CN111499845A - Adipic acid copolyester and preparation method thereof - Google Patents

Abstract

The invention provides an adipic acid copolyester and a preparation method thereof, and the prepared adipic acid copolyester product has a stable a value under the condition of thermal oxygen. The invention provides a preparation method of adipic acid copolyester, wherein the adipic acid copolyester is prepared by reacting raw materials comprising dibasic acid A and dibasic acid B, C2-C12 dihydric alcohol, the dibasic acid A is adipic acid, the dibasic acid B is aromatic dibasic acid or one or more of anhydride or esterified derivatives thereof, and reducing organic matters are added into a reaction system after the adipic acid is added into the reaction system and before the reaction temperature is increased to be higher than 200 ℃.

Description

Adipic acid copolyester and preparation method thereof

Technical Field

The invention belongs to the field of polyester synthesis, and particularly relates to copolyester and a preparation method thereof.

Background

With the development of the plastic industry, synthetic polymer materials play an extremely important role in various fields of industrial and agricultural production and daily life. But many traditional plastics are not degradable after being discarded, which brings serious pollution to social life. The search for a novel degradable plastic which is environment-friendly and can replace the performance of the traditional plastic causes the attention of the vast scientists. In recent years, degradable polyesters have become hot spots of research at home and abroad due to their degradation characteristics and economical efficiency. The traditional polyester such as PET and PBT uses aromatic dibasic acid, which is slowly degraded in natural condition and replaced by aliphatic dibasic acid such as adipic acid, succinic acid, etc., thus greatly improving the degradation rate and obtaining the degradable polyester. Among them, polybutylene terephthalate-adipate (PBAT) is the most commercially valuable.

PBAT is a copolyester of butylene adipate and butylene terephthalate, and has the characteristics of both PBA and PBT. The PBAT contains flexible aliphatic chains and rigid aromatic chains, thus has high toughness and high temperature resistance, and the PBAT simultaneously has biodegradability due to the existence of adipate bonds, so the PBAT is one of the most active biodegradable materials in the research of the biodegradable plastics and the best degradable materials in the market.

Meanwhile, adipic acid is introduced, so that new problems are caused to the production process and products. One of the problems is the color of the product. GB/T32366 states that the a value of PBAT products is less than or equal to 5, whereas even PBAT resin particles with an a value of 3 still have a macroscopic red colour, so that it is necessary to reduce the a value of the product even further.

Further studies have found that the PBAT products tend to be reddish under the processing conditions, in particular, above 200 ℃ and under air exposure, the redness is further deepened. Above 200 c, the conditions of contact with air are difficult to avoid. One of the reasons is that, in the chain extension method, which is one of the PBAT synthesis methods, PBAT resin particles with a relatively low molecular weight and a chain extender are required to be reacted and extruded together in a screw extruder to obtain a final product with a high molecular weight, and the temperature in the screw extruder is usually 200 ℃ or higher, and air cannot be completely isolated. The other reason is that before the PBAT resin is applied, a modifier is often needed to be added, and blending modification is carried out in a screw extruder, for example, in CN1071342C example 14, PBAT resin particles and starch are blended and modified at the temperature of 220 ℃ at most. The third reason is that when the PBAT is made into a final product, the PBAT modified material is often extruded by a screw extruder and then subjected to processing means such as film blowing. In order to improve the color of PBAT products, it is necessary to develop a PBAT product that is stable to a-values under hot oxygen conditions.

Disclosure of Invention

The invention aims to provide a preparation method of adipic acid copolyester with stable a value under the condition of hot oxygen and an adipic acid copolyester product prepared by the preparation method.

In order to achieve the purpose of the invention, the following technical scheme is provided:

the invention provides a preparation method of adipic acid copolyester, wherein the adipic acid copolyester is prepared by reacting raw materials comprising dibasic acid A and dibasic acid B, C2-C12 dihydric alcohol, the dibasic acid A is adipic acid, the dibasic acid B is aromatic dibasic acid or one or more of anhydride or esterified derivatives thereof, and reducing organic matters are added into a reaction system after the adipic acid is added into the reaction system and before the reaction temperature is increased to more than 200 ℃.

In a preferred embodiment, the reducing organic is selected from glucose and/or glyoxylic acid.

In some embodiments, the reducing organic is added in an amount of 0.005 to 0.5 wt% (e.g., 0.005 wt%, 0.05 wt%, 0.10 wt%, 0.15 wt%, 0.50 wt%, etc.) based on 100 wt% of theoretical yield of the adipic copolyester.

In some embodiments, the adipic copolyester is produced with 2 to 50ppm of elemental iron.

The core of the invention is to find out the reason of the increased a value in synthesis and processing and adopt a corresponding inhibition scheme.

In a study of reddening of an adipic copolyester such as PBAT, the present inventors first identified that reddening requires 3 factors in combination: adipic acid, temperature, oxygen. When no adipic acid or derivatives thereof are contained in the starting material, i.e. no adipated residues are contained in the product, or the product is not at high temperature (e.g. above 200 ℃), or the product is exposed to high temperature but not to oxygen, no significant reddening of the PBAT resin occurs. Further studies have found that this conclusion applies to all polyester resins containing adipate esterified residue structures, and the relationship with aromatic dibasic acid esterified residues and dibasic alcohol esterified residues is not obvious.

