JP2019094366A - Heat treatment method of polyester - Google Patents

Abstract

To provide a heat treatment method of polyester capable of accurately controlling a polymerization degree of polyester by heat treatment, and preventing from having a high melting point.SOLUTION: A method includes treating a polyester having a melting point of 170°C or higher, having a content of a fine powder passing through a tyler 100 mesh and not passing through a nickel screen having an opening of 10 μm of more than 0.10 wt.%, and a water content of 0.30 wt.% or less by an airtight-system heat treatment of following (1), or a flow-system heat treatment of following (2). (1) The airtight-system heat treatment includes heat-treating in a heat treatment region sealed with an inert gas by a pressure of atmospheric pressure or higher and lower than 0.98 MPa at the heat treatment temperature. (2) The flow-system heat treatment includes heat-treating in a heat treatment region having an inert gas passed through by a pressure of atmospheric pressure or higher and lower than 0.98 MPa at the heat treatment temperature under such flow condition of the inert gas that the gas in the heat treatment region is replaced by 100 times/10 hr. or less.SELECTED DRAWING: None

Description

The present invention relates to a method of heat treating polyester. In particular, it is possible to improve the degree of control of polymerization degree and suppress the increase in melting point during solid phase polymerization, and to increase the degree of polymerization and reduce the degree of polymerization during modeling using a rapid prototyping device (SLS method 3D printer) for three-dimensional objects. The present invention relates to a heat treatment method of polyester which is excellent in the suppression of the heat resistance and the suppression of high melting point.
The polyester obtained by using the heat treatment method of the present invention is suitable as a material for molded articles such as hollow molded articles such as molded articles for automobiles, electric and electronic products, articles for general plastic products and bottles for beverages, films and sheets. It can be used for

  Polyester occupies an industrially important position because of its excellent mechanical and chemical properties. For example, aromatic polyesters such as polyethylene terephthalate (hereinafter sometimes referred to as PET) and polybutylene terephthalate (hereinafter referred to as PBT) are resins excellent in heat resistance and chemical resistance, In addition, it is widely used in the fields of extrusion molding applications such as fibers, films, sheets, bottles, electric and electronic parts, automobile parts, precision equipment parts and the like, injection molding applications and the like because of ease of molding and economy.

  When polyester is applied to these uses, heat treatment of polyester is conventionally performed for the purpose of removing low molecular weight components that affect product quality or improving physical properties such as heat resistance and rigidity. .

For example, in Patent Document 1, polyester pellets are heated to a predetermined temperature under an inert gas atmosphere or under reduced pressure to reduce cyclic oligomers while maintaining the degree of polymerization using polyester pellets with less fine powder. It is described.
Further, Patent Document 2 describes heating to a predetermined temperature under pressurization of an inert gas atmosphere to increase the melting point and crystallization in order to increase the heat resistance and rigidity of the polyester.
In these Patent Documents 1 and 2, although the polyester is heat-treated by heating it at a temperature close to its melting point, no study is made on the suppression of the increase in the melting point by the heat treatment and the maintenance of the polymerization degree.

Japanese Patent Application Laid-Open No. 2002-173528 Japanese Patent Application Laid-Open No. 7-300530

  The inventors of the present invention have found that when the polyester is heat-treated in the vicinity of its melting point by the conventional method, the degree of polymerization of the polyester becomes low or high, and it is difficult to control the degree of polymerization precisely. In addition, it was found that there is a problem that the melting point goes up contrary to intention.

  It is an object of the present invention to solve the above-mentioned conventional problems, and to provide a heat treatment method of polyester capable of controlling the polymerization degree of polyester with high accuracy by heat treatment and capable of suppressing an increase in melting point. Do.

  As a result of intensive studies to solve the above problems, the present inventor has found that it is possible to solve the above problems by adopting a specific heat treatment method, resulting in the present invention.

  That is, the present invention is as follows.

[1] Melting point is 170 ° C or more, content of fine powder passing through Tyler 100 mesh and not passing through nickel screen with 10 μm opening exceeds 0.10% by weight, and moisture content is 0.30% by weight or less A heat treatment method of polyester which heats polyester, wherein the heat treatment is carried out by closed system heat treatment of the following (1) or flow system heat treatment of the following (2).
(1) In the heat treatment area sealed with an inert gas, the heat treatment is performed at a pressure of not less than atmospheric pressure and less than 0.98 MPa at the heat treatment temperature.
(2) In the heat treatment area through which the inert gas is circulated, the circulation condition of the inert gas is a condition for replacing the gas within the heat treatment area 100 times / 10 hours or less, and the pressure is atmospheric pressure at the heat treatment temperature. Heat treatment as less than 0.98 MPa.

[2] The heat treatment method of polyester according to [1], wherein the polyester is polybutylene terephthalate or copolymerized polybutylene terephthalate.

[3] The heat treatment method of polyester according to [1], wherein the polyester is a copolymerized polyethylene terephthalate.

[4] A solid phase polymerization method using the heat treatment method of polyester according to any one of [1] to [3].

[5] A method for using a rapid prototyping device for a three-dimensional object, using the method for heat-treating polyester according to any one of [1] to [3].

