JP2020093455A - Copolymerized polybutylene terephthalate for powder laminate molding method - Google Patents

Abstract

To provide a copolymerized polybutylene terephthalate for a powder laminate molding method, which can effectively suppress an increase in intrinsic viscosity and an increase in yellow tint during molding and/or reuse of a three-dimensional object by a powder laminate molding apparatus.SOLUTION: Copolymerized polybutylene terephthalate for a powder laminate molding method, contains a terephthalic acid component and a 1,4-butanediol component as main components, has a melting point of 150 to 215°C, and has a terminal carboxyl group amount of 42 to 90 equivalents/ton. It is preferable that the melting point is 170 to 199°C and the terminal carboxyl group amount is 45 to 90 equivalents/ton, particularly 65 to 90 equivalents/ton.SELECTED DRAWING: None

Description

The present invention relates to a copolymerized polybutylene terephthalate (hereinafter, the polybutylene terephthalate may be referred to as PBT) used in a powder layered manufacturing method. In particular, for a powder additive manufacturing method capable of effectively suppressing an increase in intrinsic viscosity and an increase in yellow tint due to a high degree of polymerization during modeling and/or reuse of a three-dimensional object manufactured by a powder additive manufacturing apparatus. It relates to copolymerized PBT.

Polyester occupies an industrially important position because of its excellent mechanical and chemical properties. For example, aromatic polyester such as PBT is a resin having excellent heat resistance and chemical resistance, and is easy to process and is economical, so that fibers, films, sheets, bottles, electric and electronic parts, automobile parts, precision instruments are used. It is widely used in fields such as extrusion of parts and injection.

The powder layered modeling method, which is one of the three-dimensional modeling methods, heats and sinters a thin layer of a powder material such as a resin in a modeling section by using a heating unit to form a model, which is repeated to form a layered product. This is a method of obtaining a three-dimensional modeled product.
A laser, an infrared lamp, a xenon lamp, a halogen lamp or the like is used as the heating means.
The powder additive molding method does not require the use of molds, and various resin powders can be used as raw materials as long as they have heat resistance to some extent, and the reliability of the obtained molded products is high. It is a technology that is being used.

In this technical field, for example, the following techniques are known.
Patent Document 1 discloses a copolymerized PBT having a copolymerization component of 3 to 30 mol% and a melting point of 200 to 215° C. as a copolymerized PBT that is difficult to absorb water and is suitable for obtaining a shaped article having high heat resistance. Has been done. This Patent Document 1 describes the melting point of the copolymerized PBT, but does not describe the amount of terminal carboxyl groups.
Patent Document 2 discloses a technique in which two resins having different melting points, for example, a copolymerized PBT and a homo PBT, are used in combination in order to enhance robustness against temperature control and to improve heat resistance of a molded article. Has been done. This Patent Document 2 also describes the melting point of the copolymerized PBT used, but does not describe the amount of terminal carboxyl groups.

When three-dimensional modeling is performed by a powder layered modeling method using powder of a crystalline resin such as PBT, the resin powder is heated to a temperature near the melting point for modeling. Although it depends on the design of the modeling apparatus, the powder (recovered powder) recovered as an excess during the modeling is mixed with the powder (initial powder) initially charged and reused for modeling.

Regarding the temperature of the molding area at the time of molding, for example, in Patent Document 1, the temperature of the molding area is set to a temperature lower by about 5 to 15° C. than the melting point of the resin, or specifically, when molding a resin having a melting point of 208° C. Is set to 190°C. In this case, modeling is performed in a temperature area that is 18° C. lower than the melting point. Further, in Patent Document 2, for example, in molding a resin having a melting point of 208° C., it is described that the temperature of the molding area is 190° C. and the temperature of the storage area is 175° C.

As described above, in the powder layered manufacturing method, the resin powder is subjected to the heat treatment in the modeling area having a temperature lower by about 20° C. than the melting point.
Note that Patent Documents 1 and 2 describe that the modeling area is preferably under an inert atmosphere such as nitrogen.
The time spent for modeling may vary depending on the number of stacked layers and the size thereof, but is, for example, about 10 to 20 hours.

International Publication No. 2016/121013 International Publication No. 2017/179139

When a crystalline resin such as PBT is subjected to heat treatment at a temperature near the melting point as described above, so-called solid phase polycondensation occurs in which polymerization proceeds in a solid phase state, resulting in an increase in intrinsic viscosity of the resin. Will end up. In addition, it causes undesirable changes in physical properties such as yellowing due to heating. For this reason, even with the initial powder, the heat generated during the molding process may cause problems such as changes in physical properties and yellowing of the obtained molded product, and the recovered powder has a higher intrinsic viscosity than the initial powder. , Becomes yellowish. In addition, when the recovered powder that has increased intrinsic viscosity and yellowed is mixed and reused with the new powder, the recovered powder has a higher intrinsic viscosity than the new powder and there is a difference in the intrinsic viscosity. When melted, uneven viscosity occurs, which results in uneven melting, which causes a problem in modeling. In addition, when the temperature of the heat treatment increases, the yellowness of the molded product increases, and color unevenness easily occurs.

In order to solve such a problem, it is an object of the present invention to provide a PBT powder having a small increase in intrinsic viscosity even when subjected to a heat treatment and a small yellowing.
That is, the present invention can effectively suppress an increase in intrinsic viscosity and an increase in yellowness due to a high degree of polymerization during modeling and/or reuse of a three-dimensional modeled article by a powder layered modeling apparatus. An object of the present invention is to provide a copolymerizable PBT for a powder layered manufacturing method that can be used.