However, when considering only the above 3 factors, the method of increasing the airtightness and vacuum degree of the reaction vessel to isolate oxygen is adopted, and after obtaining PBAT product with a value a of 3 or less under small test conditions, it is found that the product produced by scale-up under the same conditions of airtightness and vacuum degree has a value a of 5 or more after heating the sample bar in hot air at 200 ℃ for 1 hour although the value a of 3 or less, and the sample bar has no such problem, the inventors of the present application have found that the influence of the iron element is the main cause through detailed analysis of the raw materials and the product, although the iron content in the raw materials is 1ppm, since adipic acid and aromatic dibasic acid such as terephthalic acid have a certain acidity, the iron element content in the product increases under high temperature reaction conditions, the increase of the value a of the product is significant even though the trace amount of the iron element has a value in the product under hot oxygen conditions, the small test equipment has a certain influence on the increase of the iron element due to the material (HAC or 316L) and corrosion resistance is superior to that the scale-up equipment (304, the corrosion resistance is partially superior to scale-up the product) under hot oxygen condition, and thus the increase of the product is achieved by 2ppm, and the heat addition of the co-polymerization of the co-polyester product, and the co-heating process can be optimized at 50 ppm.

Based on the newly discovered influencing factors, the inventor determines a targeted solution through a plurality of times of experimental exploration, and the core of the method is to add a reducing organic matter in the polymerization reaction process, wherein the adding time is to increase the reaction temperature to be higher than 200 ℃ after adipic acid is introduced into a reaction system; the dosage of the reducing organic matter is 0.005-0.5 wt%. And when the used reducing organic matter is glucose and/or glyoxylic acid, the oxidation products of the glucose acid and the glyoxylic acid are polyfunctional compounds, can participate in esterification reaction and enter the adipic acid copolyester product, and do not form micromolecule residues in the product. Therefore, both are listed as preferred reducing organics.

The preparation method provided by the invention has the main process requirements that after the adipic acid is added into the reaction system and before the reaction temperature is increased to be higher than 200 ℃, the reducing organic matter is added into the reaction system. On the premise, the remaining process requirements can refer to the conventional technology for preparing adipic acid copolyester products based on adipic acid in the field, specific process step arrangements, raw material addition sequences, raw material addition modes, raw material using amounts and the like, and can be selected and determined by the skilled person according to the conventional technology mastered by the skilled person, and the method is not particularly limited.

In some embodiments, the dibasic acid B is one or more of phthalic acid, isophthalic acid, terephthalic acid, phthalic anhydride, preferably terephthalic acid; the C2-C12 diol is preferably 1, 4-butanediol, and the adipic acid copolyester is preferably polybutylene terephthalate-adipate (PBAT).

In some embodiments, the molar ratio of the sum of the moles of adipic acid and diacid B to the moles of C2-C12 diol is 1:1.4 to 1: 3. The molar percentage of the adipic acid is 35-95 mol% and the molar percentage of the dibasic acid B is 5-65 mol% based on the total molar number of the adipic acid and the dibasic acid B being 100 mol%.

In some embodiments, the method of making is carried out using any of the following schemes one, two, three, or four (all pressures involved in schemes one through four are absolute pressures), wherein,

the first scheme comprises the following steps:

1.1) putting the dibasic acid B and the C2-C12 dihydric alcohol into a reaction kettle, and heating to 220-240 ℃ for reaction until the conversion rate is more than 90%;

1.2) controlling the temperature of the reaction kettle to be 180-200 ℃, putting the adipic acid into the reaction kettle, and continuing to react at 180-200 ℃ until the conversion rate is more than 90%;

1.3) feeding the reducing organic matter, and reducing the pressure in the reaction kettle to be lower than 5 kPa;

1.4) heating to 230-280 ℃, reducing the pressure in the reaction kettle to be less than 133Pa, and continuously reacting to obtain an adipic acid copolyester product;

in the first scheme, the ratio of the total acid (i.e., diacid B and adipic acid): the amount of the C2-C12 diol added in each step can be flexibly adjusted according to the production requirements under the condition of the molar ratio of the C2-C12 diol, for example, the required amount of the C2-C12 diol is added in the step 1.1) in whole, or the C2-C12 diol is added in two parts in the steps 1.1) and 1.2) respectively, and the C2-C12 diol is added in the step 1.1) in excess relative to the mole number of the diacid B. Such addition of the C2-C12 diol is conventional in the art, and one skilled in the art may choose to add all of the C2-C12 diol in the first step, so that additional additions are not required in subsequent steps. It is also possible to add only a portion, for example half the amount of alcohol, in the first step and the remainder in step 2.2). It is usually satisfied that the C2-C12 diol is added in the first step in a molar excess (i.e., in excess) relative to the diacid B, and whether or not the second step is supplemented, the amount of the additional diol is not particularly limited. The following scheme two can also be operated in this way, and details are not described later.

The reaction system of the first scheme is also added with a catalyst, and the catalyst is completely added in the step 1.1), or the catalyst is added in two parts respectively in the step 1.1) and the step 1.3).

