl acetate structural units in the copolymer for saponification. As the saponification reaction proceeded, particulate saponification products precipitated, which were separated by filtration. The separated particles were thoroughly washed with methanol and then dried in a hot air dryer, thereby providing a composition containing not only PVA-based resins with sulfonic acid groups or their salt-containing groups but also chlorine. The sodium acetate content was 1.3 parts per 100 parts by weight of PVA-based resins with sulfonic acid groups or their salt-containing groups.

[0199] The obtained sulfonic acid modified PVA resin 1 has a saponification degree of 87.3 mol%, a number-average degree of polymerization of 250, and the amount or modification rate of structural units with sulfonic acid groups or their salt-containing groups is 2.7 mol%.

[0200] (2) PVA resins 2, 3, 4 and 5, each having a sulfonic acid group or a salt-containing group (hereinafter referred to as "sulfonic acid modified PVA resins 2, 3, 4 or 5").

[0201] In the manufacture of sulfonic acid modified PVA resin 1, the following sulfonic acid modified PVA resins 2, 3, 4, and 5 were prepared by varying the amount of sodium allyl sulfonate added, the polymerization time, or the time taken to wash the PVA resin with sulfonic acid groups or their salt-containing groups obtained by methanol washing. They differ in their modification rate, degree of polymerization, and the amount of sodium acetate contained in the resin.

[0202] Sulfonic acid modified PVA resin 2

[0203] The modification rate was 1.6 mol%, the number-average degree of polymerization was 370, and the sodium acetate content was 0.9 parts per 100 parts of PVA resin.

[0204] Sulfonic acid modified PVA resin 3

[0205] The modification rate was 1.1 mol%, the number-average degree of polymerization was 370, and the sodium acetate content was 0.9 parts per 100 parts of PVA resin.

[0206] Sulfonic acid modified PVA resin 4

[0207] The modification rate was 1.1 mol%, the number-average degree of polymerization was 370, and the sodium acetate content was 0.2 parts per 100 parts of PVA-based resin; and

[0208] Sulfonic acid modified PVA resin 5

[0209] The modification rate was 0.3 mol%, the number-average degree of polymerization was 370, and the sodium acetate content was 0.8 parts per 100 parts of PVA resin.

[0210] (3) PVA resin modified with side chain 1,2-diol

[0211] 85 parts (corresponding to an initial concentration based on 10% of the total charge) of vinyl acetate, 460 parts of methanol, and 7.6 parts of 3,4-diacetoxy-1-butene were charged into a reactor equipped with a reflux condenser, a dropping funnel, and a stirrer. After adding 0.32 parts of azobisisobutyronitrile (AIBN) to the reactor, the reactor was heated to initiate polymerization with stirring and nitrogen blowing. 0.5 hours after the start of polymerization, 765 parts of vinyl acetate were added dropwise over 8 hours (dropping rate 95.6 parts / hour). 0.2 parts of AIBN were added at 2.5 hours after the start of polymerization, and another 0.2 parts of AIBN were added at 4.5 hours after the start of polymerization. When the polymerization rate of vinyl acetate reached 85%, a predetermined amount of m-dinitrobenzene was added to terminate the polymerization. Subsequently, unreacted vinyl acetate monomers in the reaction system were removed by distillation while methanol vapor was blown in, yielding a methanol solution of the copolymer.

[0212] The above solution was then diluted with methanol to adjust the solid content concentration to 50%. The diluted methanol solution was then loaded into a mixer for saponification. The saponification reaction was carried out by adding a methanol solution with a sodium content of 2% sodium hydroxide at a ratio of 9 mmol per mol relative to the total amount of vinyl acetate and 3,4-diacetoxy-1-butene structural units in the copolymer, while maintaining the solution temperature at 35°C. As the saponification reaction proceeded, the saponification product precipitated. When the saponification product became granular, a 2% methanol solution was further added at a ratio of 4 mmol per mol relative to the total amount of vinyl acetate and 3,4-diacetoxy-1-butene structural units. Subsequently, acetic acid was added for neutralization at an amount equivalent to 0.8 mmol of sodium hydroxide. The saponification product was separated by filtration, thoroughly washed with methanol, and dried in a hot air dryer. Thus, a PVA-based resin with a 1,2-diol side chain was obtained, which is a 1,2-diol-modified PVA-based resin. The content of sodium acetate is 1.3 parts relative to 100 parts by weight of 1,2-diol-modified PVA resin.