  According to the heat treatment method of polyester of the present invention, the degree of polymerization of the polyester can be precisely controlled by the heat treatment, and the increase in the melting point can be suppressed. The heat treatment method of the polyester of the present invention is used, for example, as a method for improving the accuracy of control of the degree of polymerization near the end of solid phase polymerization and preventing the increase of the melting point, in high degree of polymerization of polyester Is possible. For this reason, polyester of stable quality can be obtained. In addition, in the case of SLS method 3D printer application, in the heating and holding state at the time of modeling for a long time, the undesirable deterioration of polyester such as high polymerization degree, low polymerization degree and high melting point of polyester as a molding material is prevented. And stable formation is possible. Furthermore, even when excess polyester is recycled, stable formation is possible by suppressing deterioration of the polyester.

  Although the modes for carrying out the present invention will be described in detail below, the descriptions of the constituent requirements described below are representative examples of the embodiments of the present invention, and the present invention is not limited to these contents. Absent.

In the heat treatment method of the polyester of the present invention, the following closed heat treatment (1) or flowing heat treatment (2) is performed on a specific polyester.
(1) In the heat treatment area sealed with an inert gas, the heat treatment is performed at a pressure of not less than atmospheric pressure and less than 0.98 MPa at the heat treatment temperature.
(2) In the heat treatment area through which the inert gas is circulated, the circulation condition of the inert gas is a condition for replacing the gas within the heat treatment area 100 times / 10 hours or less, and the pressure is atmospheric pressure at the heat treatment temperature. Heat treatment as less than 0.98 MPa.

Although the details of the reason why the effects of the present invention are exhibited are not clear by adopting the two heat treatment methods described above, the closed system heat treatment of (1) does not have the above specific conditions. It is considered that condensation reactions such as glycol reaction and dehydration reaction are suppressed, and increase in intrinsic viscosity can be controlled. Moreover, the effect of suppressing the increase in the melting point is also achieved.
Further, in the case of the flow system heat treatment of (2), by setting the above specific conditions, even if the flow system is under pressure, condensation reactions such as deglycolization reaction and dehydration reaction are suppressed. Furthermore, it is thought that the effect similar to a closed system is show | played that there are few amounts of circulation, and condensation reactions, such as a deglycolization reaction and a dehydration reaction, can be suppressed, and a raise of intrinsic viscosity can be controlled. Moreover, the effect of suppressing the increase in the melting point is also achieved.

  Hereinafter, the specific polyester to be subjected to the heat treatment of the present invention may be referred to as "the polyester of the present invention".

[polyester]
Preferred examples of the polyester of the present invention include polybutylene terephthalate, copolymerized polybutylene terephthalate and copolymerized polyethylene terephthalate.

  Polybutylene terephthalate is a polyester obtained by using 100% by weight of terephthalic acid or its ester-forming derivative as a dicarboxylic acid component of the reaction raw material and 100% by weight of 1,4-butaneol as a diol component.

  Copolymerized polybutylene terephthalate is a copolymerized poly (ethylene terephthalate) obtained using terephthalic acid or its ester-forming derivative and other dicarboxylic acid components as the dicarboxylic acid component of the reaction raw material and using only 1,4-butaneol as the diol component. It may be butylene terephthalate, and is a copolymerized polybutylene terephthalate obtained using only terephthalic acid or its ester-forming derivative as the dicarboxylic acid component and 1,4-butaneol and other diol components as the diol component. Copolymerized polybutylene terephthalate obtained using terephthalic acid or its ester-forming derivative and other dicarboxylic acid component as the dicarboxylic acid component, and using 1,4-butaneol and other diol components as the diol component. May be

In the case where other dicarboxylic acid components are copolymerized in addition to terephthalic acid or its ester-forming derivative as the dicarboxylic acid component, the proportion of terephthalic acid or its ester-forming derivative is at least 70 mol% with respect to all dicarboxylic acid components. The content is preferably 85% by mol or more, more preferably 90% by mol or more. When the ratio of terephthalic acid or its ester-forming derivative is at least the above lower limit, a polyester having high crystallinity and excellent mechanical properties can be obtained.
Further, depending on the application, a composition having a low melting point while maintaining crystallinity may be preferred. In this case, the proportion of terephthalic acid or an ester-forming derivative thereof is preferably 90 mol% or less, more preferably 85 mol% or more and less than 90 mol%, and more preferably 70 mol% with respect to all dicarboxylic acid components. More preferably, it is at least 85 mol%.

  Examples of other dicarboxylic acid components other than terephthalic acid include isophthalic acid, aromatic dicarboxylic acids such as naphthalene dicarboxylic acid, alicyclic dicarboxylic acids such as cyclohexane dicarboxylic acid, fatty acids such as succinic acid, adipic acid and sebacic acid It is possible to use one or two or more kinds of group dicarboxylic acids and the like.

In the case of copolymerizing other diol components in addition to 1,4-butanediol as a diol component, the ratio of 1,4-butaneol is preferably 70 mol% or more to all diol components, and 85 mol % Or more is more preferable, and 90 mol% or more is more preferable. When the ratio of 1,4-butanediol is equal to or more than the above lower limit, a polyester having high crystallinity and excellent mechanical properties can be obtained.
Further, depending on the application, a composition having a low melting point while maintaining crystallinity may be preferred. In this case, the proportion of 1,4-butaneol is preferably 90 mol% or less, more preferably 85 mol% or more and less than 90 mol%, and more preferably 70 mol% or more and 85 mol% with respect to all diol components. More preferably, it is less than 10%.

