JPS6133855B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a polyester whose main repeating unit is polyethylene terephthalate, which has improved electrostatic castability and excellent softening point, transparency, and heat resistance, by a direct polymerization method. Polyester, typified by polyethylene terephthalate, has excellent physical and chemical properties and is therefore widely used in film fields such as magnetic tapes, electrical insulation, capacitors, photography, and packaging. The polyester film is usually obtained by melt-extruding polyester using an extruder and then biaxially stretching it in the longitudinal and transverse directions, but in order to improve the uniformity of the film thickness and transparency, it is melt-extruded from an extrusion die. When rapidly cooling a sheet-shaped material on the surface of a rotating cooling drum, a wire or knife-shaped electrode is installed between the extrusion die and the rotating cooling drum, and a high voltage is applied to remove static charges on the top surface of the unsolidified sheet-like material. A method is known in which the sheet is precipitated and then rapidly cooled while the sheet is brought into close contact with the surface of a cooling body (hereinafter referred to as electrostatic casting method). Since the productivity of polyester films is directly dependent on the casting speed, it is extremely important to increase the casting speed in order to improve productivity, and much effort is being devoted to this point. In the electrostatic application casting method, when the surface speed of the cooling body is increased in order to increase the film forming rate, the amount of static charge per unit area on the surface of the sheet-like object that is in close contact with the surface of the cooling body decreases, and the sheet-form The adhesion between the object and the surface of the cooling body decreases, causing pin-like defects on the film surface. On the other hand, in order to solve this problem, if the applied voltage is increased in order to increase the amount of static charge deposited on the surface of the sheet-like material, arc discharge will occur between the electrode and the surface of the cooling body, and the surface of the cooling body will be A problem arises in that the sheet-like material is destroyed. Therefore, there is a limit to simply increasing the applied voltage as described above, and in order to increase the amount of charge on the surface of the sheet-like material, a large amount of metal must be added to the polyester. However, adding a large amount of metal to polyester not only promotes thermal decomposition of polyester and deteriorates heat resistance, but also promotes the formation of diethylene glycol (hereinafter abbreviated as DEG), lowering the softening point of polyester. There is a drawback. In particular, when the polycondensation reaction is carried out at high temperatures and in a short period of time in order to increase productivity, the influence is magnified. In addition, bis-(β-hydroxyethyl terephthalate) and/or its low polymer (hereinafter referred to as BHT) are obtained by an esterification reaction from terephthalic acid (hereinafter referred to as TPA) and ethylene glycol (hereinafter referred to as EG), and then The so-called direct polymerization method, in which polyester is obtained by polycondensation, has a greater influence than the so-called transesterification method, in which BHT is obtained from dimethyl terephthalate and EG, and then polycondensation is performed. A biaxial stretching method is generally used to produce polyester films, but in this method, the selvedges and non-standard film produced during transverse stretching are generally remelted and used repeatedly. If the heat resistance of the polyester is poor, it may not be possible to reuse it, or the performance of the polyester film itself may deteriorate, which is undesirable. Furthermore, if the softening point of the polyester is lowered, the film tends to stick to a cooling casting drum during film formation, and the film tends to tear more often during stretching, resulting in a reduction in film formation yield. The present inventors have improved the above-mentioned drawbacks by using a direct polymerization method, which has excellent electrostatic application castability during film formation.
As a result of extensive research into a method for producing polyester that has a high softening point, excellent heat resistance, and transparency, the present invention was achieved. That is, the present invention involves adding TPA and EG to a predetermined amount of BHT when producing polyester from a dicarboxylic acid mainly consisting of TPA and a glycol mainly consisting of EG.
