JP2003081914A - Recycled monomer and method for obtaining the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for recovering ester-forming monomers in a high yield obtained by depolymerizing a resin mixture comprising PTT and PBT without separating PTT from PBT, to provide highly pure depolymerized monomers which can give the polymers having the equal qualities to those of the polymers produced from new monomers, even when the depolymerized monomers are reused for producing the polymers, and to provide a method for producing the monomers. SOLUTION: The ester-forming monomers obtained by depolymerizing a resin mixture comprising polytrimethylene terephthalate and polybutylene terephthalate containes an acetone content of <=1.0 wt.%, an acrolein content of <=0.5 wt.%, a tetrahydrofuran content of <=1.0 wt.%, a 1,3-butadiene content of <=0.10 wt.% and a bis(3-hydroxypropyl)ether content of <=1.0 wt., and the method for producing the ester-forming monomers.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ester-forming agent obtained by depolymerizing a resin mixture consisting of polytrimethylene terephthalate (hereinafter abbreviated as PTT) and polybutylene terephthalate (hereinafter abbreviated as PBT). The present invention relates to a monomer (hereinafter sometimes referred to as a depolymerization monomer) and a method for producing the same. More specifically, the present invention relates to a high-purity depolymerized monomer that can obtain a polymer having the same quality as when an unused monomer is used even when the depolymerized monomer is used again for polymer production, and a method for producing the same.

[0002]

2. Description of the Related Art The society of the 20th century was a society that consumes a large amount of material and discards it. In the beginning of the 21st century, such a large amount of waste has a great adverse effect on the global environment and socio-economics as a relic of the 20th century, and has become a serious social problem.
The social system of the 21st century is shifting to a recycling-oriented society based on the lessons of the society of mass consumption and mass disposal in the 20th century. A particularly large trend is the use of chemically recyclable materials for the large amount of discarded parts, such as automobile engine peripheral parts, large exterior and outer panel parts such as hoods, bumpers, and fenders, and the exterior of electrical appliances. It is the one to use. And, PTT and PBT, which are excellent in electrical characteristics and moldability, are drawing attention as alternative materials that can be chemically recycled.

Several techniques for recycling PBT have been disclosed so far, for example, a method of hydrolyzing PBT waste in the presence of a hydrogenation catalyst under hydrogen pressure to obtain terephthalic acid. 6-72922), and a method of recovering an aromatic dicarboxylic acid by decomposing a polyester composed of an aromatic dicarboxylic acid and an aliphatic glycol having 2 to 6 carbon atoms in the presence of a fatty acid such as acetic acid and an ester exchange catalyst (special feature KAISHO 53-63338) and the like are known. Regarding PTT, there is a background that stable production technology of raw materials was finally established in the latter half of the 1990's, and it is the current situation that it has not been studied so much. However, in the International Publication (WO) 01/19764 pamphlet Is a factor that deteriorates the monomer recovery rate by distilling and purifying the monomer obtained by depolymerization under specific conditions in the presence of a basic substance, and a coloring factor when it is used again for polymer production. A method of reducing the amount of acrolein is disclosed. However, although these technical ranges show excellent properties for depolymerization of PBT alone or PTT alone, depolymerization of a resin mixture consisting of PTT and PBT is performed, and the resulting depolymerized monomer is again used for the production of polyester. When it was used, the coloring was severe, the heat resistance was lowered, the dyeing characteristics were uneven, and in the worst case, the depolymerization monomer itself had a low purity and was colored.

[0004]

No matter how much the social system is shifting to a recycling-oriented society, it is essential to separate and collect polyesters by type and depolymerize them by separate equipment and method. Is impossible. Therefore, P is expected to be discharged in large quantities in the future.
It is essential to establish a technique capable of depolymerizing the resin mixture composed of TT and PBT at one time without separating it. If we can establish these technologies,
Side-by-side yarns of PTT and PBT, as well as collected waste such as automobile engine peripheral parts made of PTT and / or PBT, large outer and outer plate parts typified by hoods, bumpers, fenders, etc.
A composite fiber such as a sheath-core yarn or a mixed yarn, or a front and back two-layer knitted fabric using PBT and a connecting yarn for connecting the two-layer knitted fabric with PT
Three-dimensional knitted fabric using T monofilament (JP-A-11-2
69747), and a sheet in which the three-dimensional knit is stretched on a metal frame, PBT ultrafine yarn on the surface, stretchable artificial leather using PTT fiber as a base fabric (JP-A-11-269751), and the like. It is very useful because it can be applied to the collection of textile products that are difficult to separate morphologically, and also products such as toothbrushes, polishing brushes, tennis guts, fishing lines, fishnets and artificial lawns.

The problem to be solved by the present invention is P
It is to establish a technique for recovering an ester-forming monomer obtained by depolymerizing a resin mixture composed of TT and PBT in a high yield without fractionation. Further, by providing a high-purity depolymerized monomer and a method for producing the same, even if the depolymerized monomer is used again for polymer production, a polymer having the same quality as when an unused monomer is used can be obtained. is there. Furthermore, by providing a high-purity depolymerization monomer that can be reused for polymer production from a large amount of waste and a method for producing the same, closed loop recycling can be completed and a sustainable recycling-based social system can be constructed. is there.

[0006]

Means for Solving the Problems The present inventors have found that impurities produced when a resin mixture composed of PTT and PBT is decomposed into monomers affect the quality of the monomer and the repolymerized polymer. , Especially acetone,
Acrolein, tetrahydrofuran (hereinafter abbreviated as THF), 1,3-butadiene (hereinafter abbreviated as BTD), and bis (3-hydroxypropyl) ether (hereinafter abbreviated as BHP) have the most adverse effects. Is that if the mixing ratio in these depolymerization monomers is set to a specific amount or less, the quality of the repolymerized polymer will be an industrially sufficient level, and as a result of detailed examination of depolymerization conditions, the present invention Arrived That is, the present invention is an ester-forming monomer (depolymerization monomer) obtained by depolymerizing a resin mixture composed of PTT and PBT, wherein the acetone content is 1.0% by weight or less and the acrolein content is based on the weight of the monomer. 0.5% by weight or less, THF content 1.0
The present invention provides a depolymerized monomer having a BTD of 0.10% by weight or less, a BTD of 0.10% by weight or less, and a BHP content of 1.0% by weight or less.

Here, the depolymerization monomer means a monomer which can be used as a raw material when producing a polyester, and means dicarboxylic acid, dicarboxylic acid ester or diol.
Specifically, dialkyl terephthalate represented by dimethyl terephthalate, monoalkyl terephthalate represented by monomethyl terephthalate, bis (3-hydroxypropyl) terephthalate, methyl terephthalate (3-hydroxypropyl), metal terephthalate. Salt, 1,3-propanediol (hereinafter abbreviated as PDO), PDO monoester, PDO diester, 1,4-butanediol (hereinafter abbreviated as BG), terephthalic acid bis (4-)
(Hydroxybutyl), BG monoester, BG diester and the like. Of these depolymerization monomers, dimethyl terephthalate, PDO, and BG are particularly preferable because they have excellent polymerization reactivity as a polyester raw material.

