JPH0753690A - Production of polyester - Google Patents

Abstract

PURPOSE:To provide production method of a polyester resin with improved crystallization rate during molding, excellent in mechanical properties, moldability, processability, etc. CONSTITUTION:In producing this polyester from an acid component consisting essentially of terephthalic acid and its lower alcohol ester and a diol component consisting essentially of 1, 4-butanediol, a reactional product obtained by transesterification or esterification is subjected to melt polycondensation to give a prepolymer having <=0.70 intrinsic viscosity. The prepolymer is solidified once and subjected to solid-phase polymerization in an inert gas flow or under reduced pressure in such a way that the increase in crystal melt enthalpy of the polymer is >=10 J/g and intrinsic viscosity of production chip is >=0.70 and <=1.05.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyester resin which has an improved crystallization rate during molding and is excellent in mechanical properties and molding processability.

[0002]

2. Description of the Related Art Polybutylene terephthalate (hereinafter abbreviated as PBT) is widely used in the field of industrial plastics such as automobile parts, electric equipment parts and machine parts, and its mechanical properties. The moldability is highly dependent on the crystallinity of the raw material polymer. For this reason, it is necessary to produce a raw material polymer having a high crystallinity and a high crystallization rate in order to use it as a preferable molded article in the field of industrial plastics which requires high mechanical properties. Although PBT has a relatively high crystallization rate as compared with other resins, it is often not sufficient for mechanical properties, high cycle molding, etc., and especially PBT has a copolymerization component. In general, the copolyester produced by using the above-mentioned compound has a copolymer component as an inhibitor of crystallization and remarkably lowers the crystallization rate, resulting in impaired mechanical properties and moldability. Generally, as a method for producing PBT having a high crystallization rate, a method of melt-mixing a specific crystal nucleating agent and / or a crystallization accelerator using an extruder or the like after completion of the melt polycondensation reaction, or melting of these substances Although the method of addition before the completion of polycondensation has been adopted, the compounding of such a crystal nucleating agent and a crystallization accelerator is complicated, and the dispersion becomes nonuniform, so that the crystallization rate is not always sufficiently improved. May not be obtained, the mechanical strength may not be sufficiently improved, and it may cause other side effects, which is not preferable. It is also known that a molded product once molded is crystallized by heat treatment (annealing) to improve mechanical properties, but this is also not preferable because the process is complicated.

[0003]

Means for Solving the Problems The inventors of the present invention have made extensive studies in order to further improve this point, improve the crystallization rate during melt molding, and directly obtain a molded product having excellent mechanical properties. As a result, they have found that a molded product satisfying the above characteristics can be obtained by solid-phase polymerizing a specific melt-polycondensed polyester under specific conditions, and completed the present invention.
That is, in the present invention, when a polyester is produced from an acid component mainly composed of terephthalic acid or its lower alcohol ester and a diol component mainly composed of 1,4-butanediol, a product obtained by a transesterification reaction or an esterification reaction is produced. The product is melt-polycondensed to a prepolymer having an intrinsic viscosity of 0.70 or less, and after solidifying it once, the increase in its crystal melting enthalpy becomes 10 J / g or more under an inert gas stream or under reduced pressure, The present invention relates to a method for producing polyester, which comprises performing solid-phase polymerization so that the intrinsic viscosity is 0.70 or more and 1.05 or less.

The present invention will be described in detail below. The polyester of the present invention is PBT and its copolymer obtained by using terephthalic acid or a lower alcohol ester such as dimethyl ester thereof as a main constituent acid component and 1,4-butanediol as a main constituent alcohol component. When the copolymerized PBT is prepared, the acid constituent comonomer is an acid component other than the main constituent acid component.
Conventionally known 4,4'-biphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenic acid, adipic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid and their dimethyl esters It is possible to use one type or two or more types of the bifunctional carboxylic acid or its lower alcohol ester.
The diol constituent comonomer is a diol component other than the main constituent diol components such as ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6- Hexanediol, 1,10-decanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, p-xylidene glycol, alkylene oxide adduct of hydroquinone, 2,2-bis (4-hydroxyphenyl) propane Alkylene oxide adduct of bis (4-hydroxyphenyl) sulfone alkylene oxide adduct, 2,6
It is possible to use one or more kinds of conventionally known bifunctional diols such as an alkylene oxide adduct of dihydroxynaphthalene. Further, a halogen-substituted product of the above substances may be used as a comonomer for imparting flame retardancy. The amount of these copolymerization components introduced is preferably 20 mol% or less, and particularly preferably 15 mol% or less, based on the total repeating ester units. When the introduced amount of the copolymerization component exceeds 20 mol% with respect to the repeating ester units of all constituents, the crystallization rate and the mechanical strength remarkably decrease, which is not preferable. In addition, trifunctional or higher functional compounds such as trimethyl trimesate, trimethyl trimellitate, trimethylolpropane and pentaerythritol, stearyl alcohol, monofunctional compounds such as methyl o-benzoylbenzoate and monoepoxy compounds, and p-hydroxyethoxy. It is also possible to use a small amount of a hydroxycarboxylic acid derivative such as a benzenecarboxylic acid ester, a polypropylene glycol, a polyalkylene glycol such as polytetrahydrofuran, or a combination with the above-mentioned copolymerization component.