The second scheme comprises the following steps:

2.1) putting the adipic acid and the dihydric alcohol C2-C12 into a reaction kettle, and heating to 160-200 ℃ for reaction until the conversion rate is more than 90%;

2.2) adding the reducing organic matter, adding the dibasic acid B into a reaction kettle, and continuing to react at the temperature of 200-240 ℃ until the conversion rate is more than 90 percent;

2.3) reducing the pressure in the reaction kettle to be below 5 kPa;

2.4) heating to 230-280 ℃, reducing the pressure in the reaction kettle to be less than 133Pa, and continuously reacting to obtain an adipic acid copolyester product;

in the second variant, the desired amount of the C2-C12 diol is added in step 2.1) in its entirety, or in two portions to steps 2.1) and 2.2) respectively and in step 2.1) an excess of the C2-C12 diol relative to the moles of adipic acid is added;

adding a catalyst into the reaction system of the second scheme, wherein the catalyst is completely added in the step 2.1), or the catalyst is added in two parts respectively in the step 2.1) and the step 2.3);

the third scheme comprises the following steps:

3.1) putting the dibasic acid B, the adipic acid and the C2-C12 dihydric alcohol into a reaction kettle, and heating to 160-200 ℃ for reaction until the conversion rate is more than 50%;

3.2) adding the reducing organic matter, then heating to more than 200 ℃ and less than or equal to 240 ℃, and continuing the reaction until the conversion rate is more than 90%;

3.3) reducing the pressure in the reaction kettle to be below 5 kPa;

3.4) heating to 230-280 ℃, reducing the pressure in the reaction kettle to be less than 133Pa, and continuously reacting to obtain the adipic acid copolyester product.

Adding a catalyst into the reaction system of the third scheme, wherein the catalyst is completely added in the step 3.1), or the catalyst is added in two parts respectively in the step 3.1) and the step 3.3);

the fourth scheme comprises the following steps:

4.1) putting dibasic acid B, C2-C12 dibasic alcohol into a reaction kettle I, heating to 220-240 ℃ and reacting until the conversion rate is more than 90%; in another reaction kettle, putting adipic acid and C2-C12 dihydric alcohol into a reaction kettle II, heating to 160-200 ℃ for reaction until the conversion rate is more than 90 percent;

4.2) combining the materials in the two reaction kettles, and adding the reducing organic matter;

4.3) reducing the pressure in the reaction kettle to be below 5 kPa;

4.4) heating to 230-280 ℃, reducing the pressure in the reaction kettle to be less than 133Pa, and continuously reacting to obtain the adipic acid copolyester product.

In step 4.1) of the fourth scheme, the moles of the C2-C12 diol charged in the reaction vessel I are in excess relative to the diacid B, and the moles of the C2-C12 diol charged in the reaction vessel II are in excess relative to the adipic acid; the fourth scheme is that a catalyst is added into the reaction system, and the catalyst is added in the step 4.1) completely, or the catalyst is added in two parts in the step 4.1) and the step 4.3).

In the first to fourth schemes, in steps 1.4), 2.4), 3.4) and 4.4), the reaction is continued when the pressure is reduced to below 133Pa, and the skilled person determines the final reaction time according to different requirements of the target product, such as different requirements of molecular weight.

The pressure in the scheme is absolute pressure.

The conversion rate involved in the present invention is calculated from the chemical reaction formula by recording the mass of water of the fraction withdrawn from the reaction, as is well known to those skilled in the art. The conversion rate is the mass of actually generated water in the esterification reaction/the theoretical amount of the fed acid corresponds to the mass of generated water by 100 percent; the mass calculation method of the theoretical amount of the feed acid corresponding to the generated water is that 2mol of water is generated per mol of dibasic acid, 1mol of water is generated per mol of dibasic acid anhydride, and the mass of each mol of water is 18 g.

When 1, 4-butanediol is contained in the raw material, dehydration reaction occurs and tetrahydrofuran and water are by-produced in the esterification reaction, so that the mass of water produced in the esterification reaction is converted by measuring the amounts of water and tetrahydrofuran in the fraction (the mass of 18g of water is subtracted per 72g of tetrahydrofuran). Tetrahydrofuran can be quantified by GC. The use of 1, 4-butanediol for polyester synthesis has been practiced industrially for many years, and the specific calculation of the conversion of the reaction is known to the person skilled in the art and will not be described in detail here and can be simply expressed as:

conversion ═ (mass of water in the fraction-mass of tetrahydrofuran in the fraction/72 × 18)/(moles of dibasic acid a × 2 × 18+ moles of dibasic acid B × f 18) × 100%

When the dibasic acid B is selected from dibasic acids such as phthalic acid, isophthalic acid and terephthalic acid, f is 2; when the dibasic acid B is selected from phthalic anhydride, f is 1.

In the preparation method of the present invention, for example, in the first to fourth schemes, when preparing the adipic acid copolyester, a catalyst and an optional stabilizer are added to the reaction system. The catalyst as described above may be added in one portion or in multiple portions (e.g., two portions). The manner of addition of the catalyst can be varied by the skilled person depending on the nature of the catalyst and/or the particular arrangement of the process steps, for example by adding it in one portion or in a plurality of portions (for example in two portions) in different steps. For example, in some embodiments, in the above four schemes, the catalyst is added in one portion or only in one portion (for example, 10 to 20% of the total mass of the catalyst) in step 1.1), 2.1), 3.1) or 4.1), respectively, and if only a portion of the catalyst is added in the previous step, the remaining catalyst is added in step 1.3), 2.3), 3.3) or 4.3).