  As diol other than 1,4-butaneol, one or more of ethylene glycol, diethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, 1,4-cyclohexanedimethanol, etc. may be used it can.

  The copolymerized polyethylene terephthalate is a copolymerized polyethylene terephthalate obtained using terephthalic acid or its ester-forming derivative and other dicarboxylic acid components as the dicarboxylic acid component of the reaction raw material and using only ethylene glycol as the diol component. It may be a copolymerized polyethylene terephthalate obtained using only terephthalic acid or its ester-forming derivative as the dicarboxylic acid component and ethylene glycol and other diol components as the diol component, and terephthalic acid or as the dicarboxylic acid component It may be a copolymerized polyethylene terephthalate obtained using the ester-forming derivative and the other dicarboxylic acid component and using ethylene glycol and the other diol component as the diol component.

In the case where other dicarboxylic acid components are copolymerized in addition to terephthalic acid or its ester-forming derivative as the dicarboxylic acid component, the proportion of terephthalic acid or its ester-forming derivative is at least 70 mol% with respect to all dicarboxylic acid components. The content is preferably 85% by mol or more, more preferably 90% by mol or more. When the ratio of terephthalic acid or its ester-forming derivative is at least the above lower limit, a polyester having high crystallinity and excellent mechanical properties can be obtained.
Further, depending on the application, a composition having a low melting point while maintaining crystallinity may be preferred. In this case, the proportion of terephthalic acid or an ester-forming derivative thereof is preferably 90 mol% or less, more preferably 85 mol% or more and less than 90 mol%, and more preferably 70 mol% with respect to all dicarboxylic acid components. More preferably, it is at least 85 mol%.

  Examples of other dicarboxylic acid components other than terephthalic acid include isophthalic acid, aromatic dicarboxylic acids such as naphthalene dicarboxylic acid, alicyclic dicarboxylic acids such as cyclohexane dicarboxylic acid, fatty acids such as succinic acid, adipic acid and sebacic acid It is possible to use one or two or more kinds of group dicarboxylic acids and the like.

As a diol component, when copolymerizing other diol components in addition to ethylene glycol, the ratio of ethylene glycol is preferably 70 mol% or more, more preferably 85 mol% or more based on all diol components. More preferably, it is 90 mol% or more. When the proportion of ethylene glycol is at least the above lower limit, a polyester having high crystallinity and excellent mechanical properties can be obtained.
Further, depending on the application, a composition having a low melting point while maintaining crystallinity may be preferred. In this case, the proportion of ethylene glycol is preferably 90 mol% or less, more preferably 85 mol% or more and less than 90 mol%, and more preferably 70 mol% or more and less than 85 mol% with respect to all diol components. Is more preferred.

  As diol other than ethylene glycol, one or more kinds such as 1,4-butaneol, diethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, 1,4-cyclohexanedimethanol, etc. may be used it can.

  The method for producing the polyester as described above is not particularly limited, and a usual method can be applied. For example, a step of mixing a dicarboxylic acid component containing terephthalic acid or an ester-forming derivative thereof with a diol component containing 1,4-butanediol or ethylene glycol in a predetermined ratio under stirring to form a raw material slurry, A step of heating the raw material slurry under reduced pressure, normal pressure or elevated pressure to carry out an esterification reaction or transesterification reaction to obtain a polyester low polymer (hereinafter sometimes referred to as "oligomer"), The polyester can be obtained through a melt polycondensation step of heating the oligomer under reduced pressure to cause a melt polycondensation reaction.

  As an example of the process of obtaining an oligomer, using a single esterification reaction tank or a multistage reaction apparatus in which a plurality of esterification reaction tanks are connected in series, a system of water and excess diol component generated in the esterification reaction A method can be mentioned in which removal to the outside is carried out until the esterification reaction rate (proportion of the total carboxyl group of the raw material dicarboxylic acid component reacted with the diol component and esterified) reaches 90% or more.

As an example of the melt polycondensation process, while distilling out the diol to be generated out of the system under reduced pressure using a single melt polycondensation tank or a multi-stage reaction apparatus in which a plurality of melt polycondensation tanks are connected in series The method to do is mentioned.
Examples of the polyester polycondensation catalyst used at this time include compounds such as antimony, germanium, titanium, and aluminum. The addition of the polyester polycondensation catalyst to the reaction system may be any of a step of obtaining a slurry from the dicarboxylic acid component and the diol component, a step of obtaining an oligomer, or an initial step of the melt polycondensation step.

  In the production of the polyester of the present invention, an antioxidant and a basic compound can be added in order to suppress side reactions such as thermal decomposition and dimerization of diol in the step of obtaining an oligomer and the melt polycondensation step. . Specific examples of the antioxidant include Irganox 1330 (manufactured by BASF), Irganox 1010 (manufactured by BASF), and the like. Examples of basic compounds include tertiary amines such as triethylamine, tri-n-butylamine and benzyldimethylamine, tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide, and quaternary hydroxides such as trimethylbenzylammonium hydroxide. Ammonium, lithium carbonate, sodium carbonate, potassium carbonate, sodium acetate and the like can be mentioned.