Even if the depolymerized monomer of the present invention is used again for polymer production, it is possible to obtain a polymer having the same quality as that when an unused monomer is used, in order to obtain acetone, acrolein, THF, BTD. It is important to keep the amount of BHP and BHP below a specific value. First, the acetone content needs to be 1.0% by weight or less. Acetone is generated in the thermal decomposition process of PTT, but if acetone is used again as a raw material for polymerization of polyester while remaining, it causes problems such as a slow polymerization rate and a decrease in whiteness of the obtained polymer. It is preferably 0.3% by weight or less, and more preferably 0.05% by weight or less. Of course, the smaller the amount, the more preferable, and the absence is most preferable.

Next, the acrolein content is 0.5% by weight or less.
It is necessary to be. Unloading of acrolein remaining
When the combined monomer is used as a raw material for polymerization of polyester,
Depolymerization monomer is easy to denature or re-polymerize
When the polymerization rate becomes slower or the whiteness of the obtained polymer
It leads to a defect such as a decrease in degree. In addition, B in the monomer
In the presence of TD, acrolein is a polymer manufacturing process
And react with BTD △ ³-Tetrahydrobenzoaldeh
Of the polymer obtained by producing resinous products such as
It has a great impact on quality. Preferably 0.2% by weight or less
And more preferably 0.05% by weight or less. Also
Of course, the smaller the number, the more preferable, and the one containing nothing is most preferable.
Good

Next, the THF content must be 1.0% by weight or less. Although THF is generated in the thermal decomposition process of PBT, if THF is used again as a raw material for the polymerization of polyester while remaining, it causes problems such as a slow polymerization rate and a decrease in whiteness of the obtained polymer.
It is preferably 0.3% by weight or less, and more preferably 0.05% by weight or less. Of course, the smaller the amount, the more preferable, and the absence is most preferable.

Next, the BTD content must be 0.10% by weight or less. Similar to THF, BTD is also generated during the thermal decomposition process of PBT, but if BTD remains and is used again as a raw material for the polymerization of polyester, the polymerization rate becomes slower, and because BTD is extremely reactive, it itself It polymerizes or reacts with a substance such as acrolein to form a resin product as described above, and reduces the purity and quality of the obtained polymer. Preferably 0.03% by weight
It is below, and more preferably 0.01% by weight or less. Of course, the smaller the amount, the more preferable, and the absence is most preferable.

Further, the BHP content must be 1.0% by weight or less. BHP is a dimer produced by dehydration etherification of PDO. If a depolymerized monomer having BHP remaining is used as a raw material for the polymerization of PTT or PET, the whiteness of the obtained polymer will be reduced. Further, BHP is copolymerized with a polymer, and the content thereof greatly affects the dyeability, causing a problem that the dyeability varies from lot to lot. It is preferably 0.3% by weight or less, and more preferably 0.05% by weight or less. Of course, the smaller the amount, the more preferable, and the absence is most preferable.

Further, PDO has an acetone content of 1.0% by weight or less, an acrolein content of 0.5% by weight or less, and THF.
The content is 1.0% by weight or less, the BTD content is 1.0% by weight or less, and the BHP content is 1.0% by weight or less, and the higher the transparency, the better the whiteness of the PTT obtained by repolymerization. Therefore, the Hazen color is preferably 20 or less, more preferably 10 or less, and most preferably 5 or less.
It is the following. The BG content of PDO affects the whiteness of the re-polymerized PTT and fiber properties such as stretchability and softness, and is therefore preferably 1.0% by weight or less, more preferably 0.5% by weight or less.

BG, like PDO, has a Hazen color of preferably 20 or less, more preferably 10 or less, and most preferably 5 in order to improve the whiteness of the repolymerized PBT.
It is the following. Since the content of PDO in BG also affects the whiteness of repolymerized PBT, fiber characteristics and resin characteristics, it is preferably 1.0% by weight or less, more preferably 0.5% by weight or less. In the case of dialkyl terephthalate, repolymerized PT
In order to improve the whiteness of T, the b value is preferably 2 or less, more preferably 0.5 or less. The acid value of the dialkyl terephthalate is preferably 0.05 or less, more preferably 0.02 or less so as not to impair the whiteness of the repolymerized polyester and the polymerizability such as reaction rate and reaction rate. .

The preferred method for producing the depolymerized monomer of the present invention will be described below. In the present invention, the depolymerized monomer is obtained by the following method. (0) Glycol is reacted with a resin mixture composed of PTT and PBT to once produce bis (3-hydroxypropyl) terephthalate (A) and bis (4-hydroxybutyl) terephthalate (B). This reaction is shown by the following formula. HO- (CH ₂ CH ₂ CH ₂ -O-OC-φ-CO) n-OH + HO-R ₁ -OH → HO-CH ₂ CH ₂ CH ₂ -O-OC-φ-COO-CH ₂ CH ₂ CH ₂ -OH (A) HO- (CH ₂ CH ₂ CH ₂ CH ₂ -O-OC-φ-CO) n-OH + HO-R ₁ -OH → HO-CH ₂ CH ₂ CH ₂ CH ₂ -O -OC-φ-COO-CH ₂ CH ₂ CH ₂ CH ₂ -OH (B) (φ: benzene ring, para bond) (R ₁ : divalent organic group)

(1) Bis (3) terephthalate produced once
-A basic substance is present when the monoalcohol is reacted with -hydroxypropyl) (A) and bis (4-hydroxybutyl) terephthalate (B). This reaction is shown by the following formula.

(2) The dialkyl terephthalate (C) produced in the reaction of (1) is separated from the liquid containing PDO and BG and the monoalcohol. (3) Dialkyl terephthalate (B), PDO and BG
Isolation of Acetone content is less than 1.0% by weight, Acrolein content is less than 0.5% by weight, THF content is less than 1.0% by weight
Then, distillation is performed so that the BTD content is 0.10% by weight or less and the BHP content is 1.0% by weight or less.

First, the step (0) will be described in detail. Step (0) is a step of reacting a resin mixture of PTT and PBT with glycol to temporarily generate bis (3-hydroxypropyl) terephthalate and bis (4-hydroxybutyl) terephthalate. The PTT component of the resin mixture consisting of PTT and PBT used here is the unused or used PTT chip waste, the drain polymer of the extruder,
There are no particular restrictions on waste yarns, waste films, waste resin products, unnecessary clothing, unnecessary industrial materials, unnecessary nonwoven fabrics, unnecessary carpets, etc. Further, it may be treated with a processing agent such as dyeing or a surface treatment agent, and further may be an emulsion, suspension, solution or the like. Further, PTT may be copolymerized, for example, 5-sodium sulfoisophthalic acid, tetrabutylphosphonium 5-sulfoisophthalate, isophthalic acid,
Ethylene glycol, 1,4-butanediol, adipic acid, polyalkylene glycol, etc. are, for example, 0.05
~ 98 wt% copolymerized.

The PBT component of the resin mixture consisting of PTT and PBT is the unused or used PET chip waste,
There are no particular restrictions on the drain polymer of the extruder, waste thread, waste film, waste resin product, unnecessary clothing, unnecessary industrial materials, unnecessary nonwoven fabric, unnecessary carpet, etc. Further, it may be treated with a processing agent such as dyeing or a surface treatment agent, and further may be an emulsion, suspension, solution or the like. Further, PBT may be copolymerized, for example, 5-sodium sulfoisophthalic acid, tetrabutylphosphonium 5-sulfoisophthalate, isophthalic acid, ethylene glycol, PD
O, adipic acid, polyalkylene glycol, etc. may be copolymerized by 0.05 to 98% by weight.

