JP3444870B2 - Depolymerization method of polyethylene terephthalate - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for depolymerizing polyethylene terephthalate to be recycled. In the following, polyethylene terephthalate is abbreviated as “PET” and polyethylene terephthalate to be recycled is abbreviated as “R-PET”.

[0002]

2. Description of the Related Art Although a container and packaging recycling method is implemented, a method for obtaining an unsaturated polyester resin by using R-PET generated as a result of the container and packaging recycling method as a raw material is known.

In this method, glycol is generally charged in a reaction vessel, and R is added at a temperature below the boiling point of glycol.
-PET is added in portions to decompose glycol to form an oligomer, and then a desired amount of α-β unsaturated polybasic acid (or its acid anhydride) is added to carry out polycondensation to obtain an unsaturated alkyd and a crosslinking agent. A method of dissolving this in a styrene monomer that acts as is adopted.

The disadvantages of this method are that depolymerization requires time because the temperature cannot be raised above the boiling point of glycol, and in terms of mass ratio, glycol: R-PET =
Only about 1: 1 R-PET can be used and charged, and R-PE
That is, the addition ratio of T cannot be increased.
It is self-evident that the shorter the reaction time, the more advantageous in terms of cost, and the higher the ratio of R-PET used, the better from the viewpoint of waste material utilization and recycling.

[0005]

As a solution to this problem,
A method has been proposed in which R-PET is melted and a tin-based catalyst or a titanium-based catalyst is added in a necessary amount, and glycol is added dropwise therein to promote the decomposition of R-PET (Japanese Patent Laid-Open No. 2000-7770). Japanese Patent Laid-Open No. 11-60707
Japanese Patent Application No. 2000-248270). Further, in order to shorten the melting time of R-PET in the reaction container, it has been proposed to melt R-PET at a temperature equal to or higher than its melting point by using an extruder and then charge the reaction container. (Japanese Patent Application No. 2000-306218).

However, even in the above method, in order to keep the molten state of R-PET in the reaction vessel, it is necessary to keep the temperature of the reaction vessel above the melting point of R-PET, and the depolymerization reaction takes several hours. is necessary.

According to such a conventional method, for example, in order to prepare flaky R-PET in a reaction vessel and heat and melt it to obtain an oligomer having an average molecular weight of 3,000 or less, R-heat reaction is performed. -It needs 120 minutes or more at the melting point of PET or more, and 300 minutes or more for the depolymerization reaction.

Therefore, an object of the present invention is to enable depolymerization of R-PET in a short time.

[0009]

In order to achieve this object, the present inventors introduced R-PET into an extruder and applied shearing force at low speed while heating the cylinder to heat the input material. -It was found that a PET oligomer can be obtained by melting and kneading at the same time, and this heating, melting, and depolymerization reactions lead to the initial decomposition and depolymerization of R-PET molecular chains. As a result, the present invention has been completed.

That is, the present invention uses one or more extruders when heating and melting R-PET to perform depolymerization, or using an extruder and a reactor provided at the outlet of the extruder. To the extruder, in the depolymerization process
The type of glyco that is used as an ingredient in the final product
And tin such as dibutyltin oxide that facilitates depolymerization.
System catalyst or tetraisopropoxy titanate
Titanium-based catalyst is added simultaneously or separately,
Performs heating, melting and depolymerization reactions of R-PET at once
At the final extruder exit or reactor exit
Produce T as an oligomer with an average molecular weight of 3000 or less
It is characterized by being formed .

In this way, the average molecular weight of R-PET from, for example, waste PET bottle flakes, is 300.
It is possible to realize a great improvement in productivity and simplification of the process for producing an oligomer having a number of 0 or less. The obtained oligomer can be used for producing resins such as unsaturated polyester resin synthesized based on the molecular skeleton of PET.