As a result of intensive studies to solve the above problems, the present inventors have found that these problems can be solved by a copolymerized PBT having a melting point and an amount of terminal carboxyl groups within a predetermined range, and the present invention has been made. It came to completion.

That is, the present invention is
A copolymerized polybutylene terephthalate containing a terephthalic acid component and a 1,4-butanediol component as main components, which is used in the powder layering method, and has a melting point of 150 to 215° C. and a terminal carboxyl group amount of 42 to 90 equivalents. /Ton, copolymer polybutylene terephthalate for powder lamination manufacturing method,
Exist in.

The present invention also provides
A polybutylene terephthalate-based composition for powder lamination molding, comprising 5 to 100% by mass of the copolymerized polybutylene terephthalate for powder lamination molding,
A powder material for a powder laminating method comprising a copolymerized polybutylene terephthalate for the powder laminating method or a polybutylene terephthalate-based composition for the powder laminating method,
A molding method for manufacturing a molded article by the powder lamination molding method using the powder material for the powder lamination molding method,
A shaped article using the powder material for the powder layering method,
Exist in.

The copolymerized PBT of the present invention can suppress an increase in intrinsic viscosity and an increase in yellowness even when subjected to a heat treatment at a temperature close to the melting point in an inert gas atmosphere or an air atmosphere for a long time. In particular, the effects of the present invention are preferably exhibited when heat treatment is performed in an inert gas atmosphere.
Even when such a copolymerized PBT of the present invention is used in a powder layered manufacturing method to recover and reuse an excessive powder, these undesirable physical property changes are small, and the recovered powder is mixed with the initial powder. Even if it is used, stable modeling can be performed and a high quality molded article can be obtained.

BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described in detail below, but the description of the constituent elements described below is a representative example of the embodiment of the present invention, and the present invention is limited to these contents. Not a thing.

[Copolymerized PBT for powder additive manufacturing]
The copolymerized PBT for the powder layered manufacturing method of the present invention (hereinafter sometimes referred to as “copolymerized PBT of the present invention”) is a copolymerized PBT containing a terephthalic acid component and a 1,4-butanediol component as main components. And has a melting point of 150 to 215° C. and a terminal carboxyl group content of 42 to 90 equivalents/ton.
Preferred is a copolymerized PBT that has not been used for modeling by the powder layered modeling method (has no history of use).

<Composition of copolymerized PBT>
The copolymerized PBT of the present invention is a polyester in which the main component (65 mol% or more) of the dicarboxylic acid component is a terephthalic acid component and the main component (65 mol% or more) of the diol component is 1,4-butanediol. PBT containing a copolymerization component in which 35 mol% or less of the dicarboxylic acid component is a component other than terephthalic acid and/or 35 mol% or less of the diol component is a component other than the 1,4-butanediol component.
That is, in the copolymerized PBT of the present invention, 65 mol% or more out of 100 mol% of the constituent units derived from all dicarboxylic acid components are constituent units derived from the terephthalic acid component, and 35 mol% or less are dicarboxylic acids other than terephthalic acid. Constituent units derived from the components, 65 mol% or more of 100 mol% of the constituent units derived from all the diol components are constituent units derived from 1,4-butanediol, and 35 mol% or less are 1,4- It is a copolyester which is a constitutional unit derived from a diol component other than butanediol.

As the copolymerization component, isophthalic acid, naphthalenedicarboxylic acid, succinic acid and the like (may be derivatives thereof) as the dicarboxylic acid component, and ethylene glycol, diethylene glycol, 1,3-propanediol as the diol component, 1 ,4-Cyclohexanedimethanol, 2,4-diethyl-1,5-pentanediol, butylethylpropanediol, spiroglycol, tricyclodecanedimethanol, 9,9-bis[4-(2-hydroxyethoxy)phenyl] Examples thereof include fluorene, but are not limited thereto.
Among these copolymerization components, isophthalic acid is particularly preferably used because it is industrially available and the polymer can be easily produced. A plurality of these copolymerization components can be used at the same time.

In the case of a copolymerized PBT containing an isophthalic acid component as a copolymerization component, the terephthalic acid component is 65 to 95 mol%, particularly 70 to 90 mol%, and most preferably 75 to 85 mol% in 100 mol% of all dicarboxylic acid components, It is preferable that the isophthalic acid component is contained in an amount of 5 to 35 mol %, particularly 10 to 30 mol %, and most preferably 15 to 25 mol %, from the viewpoint of exhibiting heat resistance and appropriate crystallinity during molding.

<Physical properties of copolymerized PBT>
The melting point of the copolymerized PBT of the present invention is 150 to 215°C. If the melting point is less than 150°C, the heat resistance of the obtained shaped article is low, which is not preferable. The melting point is preferably 160°C or higher, more preferably 170°C or higher, most preferably 180°C or higher.

On the other hand, the melting point is 215° C. or lower for the following reason.
Homo-PBT (melting point 225° C.) containing no copolymerization component easily undergoes solid phase polycondensation even in an inert gas atmosphere, but copolymerization can delay the progress of solid phase polycondensation. The degree is remarkable in the range where the melting point is 215° C. or lower, and the increase in intrinsic viscosity and the increase in yellowness can be effectively suppressed. From this point of view, the melting point of the copolymerized PBT of the present invention is preferably 210° C. or lower, more preferably 199° C. or lower, particularly preferably 195° C. or lower, most preferably 190° C. or lower.