  The polyester obtained in the melt polycondensation step is usually taken out in the form of a strand or a sheet from the outlet provided at the bottom of the melt polycondensation tank, and then water cooled or water cooled and then cut with a cutter to form pellets Alternatively, it may be in the form of polyester granules such as chips. The granules are then subjected to a transfer step, in which often fines are generated or may be intentionally generated to contain fines.

  The polyester produced by the above process can be subjected to, for example, solid phase polymerization or SLS method 3D printer.

Solid phase polymerization is a heat treatment for further increasing the degree of polymerization of the polyester obtained by melt polycondensation or reducing the amount of cyclic oligomers.
Applications of polyester obtained by solid phase polymerization include fibers, films, sheets, bottles, electric and electronic parts, automobile parts, extrusion parts such as precision equipment parts, injection molding applications, etc., and widely used in various fields used.
Such polyesters may be, if necessary, crystal nucleating agents, antioxidants, coloring inhibitors, pigments, dyes, UV absorbers, mold release agents, lubricants, flame retardants, antistatic agents, inorganic particles. And organic particles can be blended. Moreover, you may mix | blend the polymer containing other polyester in the range which does not impair the meaning of this invention.

  Also in the use of polyester in 3D printer, if necessary, polyester, nucleating agent, antioxidant, coloring inhibitor, pigment, dye, UV absorber, releasing agent, lubricant, flame retardant, antistatic agent, inorganic substance Particles and organic particles can be blended. Moreover, you may mix | blend the polymer containing other polyester in the range which does not impair the meaning of this invention.

  The polyester of the present invention can be in the form of granules, fine powders, etc. alone or in combination depending on the purpose.

When polyester is used as a raw material to be subjected to solid phase polymerization, it is preferable to use a form mainly composed of particles. That is, in the solid phase polymerization, for example, polyester pellets are subjected to heat treatment using a countercurrent high temperature gas, but in this case, the powder is blown up as fine powder to impair the stability of the heat treatment and partially solidify. It is preferable to control the content of fine powder, because the phase polymerization rate is increased or the reaction rate is difficult to control.
On the other hand, in the SLS method 3D printer, since it is shaped by irradiating a finely powdered polyester with a laser, it is necessary to make it finely powdered.

  The polyester of the present invention has a melting point of 170 ° C. or more, a content of fine powder (hereinafter referred to as “fine powder amount” or “containing fine powder amount”) exceeding 0.10% by weight, and a water content of 0.30% by weight In the heat treatment method of the polyester of the present invention, the polyester having such specific melting point, fine powder amount and moisture content is heat-treated.

The melting point of the polyester of the present invention needs to be 170 ° C. or higher. If the melting point is less than 170 ° C., fusion between polyesters is likely to occur during heat treatment, which is not preferable. The melting point of the polyester of the present invention is preferably 175 ° C. or higher.
The upper limit of the melting point of the polyester of the present invention is not particularly limited, but is preferably 270 ° C. If this is exceeded, more energy will be required since melt-molding of the heat-treated polyester requires higher temperatures. The melting point of the polyester of the present invention is more preferably 260 ° C. or less, still more preferably 230 ° C. or less.
In addition, the measuring method of melting | fusing point of polyester is as being described in the term of the below-mentioned Example.

The amount of fine powder contained in the polyester of the present invention is more than 0.10% by weight, preferably 0.11% by weight or more, more preferably 0.13% by weight or more. When the amount of the contained fine powder is 0.10% by weight or less, the slipperiness of the polyester mainly composed of the particles to be supplied to the heat treatment step is bad, and often trouble occurs in smooth supply. The upper limit of the amount of fine powder contained in the polyester of the present invention is 100.0% by weight, that is, all is fine powder polyester.
In particular, when the polyester of the present invention is used in an SLS method 3D printer, the amount of fine powder contained in the polyester of the present invention is preferably 99.0 wt% or more and 100.0 wt% or less.
When the polyester of the present invention is subjected to solid phase polymerization, the amount of fine powder contained in the polyester of the present invention is preferably more than 0.10% by weight and not more than 1.0% by weight.

  When the amount of the fine powder is larger than this, the polyester contains not only granular materials but also broken fragments, fragments and the like of the granular materials, and it is a nonuniform form to be subjected to solid phase polymerization, which is not preferable in quality. Also, in 3D printer applications, the particles tend to be too large and unsuitable.

  In the present invention, the “fine powder amount” is the amount of fine powder which passes through the tiler 100 mesh and does not pass through a nickel screen having a mesh size of 10 μm, and can be determined as follows.

<Measurement of fine powder amount>
The polyester is placed on the Tyler 100 mesh and sieved, the sieve washed with water and the sieved ones are passed along with the water, then the water containing the fines under the sieve is filtered with a 10 μm nickel screen. The nickel screen to which fines have been attached by filtration of fine powder-containing water is dried at 120 ° C. for 4 hours, the weight of the solid present on the nickel screen (fine weight) is measured, and the amount of fines is calculated by the following equation.
Fine powder amount (% by weight) = (fine powder weight / weight of polyester used for measurement) × 100
In addition, the specific measuring method of the amount of fine powder is as described in the term of the below-mentioned Example.

  It is preferable that the thing other than the said fine powder of polyester of this invention is a granular material about length 3 mm, about 3 mm in long diameter, and about 2 mm in short diameter. As this granular material, for example, a pellet or a chip obtained by cutting the polyester obtained in the above-described melt polycondensation step with a cutter corresponds.