That is, according to the present invention, one or more extruders having a desired discharge rate for heating and melting R-PET are used, or provided at the extruder and the outlet of the extruder. Using the reactor described above, the depolymerization reaction of R-PET is performed inside the extruder or the reactor while setting the heating condition of the cylinder in the range of 160 to 320 ° C. (desirably 220 to 280 ° C.), A PET oligomer is obtained. To prepare R-PET as an oligomer having an average molecular weight of 3000 or less by charging this PET oligomer as a raw material into another reaction vessel and adding additional glycols as necessary, the reaction in the extruder is 10 ~ 20 minutes,
Further depolymerization reaction in another reaction vessel is 60 minutes,
It is possible to achieve a significant reduction in time compared to the past. Furthermore, by advancing the depolymerization reaction in the extruder, or by additionally providing a reactor at the exit of the extruder,
It is also possible to omit the depolymerization reaction in another reaction vessel. In this case, the whole process can be further shortened, and the time for obtaining an oligomer having an average molecular weight of 3000 or less from R-PET is 30 to 40 minutes. Moreover, according to the present invention, the melting temperature of the PET oligomer in another reaction vessel can be lowered by about 100 ° C. as compared with the conventional method, and the high content of R-PET can be maintained. Further, since glycol is present, the efficiency of heat transfer to the raw material is good.

Further, according to the present invention, a tin catalyst mainly containing dibutyltin oxide or a titanium catalyst such as tetraisopropoxy titanate which facilitates depolymerization is added to the raw material supplied to the extruder.

Although melt reactive extrusion in an extruder has been conventionally used for urethane resins and the like, they are not aimed at depolymerization, but are a reprocessing method technique. It is not decomposed to be used as a raw material (Japanese Patent Laid-Open No. 8-300352 and Japanese Patent Laid-Open No. 2000-2).
No. 81831).

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION R-PET used in the present invention
Is a recycled product mainly from PET bottles and is generally in the form of flakes or pellets.

Further, when R-PET passes through the extruder while being heated, the water content does not adversely affect the decomposition of R-PET, and the presence of water is almost unrelated to the depolymerization of R-PET. Is. Therefore, it is not necessary to dry the R-PET.

The extruder used in the present invention may be a normal single-screw or twin-screw extruder or any other extruder as long as the raw materials can be uniformly heated and kneaded and a shearing force can be applied.

In the heating / melting / depolymerization reaction in the extruder,
R-PET melted in the extruder cylinder
For the purpose of facilitating depolymerization in the depolymerization step of R-PET, a tin-based catalyst mainly containing dibutyltin oxide or a titanium-based catalyst such as tetraisopropoxy titanate is added, and the final product is further added. Glycols of the type used as a component of can be added. These catalyst and glycol may be separately supplied to the extruder and added, or a mixture of R-PET to which a predetermined amount of the catalyst and glycol is added in advance and mixed may be introduced into the extruder. In the former case, the catalyst and glycol are metered in with respect to the extrusion rate per hour.

In order to accelerate the depolymerization reaction, a predetermined amount of glycol is added to the PET oligomer that has passed through the extruder, or a predetermined amount of glycol and a catalyst are added, and the mixture is passed through the extruder several times. Alternatively, a method in which a plurality of extruders are connected and passed through is also conceivable.

The extruder controls the reaction by controlling the heat in the cylinder to control the state of the extruded PET oligomer. The extruded PET oligomer may be put into another reaction container in a molten state, or may be solidified at room temperature and stored as a raw material.

When a reactor is provided at the outlet of the extruder, this reactor is tubular as long as it can be heated and the extruded PET oligomer flows in the reactor in a molten and agitated state. Any configuration can be used, such as If you use a static mixer to perform homogeneous heat decomposition, a better PET
An oligomer can be obtained.

Examples of the catalyst used in the present invention include tin-based catalysts such as dibutyltin oxide, tin octylate and dibutyltin dilaurate, and tetrabutoxy titanate (TB).
T), alkoxides of titanium such as tetraisopropoxy titanate (TPT), and tetraethoxy titanate, and organic acid salts of zinc mainly containing zinc acetate.

The amount used is 0.01 part by mass or more and 3 parts by mass or less, more preferably 0.1 part by mass or more and 1 part by mass or less, relative to 100 parts by mass of R-PET. Thus, when these decomposition catalysts are added to the heating / melting / depolymerization reaction in the extruder, the glycol decomposition of R-PET is significantly promoted.