is supplied to conduct an esterification reaction, and then at least one ethylene glycol-soluble metal compound selected from magnesium and manganese compounds, an alkali metal hydroxide, a hydrogen carbonate,
At least one alkali metal compound selected from aliphatic carboxylates and at least one phosphorus compound selected from phosphorous acid, phosphoric acid and/or esters thereof are represented by the following general formula:
This is a method for producing polyester, which is characterized in that the polyester is added to a satisfactory level and then subjected to polycondensation. 2≦M≦40 … 0.3≦R≦15 … 0.8≦M+10.5R/P≦5.0 … [wherein M is the total number of grams of atoms per 10 ⁶ g of the metal polyester in the additive metal compound represented by (number of grams atoms/10 ⁶ g), R is the total number of grams atoms per 10 ⁶ g of the alkali metal polyester in the added alkali metal compound (gram atoms/10 ⁶ g), P is the number of added atoms shown in The total number of gram atoms (gram atoms/10 ⁶ g) of phosphorus atoms in the phosphorus compound per 10 ⁶ g of polyester is shown. ] The polyester finally obtained in the present invention has 80% or more of its constituent units composed of ethylene terephthalate units and less than 20% of them, and contains dicarboxylic acids such as phthalic acid, isophthalic acid, adipic acid, and sebacic acid. acid, P-oxybenzoic acid, P
It may also contain copolymerized components such as oxycarboxylic acids such as -(β-oxyethoxy)benzoic acid and diols such as trimethylene glycol and tetramethylene glycol. For BHT to which TPA and EG are added, the reaction product of the esterification reaction of the present invention may be used as it is, but it is also possible to use one produced by other methods, such as transesterification. Present in the system at the start of the esterification reaction
The amount of BHT is not particularly limited, but when the reaction is carried out batchwise, the amount of BHT present at the start of the esterification reaction is greater than the number of moles of the acid component in the BHT obtained after the esterification reaction is completed. It is preferable that the number of moles of the acid component is in the range of 1/5 to 1/2 because the esterification reaction time is short and the substantial amount to be esterified is large. The molar ratio of ethylene units to terephthaloyl units in BHT that is present at the start of the esterification reaction is preferably 1.05 to 1.80 from the viewpoint of stability of fluidity of the reaction system and amount of DEG by-product. Adding TPA and EG to the reaction system as a slurry of TPA and EG is easier to handle and has better workability than adding powdered TPA and liquid EG separately. Especially TPA
When EG and EG are supplied to the reaction system in conjunction, more quantitative supply can be achieved. The slurry of TPA and EG preferably has an EG/TPA molar ratio of 1.05 to 2.0 in terms of ease of handling the slurry and the amount of by-product DEG, more preferably 1.10 to 1.30. The slurry of TPA and EG is prepared using a suitable kneader, and is continuously or intermittently supplied to the reaction system using a supply pump under pressure or normal pressure. The esterification reaction can be carried out under pressure or normal pressure. When the esterification reaction is carried out under normal pressure, there is no need to use a pressurized reaction vessel, which is advantageous in terms of equipment cost. The temperature of the esterification reaction is preferably 210°C or higher, more preferably 230 to 270°C. In particular, in the esterification reaction under normal pressure, the reaction temperature is regulated by the boiling point of the reaction system, and the higher the amount of terephthalic acid units, the higher the temperature can be. The reaction temperature is
Below 210℃ the reaction time will be longer, while at 270℃
Exceeding this is not preferable because it increases the amount of DEG by-products and promotes side reactions such as coloring. The ethylene glycol-soluble magnesium and manganese compounds used in the present invention include organic acid salts of magnesium or manganese such as acetate, oxalate, and benzoate, halides,
Examples include hydroxides, specifically magnesium acetate, manganese acetate, magnesium oxalate,
Manganese oxalate, magnesium chloride, manganese chloride, magnesium bromide, magnesium hydroxide,
These include manganese hydroxide. Further, the amount of magnesium and manganese compounds represented by the general formula added is 2 to 40 g atoms/10 ⁶ g as magnesium and manganese atoms, and 20 g atoms/10 ^{6 g} to the polyester finally obtained. g or less is more preferable. If it is less than 2 g atoms/10 ⁶ g, the electrostatic application castability cannot be satisfied;
If it exceeds 10 ⁶ g, the number of fine metal particles increases, which deteriorates transparency and increases side reactions such as thermal decomposition caused by metals, resulting in a decrease in the quality of the polyester. Alkali metal hydroxide used in the present invention,