The water content of the polyester of the present invention is 0.30 wt% or less, preferably 0.20 wt% or less, more preferably 0.10 wt% or less. If the water content exceeds 0.30% by weight, hydrolysis proceeds significantly during heat treatment, and the degree of polymerization of the resulting polyester decreases.
The water content of the polyester of the present invention is preferably as low as possible, and most preferably 0% by weight, but 0.005% by weight can also be used due to circumstances such as the drying step.
In addition, the measuring method of the moisture content of polyester is as having described in the term of the below-mentioned Example.

[Heat treatment]
In the present invention, the above-mentioned polyester of the present invention is subjected to closed system heat treatment of the following (1) or flow system heat treatment of the following (2).
(1) In the heat treatment area sealed with an inert gas, the heat treatment is performed at a pressure of not less than atmospheric pressure and less than 0.98 MPa at the heat treatment temperature.
(2) In the heat treatment area in which the inert gas is allowed to flow, the flow conditions of the inert gas are set to 100 times / 10 hours or less, preferably 0.004 times / 10 hours or more 100 times for the gas in the heat treatment area. The heat treatment is performed at a pressure of less than 0.98 MPa above atmospheric pressure at the heat treatment temperature under conditions of replacement for 10 hours or less.
In the present invention, the pressure refers to a gauge pressure, and the atmospheric pressure is 0 MPa.

In the present invention, the heat treatment area is an area where the heat treatment of the polyester is performed in the presence of an inert gas, and is composed of the polyester and the space portion. The size is arbitrary and can be in the order of cm ³ to m ³ . There is no restriction on the shape of the structure surrounding the heat treatment region, as long as the conditions for performing the desired heat treatment are satisfied.
Usually, in the case of the closed system heat treatment of (1), the closed container corresponds, and in the case of the flow system heat treatment of (2), the container having the circulation means of the inert gas corresponds.

  The relationship between the volume of the polyester of the present invention to be subjected to heat treatment and the volume of the heat treatment vessel is not particularly limited, but if the volume of the heat treatment vessel is excessively small, specific pressure conditions in an inert gas atmosphere should be obtained. However, if the capacity of the heat treatment container is excessively large, the heat treatment container becomes excessively large, which is not preferable. Usually, the volume of the heat treatment vessel is 2 to 20 times the apparent volume of the polyester of the present invention subjected to the heat treatment, and the polyester occupies about 1/2 to 1/20 of the volume in the heat treatment vessel. Is preferred.

  The supply of thermal energy for the heat treatment is often by heating from outside the heat treatment region, but in the case of circulating an inert gas, a method using a heated inert gas may be used in combination.

  As an inert gas, 1 type (s) or 2 or more types of inert gas, such as nitrogen, a carbon dioxide, and argon, are mentioned. In particular, an inert gas containing 95% by volume or more, preferably 99% by volume or more of nitrogen is preferably employed.

  When the polyester is heat-treated in the heat treatment region, the polyester may be in a stationary state or in a dynamic state such as being moved or stirred.

  The heat treatment temperature is not particularly limited, but is preferably 165 ° C. or more and not more than the melting point of the polyester to be heat treated. For example, in the case of solid-phase polymerization, the reaction proceeds at 165 ° C. or higher, at or below the melting point of the polyester to be heat-treated, particularly at 180 ° C. or more, and about 10 to 40 ° C. lower than the melting point of the polyester to be heat-treated Temperature is preferred. When applied to the SLS method 3D printer, the temperature is 165 ° C. or more and the melting point of the polyester to be heat treated or less, particularly 167 ° C. or more to suppress rapid crystallization, 3 to 40 from the melting point of the polyester to be heat treated Temperatures as low as ° C or more are preferred.

  The heat treatment time may be selected according to the purpose, but for example, the residence time in the heat treatment region of the polyester to be heat treated is preferably 1 to 48 hours, particularly about 3 to 30 hours.

In the closed system heat treatment of (1), the heat treatment is performed with the pressure set to the atmospheric pressure or more and less than 0.98 MPa at the heat treatment temperature. When the pressure is less than atmospheric pressure, the degree of polymerization and the melting point increase, which is not preferable. On the other hand, when the pressure is 0.98 MPa or more, it is necessary to make the heat treatment region into a pressure-resistant structure, which increases the cost. The pressure in the closed heat treatment is preferably atmospheric pressure or more and less than 0.5 MPa, more preferably 0.001 MPa to 0.3 MPa, and still more preferably 0.01 MPa to 0.2 MPa.
In the case of heat treatment as a closed system, after introducing an inert gas into the container, the heat treatment may be performed by closing the inlet and the outlet.

  In the flow system heat treatment of (2), the heat treatment is performed such that the pressure exceeds atmospheric pressure and is less than 0.98 MPa at the heat treatment temperature. When the pressure is 0.98 MPa or more, it is necessary to make the heat treatment area into a pressure-resistant structure, which increases the cost. On the other hand, when the pressure is lower than the atmospheric pressure, gases other than the inert gas to be circulated may be unintentionally mixed in the heat treatment region, which is not preferable. The pressure in the flow system heat treatment is preferably 0.001 MPa to 0.5 MPa, more preferably 0.005 MPa to 0.3 MPa, and still more preferably 0.01 MPa to 0.2 MPa.