The form of the resin mixture composed of PTT and PBT may be a mixture of the above PTT waste and PBT waste at the recovery stage, or a copolymer of PTT and PBT. Further, it may be a composite fiber such as a side-by-side yarn of PTT and PBT, a sheath-core yarn, and a mixed yarn. Further, a three-dimensional knitted fabric (JP-A No. 11-269747), a sheet in which the three-dimensional knitted fabric is stretched on a metal frame, a stretchable artificial leather (JP-A No. 11-269751), and the like are also commercially available. good. The composition ratio of PTT and PBT in the resin mixture composed of PTT and PBT is not particularly limited,
From the viewpoint of monomer recovery efficiency, it is preferable that PTT / PBT = 5/95 to 95/5 based on the total weight of PTT and PBT. 30/70 to 70/30 are more preferable. Polyethylene terephthalate may be contained in the resin mixture composed of PTT and PBT.

In the step (0) of the present invention, PTT and P
The glycol used when bis (3-hydroxypropyl) terephthalate and bis (4-hydroxybutyl terephthalate) are reacted with a resin mixture of BT to produce ethylene glycol, PDO, BG,
1,5-pentanediol and the like can be mentioned. It is preferable to use PDO and BG from the viewpoint of easy recovery of the depolymerized monomer. As the glycol used in the step (0), a commercially available glycol or a recovered glycol may be used, but acetone, acrolein and TH in the depolymerization monomer may be used.
In order to reduce the content of F, BTD and BHP, the content of acetone is 1.0% by weight or less and the content of acrolein is 0.5% by weight based on the weight of glycol used in the step (0).
Hereinafter, it is preferable to use a glycol having a THF content of 1.0% by weight or less, a BTD content of 0.10% by weight or less and a BHP content of 1.0% by weight or less.

The amount of glycol used is not particularly limited, but in order to obtain a sufficient reaction rate, PTT and PB are used.
With respect to the weight of the resin mixture consisting of T, preferably 1
It is used 100 times, more preferably 1 to 10 times. Also PT
When bis (3-hydroxypropyl) terephthalate and bis (4-hydroxybutyl) terephthalate are produced by reacting glycol with a resin mixture composed of T and PBT, it is preferable to carry out at a temperature of 50 to 450 ° C. Fifty
If the temperature is lower than ℃, the reaction rate is slow and bis (3-hydroxypropyl) terephthalate and bis (4 terephthalate)
-Hydroxybutyl) production efficiency becomes poor. Again 45
If the temperature exceeds 0 ° C, the amount of acetone, acrolein, THF and BTD generated by thermal decomposition increases, and the quality of the recovered product deteriorates. Acetone, acrolein, THF and BTD
It is preferable to carry out at 50 to 300 ° C. from the viewpoint of suppressing the occurrence of

To increase the reaction rate, 100 to 3
More preferably, it is carried out at 00 ° C. In step (0), basic substances such as sodium carbonate, magnesium carbonate, potassium carbonate, barium carbonate, lithium carbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, magnesium hydroxide, sodium acetate, potassium acetate are used. It may be added to increase the reaction rate. The amount of these basic substances used is not particularly limited, but the total number of moles of repeating units of all polyesters to be depolymerized (for example,
Consider 206 g of homo PTT as 1 mol. ),
It is 0.01 to 200 mol%, preferably 0.1 to 50 mol% from the viewpoint of depolymerization rate.

Next, the step (1) will be described. In step (1), bis (3-hydroxypropyl) terephthalate and bis (4-hydroxybutyl) terephthalate produced in step (0) are reacted with a monoalcohol in the presence of a basic substance to give a dialkyl terephthalate, PDO.
And the step of generating BG. Examples of the monoalcohol used in the step (1) include lower saturated monoalcohols such as methanol, ethanol, propanol, isopropanol, butyl alcohol and isobutyl alcohol. Methanol and ethanol are particularly preferable, and methanol is particularly preferable, because dialkyl terephthalate is easily distilled. The amount of monoalcohol to be used is not particularly limited, but in order to obtain a sufficient reaction rate, it is necessary to use bis (3-hydroxypropyl) terephthalate and bis (4-hydroxybutyl) terephthalate in terms of the total number of moles. Therefore, it is preferably 2 to 100 times mol, more preferably 2 to 20 times mol.

Whether the basic substance in the step (1) reacts with acetone or acrolein and has no volatility or solubility.
Alternatively, change it to a substance that has extremely low volatility or solubility,
It acts to prevent the depolymerization monomer isolated by an operation of isolating the depolymerization monomer, for example, an operation such as precipitation, distillation, recrystallization, or the like, from mixing acetone, acrolein, and modified products thereof. In addition, the basic substance may be added to the PTT and PBT when the generated depolymerized monomer is isolated, for example, in the process of operation such as distillation.
It also has the effect of suppressing the repolymerization due to the catalyst present in the resin mixture consisting of, and increasing the recovery rate. If an acidic substance is used in place of the basic substance, the depolymerization reaction rate will decrease significantly, and the acidic substance will act as a catalyst to accelerate the dehydration reaction of PDO and increase the amount of allolein produced, or dehydration of BG. The reaction is accelerated to increase the production amount of THF or the production amount of BHP remarkably, so that the purity of the depolymerized monomer is lowered.

The basic substance is not particularly limited as long as it reacts with an acid such as hydrochloric acid, sulfuric acid or acetic acid, and is a substance which shows alkalinity when dissolved in water or alcohol, but is not dissolved in water or alcohol. Examples thereof include salts that can react with a protonic acid and a Lewis acid. Particularly preferred basic substances are basic metal salts that are alkaline when dissolved in water because side reactions are unlikely to occur, more preferably a metal salt having a pH of 8 to 14, and more preferably 9 to 12. Specific basic substances include sodium carbonate, magnesium carbonate, potassium carbonate, barium carbonate, lithium carbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, magnesium hydroxide, melamine resin, polyurea, amino group-substituted polystyrene, Examples thereof include sodium acetate, sodium formate, potassium acetate and potassium formate, with sodium carbonate and potassium carbonate being particularly preferred.

The basic substance may be the same as the basic substance added in the step (0) or may be newly added. The amount of the basic substance to be used is not particularly limited, but is 0.01 to 200 mol%, preferably 0.01 to 200 mol% with respect to the total number of repeating unit moles of all polyesters to be depolymerized (for example, 206 g of homo PTT is regarded as 1 mole). Is 0.1 to 50 mol%. The reaction temperature in step (1) is preferably 50 to 300 ° C. If the temperature is lower than 50 ° C, the reaction occurs only gradually and the recovery efficiency becomes poor.
On the other hand, when the temperature exceeds 300 ° C., the amounts of acrolein, acetone, THF and BTD generated by thermal decomposition increase, and the coloring of the recovered product becomes severe. Preferably, 60-150 ℃,
More preferably, it is 60 to 100 ° C. When the temperature at this time exceeds the boiling point of the solvent used, pressure may be applied to maintain the liquid state, and the solvent may be in a critical state at this time.