The glycols used in the present invention include, for example, the following types. That is, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 2-
Methyl propane diol, 1,3 butane diol, 1,
4-butanediol, 3-methylpentanediol, 1,
2-butanediol, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, bisphenol A propylene oxide adduct and the like can be mentioned. It is also possible to use a polyhydric alcohol having three or more functional groups such as polyethylene glycol, polypropylene glycol, glycerin, trimethylethane, trimethylpropane and pentaerythritol. Can be used together.

The amount used is 0.1 mol or more and 10 mol or less with respect to 1 mol of the condensation unit of R-PET (1 mol of the repeating unit). In this case, a desired amount of glycol may be added in the extruder and the product may be further depolymerized in another reaction vessel. Alternatively, the depolymerization reaction in another reaction vessel may be omitted by adding a necessary amount in the extruder.

When producing a resin such as an unsaturated polyester resin according to the present invention, one or a plurality of extruders are used, or an extruder and a reactor provided at the outlet of this extruder are used. Then, heat and melt R-PET
A depolymerization reaction is performed to obtain an oligomer having an average molecular weight of 3000 or less. Then, in the case of producing the above-mentioned unsaturated polyester resin, the PET oligomer as the product is used as a raw material, or a desired amount of glycol is added to the oligomer in a separate reaction vessel to further carry out a depolymerization reaction. Then, polycondensation is performed by adding α-β unsaturated polybasic acid (or its acid anhydride) and, if necessary, other saturated or unsaturated polybasic acid (or its acid anhydride) together. I do.

When the unsaturated polyester resin is produced, maleic anhydride or fumaric acid can be generally used as the α-β unsaturated polybasic acid (or its acid anhydride). The use of other saturated or unsaturated polybasic acid (or its acid anhydride) is free. After the polycondensation is completed by adding one or more kinds of α-β unsaturated acids or acid anhydrides thereof, the unsaturated polyester resin is obtained by dissolving the polycondensation in a desired monomer.

The monomer is generally styrene. In addition, methyl methacrylate, diallyl phthalate and the like can be used depending on the application. R
-The proportions of PET, glycol, and unsaturated acid used vary depending on the application, but R-PET is generally 10 to 80 mol (%), glycol 20 to 90 mol (%), and unsaturated acid 1
It is 0 to 80 mol (%).

The number of moles of PET is calculated assuming that the structure of the following formula is 1 mole.

[0030]

[Chemical 1] The unsaturated polyester resin thus obtained is useful for various applications, but various additives depending on practical use,
For example, it is needless to say that a thermoplastic polymer or oligomer, a colorant, a release agent, a stabilizer and the like can be used.

Incidentally, according to the present invention, it is also possible to manufacture a resin other than the unsaturated polyester resin as described above.

[0032]

[Example 1]

  Extruder: S-1 manufactured by Kurimoto Iron Works Co., Ltd.               Different direction twin screw extruder   Extruder temperature: 220 ° C to 280 ° C   Material: Waste PET bottle flake (R-PET): Yono PET bottle                 Cycle Co., Ltd.               Propylene glycol               Catalyst: dibutyltin oxide

Method (1) The extruder was heated to a predetermined temperature and R-PET was fed with a material to which propylene glycol and dibutyltin oxide were previously added.

(2) The molten R-PET, which had undergone the depolymerization reaction by passing through the extruder, solidified at room temperature.
When the molecular weight and melting point of the solidified product were measured after each addition, both decreased as shown in the table below with each addition.

[0035]

[Table 1]

(3) Subsequently, an unsaturated polyester resin was synthesized by using the obtained PET oligomer PET oligomer e in Table 1 as a raw material. In detail, 200 g of PET oligomer e) and 30 g of propylene glycol were charged into a 1 L separable flask equipped with a stirrer, a return condenser, a dropping funnel, and a thermometer with a gas introduction tube, and the mixture was heated at 210 to 220 ° C. in a nitrogen stream at 1 Glycolysis was performed for an hour. Then, the average molecular weight is approximately 600-8.
It dropped to 00. Furthermore, the condenser was changed to a fractional distillation type, the temperature was lowered to 210 ° C, and maleic anhydride 130 was added.
After adding g and performing esterification for 2 hours, about 30 To
The polycondensation reaction was performed for 1 hour under reduced pressure of rr. Then, when the acid value was 31, 0.17 g of hydroquinone was added, and 338 g of styrene was added under a stream of air at a temperature of 140 ° C. to uniformly dissolve the styrene. As a result, a light yellowish brown liquid unsaturated polyester resin was obtained.