When the melting point of the copolymerized PBT is within the above-mentioned desired range, it is possible to obtain the effect that the obtained shaped article has both excellent heat resistance and strength.

The melting point of the copolymerized PBT is measured by the method described in the section of Examples below.

The amount of terminal carboxyl groups of the copolymerized PBT of the present invention is 42 to 90 equivalents/ton.
The amount of this terminal carboxyl group is higher than the amount of the terminal carboxyl group of the copolymerized PBT obtained under normal production conditions, and in order to produce such a copolymerized PBT having such an amount of terminal carboxyl group, the production conditions and the like should be devised as described below. Although it is required, the present inventor effectively suppresses an increase in intrinsic viscosity during heat treatment, particularly in an inert gas atmosphere, when the amount of terminal carboxyl groups of the copolymerized PBT is within this range. It was discovered that The reason why such an effect is exerted is not clear, but in this case, it is also considered that the progress of polycondensation due to the heat treatment, the progress of depolymerization due to the diol component, and the unbalance between the carboxyl terminal and the diol terminal occur in combination.

The amount of terminal carboxyl groups of the copolymerized PBT in the present invention is preferably 45 to 90 equivalents/ton, more preferably 65 to 90 equivalents/ton. When the amount of terminal carboxyl groups is within such a range, the effect of the present invention is remarkably exhibited.

Further, the present inventor has found that, when the influence of the molecular weight is further considered, the ratio of the amount of terminal carboxyl groups to the total amount of terminal groups of the copolymerized PBT affects the effect of the present invention. Here, the total amount of terminal groups is the total number of terminal groups of the polymer, and is approximately the total of terminal carboxyl groups, terminal hydroxyl groups, and terminal vinyl groups.

The amount of terminal carboxyl groups of the copolymerized PBT of the present invention is preferably 42 to 90%, particularly 45 to 90%, and especially 65 to 90% based on the total amount of terminal groups. When the ratio of the amount of terminal carboxyl groups to the total amount of terminal groups is within such a range, the effect of the present invention is more remarkably exhibited.

The amount of terminal carboxyl groups and the total amount of terminal groups of the copolymerized PBT can be determined by the method described in the section of Examples below.

The glass transition temperature of the copolymerized PBT of the present invention is preferably 30°C or higher and 49°C or lower. When the glass transition temperature is lower than 30° C., the obtained shaped product tends to be softened, which causes problems. The glass transition temperature of the copolymerized PBT of the present invention is preferably 32°C or higher, more preferably 34°C or higher. On the other hand, when the glass transition temperature exceeds 49° C., uneven melting often occurs in the shaped product. In addition, depending on the copolymerization component, the crystallinity of the molded article tends to be low, and the heat resistance tends to be poor. The upper limit of the glass transition temperature of the copolymerized PBT of the present invention is more preferably 48°C, further preferably 46°C.

The glass transition temperature of the copolymerized PBT is measured by the method described in the section of Examples below.

<Method for producing copolymerized PBT>
The method for producing the copolymerized PBT of the present invention is not particularly limited, and a known method can be used. For example, first, a copolymerization component is added together with a terephthalic acid component and 1,4-butanediol, a transesterification reaction and/or an esterification reaction is performed to obtain a low polymer, and then a melt polycondensation reaction of the obtained low polymer is performed. Can be used to obtain a polymer. These reactions may be batch type or continuous type.

As the terephthalic acid component, in addition to terephthalic acid, one or more kinds of terephthalic acid alkyl esters (the carbon number of the alkyl group is preferably 1) and terephthalic acid derivatives such as halides can be used. As the isophthalic acid component as a copolymerization component, in addition to isophthalic acid, one or more isophthalic acid derivatives such as an alkyl ester of isophthalic acid (the carbon number of the alkyl group is preferably 1) and a halide are used. it can. The same applies to other dicarboxylic acid components.

Examples of the method of obtaining the low polymer include a method of performing a transesterification reaction and/or an esterification reaction under normal pressure or pressure using a single-stage or multi-stage reaction apparatus, with or without a catalyst. Be done.

As an example of the melt polycondensation method, there is a method of distilling out water or alcohol produced while heating under reduced pressure in the presence of a catalyst using a single-stage or multi-stage reaction apparatus. Examples of the polycondensation catalyst used at this time include compounds such as antimony, germanium, titanium and aluminum.

In addition to the above catalysts, phosphorus compounds such as orthophosphoric acid, phosphorous acid, hypophosphorous acid, polyphosphoric acid and their esters and metal salts; sodium compounds such as sodium hydroxide and sodium benzoate; lithium such as lithium acetate. Compounds, alkali metal compounds such as potassium compounds such as potassium hydroxide and potassium acetate; reaction aids such as alkaline earth metal compounds such as magnesium acetate and calcium acetate, and additives such as antioxidants may be used. ..

In order to increase the reaction rate, conditions such as increasing the degree of pressure reduction, increasing the rate of temperature increase, and increasing the rate of updating the reaction liquid surface may be used.

The copolymerized PBT obtained by melt polycondensation is usually pelletized by cutting it with a cutter after water-cooling or water-cooling after withdrawing it in a strand or sheet form from an outlet provided at the bottom of the melt polycondensation tank. It is a granular body having a shape of a chip or the like (for example, a length of about 3 to 10 mm).