  The flow state of the inert gas in the flow system heat treatment may be continuous or intermittent. In order to circulate the inert gas in the heat treatment area, for example, a method of introducing the inert gas from one opening provided in the container constituting the heat treatment area and extracting the inert gas from the other opening However, each of these openings may be plural.

In the flow system heat treatment of (2), the inert gas is used under the condition (hereinafter, this condition may be referred to as “the number of times of substitution”) for replacing the gas in the container constituting the heat treatment region 100 times / 10 hours or less. Distribute.
The number of times of substitution refers to “a value obtained by dividing the amount of inert gas supplied in 10 hours by the volume of the space in the heat treatment area”. The volume of the space of the heat treatment area is the space occupied by the heat treatment area, for example, the volume of the heat treatment container minus the volume of the polyester contained in the container. The larger the number of times of substitution, the larger the amount of inert gas flowing to the heat treatment region. In the present invention, the number of substitutions is 100 times / 10 hours or less, preferably 25 times / 10 hours or less, and more preferably 5 times / 10 hours or less. The lower limit of the number of times of substitution is not particularly limited, but is preferably 0.004 times / 10 hours or more, more preferably 0.05 times / 10 hours or more. With such a gentle inert gas flow rate, the change in the degree of polymerization of the polyester during heat treatment and the increase in the melting point are suppressed.

Such a heat treatment method of the polyester of the present invention is utilized as a method for preventing the high melting point by improving the accuracy of control of the polymerization degree near the end of the solid phase polymerization in the high polymerization degree of the polyester by solid phase polymerization. It is possible to obtain polyester of stable quality.
In addition, in the case of SLS method 3D printer application, undesirable deterioration of polyester such as high polymerization degree or low polymerization degree of polyester which is a molding material, and high melting point in a heating and holding state at modeling at a long time It can be prevented and stable shaping becomes possible.
Furthermore, even when excess polyester is recycled, stable formation is possible by suppressing deterioration of the polyester.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

<Measurement of fine powder amount>
1 kg of polyester containing granules and fine powder was placed on Tyler 100 mesh and sieved, and then 2 L of water was divided into 5 portions and sprayed to wash polyester on Tyler 100 mesh. The sieved fines and the water used for washing were recovered under Tyler 100 mesh. Then, the recovered fine powder-containing water is further filtered through a 10 μm mesh nickel screen, and the nickel screen is dried at 120 ° C. for 4 hours to recover the solid on the nickel screen into a fine powder. The fine powder weight was measured, and the amount of fine powder was calculated by the following equation.
Fine powder amount (% by weight) = (fine powder (Kg) / polyester (Kg) used for measurement) × 100

<Measurement of moisture>
About 1 to 3 g of polyester was precisely weighed into a water measuring sampling container in a dry box. This sample is put into a moisture evaporation apparatus "VA-200" manufactured by Dia Instruments Co., and a nitrogen gas of 200 mL / min is allowed to flow under heating at 180 ° C., and the volatilized water is removed by a trace moisture measurement apparatus "CA- manufactured by Dia Instruments Co." It was collected in a 200 "anhydrous titration tank. The water content was measured with a trace water content measuring device to determine the water content.

<Measurement of melting point>
3 to 9 mg of polyester was cut out, weighed, and packed in a sample pan to prepare a measuring pan.
The temperature is measured from 30 ° C to 300 ° C at a heating rate of 20 ° C / min under nitrogen using a DSC measurement apparatus "DSC 822e" manufactured by METTLER TOLEDO, the obtained DSC curve is analyzed, and the melting point is determined from the endothermic peak The

<Measurement of intrinsic viscosity>
After dissolving about 0.25 g of polyester 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, 30 The sample solution is allowed to cool down to 30 ° C, and the number of seconds dropped by the sample solution and the number of seconds dropped by the solvent alone are measured with a full automatic solution viscometer "DT553" manufactured by Sentech Co., Ltd. did.
Intrinsic viscosity = ((1 + 4 K _H η _sp ) ^0.5 -1) / (2 K _H · C)
Here, η _sp = // η ₀ -1, η is the number of seconds dropped of the sample solution, η ₀ is the number of seconds dropped of the solvent alone, C is the concentration of the sample solution (g / dL), and K _H is Huggins It is a constant. K _H adopted 0.33. The dissolution condition of the sample was 110 ° C. for 30 minutes.

Example 1
The starting material which made the ratio of 1.8 mol of 1, 4- butanediol with respect to 1 mol of terephthalic acid was supplied to a slurry preparation tank from a raw material supply port, and was stirred and mixed, and the slurry was prepared. The slurry is continuously supplied to the esterification reaction tank adjusted to a temperature of 230 ° C. and a pressure of 78.7 kPa at 1,836 parts by weight / hour, and tetra-n- from the catalyst supply port provided in the esterification reaction tank. The butyl titanate was continuously supplied at 1.06 parts by weight / hour, and the esterification reaction was carried out with a residence time of 3 hours under stirring to obtain an oligomer having an esterification conversion rate of 97.5%.

Subsequently, the obtained oligomer was continuously supplied to a first polymerization reaction tank adjusted to a temperature of 250 ° C. and a pressure of 2.66 kPa, and was subjected to a polymerization reaction for 2 hours with a residence time under stirring to obtain a PBT prepolymer. The intrinsic viscosity of this PBT prepolymer was 0.250 dL / g.
The PBT prepolymer was continuously supplied to a second polymerization reaction tank adjusted to a temperature of 250 ° C. and a pressure of 0.133 kPa, and the polymerization reaction was further advanced under stirring for a residence time of 3 hours to obtain PBT.