[0213] The obtained 1,2-diol-modified PVA resin had a saponification degree of 86 mol%, a number-average degree of polymerization of 380, and a content of 4 mol% of 1,2-diol structural units.

[0214] [Production of Supporting Materials]

[0215] Support materials No. 1 to 6:

[0216] 100 parts of one of the above-produced sulfonic acid modified PVA resins 1 to 5 and PBAT (“Ecoflex C1200”, manufactured by BASF) as (B) a biodegradable polyester were mixed in the proportions shown in Table 1. The resulting blend was fed into a twin-screw extruder to prepare a granular composition. The granules were melt-blended using a single-screw extruder, extruded into filaments with a diameter of 2.85 mm, cooled with air on a belt, and wound onto a spool to obtain a filamentous support material.

[0217] Single screw extruder ("SZW20GT-24MG-STD", manufactured by TECHNOVEL CORPORATION): 20mm φ, L / D = 24

[0218] Extrusion temperature mode: C1 / C2 / C3 / H / D=190 / 210 / 220 / 220 / 220℃

[0219] Rotation speed: 40 rpm

[0220] Discharge rate: 1.0 kg / hour

[0221] Support materials No. 7 and 8:

[0222] 100 parts of the above-synthesized 1,2-diol-modified PVA resin and biodegradable polyester ("Ecoflex C1200", manufactured by BASF) were dry-blended in the proportions shown in Table 1. Filamentous support materials were prepared using the blend in the same manner as support material No. 1.

[0223] The dispersion (PBAT domain size), deviation of wire diameter fluctuation (wire diameter stability), adhesion to model materials, and water washability of the (B) biodegradable polyesters of the support materials No. 1 to 8 prepared above were evaluated according to the previously mentioned measurement and evaluation methods. The results are shown in Table 2.

[0224]

[0225]

[0226] As shown in Table 2, compared with support materials No. 7 and 8 using 1,2-diol-modified PVA resins, support materials No. 1 to 6 using PVA resins with sulfonic acid groups or their salt-containing groups (hereinafter referred to as "sulfonic acid-modified PVA resins") exhibit a finer dispersion of biodegradable polyesters. Regarding water washability, support materials No. 1 to 5 using sulfonic acid-modified PVA resins did not produce aggregates and had shorter complete dissolution times compared with support materials (No. 7 and 8) using 1,2-diol-modified PVA resins.

[0227] When the modification rate of sulfonic acid-modified PVA resin is 0.3 mol% (No. 6), the expected water washability is not achieved due to insufficient modification effect of sulfonic acid.

[0228] Furthermore, a comparison of No. 1 to 6 and No. 7 and 8 shows that sulfonic acid modified PVA resins can provide filamentous support materials with superior wire diameter stability (deviation of wire diameter fluctuation) compared to 1,2-diol modified PVA with side chains.

[0229] Furthermore, regarding adhesion to modeling materials, support materials No. 7 and 8, which use 1,2-diol-modified PVA resins, are inferior in the β-plane compared to those using sulfonic acid-modified PVA resins. In particular, the adhesion of No. 7 and No. 8 to modeling materials such as ABS, PA, PETG, and PC limits the types of modeling materials that can be used in combination with support materials using 1,2-diol-modified PVA resins. In contrast, support materials No. 1 to 5, especially No. 1 to 4, which use sulfonic acid-modified PVA resins, exhibit excellent adhesion to various modeling materials including PLA, ABS, PA, PETG, and PC, indicating superior versatility. Therefore, support materials using sulfonic acid-modified PVA resins can be applied to a wide variety of modeling materials used in layered modeling.

[0230] A comparison of sulfonic acid-modified PVA resins No. 3 and No. 5 confirmed that even with the same modification rate, degree of saponification, and degree of polymerization, the α- and β-faces may exhibit different adhesion properties when the sodium acetate content in the sulfonic acid-modified PVA resin is too low. When supporting model materials with complex shapes, it is preferable to adjust the amount of sodium acetate to 0.5 to 2.0 parts by weight relative to 100 parts by weight of PVA resin.