(Polycondensation catalyst)
In the production of the copolymerized PBT of the present invention, it is particularly desirable to use a titanium compound such as tetrabutyl titanate as a polycondensation catalyst. When a titanium compound is used, the catalytic activity is generally high, the generation of foreign matters due to the catalyst is small, and a copolymerized PBT particularly suitable for powder lamination molding can be produced. When the titanium compound is added as a catalyst in the low polymer production step and the polycondensation step separately, the production of the copolymerized PBT can be carried out particularly effectively. The amount of the titanium compound added is 10 to 40 mass ppm in terms of titanium element conversion in the low polymer production step and 30 to 70 mass ppm in the polycondensation step with respect to the produced copolymerized PBT, and the total is 40 to 110 mass ppm. Good to do. When the total addition amount is less than 40 mass ppm, the polycondensation rate is often slowed, and when it exceeds 110 mass ppm, the yellow tint during heat treatment tends to be strong. It should be noted that the smaller the amount of this titanium compound added, the less the yellow tint during heat treatment. From the viewpoint of reducing the yellow tint of the heat treatment, the preferable addition amount of the titanium compound is 10 to 40 mass ppm in the low polymer production process in terms of titanium element, 30 to 70 mass ppm in the polycondensation process, and 40 to 110 mass ppm in total. ..

(Device for obtaining the copolymerized PBT of the present invention)
A material having a melting point of 150 to 215° C., an amount of terminal carboxyl groups of 42 to 90 equivalents/ton, preferably a ratio of the amount of terminal carboxyl groups to the total amount of terminal groups of 42 to 90%, and a glass transition temperature of 30 to 49° C. Examples of the method for producing the copolymerized PBT of the invention include a method for directly obtaining the copolymerized PBT satisfying the above physical properties by melt polycondensation by selecting the production conditions for the copolymerized PBT. Since the conditions vary depending on the process and equipment, it cannot be unconditionally determined, but for example, using a relatively large-scale PBT production equipment (for example, 10 m ³ polymerization tank), the amount of catalyst, the production temperature, the degree of pressure reduction, etc. And a method of carrying out polycondensation.

Conventionally, the final stage of the polycondensation step of PBT including co-assembly is generally performed at a temperature of about 245° C. and a pressure of about 0.13 to 0.4 kPa. The amount of terminal carboxy groups of the copolymerized PBT obtained on the industrial scale (for example, 4 m ³ polymerization tank) under such conventional general PBT production conditions is usually about 20 to 40 equivalents/ton. Smaller than the specified range.
On the other hand, in the production of the copolymerized PBT of the present invention, the end temperature of the polycondensation step is set to a temperature of, for example, about 255° C., which is higher than that in the conventional method, and the pressure during the polycondensation exceeds 0.4 kPa at a normal pressure side. It is preferable to set to. The polycondensation reaction time is preferably about 2 to 3 hours.

(Powderization of copolymerized PBT)
The copolymerized PBT produced by the above steps is pulverized for use in the powder layered manufacturing method. Regardless of the powdering means, for example, a ball mill, a jet mill, a stamp mill, freeze pulverization, or the like can be used. In particular, the jet mill has a high crushing effect and is preferably used. The particle size after pulverization is preferably 20 to 150 μm as an average particle size by classification means including sieving and fluid classification.

<Compounding agent for copolymerized PBT>
The copolymerized PBT of the present invention has a crystal nucleating agent, an antioxidant, a coloring preventing agent, a pigment, a dye, an ultraviolet absorber, a release agent, a slip agent, a flame retardant, if necessary, at the production stage or after the production. , An antistatic agent, inorganic particles, organic particles and the like can be blended to form a compound. Further, other polymers such as polyester may be blended within a range not impairing the gist of the present invention.

[PBT-based composition for powder additive manufacturing method]
The PBT-based composition for the powder layered manufacturing method of the present invention contains 50 to 100% by mass of the copolymerized PBT of the present invention.
That is, the PBT composition for the powder layered manufacturing method of the present invention may be composed only of the copolymerized PBT of the present invention, and the copolymerized PBT of the present invention and the above-mentioned compounding agent or the copolymerization of the present invention. It may contain other polymer such as polyester other than PBT in a proportion of 50% by mass or less.

[Powder Material for Powder Additive Manufacturing]
The powder material for powder additive manufacturing method of the present invention comprises the copolymerized PBT of the present invention or the PBT composition for powder additive additive manufacturing method of the present invention containing the copolymerized PBT, and the particle diameter thereof is the above-mentioned average particle diameter. It is preferably 20 to 150 μm, more preferably 35 to 150 μm. When the average particle diameter is at least the above lower limit, the powder material is excellent in fluidity and handleability, and is also preferable in terms of manufacturing cost. When the average particle diameter is not more than the above upper limit, the molding accuracy can be improved, which is preferable.

When the copolymerized PBT of the present invention is used as a modeling raw material for a powder layered modeling method, it is needless to say that the copolymerized PBT of the present invention may be mainly used as a modeling raw material containing, for example, 50% by mass or more. Even in a small amount, it is possible to exert an effect on the stabilization of modeling.
Therefore, the powder material for the powder layered manufacturing method of the present invention usually contains the copolymerized PBT of the present invention in an amount of 5 to 100% by mass, preferably 10 to 100% by mass, more preferably 20 to 100% by mass, and further preferably 30 to As a modeling raw material containing 100% by mass, most preferably 50 to 100% by mass, it can be subjected to powder layered modeling.

[Modeling method]
The modeling method of the present invention is a method for producing the molded article of the present invention by the powder additive manufacturing method using the powder material for the powder additive manufacturing method of the present invention.

The powder additive manufacturing method in the present invention can be carried out according to a conventional method using an ordinary powder additive manufacturing apparatus.