In the reaction of the step (1), the dialkyl terephthalate is precipitated as a solid from the reaction system, but in order to enhance the separation efficiency between the PDO and BG and the liquid layer containing the monoalcohol as the main component in the step (2). For this reason, it is preferable to grow a large amount of dialkyl terephthalate and to grow it as large as possible. The size of the lump of dialkyl terephthalate is 0.01 to 2 per weight of the lump.
The amount is preferably 0 g, preferably 0.1 to 10 g, and the reaction temperature and the reaction time are preferably set with the size of the lump as a guide. In particular, in order to grow a large amount of a dialkyl terephthalate mass and to grow the mass as large as possible, it is preferable to set the temperature of the reaction product to 50 ° C. or lower, preferably 30 ° C. or lower after the reaction, and leave it for at least 10 minutes or longer.

Next, the step (2) will be described. Process (2)
Is a step of separating the dialkyl terephthalate, which has grown into a certain size of mass in the reaction of step (1), from the liquid containing PDO and BG and the monoalcohol. In step (2), BHP produced as a by-product in the previous step, BTD, P
Move DO and BG to the liquid layer as much as possible. In particular, the BHP content remaining in the dialkyl terephthalate is preferably 1.0% by weight or less, more preferably 0.5% by weight or less. BH in dialkyl terephthalate in step (2)
When P remains in an amount of more than 1.0% by weight, the boiling points of both are close to each other, making it difficult to isolate by distillation in the step (3),
The BHP content in the final monomer exceeds 1.0% by weight.

In the distillation step of step (3), BTD is polymerized by the heat of distillation to form a resin product, which lowers the recovery rate of dialkyl terephthalate. Further, if PDO and BG remain in the dialkyl terephthalate, the dialkyl terephthalate and P are heated by the heat of distillation in the distillation process in the step (3).
Since bis (3-hydroxypropyl) terephthalate or bis (4-hydroxybutyl) terephthalate is regenerated by reaction with DO or BG, the recovery rate of dialkyl terephthalate deteriorates. It is preferable to move it. From the viewpoint of increasing the recovery efficiency of dialkyl terephthalate, it is preferable to move THF to the liquid layer as much as possible in step (2).

The separation method is not particularly limited, such as filtration and centrifugation, but centrifugation is preferred. The centrifugal separator used for centrifugation is not particularly limited and may be a continuous type or a batch type. When centrifuging, the rotation speed and time are important, and the rotation speed is 300r.
It is preferably at least pm. Rotation speed is 300 rp
When it is less than m, separation is insufficient and the contents of PDO, BG, THF, BTD and BHP in the dialkyl terephthalate increase, and further, microcrystalline dialkyl terephthalate remains in the liquid layer, resulting in poor recovery. Preferably 500
rpm or more. The centrifugation time is preferably 10 minutes or more. The temperature at the time of centrifugation does not need to be particularly controlled, but is preferably set to 30 ° C. or lower from the viewpoint of safety.

The centrifugation is preferably repeated. At that time, it is possible to wash the dialkyl terephthalate with the same monoalcohol as used in the step (2) in order to remove PDO, BG and TH in the dialkyl terephthalate.
Further preferred for reducing F, BTD and BHP content. Prior to separating the dialkyl terephthalate and the liquid layer, it is important not to neutralize the basic substance at all or completely. That is, when it is excessively neutralized with an acid, problems such as the formation of THF and BHP are likely to occur due to the action of the acid catalyst, and on the contrary, all or part of the basic substance maintains the basic function. By being in the state, it has a great effect of preventing the mixture of acetone, acrolein, and their modified products during the distillation performed in the step (3).

Next, the step (3) will be described. The step (3) comprises isolating each of the dialkyl terephthalate, PDO and BG separated in the step (2) with an acetone content of 1.0% by weight or less, an acrolein content of 0.5% by weight or less, and a THF content of 1%. 0.0 wt% or less, BTD content 1.
In this step, distillation is performed so that the content of BHP is 0% or less and the content of BHP is 1.0% or less. PD in step (3)
There is no particular limitation on the method for distilling the O, BG, THF, BTD and BHP contents to the specified value or less, but in the presence of a basic substance, dialkyl terephthalate, P
The method of distilling DO and BG respectively is mentioned. The basic substance suppresses the repolymerization by the catalyst present in the resin mixture composed of PTT and PBT during the distillation operation, and further, as mentioned above, the mixture of acetone, acrolein, and their modified products into the depolymerization monomer. Control and TH
By suppressing the generation of F and BHP, it has the effect of increasing the recovery rate. As described above, the basic substance is preferably used as it is without neutralizing the substance used in the step (0) or the step (1). Of course, it may be newly added. In this case, the addition amount of the basic substance is preferably 0.01 to 100 mol%, preferably 0.1 to 30 mol% with respect to the theoretical recovery amount of dialkyl terephthalate, PDO and BG.
Mol%.

More preferable distillation conditions include dialkyl terephthalate and PD in the presence of a basic substance and a sulfite.
In this method, O and BG are independently distilled. Sulfite reacts with acetone and acrolein that could not react with basic substances and changes to substances that are volatile or insoluble or have extremely low volatility or solubility, resulting in isolated depolymerization monomers. It acts to prevent the mixture of acetone, acrolein, and their modified products. As the sulfite used, potassium sulfite, potassium hydrogen sulfite,
Examples thereof include calcium sulfite, sodium hydrogen sulfite, sodium sulfite, barium sulfite, ammonium sulfite, and the like, and sodium sulfite is particularly preferable from the viewpoint of reacting with acetone to form a crystalline substance. The amount of sulfite used is not particularly limited, but the theoretical amount of dialkyl terephthalate, PDO and BG is
It is 0.01 to 100 mol%, preferably 0.1 to 30 mol%.

The preferred distillation conditions for dialkyl terephthalate, PDO and BG will be described below. The dialkyl terephthalate separated in the step (2) is preferably distilled at 180 to 250 ° C. and 30 to 250 torr in the presence of a basic substance. When the pressure exceeds 250 torr, the boiling point becomes high, which causes problems such as the dialkyl terephthalate being colored in the distillation process and the acid value becoming high. On the other hand, if it is less than 30 torr, the temperature can be set low, but since the degree of vacuum is too high, it is sucked into the vacuum pump,
The recovery rate will be low. Preferably, 180-23
It is 0 ° C. and 30 to 150 torr.

As a more preferable distillation condition for dialkyl terephthalate, there is a method in which a basic substance and a sulfite such as sodium sulfite are added, and distillation is performed under the above temperature and pressure conditions. As a method for adding the sulfite, it may be added in the form of powder, may be added in the form of a solution by dissolving in water, or may be added in the form of a slurry in alcohol.
It is preferable to add it after dissolving it in water to a concentration of 1 to 30% by weight. Then, distillation is performed under the above-mentioned proper conditions to isolate the dialkyl terephthalate.

Next, preferable distillation conditions for PDO and BG will be described below. The main components of the liquid part centrifuged in step (2) are PDO, BG and monoalcohol. Further, impurities such as PDO, BG, THF, BTD and BHP are also included. PDO from these liquid components
In order to isolate BG and BG respectively, it is preferable to perform three-stage distillation. The first step is 50 ~ in the presence of a basic substance.
It is preferable to carry out distillation at 150 ° C. At this time, it is preferable to appropriately reduce the pressure. In the first stage, mainly monoalcohol, acetone, acrolein, THF and BT
Distill off D. Monoalcohol, if less than 50 ℃,
Acetone, acrolein, THF and BTD are insufficiently distilled off and remain in PDO and BG. While 120
If the temperature exceeds ℃, PDO and BG that remain as a residual liquid are thermally deteriorated and the recovery rate is deteriorated. Preferably 50 to 1
20 degreeC, More preferably, it is 60-110 degreeC.