The manner of addition of the stabilizer is well known to the person skilled in the art and is not particularly required, for example in some embodiments the stabilizer is added in step 1.3), 2.3), 3.3) or 4.3).

The catalyst and stabilizer may be those conventionally used in the art, and are not particularly limited. In some embodiments, the catalyst is a titanium-based catalyst, and the amount of the catalyst is 40-250ppm based on the theoretical yield of the adipic copolyester as titanium element; the stabilizer is preferably a phosphorus compound, and the mass ratio of the phosphorus compound to the titanium element in the titanium catalyst is 1/5-2 in terms of phosphorus element. The phosphorus compound is one or more of phosphoric acid, triethyl phosphate and triphenyl phosphite, and the titanium catalyst is one or more of isopropyl titanate, n-butyl titanate and the like.

The a value of the adipic acid copolyester prepared by the preparation method is less than or equal to 3, and the a value is increased by less than or equal to 5 after the adipic acid copolyester is kept in hot air at 200 ℃ for 1h, wherein the 'a value' refers to L, the a value of an a, b color system, the a value is positive and indicates that the product is reddish, the a value is negative and indicates that the product is green, the method is a known technology, and the a value referred to in the invention is obtained by testing according to GB/T32366-2015 biodegradable polybutylene terephthalate-adipate (PBAT).

The invention also provides an adipic acid copolyester product, wherein the adipic acid copolyester product contains 2-50ppm of iron element;

the esterification reaction residues of the dibasic acid contained in the adipic acid copolyester comprise 35 to 95mol percent of esterification residues of adipic acid and 5 to 65mol percent of esterification residues of dibasic acid B, wherein the esterification reaction residues of the dibasic acid are 100mol percent; the molar ratio of the esterified residue of adipic acid to the esterified residue of dibasic acid B in the resulting adipic acid copolyester product can be determined by one skilled in the art based on the molar ratio of adipic acid to dibasic acid B charged.

The a value of the adipic acid copolyester is less than or equal to 3, and the a value is increased by less than or equal to 5 after heat preservation is carried out for 1h in hot air at the temperature of 200 ℃.

The adipic acid copolyester is prepared by the preparation method.

The technical scheme provided by the invention has the following beneficial effects:

the inventor adds reducing organic matter at a specific time to enable the a value of the prepared copolyester product to be less than or equal to 3, and the a value is increased by less than or equal to 5 after heat preservation is carried out for 1h in hot air at the temperature of 200 ℃.

Detailed Description

In order to better understand the technical solution of the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.

Adipic Acid (AA) is purchased from Henan Marma, terephthalic acid (PTA) is purchased from Henan petrochemical industry, 1, 4-Butanediol (BDO) is purchased from Xinjiang Meike, Ethylene Glycol (EG) is purchased from Henan petrochemical industry, the four raw materials are industrial-grade products, Fe in the raw materials is less than 1ppm, isopropyl titanate, 85% phosphoric acid, isophthalic acid, glucose, glyoxylic acid and ferric trichloride are purchased from Aladdin, and are reagent grade, and a titanium composite catalyst XD L-085E is purchased from Hangzhou New equivalent chemical technology Co.

GPC testing (determination of molecular weights Mn and PDI): dichloromethane was used as the mobile phase and polystyrene was used as the standard reference.

Fe. And (3) detecting the content of Ti and P elements: detection by ICP.

In some examples, iron was intentionally added to the raw material in order to test the effect of the present invention to inhibit the iron element from causing the product to turn red, and these examples are for the purpose of showing the technical solution only, and there is no need to intentionally add the iron element in the actual production.

Method for thermal oxygen evaluation: dividing the resin particles to be tested into two parts, and testing the a value of one part according to the GB/T32366 standard. Uniformly placing 20g of the powder per 100 square centimeters into a stainless steel tray, and placing the stainless steel tray in a 200 ℃ oven, wherein the distance between the tray and a heating surface is not less than 10 cm; after incubation at 200 ℃ for 1h, granules were produced and tested for the value of a according to GB/T32366, which is designated as a'. And calculating the value of a' minus a to be the increment of the value of a.

Example 1 (scheme one)

61.2kg of PTA (terephthalic acid), 71.5kg of BDO (1, 4-butanediol) and 2.9g of isopropyl titanate (catalyst) are added into a 200L reaction kettle with a rectifying column and a condenser, and the temperature is raised to 230 ℃ for reaction until the conversion rate reaches 91%.

29kg of AA (adipic acid) was added and the temperature of the system was lowered to 200 ℃. The reaction was continued at 200 ℃ until a conversion of 91%.

6.0g glyoxylic acid (reducing organic substance, 0.005 wt.% based on 100 wt.% of theory yield of adipic acid copolyester product) and 25.8g isopropyl titanate (catalyst) were added and stirred until homogeneous, 18.0g phosphoric acid (stabilizer, mass ratio P: Ti 1:1) was added. The pressure in the kettle was reduced to 3kPa in 0.5 h.

Further reducing the pressure in the reaction kettle to 50Pa, increasing the reaction temperature to 280 ℃, and reacting for 3 hours under the temperature and the pressure to obtain the adipic acid copolyester product.

The molecular weight, molecular weight distribution, a value, and a value after thermo-oxidative aging of the product are shown in Table 1.