That is, for example, the particles of the powder material are melt-bonded by heating the molding stage, a thin film forming means for forming a thin film of the powder material on the molding stage, and irradiating the formed thin film with a laser. The heating means for forming the modeled layer by moving the modeled stage and the moving means for moving the modeled stage in the stacking direction (vertical direction) and the thin film formation, heating, and movement of the stage are controlled repeatedly to form the modeled layer. For example, in the case of laser heating, modeling can be performed through the following steps (1) to (4) using a powder lamination molding apparatus having a control unit for stacking.
(1) A step of forming a thin layer of powder material (2) A step of selectively irradiating a preheated thin layer with a laser beam to form a shaped article layer formed by melting and bonding the powder material, or a preliminary step The heated thin layer is selectively sprayed with a melting accelerator (a component that accelerates the melting of the resin) and a surface decoration agent (a component that forms the outline of the layer), and then an infrared lamp, xenon lamp, and halogen lamp are used as a whole. In some cases, the step of irradiating the surface with the powder material is performed to form a shaped article layer formed by fusion bonding of the powder materials.
(3) A step of lowering the modeling stage by the thickness of the formed modeling layer (4) A step of repeating the steps (1) to (3) a plurality of times in this order to stack the modeling layers

In step (1), a thin layer of the powder material is formed. For example, the powder material supplied from the powder supply unit is spread flat on a modeling stage by a recoater. The thin layer may be formed directly on the build stage, or may be formed on top of the powder material that has already been spread or the build layer that has already been formed.

The thickness of the thin layer can be set according to the thickness of the modeled article layer. The thickness of the thin layer can be arbitrarily set according to the accuracy of the three-dimensional model to be manufactured, but is usually about 0.01 to 0.3 mm.

In the step (2), a laser is selectively irradiated to the position where the shaped object layer is to be formed among the formed thin layers, and the powder material at the irradiated position is melt-bonded. As a result, the adjacent powder materials are fused to each other to form a melt-bonded body to form a shaped article layer. At this time, the powder material which has received the energy of the laser is also melt-bonded with the already formed layer, so that adhesion between adjacent layers also occurs. The powder material that has not been irradiated with the laser is recovered as a surplus powder and reused as a recovered powder.
Alternatively, instead of selectively irradiating a laser, a melting accelerator (a component that accelerates the melting of the resin) and a surface decoration agent (a component that forms the outline of the layer) are selectively sprayed, followed by an infrared lamp and xenon. The powder material is melt-bonded by irradiating the whole of the lamp and the halogen lamp. As in the case of the laser, the powder material that has not been melt-bonded is recovered as a surplus powder and reused as a recovered powder.

In the step (3), the modeling stage is lowered by the thickness of the modeling object layer formed in the step (2) to prepare for the next step (1).

The physical properties of the excess powder can be confirmed by sampling it. In the powder lamination molding method, for example, a supply tank, a molding tank, and an excess powder receiving tank are provided, and excess powder dropped in this excess powder receiving tank may be recovered and returned to a path connected to the supply tank. Sampling can be done in the middle of this path.
Alternatively, it is possible to sample the surplus powder remaining in the modeling tank after the modeling is completed and cooled, for example, the powder in the vicinity of the modeled object.

The copolymerized PBT of the present invention suppresses an increase in intrinsic viscosity and an increase in yellowishness even after undergoing a thermal history at the time of modeling by the powder lamination molding method, but such a characteristic effect of the present invention is Especially, it is more preferable to perform the heat treatment in an inert gas atmosphere. Therefore, the copolymerized PBT of the present invention is suitable for the powder layered manufacturing method under an inert gas atmosphere. In this case, the inert gas atmosphere means that the ratio (volume %) of the inert gas in the gas other than the copolymerized PBT in the space for heat treatment is 90% or more, preferably 92% or more, more preferably 95% or more. , More preferably 98% or more, most preferably 99% or more. Further, examples of the inert gas include nitrogen and argon.

Further, the effect of the copolymerized PBT of the present invention is exhibited even when heat treatment is performed in an air atmosphere. Therefore, the copolymerized PBT of the present invention can also be used in a powder layered manufacturing method under an air atmosphere. In this case, the increase in the intrinsic viscosity can often be suppressed to the same level as or higher than that in the inert gas atmosphere. Regarding the suppression of the increase in yellowness, the absolute value is larger than that in the case of an inert gas atmosphere, but the increase is obviously smaller than that in the case of using the copolymerized PBT which does not satisfy the requirements of the present invention, and the increase is remarkable. The effect is recognized.
In recent years, in the powder layered modeling method, there has been an attempt to carry out modeling under an air atmosphere instead of an inert gas atmosphere for the purpose of reducing the cost of the apparatus and simplifying the handling. The effect of the copolymerized PBT of the present invention is also effectively exhibited in this case. The air atmosphere refers to air existing in the natural world in which oxygen is around 21% by volume and most of the rest is an inert gas such as nitrogen gas.

The effect of the copolymerized PBT of the present invention can be effectively exhibited even in an atmosphere having an oxygen concentration intermediate between an inert gas atmosphere and an air atmosphere, and the technical idea of the present invention extends to these ranges.

Further, the temperature of the modeling area during the powder layered modeling is preferably about 5 to 20° C. lower than the melting point of the copolymerized PBT to be used, and the modeling time varies depending on the size of the modeled product.