(4) Also, using the same device, PET
Oligomer e) 200 g, propylene glycol 30 g
Then, 130 g of maleic anhydride was charged, esterification was carried out at 210 ° C. for 2 hours in a nitrogen stream without additional glycol decomposition, and then polycondensation reaction was carried out for 1 hour under reduced pressure of about 30 Torr. And hydroquinone 0.17
g, styrene 338 at a temperature of 140 ° C under an air stream
g was added and the mixture was uniformly dissolved. As a result, a slightly opaque light yellowish brown liquid unsaturated polyester resin was obtained.

[0038] [Example 2]   Extruder: SRV-P40 / 30 manufactured by Nippon Oil Machine Co., Ltd.               Single screw extruder L / D = 22   Extruder temperature: 220 ° C to 280 ° C   Material: Waste PET bottle flake (R-PET): Yono PET bottle                 Cycle Co., Ltd.               Propylene glycol               Catalyst: dibutyltin oxide

Method (1) The extruder was brought to a predetermined temperature and the raw materials having the above contents were supplied.

(2) Molten R-PET that passed through the extruder
Solidified at room temperature. When the molecular weight and the melting point of the solidified product were measured after each addition, both decreased as shown in the table below with each addition.

[0041]

[Table 2]

[0042] [Example 3]   Extruder: PMT47-III manufactured by IK G Co., Ltd.               Twin screw extruder L / D = 30   Extruder temperature: 220 ° C to 280 ° C   Material: Waste PET bottle flake (R-PET): Yono PET bottle                 Cycle Co., Ltd.               Propylene glycol               Catalyst: dibutyltin oxide, tetraisopropoxy titanate

Method (1) The extruder was brought to a predetermined temperature and the raw materials having the above contents were supplied.

(2) Regarding the content of addition, 0.3% by mass of the catalyst was added to R-PET in advance, and 50% by mass of propylene glycol was quantitatively supplied from the middle of the extruder using a metering pump. (3) The molten R-PET that passed through the extruder was white solidified at room temperature. The molecular weight and melting point of the solidified product were measured and the results are shown in the table below.

[0045]

[Table 3] (4) The obtained PET oligomer (PET oligomer b in Table 3), propylene glycol and maleic anhydride were charged at the same time, and esterification was performed at 210 ° C. for 2 hours in a nitrogen stream, and then under reduced pressure of about 30 Torr. The polycondensation reaction was performed for 1 hour. Further, hydroquinone was added, and styrene was added under a stream of air at a temperature of 140 ° C. to uniformly dissolve it. As a result, a slightly turbid pale yellowish brown liquid unsaturated polyester resin was obtained.

[0046] [Example 4]   Extruder: KZW15 manufactured by Techno Bell Co., Ltd., same-direction twin-screw extruder L / D = 75   Reactor: Static mixer manufactured by Noritake Company   Temperature condition: 220 ° C-280 ° C   Material: Waste PET bottle flake (R-PET): Chukyo cargo handling PET Made by Le Recycle Factory               Propylene glycol               Catalyst: dibutyltin oxide

Method (1) The extruder is heated to a predetermined temperature and R-
0.3% by mass of the catalyst was added to PET in advance, and 50% by mass of propylene glycol was quantitatively supplied from the middle of the extruder cylinder using a metering pump.

(2) A static mixer heated to a predetermined temperature is installed at the exit of the extruder, and the molten R that has passed through the extruder
-Passed through PET. (3) As a result, a PET oligomer in a slurry form was obtained. The average molecular weight at that time was 600 to 800.

(4) Then, an unsaturated polyester resin was synthesized using the obtained PET oligomer as a raw material. That is, PET oligomer and maleic anhydride were charged at the same time, esterification was carried out at 210 ° C. for 2 hours in a nitrogen stream, and then polycondensation reaction was carried out for 1 hour under reduced pressure of about 30 Torr. Further, hydroquinone was added, and styrene was added under a stream of air at a temperature of 140 ° C. to uniformly dissolve the product, and as a result, a light yellowish brown liquid unsaturated polyester resin was obtained.