Examples of hydrogen carbonates and aliphatic carboxylates include lithium acetate, sodium acetate, potassium acetate, barium acetate, lithium oxalate, sodium oxalate, potassium oxalate, lithium hydrogen carbonate, lithium hydroxide, sodium hydroxide, and hydroxide. Examples include potassium. Further, the amount of the alkali metal compound represented by the general formula to be added is in the range of 0.3 to 15 gram atoms/10 ⁶ g as alkali metal atoms to the final polyester obtained, and 10 gram atoms/10 ⁶ g or less. More preferred. If it is less than 0.3 gram atom/10 ⁶ g, DEG will be produced as a by-product in the polyester, and the softening point will decrease. If it exceeds 15 gram atoms/10 ⁶ g, the resulting polyester will contain more insoluble particles and its transparency will deteriorate. Specific examples of phosphorus compounds used in the present invention include trimethyl phosphonate, monophosphoric acid (methyl acid phosphonate), phosphoric acid, triethyl phosphorite, diethyl phosphorite, phosphorous acid, etc. . In addition, the amount of the phosphorus compound represented by the general formula to be added is (M+0.5R)/P when the content of phosphorus atoms is P (gram atom/10 ⁶ g) in the final polyester. The value ranges from 0.8 to 5.0, with 1.2 to 3 being more preferred. If the value of (M+0.5R)/P is less than 0.8, even if magnesium, manganese compounds, and alkali metal compounds are added within a range that satisfies the general formula, they will react with phosphorus compounds in some way, causing electrical It becomes conductively inert and does not contribute to improving the electrostatic application cast. On the other hand, the value of (M+0.5R)/P is 5.0
If it exceeds this amount, the transparency of the film may deteriorate, and the product may become colored due to progress of side reactions caused by the metal compound, which is not preferable. The magnesium, manganese compounds, and alkali metal compounds used in the present invention are added to the reaction system when the esterification reaction is substantially completed and the BHT reaction rate is 80% or more, preferably 90% or more. It is good to add. If magnesium, manganese compounds, and alkali metal compounds are added when the reaction rate is less than 80%, they will react with the carboxy end groups, and will likely generate insoluble fine particles and foreign substances in the BHT system. Further, the timing of addition of the phosphorus compound is not particularly limited as long as it is after the completion of the esterification reaction, but it is preferably added between the addition of the magnesium and manganese compounds and the alkali metal compound. Polycondensation of the esterification reaction product can be carried out using one or more conventional polycondensation catalysts such as antimony trioxide, germanium dioxide, organic titanium compounds, and the like. In addition, one important objective of the present invention is to obtain a polyester with extremely excellent transparency, but depending on the application, silicon dioxide, aluminum silicate, calcium, and magnesium may be added to the polyester as main components. Various additives such as salts, lubricants such as titanium dioxide, matting agents, and even pigments can be added. As described above, the features of the present invention are (1) A slurry of TPA and EG is added continuously or intermittently to a system in which a predetermined amount of BHT is stored under pressure or normal pressure, and A means for carrying out an esterification reaction; (2) a means for carrying out polycondensation after adding a magnesium, manganese compound, and a phosphorus compound; and (3) a means for carrying out polycondensation by adding a specific amount of a specific alkali metal compound. The advantage is that these are suitably combined, and the effects obtained are as follows. A: By adding at least one kind of magnesium and manganese compounds and a specific amount of a phosphorus compound, a polyester having good electrostatic casting properties during film molding and excellent transparency can be obtained. B. By adding a slurry of TPA and EG to stored BHT and performing an esterification reaction under pressure or normal pressure, and by adding a specific amount of a specific alkali metal compound, a product with a high softening point and heat resistance can be obtained. Excellent polyester is obtained. As described above, the method of the present invention has good polyester polycondensation productivity, good electrostatic casting properties, excellent film forming productivity, and is optimal for producing a film raw material with good transparency. The present invention will be explained in detail by referring to Examples below. In addition, parts in Examples are parts by weight, and the measurement method of each characteristic is as follows. [Intrinsic viscosity] Measured at 25°C using O-chlorophenol as a solvent. [Softening point] Measured with a penetrometer. [DEG content] Quantified by gas chromatography. [Solution haze] Measured according to ASTM-D-1003-52. [Color tone] Using a direct reading color difference meter (Suga Test Instruments Co., Ltd.), it was measured in the form of a chip and expressed as L and b values. [Carboxy terminal] Dissolve polyester in O-cresol and add N/
Titrate with 50 NaOH. [Heat resistance] Polyester is melted at 300°C under nitrogen gas substitution, and the intrinsic viscosity is measured at 8 minutes and 68 minutes after the start of melting, and is expressed by the following formula. The smaller ΔIV is, the better the heat resistance is. △IV = (Intrinsic viscosity at 8 minutes) - (Intrinsic viscosity at 68 minutes) [Electrostatic application casting property] At the mouth of the extruder, between the thin wire electrode left on the top of the extruded film and the casting drum. Apply a voltage of 10KV to the cast speed of 45m/m.