In the second stage, a distillation column having a theoretical plate number of 8 or more is used in the presence of a basic substance at 100 to 200 ° C. and 50 to 20.
It is preferable to carry out the distillation at 0 torr. In the second stage, PDO is distilled off. If the theoretical plate number is less than 10, the separation of PDO and BG is insufficient, and BG is contained in PDO.
Remains above 1.0% by weight. Also the pressure is 2
If it exceeds 00 torr, the boiling point becomes high, which causes a problem that BG or PDO is colored during the distillation process. 50 on the contrary
If it is less than torr, the temperature can be set low, but since the degree of vacuum is too high, it is sucked into the vacuum pump and the recovery rate becomes low. Preferably, the number of theoretical plates is 10 or more, 100
˜180 ° C., 50˜150 torr.

The third step is 100% in the presence of a basic substance.
It is preferable to carry out the distillation at -200 ° C and 50-200 torr. In the third stage, BG is distilled off. Two
When it exceeds 00 torr, the boiling point becomes high, which causes a problem such as coloring of BG in the distillation process. Conversely, 50 torr
If it is less than 1, the temperature can be set low, but since the degree of vacuum is too high, it is sucked into the vacuum pump and the recovery rate becomes low. Preferably 120-180 ° C, 50-150tor
r. At this time, it is preferable to set the reflux ratio to 0.5 or more in order to avoid mixing of BHP.

As a more preferable distillation condition for PDO and BG, there is a method in which a basic substance and a sulfite such as sodium sulfite are added and distillation is carried out under the above temperature and pressure conditions.
The sulfite may be added in the form of powder, dissolved in water and added in the form of a solution, or further mixed with alcohol in the form of a slurry and added. When it is dissolved in water, it is preferably added after being dissolved in a concentration of 1 to 30% by weight. Then, PDO and BG can be isolated by performing distillation under the proper conditions described above.

Thus, the dialkyl terephthalate obtained by depolymerizing the resin mixture consisting of PTT and PBT, PD
The depolymerized monomers such as O and BG are again mixed with PTT and P
It can be used as a raw material for polyester such as ET and PBT. As a polymerization method in this case, a known method may be applied as it is. Of course, the depolymerized monomer of the present invention may be used as a mixture with an unused monomer, and again,
1.0% by weight of the monomers used to polymerize the polyester
Above, further, 10% by weight or more, and even 70% by weight or more can be used. Since the depolymerized monomer of the present invention has high purity, the polyester obtained again has high quality. In particular, whiteness equivalent to that when using an unused monomer is obtained, and an L value showing brightness can be achieved of 75 or more, preferably 80 or more, more preferably 85 or more. Further, the b value representing yellowness is 10 or less, preferably 7 or less, and more preferably 5 or less.

[0042]

EXAMPLES The present invention will be described in more detail below with reference to specific examples. Various measured values used in Examples of the present invention were measured by the following measuring methods. (1) Acetone amount It was measured from the ¹ H-NMR spectrum (nuclear magnetic resonance spectrum) of the recovered depolymerized monomer. (2) Acrolein amount It was measured from the ¹ H-NMR spectrum (nuclear magnetic resonance spectrum) of the recovered depolymerized monomer. (3) THF amount It was measured from the ¹ H-NMR spectrum (nuclear magnetic resonance spectrum) of the recovered depolymerized monomer. (4) BTD amount It was measured from the ¹ H-NMR spectrum (nuclear magnetic resonance spectrum) of the recovered depolymerized monomer.

(5) BHP amount Dissolved in 2 g of depolymerized monomer in 25 ml of methanol and measured by gas chromatography.・ Column: DURABOND DB-WAX x 0.25mm x 3m
(0.25 μm) Carrier gas: Helium 100 ml / min Temperature rise: 150 ° C. to 230 ° C. (20 ° C./min) (6) L value, b value Measured using a color computer manufactured by Suga Test Instruments Co., Ltd. (7) The Hazen color sample was put in a colorimetric tube, and the Hazen color No. 10-No. 5
A numerical value corresponding to that of the sample and the standard colorimetric tube was used as a Hazen color. If they do not match, the closest dark and light Hazen colors are obtained, and the intermediate value thereof is taken as the Hazen color.

(8) An acid value sample (10 g) was precisely weighed and dissolved in 100 ml of chloroform, and N / 40KO was obtained using phenolphthalein as an indicator.
Neutralization titration with H solution and acid value calculated according to the following formula = (SB) x f x 1.4 / 10 (KOHmg
/ G) S: consumption of N / 40KOH consumed in this titration (ml) B: consumption of N / 40KOH consumed in the blank test (ml) f: titer of N / 40KOH (9) Recovery rate Recovery rate Was measured according to the following formula. Recovery rate = (A / B) x 100 (%) A: Weight of depolymerized monomer actually recovered B: Theoretical weight of depolymerized monomer that can be recovered when the polymer used is depolymerized

(10) Intrinsic Viscosity The intrinsic viscosity [η] is a value obtained based on the definition of the following equation. [η] = lim (ηr-1) / C C → 0 In the definition formula, ηr is 35 ° C. of a dilute solution of polytrimethylene terephthalate polymer or polybutylene terephthalate polymer dissolved in 98% pure O-chlorophenol. Is a value obtained by dividing the viscosity of the solvent by the viscosity of the solvent itself measured at the same temperature, and is defined as the relative viscosity. C is a solute weight value in gram units in 100 ml of the above solution.

(11) K / S (evaluation of bathochromaticity of dyed product) -Pretreatment using a tubular knitted fabric, using hot water containing Score Roll 400 at a concentration of 2 g / l, polishing treatment at 70 ° C for 20 minutes Then, after drying, heat setting is performed using a pin tenter at 180 ° C. for 30 seconds.・ Dyeing dye: Kayaron Polyester Blue 3RSF (manufactured by Nippon Kayaku Co., Ltd.) Dye concentration: 6% owf, bath ratio: 1/50, Dispersant: Nikkasan Salt 7000 (Nikaka Chemical Co., Ltd.)
Manufactured), pH: 5 Dyeing conditions: 40 to 110 ° C. (5 ° C./min) after heating up,
Hold as it is for 1 hour / Post-treatment After sufficiently washing in running water, air-drying and heat setting at 180 ° C for 30 seconds using a pin tenter. -K / S The spectral reflectance R of the cylindrical knitted fabric after dyeing was measured and determined from the Kubelker-Munk equation shown below. The larger this value, the greater the bathochromic effect, that is, the better the color is developed. As R, the value at the maximum absorption wavelength of the dye was adopted. K / S = (1-R) ² / 2R

[0047]

Example 1 72 g of PTT chips having an intrinsic viscosity of 0.9 and 72 g of PBT chips having an intrinsic viscosity of 0.6 (PTT / PBT
(Weight ratio: 50/50), 255 g of PDO, 144 mg of sodium acetate (0.1% by weight / polymer, this unit represents% by weight based on the weight of the polymer) were charged in an autoclave of 1 liter and reacted at 210 ° C. for 60 minutes. After the reaction, PDO was distilled under reduced pressure at a pressure of 0.4 mmHg. The obtained white solid was analyzed by ¹ H-NMR (measurement device: Buru
ker 400 MHz), FT-NMR (model: DP
X-400) and the like to analyze bis (3) terephthalate
-Hydroxypropyl) and bis (4-hydroxybutyl) terephthalate were confirmed. The conversion rate was almost 100%.