[0050] [Example 5]   Extruder: KZW15 manufactured by Techno Bell Co., Ltd., same-direction twin-screw extruder L / D = 75   Tube type reactor: Steel tube (filling one section with lashing ring)   Temperature condition: 220 ° C-280 ° C   Material: Waste PET bottle flake (R-PET): Chukyo cargo handling PET Made by Le Recycle Factory               Propylene glycol               Catalyst: dibutyltin oxide

Method (1) The extruder was brought to a predetermined temperature, 0.3% by mass of the catalyst was added to R-PET in advance, and 50% by mass of propylene glycol was quantitatively supplied from the middle of the extruder cylinder using a metering pump. .

(2) A steel pipe (tubular reactor) heated to a predetermined temperature is installed at the exit of the extruder, and molten R- which has passed through the extruder
Passed through PET. (3) As a result, a PET oligomer in a slurry form was obtained. The average molecular weight at that time was 600 to 800.

As described above, heating, melting, and depolymerization of R-PET are carried out by using one or a plurality of extruders or by using an extruder and a reactor provided at the exit of this extruder. The reaction is carried out all at once, and the P having an average molecular weight of 3000 or less is
The ET oligomer could be obtained efficiently. Further, by using it as a raw material, it was possible to realize a great improvement in productivity and simplification of the entire process of producing an unsaturated polyester resin and other resins from waste PET bottle flakes.

[0054]

As described above, according to the present invention, R-PE
In order to produce unsaturated polyester resin and other resins using T, when P-RET is heated and melted to perform depolymerization, one or more extruders are used in the depolymerization step of P-RET. By using or by using an extruder and a reactor provided at the exit of this extruder, heating, melting, and depolymerization reactions of R-PET are carried out at once.
PET at the final extruder exit or reactor exit
Generated as an oligomer with an average molecular weight of 3000 or less
Therefore, to realize, for example, from waste PET bottles flakes as R-PET, a significant productivity improvement and process simplification for the entire process for producing an unsaturated polyester resin and other resins to based on the molecular skeleton of PET You can

Front Page Continuation (72) Inventor Yasuhiro Iguchi 2-26 Ohamacho Amagasaki City Hyogo Prefecture Kubota Mukogawa Works (72) Inventor Enbu Yoshimura 4-115-304 Hashimoto, Sagamihara City, Kanagawa Prefecture (72) Inventor Otsuka Shin-ichi 5-1-9 Harajuku, Shiroyama-cho, Tsukui-gun, Kanagawa (56) Reference JP 2002-249557 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08J 11/00-11 / 28 C08G 63/00-63/91

Claims (3)

(57) [Claims] 1. When heating and melting polyethylene terephthalate to be recycled for depolymerization, one or more extruders are used, or an extruder and a reactor provided at the outlet of the extruder. use the door, the press
Used as a component of the final product in the depolymerization process
Types of glycol and dibutyrate that facilitate depolymerization
Ru-based catalysts such as tin oxide or tetraisopropoxide
Simultaneously with titanium-based catalysts such as xytitanate
Are added separately, and the heating, melting, and depolymerization reactions of polyethylene terephthalate to be recycled are carried out at the same time, and the final exit of the extruder or the exit of the reactor
And polyethylene terephthalate with an average molecular weight of 30
A method for depolymerizing polyethylene terephthalate, characterized in that it is produced as an oligomer of 00 or less . 2. The repeating unit of polyethylene terephthalate is 1 mol, the addition amount of glycol is 0.1 mol or more and 10 mol or less relative to 1 mol of the condensation unit of polyethylene terephthalate, and the addition amount of the catalyst is
The method for depolymerizing polyethylene terephthalate according to claim 1, wherein the amount is 0.01 part by mass or more and 3 parts by mass or less based on 100 parts by mass of the polyethylene terephthalate used. 3. A polyethylene terephthalate oligomer obtained by the method according to claim 1 or 2 as a raw material, or after adding a required amount of glycol to this oligomer to further decompose the α-β unsaturated polyunsaturated product. Addition of a basic acid or an acid anhydride thereof, and optionally, in combination with another saturated or unsaturated polybasic acid or an acid anhydride thereof, polycondensation is carried out to produce an unsaturated polyester resin. Method.