It is determined whether or not a film can be formed satisfactorily using an in-line method. [Film Haze] Using a 50μ film, measure the total haze with a haze meter. Example 1 80 parts of BHT, 86.5 parts of TPA, and 37.1 parts of EG (mole ratio
The slurry obtained by kneading 1.15) was continuously pumped for 3.5 hours to carry out the esterification reaction, and the resulting water was distilled out from the top of the rectification column.
After the slurry supply was completed, the esterification reaction was continued for another 1 hour and 30 minutes to complete the esterification reaction. During this time, the reaction temperature was raised to 255°C. The reaction rate determined from the acid value and saponification value was 99.2%. Then, 105 parts of the obtained BHT (polyester
100 parts equivalent) was transferred to a polycondensation reactor, and 0.081 part of magnesium acetate tetrahydrate (M = 3.8 g atoms/
After ⁵ minutes, 0.030 part of methyl acid phosphate (a 1:1 mixture of phosphoric acid monomethyl ester and phosphoric acid dimethyl ester, hereinafter abbreviated as MAP) was added. Antimony oxide, 0.030 parts and lithium acetate, 0.008 parts were added. [R=0.78 (gram atom/10 ⁶ g), (M+
0.5R)/P=1.64] After that, the reaction temperature was increased to 255℃.
The temperature was raised from 760 mmHg to 285°C over 60 minutes, and at the same time the vacuum level of the reaction system was reduced from 760 mmHg to 1 mmHg over 60 minutes. Furthermore, under the conditions of 285℃ and 0.5 to 1 mmHg,
The polycondensation was kept for a certain period of time to complete, and a polyester was obtained. The intrinsic viscosity of the polyester is 0.632,
Softening point is 260.1℃, DEG content is 1.00%, solution haze is 3.7%, carboxy end group 24.7 equivalents/10 ⁶
g, color tone was L value 43.4 and b value 3.7. The polyester was melt-extruded at 290°C by a conventional method, and then biaxially stretched 3.3 times in length and 3.8 times in width.
A film of μ was obtained. At that time, cast speed 45
Electrostatic casting was carried out at m/min with a voltage of 10 KV, and the film could be formed without any problems. Table 1 shows the main characteristic values of the polyester and the castability by electrostatic application during film molding. Comparative Example 1 Esterification reaction and polycondensation reaction were carried out under the same conditions as in Example 1 except that lithium acetate was not added. The properties of the obtained polyester are: intrinsic viscosity 0.615, softening point 257.3, DEG content 1.68%, L value
45.7, b value 2.9, solution haze 4.0%, and carboxy end group 38.3 equivalents/10 ⁶ g. If lithium acetate was not added, DEG was produced as a by-product, the softening point decreased, the number of carboxy end groups increased, and the heat resistance was poor. Next, when the polyester was formed into a film under the same conditions as in Example 1, the electrostatic application casting property was good, but the film often stuck to the casting drum, resulting in uneven film thickness and Breaks occurred frequently and film molding was impossible. Comparative Example 2 0.139 parts of MAP [(M+0.5R)/P=1.00] 0.163 parts of lithium acetate (R/16.0 gram atoms/10 ⁶
A polyester was obtained by carrying out the esterification reaction and polycondensation reaction under the same conditions as in Example 1 except for (g). The polyester has an intrinsic viscosity of 0.620, b
The value was 5.7, and the solution haze was 24.0%. Then, the polyester was subjected to film molding under the same conditions as in Example 1 to obtain a film. The film had a haze of 1.9%. This shows that when lithium acetate is added in an amount exceeding 15 g atoms/10 ⁶ g, the color tone of the polyester becomes yellowish and the transparency deteriorates. Comparative Example 3 0.030 parts of magnesium acetate (M = 1.41 gram atoms/10 ⁶ g) 0.015 parts of MAP [(M + 0.5R)/P
= 1.41)] The esterification reaction and polycondensation reaction were carried out under the same conditions as in Example 1, except that polyester was obtained. The softening point of the polyester is
It was 260.3℃. When the polyester was then formed into a film under the same conditions as in Example 1, the adhesion between the film and the casting drum was poor and the film had many craters. Therefore, while maintaining the casting speed at 45 m/min, the applied voltage was varied from 5 KV to 15 KV, but below 10 KV, the adhesion was poor, and above 10 KV, discharge started.