130 g of the obtained bis (3-hydroxypropyl) terephthalate and bis (4-hydroxybutyl) terephthalate were charged with 224 g (7 mol) of methanol and 25.2 g (0.24 mol) of sodium carbonate in a 1 L autoclave. It was charged and heated at 65 ° C. for 30 minutes. The pH during the decomposition reaction was 12. After the reaction, it was cooled to 20 ° C. and left for 30 minutes. Then, using a centrifuge, (8
A liquid layer (mainly composed of methanol, PDO, BG, and BHP. Also includes sodium acetate and sodium carbonate) and a solid layer (mainly composed of dimethyl terephthalate) under the conditions of 00 rpm, 30 minutes) × 3 times. Sodium acetate,
Sodium carbonate is also included). When the centrifugation was repeated, the solid layer was washed with methanol. After centrifugation, the dialkyl terephthalate has a BHP content of 0.12% by weight, a BTD content of 0% by weight, a PDO content of 0.08% by weight, a BG content of 0.05% by weight and a T
The HF content was 0.03% by weight.

For the liquid layer, methanol was completely distilled off at 70 ° C. Then, using a packed distillation column with 12 theoretical plates in the concentration section and 12 theoretical plates in the recovery section, the bottom temperature of the column was 1
PDO was completely isolated under the distillation conditions of 60 ° C., the column top temperature of 125 ° C. and 50 torr. PDO recovery rate is 88%, acetone content is 0.10% by weight, acrolein content is 0.10% by weight, THF content is 0.06% by weight, BTD
The content was 0% by weight and the BHP content was 0.11% by weight. Furthermore, the Hazen color was as good as 5. The BG content in PDO was 0.32% by weight.

Then, BG was isolated at 150 ° C., 50 torr and a reflux ratio of 1. BG recovery rate is 89%, acetone content is 0.15% by weight, acrolein content is 0.07% by weight, THF content is 0.06% by weight, BTD
Content is 0.03% by weight and BHP content is 0.14% by weight
Met. Furthermore, the Hazen color was as good as 5. Also B
The PDO content in G was 0.28% by weight. Also, with respect to the solid layer, dimethyl terephthalate was completely isolated at 220 ° C. and 50 torr. The recovery rate of dimethyl terephthalate was 89%, the acetone content in the recovered dimethyl terephthalate was 0.09% by weight, and the acrolein content was 0.
The content was 06% by weight, the THF content was 0.06% by weight, the BTD content was 0% by weight, and the BHP content was 0.08% by weight.
Further, the b value was 1.2 and the acid value was 0.01, which were good.

[0051]

Example 2 72 g of PTT chips having an intrinsic viscosity of 0.9 and 72 g of PBT chips having an intrinsic viscosity of 0.6 (PTT / PBT
Weight ratio: 50/50) instead of P with an intrinsic viscosity of 0.9
43g TT chip and PBT chip 1 with an intrinsic viscosity of 0.6
The same operation as in Example 1 was performed except that depolymerization was performed using 01 g (PTT / PBT weight ratio: 30/70). PDO recovery is 85%, acetone content is 0.2
9% by weight, acrolein content 0.11% by weight, THF
The content was 0.10% by weight, the BTD content was 0.02% by weight and the BHP content was 0.18% by weight. Furthermore, the Hazen color was as good as 10. The BG content in PDO was 0.25% by weight. On the other hand, the recovery rate of BG is 87%, the content of acetone is 0.22% by weight, the content of acrolein is 0.09% by weight, the content of THF is 0.11% by weight,
BTD content is 0.05% by weight and BHP content is 0.16
% By weight. Furthermore, the Hazen color was as good as 5.
The PDO content in BG was 0.32% by weight. The recovered dimethyl terephthalate also had a recovery rate of 91%, the content of acetone was 0.11% by weight, and the content of acrolein was 0.06.
% By weight, the THF content was 0.07% by weight, the BTD content was 0.03% by weight and the BHP content was 0.12% by weight. Further, the b value was 1.9 and the acid value was 0.02, which were good.

[0052]

Example 3 72 g of PTT chips having an intrinsic viscosity of 0.9 and 72 g of PBT chips having an intrinsic viscosity of 0.6 (PTT / PBT
Weight ratio: 50/50) instead of P with an intrinsic viscosity of 0.9
The same operation as in Example 1 was carried out except that depolymerization was carried out using 130 g of TT chips and 14 g of PBT chips having an intrinsic viscosity of 0.6 (weight ratio of PTT / PBT: 90/10). PDO recovery rate is 88%, acetone content is 0.0
7% by weight, acrolein content is 0.05% by weight, THF
Content is 0.04% by weight, BTD content is 0% by weight and BH
The P content was 0.04% by weight. Furthermore, Hazen color is 5
And was good. The BG content in PDO was 0.11% by weight. On the other hand, the recovery rate of BG is 86%, the content of acetone is 0.05% by weight, and the content of acrolein is 0.1%.
The content was 04% by weight, the THF content was 0.07% by weight, the BTD content was 0% by weight, and the BHP content was 0.10% by weight.
Furthermore, the Hazen color was as good as 10. Also P in BG
The DO content was 0.40% by weight. The recovered dimethyl terephthalate also has a recovery rate of 90%, and the content of acetone is 0.0.
9% by weight, acrolein content is 0.05% by weight, THF
Content is 0.03% by weight, BTD content is 0% by weight and BH
The P content was 0.05% by weight. Furthermore, the b value is 0.8,
The acid value was as good as 0.01.

[0053]

Comparative Example 1 The same operation as in Example 1 was carried out except that 2N sulfuric acid was added so as to have a pH of 2 instead of adding sodium carbonate. The recovery rate of PDO was as bad as 76%, and the content of acetone was 1.83% by weight.
The acrolein content is 1.88 wt% and the THF content is 1.
The content was 32% by weight, the BTD content was 0.15% by weight, the BHP content was 1.90% by weight, and the Hazen color was 45, showing remarkable coloring. In addition, the collection rate of BG is as bad as 75%,
Acetone content 1.33% by weight, acrolein content 0.81% by weight, THF content 1.96% by weight, BTD
The content was 0.15% by weight, the BHP content was 2.30% by weight, and the Hazen color was 35, which was a remarkable coloring. Furthermore, dimethyl terephthalate also has a recovery rate of 75%, an acetone content of 1.41% by weight, and an acrolein content of 1.23.
% By weight, THF content 1.10% by weight, BTD content 0.12% by weight, BHP content 1.32% by weight, b value was 14 and colored yellow, and acid value was as high as 0.07. .

[0054]

Comparative Example 2 The same operation as in Example 1 was carried out except that 2N sulfuric acid was added so as to have a pH of 2 instead of adding sodium carbonate. The recovery rate of PDO was as bad as 76%, and the content of acetone was 1.99% by weight.
The acrolein content is 2.43% by weight and the THF content is 1.
The content was 40% by weight, the BTD content was 0.21% by weight, the BHP content was 1.77% by weight, and the Hazen color was 45, showing remarkable coloring. In addition, the collection rate of BG is as bad as 77%,
Acetone content 1.42% by weight, acrolein content 0.99% by weight, THF content 1.81% by weight, BTD
The content was 0.19% by weight, the BHP content was 2.55% by weight, and the Hazen color was 35, which was a remarkable coloring. Furthermore, the recovery of dimethyl terephthalate was 73%, the acetone content was 1.55% by weight, and the acrolein content was 1.27.
%, THF content was 1.31% by weight, BTD content was 0.20% by weight, BHP content was 2.11% by weight, b value was 15 and colored yellow, and acid value was as high as 0.28. .