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

[Evaluation of physical properties]
<Measurement of melting point>
5 to 7 mg of a polyester sample was cut out, weighed, and packed in a sample pan to prepare a measuring pan. Using a differential scanning calorimeter (“DSC 822e” manufactured by METTLER TOLEDO), the temperature was raised from −10° C. to 300° C. at a heating rate of 10° C./min in a nitrogen atmosphere. Then, after holding at 300° C. for 3 minutes, the temperature was lowered from 300° C. to −10° C. at a temperature lowering rate of 10° C./min, and after holding at −10° C. for 3 minutes, subsequently, at a temperature rising rate of 10° C./min, −10° C. To 300° C. The DSC curve obtained by the second heating measurement was analyzed, and the temperature at the apex of the endothermic peak was taken as the melting point. When the melting point has a plurality of endothermic peaks, the larger endothermic peak temperature was used.

<Measurement of the amount of terminal carboxyl group>
After crushing the polyester sample, it was dried at 120° C. for 15 minutes using a hot air dryer, and 0.1 g was accurately weighed from the sample cooled to room temperature in a desiccator and collected in a test tube. 3 mL of benzyl alcohol was added, and the mixture was dissolved at 195° C. for 3 minutes while blowing dry nitrogen gas, and then 5 mL of chloroform was gradually added and cooled to room temperature. One to two drops of phenol red indicator was added to this solution, and the mixture was titrated with a benzyl alcohol solution of 0.1N sodium hydroxide while stirring while blowing dry nitrogen gas, and the reaction was terminated when the color changed from yellow to red. Further, as a blank, the same operation was carried out without dissolving the polyester sample, and the amount of terminal carboxyl groups was calculated by the following formula (1).
Terminal carboxyl amount (equivalent/ton)=(ab)×0.1×f/w (1)
(Here, a is the amount of a 0.1 N sodium hydroxide benzyl alcohol solution required for titration (μL), and b is the amount of a 0.1 N sodium hydroxide benzyl alcohol solution required for titration with a blank ( μL), w is the amount (g) of polyester sample, and f is the titer of 0.1N sodium hydroxide in benzyl alcohol.)

The titer (f) of 0.1N sodium hydroxide in benzyl alcohol was determined by the following method.
5 mL of methanol was collected in a test tube, 1 to 2 drops of an ethanol solution of phenol red was added as an indicator, titration was performed with 0.4 mL of a benzyl alcohol solution of 0.1 N sodium hydroxide until the color change point, and then a titer of 0 was obtained. 0.2 mL of a 1 N hydrochloric acid aqueous solution as a standard solution was sampled and added, and again titrated to a discoloration point with a 0.1 N sodium hydroxide benzyl alcohol solution (the above operation was performed under blowing dry nitrogen gas). ..). The titer (f) was calculated by the following formula (2).
Titer (f)=
Titer of 0.1N hydrochloric acid aqueous solution×Amount of 0.1N hydrochloric acid aqueous solution (μL)/
Titration (μL) of benzyl alcohol solution of 0.1N sodium hydroxide (2)

<Measurement of the amount of terminal hydroxyl group and the amount of terminal vinyl group>
After crushing the polyester sample, about 20 mg was dissolved in 0.75 mL of a heavy chloroform/hexafluoroisopropanol=7/3 mixed solvent, 25 μL of heavy pyridine was added, and the sample was transferred to an NMR sample tube having an outer diameter of 5 mm. ¹ H-NMR spectrum was measured at room temperature using an AVANCE400 spectrometer manufactured by Bruker. As a standard of chemical shift, the signal of TMS was set to 0.00 ppm. The obtained spectrum was analyzed according to a conventional method, and the amount of terminal hydroxyl groups and the amount of terminal vinyl groups were calculated in terms of equivalents/ton.

<Calculation of total amount of end groups>
The total amount of terminal groups was calculated by the following formula (3) from the measurement results of the amount of terminal carboxyl groups, the amount of terminal hydroxyl groups, and the amount of terminal vinyl groups.
Total amount of end groups (equivalent/ton)=
Amount of terminal carboxyl group (equivalent/ton) + amount of terminal hydroxyl group (equivalent/ton)
+Amount of terminal vinyl group (equivalent/ton) (3)

<Measurement of glass transition temperature>
A test piece having a width of 5 mm, a length of 50 mm and a thickness of 1 mm was injection molded at a resin temperature of 250° C. and a mold temperature of 60° C. The obtained test piece is measured using a solid viscoelasticity measuring device RSA-III (TA Instruments), measurement mode: Dynamic Temp Sweep, frequency: 1 Hz, temperature: 0 to 120° C. (3° C./minute), strain: 0 It was measured at 0.05%, and the obtained Tan δ peak was defined as the glass transition temperature.

<Measurement of intrinsic viscosity and yellowness>
(Heat treatment conditions)
Under an inert gas atmosphere or an air atmosphere, each resin powder was held at a temperature 20° C. lower than the melting point for 10 hours, and the intrinsic viscosity and the yellow tint were measured before and after the heat treatment.