Example 2 (scheme two)

A200L reaction kettle with a rectifying column and a condenser is added with 55kg of AA (adipic acid), 101.7kg of BDO (1, 4-butanediol) and 4.7g of isopropyl titanate (catalyst), the temperature is raised to 160 ℃ to start the reaction, the temperature is gradually raised to 200 ℃, and the reaction is continued until the conversion rate reaches 93 percent.

79.7g of glucose (reducing organics, 0.10% by weight, based on 100% of theory of adipic copolyester product), 3.3kg of PTA (terephthalic acid), 5.4kg of BDO (1, 4-butanediol) were added and the temperature of the system was raised to 220 ℃. The reaction was continued at 220 ℃ until a conversion of 91%.

42.6g of isopropyl titanate (catalyst) was added, and after stirring uniformly, 14.8g of phosphoric acid (stabilizer, P: Ti mass ratio 1:2) was added. The pressure in the kettle was reduced to 4.5kPa in 0.5 h.

Further reducing the pressure in the reaction kettle to 80Pa, increasing the reaction temperature to 230 ℃, and reacting for 3.5 hours at the temperature and the pressure to obtain the adipic acid copolyester product.

The molecular weight, molecular weight distribution, iron content, a value, and a value after thermo-oxidative aging of the product are shown in Table 1.

Example 3 (scheme three)

35kg of AA (adipic acid), 39.8kg of PTA (terephthalic acid), 86.3kg of BDO (1, 4-butanediol) and 251g of catalyst XD L-085E are added into a 200L reaction kettle with a rectifying column and a condenser, the temperature is increased to 180 ℃ to start reaction, the temperature is gradually increased to 200 ℃, and the reaction is continued until the conversion rate is 65%.

50.3g of glucose (reducing organics, 0.05% by weight based on the theoretical yield of adipic copolyester product of 100% by weight) were added and the temperature of the system was then raised to 230 ℃. The reaction was continued at 230 ℃ until a conversion of 95% was reached.

The pressure in the kettle was reduced to 2.5kPa in 0.5 h.

Further reducing the pressure in the reaction kettle to 60Pa, maintaining the reaction temperature at 230 ℃, and reacting for 3.5 hours at the temperature and the pressure to obtain the adipic acid copolyester product.

The molecular weight, molecular weight distribution, iron content, a value, and a value after thermo-oxidative aging of the product are shown in Table 1.

Example 4 (scheme three)

41kg of AA (adipic acid), 38.1kg of PTA (terephthalic acid), 82.7kg of BDO (1, 4-butanediol) and 12.7g of isopropyl titanate (catalyst) are added into a 200L reaction kettle with a rectifying column and a condenser, the temperature is increased to 180 ℃ to start the reaction, the temperature is gradually increased to 200 ℃, and the reaction is continued until the conversion rate is 55%.

534g of glyoxylic acid (reducing organic, 0.50% by weight, based on 100% of the theoretical yield of the adipic copolyester product) were added and, for the purpose of showing the technical scheme, 14.2g of ferric trichloride (46 ppm of iron, based on the theoretical yield of the adipic copolyester product) were added to the system. The temperature of the system was then raised to 240 ℃. The reaction was continued at 240 ℃ until a conversion of 94% was reached.

50.7g of isopropyl titanate (catalyst) was added, and after stirring uniformly, 79.5g of phosphoric acid (stabilizer, P: Ti mass ratio 2:1) was added. The pressure in the kettle was reduced to 3kPa in 0.5 h.

Further reducing the pressure in the reaction kettle to 120Pa, maintaining the reaction temperature at 240 ℃, and reacting for 3 hours at the temperature and the pressure to obtain the adipic acid copolyester product.

The molecular weight, molecular weight distribution, iron content, a value, and a value after thermo-oxidative aging of the product are shown in Table 1.

Example 5 (scheme four)

A100L reaction kettle with a rectifying column and a condenser is added with 52.8kg of PTA (terephthalic acid) and 68.7kg of BDO (1, 4-butanediol), isopropyl titanate (catalyst) is not added, the temperature is raised to 240 ℃, the reaction is carried out until the conversion rate reaches 92 percent, 38kg of AA (adipic acid), 56.2kg of BDO (1, 4-butanediol) and 36.2g of isopropyl titanate (catalyst) are added into another 100L reaction kettle with a rectifying column and a condenser, the reaction is started after the temperature is raised to 160 ℃, the reaction is gradually raised to 200 ℃, and the reaction is continued until the conversion rate reaches 93 percent.

The two pot contents were combined in a 200L reactor, 183g of glyoxylic acid (reducing organic matter, 0.15 wt% based on 100 wt% theoretical yield of adipic acid copolyester product) were added, 145.0g of isopropyl titanate (catalyst) were then added, and 22.7g of phosphoric acid (stabilizer, P: Ti mass ratio 1:5) were added after stirring well.

The pressure in the kettle was reduced to 3kPa in 0.5 h. The temperature was raised to 250 ℃.

Further reducing the pressure in the reaction kettle to 50Pa, maintaining the reaction temperature at 250 ℃, and reacting for 3.5 hours at the temperature and the pressure to obtain the adipic acid copolyester product.

The molecular weight, molecular weight distribution, iron content, a value, and a value after thermo-oxidative aging of the product are shown in Table 1.