[0231] Industrial availability

[0232] Because the support material for layered molding of the present invention has excellent water solubility, and the insoluble substances contained in the support material can be reduced to very small biodegradable residues in the waste liquid, the waste liquid can be directly discharged. Therefore, the water washing and removal after layered molding, and the waste liquid treatment after water washing and removal of the support material are not troublesome, and the waste liquid is environmentally friendly. For these reasons, the support material of the present invention can be used for both temporary and discarded support materials.

[0233] In addition, because the support material exhibits excellent adhesion to various materials, it can be used as a support material for a wide range of materials.

Claims

1. A support material for additive manufacturing, comprising: (A) a polyvinyl alcohol-based resin having a sulfonic acid group or a salt-containing group thereof; and (B) a biodegradable polyester, wherein the modification rate of the (A) polyvinyl alcohol-based resin having a sulfonic acid group or a salt-containing group thereof is 0.5 to 10 mol%, wherein the content of sodium acetate is 0.5 to 2.0 parts by weight with respect to 100 parts by weight of the (A) polyvinyl alcohol-based resin having a sulfonic acid group or a salt-containing group thereof.

2. The support material for additive manufacturing according to claim 1, wherein the (A) polyvinyl alcohol-based resin having a sulfonic acid group or a salt-containing group thereof is a polyvinyl alcohol-based resin having a structural unit represented by the following formula (3-1), (3-2) or (3-3) as a sulfonic acid group or a salt-containing group thereof, [Chemical Formula 3] wherein M is hydrogen or an alkali metal or an ammonium group, X and Y are each a linking group, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are each independently hydrogen, or an alkyl group having 1 to 4 carbon atoms, R c is hydrogen, an alkyl group, a sulfonic acid group, or a group containing -SO3M, and n is an integer of 2 to 4.

3. The support material for additive manufacturing according to claim 2, wherein the (A) polyvinyl alcohol-based resin having a sulfonic acid group or a salt-containing group thereof contains the structural units represented by the above (3-1), (3-2) and (3-3) at a ratio of 0.01 to 10 mol%.

4. The support material for additive manufacturing according to claim 1, wherein the content of the (B) biodegradable polyester is 5 to 100 parts by weight with respect to 100 parts by weight of the (A) polyvinyl alcohol-based resin having a sulfonic acid group or a salt-containing group thereof.

5. The support material for additive manufacturing according to claim 1, wherein the (A) polyvinyl alcohol-based resin having a sulfonic acid group or a salt-containing group thereof and the (B) biodegradable polyester have a phase separation structure in which one is a matrix and the other is finely dispersed in the matrix.

6. The support material for additive manufacturing according to claim 5, wherein the phase separation structure is an island-in-sea structure in which the (B) biodegradable polyester as an island component is dispersed in the (A) polyvinyl alcohol-based resin having a sulfonic acid group or a salt-containing group thereof as a sea component.

7. The support material for additive manufacturing according to claim 6, wherein the size of a domain composed of the (B) biodegradable polyester is 0.05 to 2 μm.

8. The support material for additive manufacturing according to any one of claims 1 to 7, wherein the ratio of an aliphatic dicarboxylic acid unit with respect to dicarboxylic acid units in the (B) biodegradable polyester is in the range of 40 to 80 mol%.

9. The support material for additive manufacturing according to claim 8, wherein the support material for additive manufacturing is a support material for additive manufacturing of a hot-melt layering type.

10. The support material for additive manufacturing according to claim 9, wherein the support material for additive manufacturing is in a filamentous form.

11. A method for producing a three-dimensional structure, comprising: a step of producing an additive manufacturing article by layering and solidifying a support material for additive manufacturing according to any one of claims 1 to 10 and a model material in a molten state; and a step of bringing the obtained additive manufacturing article into contact with water.

12. The manufacturing method according to claim 11, wherein the model material is polylactic acid, acrylonitrile-butadiene-styrene resin, polyamide resin, polyethylene terephthalate, or polycarbonate.

13. A layered molded article comprising the support material for layered molding according to any one of claims 1 to 10.

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