(Measurement of intrinsic viscosity)
About 0.25 g of a polyester sample was dissolved in about 25 mL of a mixed solvent of phenol/1,1,2,2-tetrachloroethane (weight ratio 1/1) to a concentration of 1.00 g/dL, After cooling to 30° C., the dropping speed of the sample solution and the dropping seconds of only the solvent were measured with a fully automatic solution viscometer (“DT553” manufactured by Sentec Co., Ltd.) at 30° C., and the intrinsic viscosity was calculated by the following formula (4). Was calculated.
Intrinsic viscosity=((1+4K _H η _sp ) ^0.5 −1)/(2K _H C) (4)
Here, η _sp =η/η ₀ -1, where η is the number of seconds of dropping the sample solution, η ₀ is the number of seconds of dropping only the solvent, C is the concentration of the sample solution (g/dL), and K _H is the Huggins value. It is a constant. K _H adopted the 0.33. The sample was dissolved at 110° C. for 30 minutes.
The difference between the intrinsic viscosity after heat treatment and the intrinsic viscosity before heat treatment is preferably 0.45 or less, more preferably 0.40 or less, still more preferably 0.35 or less, and most preferably 0.30 or less.

(Measurement of yellowness)
A pellet-shaped polyester sample was filled in a cylindrical powder measuring cell having an inner diameter of 30 mm and a depth of 12 mm, and a colorimetric color difference meter Z300A (manufactured by Nippon Denshoku Industries Co., Ltd.) was used to refer to JIS Z8730. The b value based on the color coordinates of the Hunter color difference formula in the Lab display system described in Example 1 was obtained as a simple average value of the values measured at four locations by rotating the measurement cell by 90 degrees by the reflection method. The more the b value is in the positive direction, the stronger the yellow color is, and the more negative the b value is, the more the bluish color is.
The difference between the b value after the heat treatment and the b value before the heat treatment is preferably 1.2 or less, more preferably 1.1 or less, and further preferably 0.8 or less.

[Example 1]
793.6 parts by mass of dimethyl terephthalate, 75.4 parts by mass of isophthalic acid and 613.8 parts of 1,4-butanediol were placed in an ester reaction tank equipped with a stirrer, a nitrogen inlet, a heating device, a thermometer, and a distillation tube. Parts by mass, and tetrabutyl titanate as a catalyst (33 mass ppm in terms of titanium element based on the produced polymer) were added.
Then, the liquid temperature was raised from 150° C. to 210° C. over 90 minutes with stirring, and the temperature was maintained at 210° C. for 90 minutes. During this period, the transesterification reaction and the esterification reaction were performed for a total of 180 minutes while distilling the produced methanol and water.

Fifteen minutes before the completion of the transesterification reaction and the esterification reaction, it was added so as to be 48 mass ppm in terms of magnesium metal with respect to the polymer that produces magnesium acetate tetrahydrate, and an antioxidant (Ciba Geigy ( Co., Ltd. "Irganox 1010") (0.15 mass% with respect to the produced polymer) was added, and then tetrabutyl titanate (61 mass ppm in terms of titanium element based on the produced polymer) was added.

This reaction product was transferred to a polycondensation reaction tank equipped with a stirrer, a nitrogen inlet, a heating device, a thermometer, a distilling pipe, and a decompression exhaust port, and a melt polycondensation reaction was carried out under reduced pressure.
In the melt polycondensation reaction, the pressure in the tank was gradually reduced from normal pressure to 0.41 KPa over 85 minutes, and continued at 0.41 KPa. The reaction temperature was kept at 210° C. for 15 minutes from the start of depressurization, and thereafter raised to 255° C. over 45 minutes and kept at this temperature. The reaction was terminated when the predetermined stirring torque was reached. The time required for the melt polycondensation reaction was 170 minutes.

Next, the inside of the tank was decompressed from the depressurized state with nitrogen and then pressurized to extract the polymer. The polymer was extruded into a strand form from a die, and the strand was cooled in a cooling water tank and then cut with a strand cutter to form a pellet. Thus, a copolymerized PBT having an isophthalic acid content of 10 mol% was obtained.

This copolymerized PBT is manufactured by raising the temperature at the end of the polycondensation and making the ultimate pressure looser as compared with the manufacturing conditions of the copolymerized PBT that is usually adopted industrially.

Then, the obtained copolymerized PBT was pulverized by a jet mill device and sieved to obtain a powder having an average particle size of 80 μm.
The melting point of this copolymerized PBT powder was 208° C., the amount of terminal carboxyl groups was 45 equivalents/ton, the glass transition temperature was 48° C., the intrinsic viscosity was 0.85 dL/g, and the b value showing yellow was −1.0. It was

Next, this powder was heat-treated in a nitrogen atmosphere (nitrogen 99.9% by volume) at 188° C., which is 20° C. lower than the melting point, for 10 hours. This condition is included in the heat treatment conditions assumed when used in the powder layered manufacturing method. The intrinsic viscosity after heat treatment was 1.20 dL/g, and the b value was 0.0. The results are shown in Table 1.

[Examples 2 to 7 and Comparative Examples 1 to 3]
Copolymerized PBTs and homo PBTs of Examples 2 to 7 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1 except that the composition and amount of the copolymerization component were changed. However, in Examples 2 to 3 and Examples 5 to 6, the temperature of the polycondensation reaction in Example 1 was 255° C., and the conditions of decompressing were loosened in Examples 2 and 5 of 0.53 KPa and Example 3, 6 was changed to hold 0.67 KPa, and the polymerization time was 175 minutes for Examples 2 and 5, and 180 minutes for Examples 3 and 6, respectively. In Comparative Examples 2 to 3, a device smaller than that of Example 1 was used, the polycondensation reaction temperature was changed to 245° C., the reduced pressure condition was changed to 0.40 KPa, and the polymerization time was 180 minutes. Table 1 shows the physical properties of the obtained copolymerized PBT and homo-PBT, and the physical properties after heat treatment in a nitrogen atmosphere.