Comparative example 1 (compared with example 1, no reducing organic substance was used)

A200L reaction kettle with a rectifying column and a condenser is added with 61.2kg of PTA (terephthalic acid), 71.5kg of BDO (1, 4-butanediol) and 2.9g of isopropyl titanate, the temperature is increased to 230 ℃ to react until the conversion rate reaches 91 percent, 29kg of AA (adipic acid) is added, the temperature of the system is reduced to 200 ℃, the reaction is continued until the conversion rate reaches 91 percent at 200 ℃, 25.8g of isopropyl titanate is added, after uniform stirring, 18.0g of phosphoric acid (P: Ti mass ratio is 1:1) is added, the pressure in the reaction kettle is reduced to 3kPa within 0.5h, the pressure in the reaction kettle is further reduced to 50Pa, the reaction temperature is increased to 280 ℃, and after reaction is carried out for 3h at the temperature and the pressure, the product molecular weight, the molecular weight distribution, the a value and the a value after thermal oxidation aging are shown in Table 1.

Comparative example 2 (comparing with example 2, no reducing organic matter is used)

A200L reaction kettle with a rectifying column and a condenser is added with 55kg of AA (adipic acid), 101.7kg of BDO (adipic acid) and 4.7g of isopropyl titanate, the temperature is raised to 160 ℃ to start the reaction, the temperature is gradually raised to 200 ℃, the reaction is continued until the conversion rate reaches 93%, 3.3kg of PTA (terephthalic acid), 5.4kg of BDO (1, 4-butanediol) are added, the temperature of the system is raised to 220 ℃, the reaction is continued until the conversion rate reaches 91%, 42.6g of isopropyl titanate is added, after the uniform stirring, 14.8g of phosphoric acid (P: Ti mass ratio is 1:2) is added, the pressure in the reaction kettle is reduced to 4.5kPa within 0.5h, the pressure in the reaction kettle is further reduced to 80Pa, the reaction temperature is raised to 230 ℃, and after the reaction is carried out for 3.5h, the adipic acid copolyester product is obtained, and the molecular weight, the molecular weight distribution, the iron content, the a value and the a value after thermal oxidation aging are listed in Table 1.

Comparative example 3 (comparison with example 3, without reducing organic)

35kg of AA (adipic acid), 39.8kg of PTA (terephthalic acid), 86.3kg of BDO (1, 4-butanediol) and 251g of catalyst XD L-085E are added into a 200L reaction kettle with a rectifying column and a condenser, the temperature is increased to 180 ℃, the reaction is started, the temperature is gradually increased to 200 ℃, the reaction is continued until the conversion rate is 65 percent, the temperature of the system is increased to 230 ℃, the reaction is continued until the conversion rate is 95 percent at 230 ℃, the pressure in the kettle is reduced to 2.5kPa within 0.5h, the pressure in the reaction kettle is further reduced to 60Pa, the reaction temperature is maintained at 230 ℃, and after the reaction is carried out for 3.5h under the temperature and the pressure, the product molecular weight, the molecular weight distribution, the iron content, the a value and the a value after thermal oxygen aging are listed in Table 1.

Comparative example 4 (comparison with example 4, without using reducing organic substance)

41kg of AA (adipic acid), 38.1kg of PTA (terephthalic acid), 82.7kg of BDO (1, 4-butanediol) and 12.7g of isopropyl titanate are added into a 200L reaction kettle with a rectifying column and a condenser, the temperature is raised to 180 ℃, the reaction is started, the temperature is gradually raised to 200 ℃, the reaction is continued until the conversion rate reaches 55 percent, for the purpose of showing the technical scheme in comparison with the embodiment 4, 14.2g of ferric trichloride (which is 46ppm of iron in the product) is added into the system, then the temperature of the system is raised to 240 ℃, the reaction is continued until the conversion rate reaches 94 percent at 240 ℃, 50.7g of isopropyl titanate is added, 79.5g of phosphoric acid (the mass ratio of P: Ti is 2:1) is added into the system after uniform stirring, the pressure in the reaction kettle is reduced to 3kPa within 0.5h, the pressure in the reaction kettle is further reduced to 120Pa, the reaction temperature is maintained at 240 ℃, and after the temperature and the pressure are reacted for 3.5h, the product molecular weight, the molecular weight distribution, the oxygen content, the aging value a value and the aging value of the a value are listed in a table.

Comparative example 5 (comparing with example 5, no reducing organic matter is used)

Adding 52.8kg of PTA (terephthalic acid) and 68.7kg of BDO (1, 4-butanediol) into a 100L reaction kettle with a rectifying column and a condenser, heating to 240 ℃ without adding isopropyl titanate, reacting until the conversion rate is 92%, adding 38kg of AA (adipic acid), 56.2kg of BDO (1, 4-butanediol) and 36.2g of isopropyl titanate into another 100L reaction kettle with the rectifying column and the condenser, heating to 160 ℃, starting the reaction, gradually increasing the temperature to 200 ℃, continuing the reaction until the conversion rate is 93%, combining the two kettle materials in a 200L reaction kettle, adding 145.0g of isopropyl titanate, uniformly stirring, adding 22.7g of phosphoric acid (P: Ti mass ratio is 1:5), increasing the temperature to 250 ℃, reducing the kettle to 3kPa within 0.5h, further reducing the pressure in the reaction kettle to 50Pa, maintaining the reaction temperature at 250 ℃, reacting for 3.5h under the temperature and the pressure, obtaining the molecular weight of adipic acid, the product, the molecular weight distribution of the copolyester and the aging value of the product a, which are listed in the table.