It was not possible to perform electrostatic casting. From this, in order to obtain good electrostatic application castability at high speed, M specified in the present invention must be set to 2.
It can be seen that it is necessary to set the value to gram atom/10 ⁶ g or more. Comparative Example 4 0.900 parts of magnesium acetate (M=42.0 gram atoms/10 ⁶ g) 0.122 parts of lithium acetate (1.20 atoms/10 ⁶ g) 0.377 parts of MAP [(M+0.5R)/R=
1.50], the esterification reaction and polycondensation reaction were carried out under the same conditions as in Example 1. However, since the polycondensation rate is faster than in Example 1,
The temperature was kept at 285°C and 0.5 to 1 mmHg for only 1 hour. The intrinsic viscosity of the obtained polyester is
0.572, solution haze is 27.0%, heat resistance (△IV) is
It was 0.117. This shows that adding more than 40 (gram atoms/10 ⁶ g) of magnesium acetate deteriorates the transparency and heat resistance of the polyester. Comparative Example 5 0.085 parts of MAP (M=3.8 gram atoms/10 ⁶ g,
Example 1 except that (M+0.5R)/P=0.58)
Esterification and polycondensation reactions were carried out under the same conditions as above to obtain a polyester with an intrinsic viscosity of 0.611 and a softening point of 259.8°C. When the film was then molded under the same conditions as in Example 1, the adhesion between the film and the casting drum was insufficient, many craters were formed, and a good film could not be obtained.
Furthermore, when the applied voltage was increased while maintaining the casting speed at 45 m/min, discharge started and high-speed film formation was not possible. From this, it can be seen that even if the metal amount M is greater than 2, high-speed and good electrostatic casting is not possible unless the value of (M+0.5)/P is 0.8 or more. Comparative Example 6 0.095 parts of magnesium acetate (M = 4.4 gram atoms/10 ⁶ g) 0.010 parts of lithium acetate (R = 0.98 gram atoms/10 ⁶ g) 0.010 parts of MAP [(M+
Polyester was obtained by carrying out the esterification reaction and polycondensation reaction under the same conditions as in Example 1, except that 0.5R)/P=5.81]. The polyester had an intrinsic viscosity of 0.611, a b value of 6.2, and a solution haze of 17.8%. Further, the haze of the film obtained by forming the film under the same conditions as in Example 1 was 1.5%. From this, it can be seen that when the value of (M+0.5R)/P exceeds 5.0, the color tone of the polyester becomes yellowish, and the heat resistance and transparency deteriorate. Example 2 Manganese acetate tetrahydrate, 0.093 parts (M=3.8 gram atoms/10 ⁶ g) in place of magnesium acetate
Trimethylphosphate instead of MAP
An esterification reaction and a polycondensation reaction were carried out in the same manner as in Example 1 except that 0.036 part (M+0.5R)/P=1.63 was used to obtain a polyester. The polyester has an intrinsic viscosity of 0.632, a softening point of 260.7°C,
DEG content 0.91%, number of carboxy end groups 23.1 equivalents/10 ⁶ g solution haze 5.1%, L value 43.8, b value 4.4,
It was hot. Next, film molding was carried out under the same conditions as in Example 1, and a desirable film with good electrostatic castability was obtained. The haze of the film was 0.35%. Comparative Example 7 Calcium acetate instead of magnesium acetate
A polyester was obtained by conducting an esterification reaction and a polycondensation reaction under the same conditions as in Example 1, except that 0.067 part of aqueous salt (M = 3.8 gram atoms/10 ⁶ g) was used. The polyester has an intrinsic viscosity of 0.631 and a softening point of
260.4℃, DEG content 1.02%, solution haze 10.2
%, L value was 41.4, and b value was 3.4. Furthermore, the haze of the film formed under the same conditions as Example 1 was 1.3.