[Examples 8 to 10 and Comparative Examples 4 to 5]
In Example 8, Example 9, and Example 10, the copolymerized PBTs produced in Example 1, Example 4, and Example 7, respectively, were used to perform heat treatment in an air atmosphere. Further, in Comparative Examples 4 and 5, heat treatment was performed in an air atmosphere using the homo PBTs produced in Comparative Example 1 and Comparative Example 2, respectively. Table 2 shows the physical properties of each copolymerized PBT and homo-PBT, and the physical properties after heat treatment in an air atmosphere.

[Discussion]
Table 1 shows the results of heat treatment of copolymerized PBT and homo PBT under a nitrogen atmosphere.
As shown in Examples 1 to 7, the copolymerized PBT of the present invention has an intrinsic viscosity even if it is subjected to a heat treatment equivalent to a long-term heat history near the melting point at the time of modeling under a nitrogen atmosphere by the powder lamination molding method. And the increase in yellowness can be suppressed. Therefore, even if the powder after heat treatment (recovered powder) is mixed with the initial powder and subjected to the powder lamination molding method, the difference in physical properties between the two is small, it is possible to suppress the occurrence of uneven viscosity, and It is possible to suppress an increase in yellowness and color unevenness.

On the other hand, Comparative Examples 1 to 3 use homo PBT or copolymer PBT lacking at least one of the requirements defined in the present invention, and are examples in which desired effects cannot be exhibited. In Comparative Example 1, although the amount of terminal carboxyl groups is within the range of the present invention, it is homo PBT and has a melting point higher than the range of the present invention, so that an increase in intrinsic viscosity and an increase in yellowness cannot be suppressed. Comparative Example 2 is a homo-PBT and has a melting point higher than the range of the present invention and an amount of terminal carboxyl groups lower than the range of the present invention, so that it is still impossible to suppress an increase in intrinsic viscosity and an increase in yellow tint. When these homo PBTs are used as a recovered powder mixed with a new powder, uneven melting occurs. Comparative Example 3 is a copolymerized PBT, but the amount of terminal carboxyl groups is lower than the range of the present invention, and the increase in intrinsic viscosity is not sufficiently suppressed.

Table 2 shows the results of heat treatment of copolymerized PBT and homo PBT in an air atmosphere.
In the case of Examples 8 to 10 using the copolymerized PBT of the present invention, the increase in intrinsic viscosity is small. Although the b value has a larger absolute value than that in the nitrogen atmosphere, it is clearly smaller than that of the homo PBTs of Comparative Examples 4 and 5, and it can be seen that the b value works advantageously. The homo-PBTs of Comparative Examples 4 and 5 have a large increase in intrinsic viscosity after heat treatment, and are not preferable in this respect as a resin for powder additive molding.

As shown in the examples, the copolymerized PBT of the present invention suppresses the increase in intrinsic viscosity and the increase in yellowness even when subjected to a heat treatment close to the melting point in an inert gas atmosphere or an air atmosphere for a long time. It Therefore, the copolymerized PBT of the present invention is exposed to a heating and holding state for a long time in an inert gas atmosphere or an air atmosphere during modeling or storage in a three-dimensional modeling material application by the powder lamination molding method. However, an increase in intrinsic viscosity and an increase in yellowishness are suppressed, and the obtained shaped product can exhibit high quality and also exhibit excellent strength and heat resistance. Further, even when the excess copolymerized PBT powder generated when the copolymerized PBT of the present invention is used as a new powder for modeling is recovered and reused, stable modeling becomes possible.

Claims (10)

A copolymerized polybutylene terephthalate containing a terephthalic acid component and a 1,4-butanediol component as main components, which is used in the powder layering method and has a melting point of 150 to 215° C. and a terminal carboxyl group amount of 42 to 90 equivalents. /Ton, Copolymer polybutylene terephthalate for powder lamination modeling. The melting point of the copolymer polybutylene terephthalate according to claim 1, which is 170 to 199°C. The copolymerized polybutylene terephthalate for powder lamination molding method according to claim 1 or 2, wherein the amount of terminal carboxyl groups is 45 to 90 equivalents/ton. The amount of terminal carboxyl groups is 65 to 90 equivalents/ton, The copolymerization polybutylene terephthalate for powder lamination manufacturing method of Claim 3 characterized by the above-mentioned. 5. The dicarboxylic acid component other than the terephthalic acid component contains at least one dicarboxylic acid component selected from the group consisting of isophthalic acid, naphthalenedicarboxylic acid, and succinic acid. The copolymerized polybutylene terephthalate for the powder layered manufacturing method described in 1. As diol components other than 1,4-butanediol, ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-cyclohexanedimethanol, 2,4-diethyl-1,5-pentanediol, butylethylpropanediol, 2. At least one diol component selected from the group consisting of spiroglycol, tricyclodecane dimethanol, and 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene is contained, and the diol component is contained. 5. The copolymerized polybutylene terephthalate for powder lamination manufacturing method according to any one of 5 above. A polybutylene terephthalate-based composition for powder laminating method, comprising 5 to 100% by mass of the copolymerized polybutylene terephthalate for powder laminating method according to any one of claims 1 to 6. A powder material for a powder additive manufacturing method comprising the copolymerized polybutylene terephthalate for a powder additive manufacturing method according to any one of claims 1 to 6 or the polybutylene terephthalate composition for a powder additive manufacturing method according to claim 7. .. A molding method for manufacturing a molded article by the powder lamination molding method using the powder material for the powder lamination molding method according to claim 8. A shaped article using the powder material for the powder layered manufacturing method according to claim 8.