Comparative example 6 (addition of reducing organic above 200 ℃ C. in comparison with example 4)

41kg of AA (adipic acid), 38.1kg of PTA (terephthalic acid), 82.7kg of BDO (1, 4-butanediol) and 12.7g of isopropyl titanate are added into a 200L reaction kettle with a rectifying column and a condenser, the temperature is increased to 180 ℃, the reaction is started, the temperature is gradually increased to 200 ℃, the reaction is continued until the conversion rate reaches 55 percent, 14.2g of ferric trichloride (46 ppm of iron in terms of the product) is added into the system for the purpose of comparing with the technical scheme shown in example 4, then the temperature of the system is increased to 240 ℃, and the reaction is continued at 240 ℃ until the conversion rate reaches 94 percent.

534g of glyoxylic acid (reducing organic matter, 0.50 wt% based on the theoretical yield of the adipic acid copolyester product) are added, 50.7g of isopropyl titanate are added, and 79.5g of phosphoric acid (P: Ti mass ratio is 2:1) are added after uniform stirring. Reducing the pressure in the kettle to 3kPa within 0.5h, further reducing the pressure in the reaction kettle to 120Pa, maintaining the reaction temperature at 240 ℃, and reacting for 3.5h under the temperature and the pressure to obtain the adipic acid copolyester product. The molecular weight, molecular weight distribution, iron content, a value, and a value after thermo-oxidative aging of the product are shown in Table 1.

TABLE 1 molecular weight, molecular weight distribution, iron content, a value, etc. of the products of examples and comparative examples

	Mn(GPC)	PDI(GPC)	Fe content	Ti content	P content	a	a'	Increase of a value
									Example 1	56157	2.21	2	40	40	0.6	2.6	2.0
Example 2	46148	2.25	6	100	50	1.3	3.1	1.8
									Example 3	48646	2.28	10	150	50	0.3	2.8	2.5
Example 4	16530	2.19	50	100	200	3	7.6	4.6
									Example 5	60148	2.29	3	250	50	0.9	1.7	0.8
Comparative example 1	46333	2.23	2	40	40	0.9	6.0	5.1
									Comparative example 2	47906	2.27	6	100	50	2.2	9.3	7.1
Comparative example 3	53103	2.23	9	150	50	2.7	11.2	8.5
									Comparative example 4	15550	2.25	50	100	200	8	21	13
Comparative example 5	57144	2.19	3	250	50	1.5	7.5	6.0
									Comparative example 6	14831	2.28	50	100	200	4.2	10.1	5.9

Remarking: in table 1, the Fe, Ti, P contents refer to the element mass contents, ppm, in the prepared adipic acid copolyester product measured by ICP.

From the experimental results of comparative examples 1, 2, 3, 5 and examples 1, 2, 3, 5, it can be seen that although a value a < 3 can be obtained by the known method, a value a of the product is significantly increased under hot oxygen conditions, whereas an increase in a value a < 5 can be controlled by the method employed in the present invention.

From the experimental results of comparative example 6 and example 4, it can be seen that the amount of increase in the a-value of the product and the a-value under hot oxygen conditions increases after introduction of adipic acid, compared to the case where the reducing organic is added at 200 ℃.

It will be appreciated by those skilled in the art that modifications or adaptations to the invention may be made in light of the teachings of the present specification. Such modifications or adaptations are intended to be within the scope of the present invention as defined in the claims.

Claims (10)

1. A method for preparing adipic acid copolyester, wherein the adipic acid copolyester is prepared by reacting raw materials comprising dibasic acid A and dibasic acid B, C2-C12 dihydric alcohol, the dibasic acid A is adipic acid, and the dibasic acid B is one or more of aromatic dibasic acid or anhydride thereof or esterified derivatives thereof, and is characterized in that after the adipic acid is added into a reaction system, reducing organic matters are added into the reaction system before the reaction temperature is increased to more than 200 ℃.

2. The method according to claim 1, wherein the reducing organic substance is selected from glucose and/or glyoxylic acid.

3. The method according to claim 1 or 2, wherein the reducing organic is added in an amount of 0.005-0.5 wt% based on 100 wt% of theoretical yield of the adipic copolyester.

4. The method according to any one of claims 1 to 3, wherein the obtained copolyester adipic acid contains 2 to 50ppm of iron element.

5. The production method according to any one of claims 1 to 4, wherein the dibasic acid B is one or more of phthalic acid, isophthalic acid, terephthalic acid, phthalic anhydride, preferably terephthalic acid;

the dihydric alcohol of C2-C12 is 1, 4-butanediol, and the adipic acid copolyester is preferably polybutylene terephthalate-adipate.

6. The method according to any one of claims 1 to 5, wherein the molar ratio of the sum of the moles of adipic acid and the moles of the dibasic acid B to the moles of the C2-C12 diol is 1:1.4 to 1: 3;

the molar percentage of the adipic acid is 35-95 mol% and the molar percentage of the dibasic acid B is 5-65 mol% based on the total molar number of the adipic acid and the dibasic acid B being 100 mol%.