In the production method of the present invention, first, terephthalic acid or its lower alcohol ester and 1,4-butanediol are used as main raw materials, and melt polycondensation is performed through an esterification or transesterification reaction to prepare a specific prepolymer. . In the transesterification reaction, the lower alcohol ester of terephthalic acid and 1,4-butanediol are used in a molar ratio of 1: 1 to 1: 1.
It is carried out at a temperature of 140 to 230 ° C. at a normal pressure of 1: 2 while removing lower alcohol such as methanol continuously produced. Examples of the catalyst for obtaining a practical reaction rate include titanium compounds, tin compounds, lead compounds, zinc compounds, manganese compounds, and the like. Among them, organic titanate compounds,
Titanium tetrachloride compounds and their hydrolyzates or alcoholysis products, tin oxide compounds, tin acetate compounds, organic tin compounds and the like are preferable. More specifically, tetrabutyl titanate, tetrapropyl titanate, tetraethyl titanate, tetramethyl titanate and hydrolysates thereof, hydrolysates such as titanium tetrachloride and titanium sulfate, potassium titanium fluoride, zinc titanium fluoride, cobalt titanium fluoride. Inorganic titanium compounds such as, titanium oxalate, titanium compounds conventionally known as polyester production catalysts such as potassium titanium oxalate, and / or dibutyltin oxide, dibutyltin acetate, dioctyltin diacetate, diphenyltin dilauryl mercaptide,
Conventionally known tin compounds are mentioned as polyester production catalysts such as polydibutyltin sebacate, dibutyltin ethylene glycolate, dioctyltin thiosalicylate, diphenyltin benzene sulfonate and dimethyltin-p-toluene sulfonate. Particularly preferred are tetrabutyl titanate, tetrapropyl titanate, hydrolyzate of titanium tetrachloride, dibutyltin oxide, dibutyltin acetate, dioctyltin diacetate and the like. If necessary, the addition of these catalysts can be divided into several times during the reaction. The esterification reaction using terephthalic acid and 1,4-butanediol as a main raw material is carried out at a ratio of 1 to 5 moles of 1,4-butanediol to 1 mole of terephthalic acid at a normal pressure or a pressure of 190 to.
It is carried out at a temperature of 250 ° C. while continuously removing water produced. At this time, it is often convenient to carry out in the presence of the above-mentioned titanium compound or tin compound.

In the melt polycondensation reaction, the product obtained by the above-mentioned transesterification reaction or esterification reaction is 180 to 26
The reaction system is depressurized at 0 ° C., and excess 1,4-butanediol and by-products are continuously removed, and melt polymerization is carried out until a specific degree of polymerization (intrinsic viscosity) is obtained. As a catalyst for obtaining a practical reaction rate in such a melt polycondensation reaction, a compound used in the above transesterification reaction or esterification reaction can be used as it is, and in order to improve the rate of the condensation reaction. It is also possible to add one or more of these before the start of the condensation reaction.
Further, it is also possible to add a phosphorus compound and / or an alkaline compound or the like in the monomer preparation step or the melt polycondensation step, and particularly when an appropriate amount of the phosphorus compound is used, the crystallization rate and the mechanical strength in the present invention. Can be efficiently increased. Typical phosphorus compounds here include triphenyl phosphite, tridodecyl phosphite, tridecyl phosphite, trioctyl phosphite, tripropyl phosphite, triethyl phosphite, diphenyl decyl phosphite, tris (2,4- Di-t-butylphenyl) phosphite, tris (4-octylphenyl) phosphite, tris (4- (1-phenylethylphenyl)) phosphite, tetrakis (2,4-di-t-butylphenyl) -4 ,
4'-bisphenylene phosphonite, 3,5-dibutyl-4-hydroxybenzylphosphonate diethyl ester, triphenylphosphine, tridodecylphosphine, tridecylphosphine, trioctylphosphine, tripropylphosphine, Examples thereof include tetraalkylphosphonium halides and tetraalkylphosphonium sulfonate compounds.