The PBT is withdrawn from the second polymerization reaction tank, transferred to a die, extruded as a cylindrical strand, cooled with cooling water at 20 ° C. for 0.9 seconds, and then formed into a pellet of 3 mm long, 3 mm long and 2 mm short. After cutting, it was dried to obtain PBT. The melting point of this PBT was 224 ° C., the intrinsic viscosity was 0.85 dL / g, the amount of fine powder contained was 0.15% by weight, and the water content was 0.05% by weight. The remainder of the PBT fines was granular (in pellet form as above).
Next, 10 g of this PBT (12.5 mL as an apparent volume) was placed in a 140 mL stainless pressure-resistant container. Then, under the condition (a number of times of substitution 50 times / 10 hours) to uniformly flow nitrogen of a volume 50 times the volume obtained by subtracting the volume of polyester contained in the container from the volume of the container in 10 hours (gauge pressure 0. Heat treatment was performed at 195 ° C. for 20 hours in a nitrogen pressurized state of 05 MPa. The melting point and the intrinsic viscosity of the heat-treated polyester were measured, and the results are shown in Table 1.

(Example 2)
10 g of the PBT (PBT before heat treatment) obtained in Example 1 was placed in a 140 mL stainless pressure-resistant container. Then, under the condition (a number of times of substitution 0.5 times / 10 hours) that nitrogen of a volume of 0.5 times the volume obtained by subtracting the volume of the polyester contained in the container from the volume of the container in 10 hours is uniformly distributed. It heat-processed at 195 degreeC for 20 hours in nitrogen pressurization state of gauge pressure 0.05MPa. The melting point and the intrinsic viscosity of the heat-treated polyester were measured, and the results are shown in Table 1.

(Example 3)
10 g of the PBT (PBT before heat treatment) obtained in Example 1 was placed in a 140 mL stainless pressure-resistant container. Then, under the condition (a number of times of substitution 50 times / 10 hours) to uniformly flow nitrogen of a volume 50 times the volume obtained by subtracting the volume of polyester contained in the container from the volume of the container in 10 hours (gauge pressure 0. The heat treatment was performed at 195 ° C. for 20 hours in a nitrogen pressurized state of 01 MPa. The melting point and the intrinsic viscosity of the heat-treated polyester were measured, and the results are shown in Table 1.

(Example 4)
10 g of the PBT (PBT before heat treatment) obtained in Example 1 was placed in a 140 mL stainless pressure-resistant container. And it sealed by nitrogen under atmospheric pressure of gauge pressure 0MPa, and heat-processed at 195 degreeC for 20 hours. The melting point and the intrinsic viscosity of the heat-treated polyester were measured, and the results are shown in Table 1.

(Example 5)
Transesterification was performed using 64.62 parts by weight of dimethyl terephthalate, 39.3 parts by weight of 1,4-butanediol, 6.14 parts by weight of isophthalic acid, and tetrabutyl titanate as a catalyst. Then, a polycondensation reaction was performed under reduced pressure. Next, the inside of the tank was recompressed from nitrogen under reduced pressure, and then pressurized for polymer withdrawal. The heat medium temperature of the die at the time of extraction was made into strands from the die by setting the heat medium temperature of the die to 235 ° C, and then the strand was cooled in a cooling water bath and then cut into pellets 3 mm long, 3 mm long, 2 mm short After drying, copolymerized PBT was obtained. The melting point of the obtained copolymerized PBT was 208 ° C., the intrinsic viscosity was 0.85 dL / g, the amount of fine powder contained was 0.15% by weight, and the water content was 0.05% by weight. The remainder of the fine powder of copolymerized PBT was in the form of granules (in the form of pellets as described above).
Then, using this copolymerized PBT, heat treatment was performed in the same manner as in Example 1 except that the heat treatment temperature was set to 190 ° C. The melting point and the intrinsic viscosity of the heat-treated polyester were measured, and the results are shown in Table 1.

(Example 6)
The ester reaction was carried out using 93.6 parts by weight of terephthalic acid, 26.4 parts by weight of isophthalic acid, 54 parts by weight of ethylene glycol, and antimony trioxide as a catalyst. Next, magnesium acetate tetrahydrate was added, and a melt polycondensation reaction was performed under reduced pressure.
After completion of the reaction, it was extracted in the form of a strand, cut into pellets of 3 mm in length, 3 mm in major diameter and 2 mm in minor diameter while cooling with water and then dried to obtain copolymerized PET.
The obtained copolymerized PET had a melting point of 198 ° C., an intrinsic viscosity of 0.71 dL / g, a fine powder content of 0.15% by weight, and a water content of 0.05% by weight. The remainder of the copolymer PET fine powder was in the form of granules (in the form of pellets as described above).
Subsequently, using this copolymerized PET, heat treatment was performed in the same manner as in Example 1 except that the heat treatment temperature was set to 170 ° C. The melting point and the intrinsic viscosity of the heat-treated polyester were measured, and the results are shown in Table 1.