It was %. From the above, it is clear that when calcium acetate other than the one used in the present invention is used, many fine particles are generated in the polyester, resulting in poor transparency, demonstrating the specificity of the magnesium and manganese compounds used in the present invention. ing. Example 3 85 parts of BHT was melted and stored in an esterification reaction vessel at 240 to 245°C, and a slurry obtained by kneading 85 parts of TPA and 34.9 parts of EG (EG/TPA molar ratio 1.1) was continuously fed over 4 hours. An esterification reaction was carried out. After the slurry supply was completed, the reaction temperature was raised to 245 to 250°C, and the esterification reaction was continued for an additional 1.5 hours to complete the reaction. The reaction rate calculated from the acid value and saponification value is
It was 98.3%. 103 parts of BHT obtained as above (polyester
100 parts equivalent) was transferred to a polycondensation vessel, and 0.081 part of magnesium acetate tetrahydrate (M = 3.8 g atoms/10 ⁶
g) as an ethylene glycol solution, and after 5 minutes, add 0.03 part of MAP, and after 5 minutes, add 0.030 part of antimony trioxide and 0.0102 part of lithium acetate dihydrate (R = 1.0 gram atom/10 ⁶ g, (M+
0.5R)/P=1.69) was added. Next, the temperature was raised from 250°C to 290°C in 60 minutes, and at the same time the degree of vacuum was reduced from normal pressure to 1 mmHg in 60 minutes, and the polycondensation reaction was continued for 2 hours and 15 minutes at 290°C and 0.5 to 1 mmHg. , polyester was obtained. The polyester has a softening point of 260.6℃ and a DEG content of 0.99.
%, solution haze 3.9%, L value 41.3, and b value 3.1. Further, when the electrostatic application castability was examined using the same method as in Example 1, the electrostatic application castability was found to be good. Examples 4 to 10 Esterification reactions and polycondensation reactions were carried out under the same conditions as in Example 3, but with different alkali metal compounds, to obtain polyesters. The characteristic values of each polyester are shown in Table 2, and all of them were at a level with no problem. Examples 11 to 14 Esterification and polycondensation reactions were carried out under the same conditions as in Example 3, changing the magnesium compound, manganese compound, alkali metal compound, and phosphorus compound to obtain polyesters. The characteristic values of the polyester are shown in Table 3, and all of them were good and at a level with no problem.

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Claims (1)

[Claims] 1. When producing polyester from a dicarboxylic acid mainly consisting of terephthalic acid and a glycol mainly consisting of ethylene glycol, a predetermined amount of bis(β-
Terephthalic acid and ethylene glycol are supplied to hydroxyethyl) terephthalate and/or its low polymer to carry out an esterification reaction, and then with at least one ethylene glycol-soluble metal compound selected from magnesium and manganese compounds. , at least one alkali metal compound selected from alkali metal hydroxides, hydrogen carbonates, and aliphatic carboxylates; and at least one phosphorus compound selected from phosphorous acid, phosphoric acid, and/or esters thereof. A method for producing polyester, which comprises adding so as to satisfy the following general formula, followed by polycondensation. 2≦M≦40 … 0.3≦R≦15 … 0.8≦M+0.5R/P≦5.0 … [wherein M is the total number of grams of atoms per 10 ⁶ g of the metal polyester in the additive metal compound represented by (gram atoms/10 ⁶ g), R is the total number of gram atoms per 10 ⁶ g of alkali metal polyester in the added alkali metal compound (gram atoms/10 ⁶ g), P is the added phosphorus compound shown in The total number of gram atoms of phosphorus atoms per 10 ⁶ g of polyester (gram atoms/10 ⁶ g) is shown. ] 2. When performing the esterification reaction by supplying terephthalic acid and ethylene glycol, the slurry is supplied continuously or intermittently, and the esterification reaction is performed under substantially normal pressure. A method for producing polyester according to claim 1.