[0055]

Example 4 In Example 3, when isolating PDO and dimethyl terephthalate, 6.0 g of 20% by weight aqueous sodium sulfite solution (sodium sulfite: 0.01 mol) was added to each of the liquid layer and the solid layer. After the addition, vacuum distillation was carried out in the same manner as in Example 3. The recovery rate of PDO was 89%, the content of acetone was 0.02% by weight, and the content of acrolein was 0.
The content was 03% by weight, the THF content was 0.02% by weight, the BTD content was 0% by weight, and the BHP content was 0.02% by weight.
Furthermore, the Hazen color was as good as 5. Also B in PDO
The G content was 0.09% by weight. On the other hand, the recovery rate of BG is 90%, the content of acetone is 0% by weight, the content of acrolein is 0% by weight, the content of THF is 0.02% by weight, and the content of BT is BT.
The D content was 0.02% by weight and the BHP content was 0.04% by weight. Furthermore, the Hazen color was as good as 5. The PDO content in BG was 0.27% by weight. The recovered dimethyl terephthalate also had a recovery rate of 92%, an acetone content of 0% by weight, an acrolein content of 0% by weight, a THF content of 0% by weight, a BTD content of 0% by weight and a BHP content of 0.03% by weight. It was Furthermore, the b value was 0.2 and the acid value was 0.01, which were good.

[0056]

[Reference Example] Commercially available dimethyl terephthalate 194 g, also commercially available PDO (acrolein content 0.01% by weight, B
HP content 0.02% by weight) 160 g, calcium acetate 9
7 mg was charged into a polymerization kettle and the transesterification reaction was performed at 243 ° C. for 7 hours. Thereafter, 97 mg of titanium tetrabutoxide and 80 mg of trimethyl phosphate were added, and then polycondensation reaction was carried out at 270 ° C. for 3 hours under a vacuum of 0.1 torr. The intrinsic viscosity of the obtained PTT polymer was 0.82. The L value was 85 and the b value was 4.

[0057]

Example 5 Using dimethyl terephthalate recovered in Example 4 and PDO recovered in Example 4, the same polymerization reaction as in Reference Example was performed. As a result, the transesterification reaction and polycondensation reaction time were almost the same as those in Reference Example, and the obtained polymer was also very good with an intrinsic viscosity of 0.85, an L value of 87 and ab value of 2.3. Further, the repolymerized PTT obtained in Example 5 was dried, extruded at 275 ° C., and then stretched so that the elongation was 40% to prepare fibers of 55 dtex / 24f. The strength of this fiber was 3.5 cN / dtex, the elastic modulus was 22 cN / dtex, and the recovery rate after 20% elongation was 84%. A tubular knitted fabric was created using this yarn. The obtained tubular knitted fabric had a very soft texture and had stretchability.

[0058]

Comparative Example 3 Using dimethyl terephthalate recovered in Comparative Example 1 and PDO recovered in Comparative Example 1, a polymerization reaction was carried out in the same manner as in Reference Example. As a result, the color of the obtained polymer was brown with an L value of 83 and ab value of 17.

Comparative Example 4 A polymerization reaction was carried out in the same manner as in Reference Example using dimethyl terephthalate recovered in Comparative Example 3 and PDO recovered in Comparative Example 2. As a result, the color of the obtained polymer was remarkably colored with an L value of 79 and ab value of 20.

[0059]

[Example 6, Comparative Examples 5 and 6] The tubular knitted fabrics obtained in Example 5 and the tubular knitted fabrics of Comparative Examples 3 to 4 obtained in the same manner as in Example 5 were dyed, and their color developability was examined. An evaluation was made. The results are shown in Table 1. The dyed product of Example 6 was very bright and was dyed in dark blue, while Comparative Examples 5 and 6 dyed only a dull purple color.

[0060]

[Table 1]

[0061]

Example 7 The PT of Example 3 with an intrinsic viscosity of 0.9
130g T-tip and PBT tip 1 with an intrinsic viscosity of 0.6
Instead of 4 g (PTT / PBT weight ratio: 90/10), PBT was used for the front and back two-layer knitted fabric, and 144 g of a three-dimensional knitted fabric using a PTT monofilament as a connecting yarn for connecting the two-layered knitted fabric was used. Except for this, the same operation as in Example 3 was performed. The recovery rate of PDO is 85%, and the content of acetone is 0.
21% by weight, acrolein content 0.18% by weight, TH
F content is 0.07% by weight, BTD content is 0% by weight and B
The HP content was 0.14% by weight. Furthermore, the Hazen color was as good as 10. BG content in PDO is 0.2
It was 5% by weight. On the other hand, the recovery rate of BG is 88%,
Acetone content 0.17% by weight, acrolein content 0.11% by weight, THF content 0.12% by weight, BTD
Content is 0.05% by weight and BHP content is 0.21% by weight
Met. Furthermore, the Hazen color was as good as 10. The PDO content in BG was 0.18% by weight. The recovered dimethyl terephthalate also has a recovery rate of 88%, the content of acetone is 0% by weight, the content of acrolein is 0.05% by weight, T
The HF content was 0.05% by weight, the BTD content was 0% by weight and the BHP content was 0.17% by weight. Furthermore, the b value is 2.
The acid value was 0, which was as good as 0.03. The three-dimensional fabric is
Before being subjected to depolymerization, it was cut into about 3 cm square.

[0062]

Example 8 In Example 3, a PT with an intrinsic viscosity of 0.9
130g T-tip and PBT tip 1 with an intrinsic viscosity of 0.6
Instead of 4 g (PTT / PBT weight ratio: 90/10), the same operation as in Example 1 was performed, except that an artificial leather 144 g having a surface of PBT and a base fabric of PTT fiber was used. It was Recovery rate of PDO is 87%, content of acetone is 0.19% by weight, acrolein content is 0.12% by weight, THF content is 0.06% by weight, BTD content is 0% by weight and BHP content is 0.12% by weight. %Met. Furthermore, the Hazen color was as good as 10. The BG content in PDO was 0.25% by weight. On the other hand, the recovery rate of BG is 88.
%, The acetone content is 0.15% by weight, the acrolein content is 0.06% by weight, the THF content is 0.05% by weight, the BTD content is 0.05% by weight and the BHP content is 0.
It was 14% by weight. Furthermore, the Hazen color was as good as 5. The PDO content in BG was 0.21% by weight. The recovered dimethyl terephthalate also has a recovery rate of 88%, an acetone content of 0% by weight, an acrolein content of 0% by weight, a THF content of 0.04% by weight, and a BTD content of 0.0%.
2% by weight and BHP content was 0.16% by weight. Further, the b value was 1.8 and the acid value was 0.03, which were good. still,
The artificial leather was cut into about 3 cm squares before being subjected to depolymerization.