In the present invention, the melt polycondensed PBT prepolymer is required to have an intrinsic viscosity at 25 ° C. in orthochlorophenol of 0.70 or less. In particular, in order to enhance the effect of the present invention, the intrinsic viscosity is preferably 0.50 or less, and when the intrinsic viscosity of the prepolymer in the melt polycondensation step exceeds 0.70, the crystallization rate and the mechanical strength are improved. It is not preferable because the effect is reduced. Further, the lower limit of the intrinsic viscosity of the prepolymer is not particularly limited, in order to efficiently discharge the prepolymer as a strand or sheet from the reactor of the melt polycondensation and solidify it, an intrinsic viscosity of 0.30 or more Are preferred.

The prepolymer is then solidified by cooling, crushed or granulated, and then transferred to solid phase polymerization. Cooling and solidification is performed by a usual method. For example, the prepolymer discharged from the melt polycondensation reactor in the form of a strand or a sheet is introduced into an air stream or in water to be cooled and solidified, and then ground or cut. At this time, it is advantageous to use a chip having a size as uniform as possible so that the increase of the molecular weight is uniformly carried out during the solid phase polymerization. Next, the solidified and crushed polymer chip is transferred to a reactor which is maintained at a temperature 5 to 60 ° C. lower than its melting point and has an appropriate gas inlet, exhaust port, vacuum connector, etc., under an inert gas stream or Solid phase polymerization is performed by heat treatment in vacuum. This reactor may be either a batch type or a continuous type. Incidentally, in order to prevent the polymer chips from being fused to each other during the solid phase polymerization, the chips may be dried before the solid phase polymerization as a pretreatment.

In the present invention, the above solid-state polymerized production chip has an intrinsic viscosity of 25 ° C. in orthochlorophenol.
It must be 0.70 or more and 1.05 or less. The desired degree of polymerization (intrinsic viscosity) can be appropriately adjusted by the residence time, the treatment temperature and the like. If the intrinsic viscosity exceeds 1.05, the crystallization speed and mechanical strength will decrease, and the improvement effect will be less, and if it is less than 0.70, the elongation and toughness will decrease, so in either case Is also not preferable. In general, such an intrinsic viscosity value can be obtained only by melt polycondensation, and it is generally known that solid phase polymerization improves the intrinsic viscosity of polyester. It is not necessary that the viscosity is in the above range, and it is not necessary to simply carry out solid phase polymerization. Further, the increment of the crystal melting enthalpy during the solid phase polymerization of the chip is 10 J / g or more. It is indispensable and important to process so that Especially 1
It is preferably 3 J / g or more. The increment of the crystal melting enthalpy is determined by the difference between the crystal melting enthalpy of the manufactured chip after the solid state polymerization and the crystal melting enthalpy of the prepolymer chip. When the increase in crystal melting enthalpy during solid state polymerization is 10 J / g or less, the effect of improving the crystallization rate and mechanical strength in melt molding is not preferable, and the condition is not preferable. It is necessary to satisfy the conditions together. Where these conditions,
In particular, in order to satisfy the increase in crystal melting enthalpy during solid phase polymerization, the intrinsic viscosity of the prepolymer to be subjected to solid phase polymerization, solid phase polymerization conditions (temperature and time, etc.), phosphorus compound, etc. The presence or absence of etc. is a very important factor. Although these conditions are not uniformly obtained by general solid-phase polymerization and require specific conditions,
It can be determined by some preliminary trial experiments. The influence of history such as crystallization (increase in crystallization enthalpy) during solid phase polymerization disappears during melting in a molded product that is once melted and should be regulated by polymer structure and molding conditions. It is common knowledge that the above-mentioned history condition during solid-state polymerization is surprisingly a significant improvement effect on the crystallization rate during melt molding, moldability during injection molding, and mechanical strength of molded products. Will bring. The chips produced in this manner can be directly subjected to melt molding, and can also be melt-kneaded and then subjected to molding as a composition. .