(Example 7)
A portion of the PBT granules before heat treatment obtained in Example 1 was cooled with liquid nitrogen using a SPEX # 6750 freezer mill and freeze-ground for 5 minutes. All of the ground product was PBT fine powder which passed through Tyler 100 mesh and did not pass through a 10 μm mesh nickel screen.
Next, the remaining 6.67 parts by weight of the PBT granular material and 3.33 parts by weight of the PBT fine powder were uniformly mixed to prepare a mixture of the PBT fine powder and the PBT granular material. The water content of this PBT mixture was 0.05% by weight. Then, heat treatment was performed in the same manner as in Example 1 using this PBT mixture. The melting point and the intrinsic viscosity of the heat-treated polyester were measured, and the results are shown in Table 1.

(Example 8)
A PBT mixture was prepared in the same manner as in Example 7 except that 3.34 parts by weight of PBT granules and 6.66 parts by weight of PBT fine powder were used. The water content of this PBT mixture was 0.05% by weight. Then, heat treatment was performed in the same manner as in Example 1 using this PBT mixture. The melting point and the intrinsic viscosity of the heat-treated polyester were measured, and the results are shown in Table 1.

(Example 9)
The moisture content of the PBT fine powder obtained in Example 7 was 0.05% by weight. The heat treatment was performed in the same manner as in Example 1 except that only this PBT fine powder was used. The melting point and the intrinsic viscosity of the heat-treated polyester were measured, and the results are shown in Table 1.

(Comparative example 1)
Using the PBT obtained in Example 1 (PBT before heat treatment), the volume of nitrogen of 50 times the volume of the container minus the volume of the polyester contained in the container is uniformly distributed in 10 hours. Under the conditions, heat treatment was performed at 195 ° C. for 20 hours at atmospheric pressure with a gauge pressure of 0 MPa. The melting point and the intrinsic viscosity of the heat-treated polyester were measured, and the results are shown in Table 1.

(Comparative example 2)
Using the PBT obtained in Example 1 (PBT before heat treatment), heat treatment was performed at 195 ° C. for 20 hours under a nitrogen gas atmosphere with a gauge pressure of −0.05 MPa. The melting point and the intrinsic viscosity of the heat-treated polyester were measured, and the results are shown in Table 1.

(Comparative example 3)
The heat treatment was performed in the same manner as in Example 4 except that the moisture content of PBT to be subjected to the heat treatment was changed to 0.35% by weight. The melting point and the intrinsic viscosity of the heat-treated polyester were measured, and the results are shown in Table 1.

The following can be understood from Table 1.
The polyester subjected to the heat treatment according to the present invention has a small change in melting point before and after the heat treatment and a small change in intrinsic viscosity as shown in the examples. Therefore, the heat treatment method of the present invention improves the accuracy of control of polymerization degree near the end of solid phase polymerization and prevents unnecessary high melting point near the end of solid phase polymerization in high polymerization degree by solid phase polymerization. It can be seen that it can be used as a method to do so, and polyester of stable quality can be obtained. In addition, in the case of SLS method 3D printer application, unwanted deterioration of polyester such as high polymerization degree, low polymerization degree, high melting point, and the like of polyester which is a molding material in a heating and holding state at modeling at a long time It can be seen that it can be prevented and stable shaping is possible. Furthermore, it can be seen that stable formation with less deterioration is possible even when the excess polyester is recycled.
On the other hand, in Comparative Example 1, since the pressure in the flow system heat treatment is low, and in Comparative Example 2, the pressure in the closed system heat treatment is low, the intrinsic viscosity largely changes, and the melting point is increased. is happening.
In Comparative Example 3, the moisture content of the polyester subjected to the heat treatment is high, and the intrinsic viscosity is low although there is no problem with the increase in melting point, and it can be seen that hydrolysis occurs during the heat treatment and the degree of polymerization is lowered.

  The polyester obtained by using the heat treatment method of the present invention is suitable as a material for molded articles such as hollow molded articles such as molded articles for automobiles, electric and electronic products, articles for general plastic products and bottles for beverages, films and sheets. It can be used for

Claims (5)

Heats up polyester having a melting point of 170 ° C or higher, containing 0.10% by weight of fine powder which passes through Tyler 100 mesh and does not pass through a 10 μm mesh nickel screen and has a water content of 0.30% by weight or less A heat treatment method of polyester according to claim 1, wherein the heat treatment is carried out by closed system heat treatment of the following (1) or flow system heat treatment of the following (2).
(1) In the heat treatment area sealed with an inert gas, the heat treatment is performed at a pressure of not less than atmospheric pressure and less than 0.98 MPa at the heat treatment temperature.
(2) In the heat treatment area through which the inert gas is circulated, the circulation condition of the inert gas is a condition for replacing the gas within the heat treatment area 100 times / 10 hours or less, and the pressure is atmospheric pressure at the heat treatment temperature. Heat treatment as less than 0.98 MPa.   The method for heat-treating polyester according to claim 1, wherein the polyester is polybutylene terephthalate or copolymerized polybutylene terephthalate.   The method for heat-treating polyester according to claim 1, wherein the polyester is copolymerized polyethylene terephthalate.   A solid phase polymerization method using the heat treatment method of polyester according to any one of claims 1 to 3.   The usage method of the rapid prototyping apparatus of a three-dimensional object using the heat processing method of polyester of any one of Claims 1-3.