7. The method according to any one of claims 1 to 6, wherein the method is carried out according to any one of the following first, second, third or fourth schemes,

the first scheme comprises the following steps:

1.1) putting the dibasic acid B, C2-C12 dibasic alcohol into a reaction kettle, heating to 220-240 ℃ and reacting until the conversion rate is more than 90%;

1.2) controlling the temperature of the reaction kettle to be 180-200 ℃, putting the adipic acid into the reaction kettle, and continuing to react at 180-200 ℃ until the conversion rate is more than 90%;

1.3) feeding the reducing organic matter, and reducing the pressure in the reaction kettle to be lower than 5 kPa;

1.4) heating to 230-280 ℃, reducing the pressure in the reaction kettle to be less than 133Pa, and continuously reacting to obtain an adipic acid copolyester product;

in the first scheme, the required amount of the C2-C12 dihydric alcohol is added in the step 1.1) in whole, or is added in two parts to the steps 1.1) and 1.2) respectively, and the C2-C12 dihydric alcohol is added in the step 1.1) in excess relative to the mole number of the dibasic acid B; adding a catalyst into the reaction system of the first scheme, wherein the catalyst is completely added in the step 1.1), or the catalyst is added in two parts respectively in the step 1.1) and the step 1.3);

the second scheme comprises the following steps:

2.1) putting the adipic acid and the dihydric alcohol C2-C12 into a reaction kettle, and heating to 160-200 ℃ for reaction until the conversion rate is more than 90%;

2.2) adding the reducing organic matter, adding the dibasic acid B into a reaction kettle, and continuing to react at the temperature of 200-240 ℃ until the conversion rate is more than 90 percent;

2.3) reducing the pressure in the reaction kettle to be below 5 kPa;

2.4) heating to 230-280 ℃, reducing the pressure in the reaction kettle to be less than 133Pa, and continuously reacting to obtain an adipic acid copolyester product;

in the second variant, the desired amount of the C2-C12 diol is added in step 2.1) in its entirety, or in two portions to steps 2.1) and 2.2) respectively and in step 2.1) an excess of the C2-C12 diol relative to the moles of adipic acid is added; adding a catalyst into the reaction system of the second scheme, wherein the catalyst is completely added in the step 2.1), or the catalyst is added in two parts respectively in the step 2.1) and the step 2.3);

the third scheme comprises the following steps:

3.1) putting the dibasic acid B, the adipic acid and the C2-C12 dihydric alcohol into a reaction kettle, and heating to 160-200 ℃ for reaction until the conversion rate is more than 50%;

3.2) adding the reducing organic matter, then heating to more than 200 ℃ and less than or equal to 240 ℃, and continuing the reaction until the conversion rate is more than 90%;

3.3) reducing the pressure in the reaction kettle to be below 5 kPa;

3.4) heating to 230-280 ℃, reducing the pressure in the reaction kettle to be less than 133Pa, and continuously reacting to obtain an adipic acid copolyester product;

adding a catalyst into the reaction system of the third scheme, wherein the catalyst is completely added in the step 3.1), or the catalyst is added in two parts respectively in the step 3.1) and the step 3.3);

the fourth scheme comprises the following steps:

4.1) putting dibasic acid B, C2-C12 dibasic alcohol into a reaction kettle I, heating to 220-240 ℃ and reacting until the conversion rate is more than 90%; in another reaction kettle, putting adipic acid and C2-C12 dihydric alcohol into a reaction kettle II, heating to 160-200 ℃ for reaction until the conversion rate is more than 90 percent;

4.2) combining the materials in the two reaction kettles, and adding the reducing organic matter;

4.3) reducing the pressure in the reaction kettle to be below 5 kPa;

4.4) heating to 230-280 ℃, reducing the pressure in the reaction kettle to be less than 133Pa, and continuously reacting to obtain an adipic acid copolyester product;

in step 4.1) of the fourth scheme, the moles of the C2-C12 diol charged in the reaction vessel I are in excess relative to the diacid B, and the moles of the C2-C12 diol charged in the reaction vessel II are in excess relative to the adipic acid; the fourth scheme is that a catalyst is added into the reaction system, and the catalyst is added in the step 4.1) completely, or the catalyst is added in two parts in the step 4.1) and the step 4.3).

8. The production method according to claim 7,

the catalyst is a titanium catalyst, and the dosage of the catalyst is 40-250ppm calculated by titanium element based on the theoretical yield of the adipic acid copolyester;

optionally, when the adipic acid copolyester is prepared, a stabilizer is also added into the reaction system; the stabilizer is preferably a phosphorus compound, and the mass ratio of the phosphorus compound to the titanium element in the titanium catalyst is 1/5-2 in terms of phosphorus element.

9. The method according to any one of claims 1-8, wherein the a value of the adipic acid copolyester prepared according to the method is less than or equal to 3, and the a value increases by less than or equal to 5 after 1h of heat preservation in hot air at 200 ℃.

10. An adipic acid copolyester, characterized by being prepared by the preparation method of any one of claims 1 to 9; wherein the adipic acid copolyester contains 2-50ppm of iron element;

the esterification reaction residues of the dibasic acid contained in the adipic acid copolyester comprise 35-95 mol% of esterification residues of adipic acid and 5-65 mol% of esterification residues of dibasic acid B, wherein the esterification reaction residues of the dibasic acid are 100 mol%;

the a value of the adipic acid copolyester is less than or equal to 3, and the a value is increased by less than or equal to 5 after heat preservation is carried out for 1h in hot air at the temperature of 200 ℃.