[0063]

EFFECTS OF THE INVENTION It is an object of the present invention to establish a technique for recovering an ester-forming monomer obtained by depolymerizing a resin mixture composed of PTT and PBT in a high yield without fractionation. Further, it is possible to provide a high-purity depolymerized monomer and a method for producing the depolymerized monomer, which can obtain a polymer having the same quality as when an unused monomer is used even if the depolymerized monomer is used again for polymer production. Large amounts of waste, such as automobile engine peripherals, automobile hoods, automobile bumpers, automobile fenders,
Reuse for polymer production from waste such as car seats, exterior of electric appliances, clothing, artificial leather, three-dimensional knit, toothbrush, polishing brush, chair stick, tennis gut, fishing line, fish net, artificial lawn, or broken pieces of these By providing a possible high-purity depolymerized monomer and a method for producing the same,
I was able to contribute to the completion of closed loop recycling and the construction of a sustainable recycling-based social system.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C07C 31/20 C07C 31/20 Z 69/82 69/82 A C08J 11/10 ZAB C08J 11/10 ZAB / / C07B 61/00 300 C07B 61/00 300 C08L 65:00 C08L 65:00 F Term (Reference) 4D076 AA07 AA16 AA22 BB04 EA12Y EA14Y GA03 GA10 HA03 JA02 4F301 AA25 CA09 CA23 CA41 CA51 CA72 CA73 4H006 AC91 BA41 AC41 BC41 AC41 BA41 AC41 BC52 BD70 BJ50 FE11 FG26 FG28 4H039 CA60 CA66 CE10

Claims (17)

[Claims] 1. An ester-forming monomer obtained by depolymerizing a resin mixture consisting of poly (trimethylene terephthalate) and poly (butylene terephthalate), having an acetone content of 1.0% by weight or less and an acrolein content of 0.5% by weight. % Or less, tetrahydrofuran content is 1.0% by weight or less, 1,3-butadiene content is 0.10% by weight or less, and bis (3-hydroxypropyl) ether content is 1.0% or less.
An ester-forming monomer, characterized in that it is contained by weight or less. 2. An ester-forming monomer obtained by depolymerizing a resin mixture comprising polytrimethylene terephthalate, polybutylene terephthalate and other resin compositions, wherein the content of acetone is 0.3% by weight or less, and acrolein is used. Content of 0.2 wt% or less, tetrahydrofuran content of 0.5 wt% or less, 1,3-butadiene content of 0.03 wt% or less and bis (3-hydroxypropyl) ether content of 0.3 wt% or less. An ester-forming monomer characterized by being present. 3. An ester-forming monomer obtained by depolymerizing a resin mixture comprising polytrimethylene terephthalate and polybutylene terephthalate, which has an acetone content of 0.05% by weight or less and an acrolein content of 0.0.
5% by weight or less, a tetrahydrofuran content of 0.05% by weight or less, a 1,3-butadiene content of 0.01% by weight or less, and a bis (3-hydroxypropyl) ether content of 0.05% by weight or less. An ester-forming monomer that 4. The ester-forming monomer is at least one selected from dialkyl terephthalate, 1,3-propanediol and 1,4-butanediol. The ester-forming monomer as described in 1. 5. The ester-forming monomer according to claim 4, wherein the b value of dialkyl terephthalate is 2 or less. 6. The acid value of dialkyl terephthalate is 0.0
It is 5 or less, The ester forming monomer of Claim 4 characterized by the above-mentioned. 7. The ester-forming monomer according to claim 4, wherein the content of 1,4-butanediol in 1,3-propanediol is 1.0% by weight or less. 8. The ester-forming monomer according to claim 4, wherein the Hazen color of 1,3-propanediol is 20 or less. 9. The ester-forming monomer according to claim 4, wherein the 1,3-propanediol content of 1,4-butanediol is 1.0% by weight or less. 10. The ester-forming monomer according to claim 4, wherein the Hazen color of 1,4-butanediol is 20 or less. 11. A resin mixture composed of polytrimethylene terephthalate, polybutylene terephthalate and other resin compositions is reacted with glycol to once obtain bis (3-hydroxypropyl) terephthalate and bis (4-hydroxybutyl) terephthalate. After being produced, the bis (3-hydroxypropyl) terephthalate and bis (4-hydroxybutyl) terephthalate are reacted with a monoalcohol to produce a dialkyl terephthalate, 1,3-propanediol and 1,4-butanediol. The method for producing an ester-forming monomer, which comprises the following steps (1) to (3). (1) When a bis (3-hydroxypropyl) terephthalate and bis (4-hydroxybutyl) terephthalate that have been once produced are reacted with a monoalcohol, a basic substance is present (2) Separating the generated dialkyl terephthalate from the liquid containing 1,3-propanediol, 1,4-butanediol and monoalcohol (3) Dialkyl terephthalate, 1,3-propanediol and 1,4-butanediol Isolate has an acetone content of less than 1.0% by weight and an acrolein content of 0.5% by weight
Hereinafter, the tetrahydrofuran content is 1.0% by weight or less,
Distilling so that the 1,3-butadiene content is 0.10% by weight or less and the bis (3-hydroxypropyl) ether content is 1.0% by weight or less. 12. The method (2) for separating a dialkyl terephthalate from a liquid containing 1,3-propanediol, 1,4-butanediol and a monoalcohol is centrifugation. Process for producing ester-forming monomer. 13. The dialkyl terephthalate has an acetone content of 1.0% by weight or less, an acrolein content of 0.5% by weight or less, a tetrahydrofuran content of 1.0% by weight or less, and a 1,3-butadiene content of 0.10. Weight% or less and bis (3-hydroxypropyl) ether content of 1.0
The method (3) of distilling so as to be less than or equal to wt% is performed in the presence of a basic substance at 180 to 250 ° C. and 30 to 250 torr.
The method for producing an ester-forming monomer according to claim 11 or 12, wherein the method is a method of distilling with a solvent. 14. Acetone content of 1,3-propanediol is 1.0 wt% or less, acrolein content is 0.5 wt% or less, tetrahydrofuran content is 1.0 wt% or less, and 1,3-butadiene content is 0. 10% by weight or less and bis (3-hydroxypropyl) ether content of 1.0
The method of distilling so as to be less than or equal to wt% is 100-
The method for producing an ester-forming monomer according to claim 11 or 12, which is a method of distilling at 200 ° C and 50 to 200 torr. 15. The acetone content of 1,4-butanediol is 1.0 wt% or less, the acrolein content is 0.5 wt% or less, and the tetrahydrofuran content is 1.0 wt% or less.
The method of distilling so that the 1,3-butadiene content is 0.10% by weight or less and the bis (3-hydroxypropyl) ether content is 1.0% by weight or less is carried out in the presence of a basic substance at 100 to 200 ° C. The method for producing an ester-forming monomer according to claim 11 or 12, which is a method of distilling at 50 to 200 torr. 16. The method for producing an ester-forming monomer according to any one of claims 11 to 15, wherein sulfite salt is further present during the distillation. 17. A resin mixture comprising polytrimethylene terephthalate and polybutylene terephthalate is used as an engine peripheral component for automobiles, automobile hoods, automobile bumpers, automobile fenders, car seats, electric appliance exteriors, clothing, artificial leather, 17. A three-dimensional knit, a toothbrush, a polishing brush, a chair, a tennis gut, a fishing line, a fishnet, an artificial lawn, or at least one selected from a broken product thereof, according to any one of claims 11 to 16. A method for producing the ester-forming monomer described.