In the production of the polyether of the present invention, as long as the requirements of the present invention are satisfied, a crystal nucleating agent and other additives, other thermoplastic resins, organic fillers, inorganic fillers, etc. may be used as needed. Alternatively, two or more kinds may be supplementarily used during the polymerization. Further, the PBT-based polyester prepared under the conditions satisfying the requirements of the present invention can obtain its effect even as a composition in which these substances are further supplemented. Examples of the additives include stabilizers such as conventionally known ultraviolet absorbers and antioxidants, antistatic agents, flame retardants, flame retardant aids, colorants such as dyes and pigments, lubricants, plasticizers, lubricants, release agents. A mold agent is exemplified. Further, as the inorganic filler, glass fiber, milled glass fiber, glass beads, glass flakes, silica, alumina fiber, zirconia fiber, potassium titanate fiber, carbon fiber, carbon black,
Graphite, calcium silicate, aluminum silicate, kaolin,
Silicates such as talc and clay, metal oxides such as iron oxide, titanium oxide, zinc oxide, antimony oxide and alumina, carbonates and sulfates of metals such as calcium, magnesium and zinc, and further silicon carbide and silicon nitride, Examples thereof include boron nitride, and examples of the organic filler include high melting point aromatic polyester fibers, liquid crystalline polyester fibers, aromatic polyamide fibers, fluororesin fibers, and polyimide fibers.
Further, as the thermoplastic resin, polyester-based resin other than the present invention, polyester-based resin, polyolefin-based resin, polystyrene-based resin, polyamide-based resin, polycarbonate, polyacetal, polyarylene oxide, polyarylene sulfide, fluorine resin and the like within a certain limit. If available, it can be used.

[0011]

INDUSTRIAL APPLICABILITY As described above, the polyester obtained according to the present invention has an improved crystallization rate, excellent moldability in injection molding, and excellent mechanical strength of a molded product, and is very useful as a molding material.

[0012]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Example 1 194 parts by weight of dimethyl terephthalate, 126 parts by weight of 1,4-butanediol, and 1.21 parts by weight of titanium tetrabutoxide were charged in a reactor equipped with a stirrer and a distilling tower, which was sufficiently replaced with nitrogen, and the reactor was placed in the reactor. The internal temperature is 140 ℃,
The temperature was gradually raised and the by-product methanol was distilled off to carry out a transesterification reaction. Distilled methanol is the theoretical amount of 85
At wt% the temperature of the reactants increased to 185 ° C, which was then transferred to another reactor at a temperature of 210 ° C and charged with 1.0 t
After decompressing to orr, simultaneously raising the reaction temperature to 250 ℃, stirring at 1.0 torr pressure for 2.0 hours to carry out melt polycondensation, and then extruding the melt as a strand from the jet outlet, cooling the strand with water. Then, the adhering water was removed by passing under hot air and cut to obtain a white, cylindrical prepolymer chip having a diameter of 2 mm and a length of 3 mm. The resulting prepolymer has an intrinsic viscosity in orthochlorophenol at 25 ° C.
Had 0.45. Next, this tip-like prepolymer was put through a preheater (residence for 30 minutes) and then jacketed (210
℃ heat medium) supplied to the top of the vertical cylindrical solid-phase reactor,
It is deposited at a certain height in the vessel to keep a certain residence time, extracted from the lower part, and dried 210 ° C nitrogen is supplied from the lower part and discharged from the upper part for continuous solid-phase polymerization under a nitrogen stream. went. The internal temperature of this reaction system is 205 at the top.
C., 208.degree. C. at the bottom, and the residence time was 10 hours.
The polymer obtained had an intrinsic viscosity of 0.95 at 25 ° C in orthochlorophenol. In addition, the increase in enthalpy of crystal fusion during solid state polymerization of manufactured chips was 14.3 J / g.
Met. The obtained manufactured chip was dried and then DS
The crystallization rate was evaluated by measuring the isothermal crystallization time by maintaining the temperature at 197 ° C. after melting once with a C measuring device. Also, make ASTM No. 1 tensile test piece by injection molding,
This was evaluated for tensile strength according to ASTM D638.
The results are shown in Table 1. The test pieces were molded under the following conditions. Molding machine: Toshiba IS30EPN Cylinder temperature: 250 ° C (nozzle) -245 ° C (third zone) -240 ° C- (second zone) -220 ° C (first zone) Mold temperature: 65 ° C Screw rotation speed: 120 rpm The specific conditions for measuring the isothermal crystallization time are as follows. Melting temperature: 260 ° C. Melting time: 3 minutes Cooling rate: 80 ° C./min (260 ° C. to 197 ° C.) Hold temperature: 197 ° C. Examples 2-3 and Comparative Example 1 Examples except that the intrinsic viscosity of the prepolymer was changed. Melt polycondensation and solid phase polymerization were carried out in the same manner as in 1. The results are also shown in Table 1. Examples 4 to 5 and Comparative Examples 2 to 3 Melt polycondensation and solid phase polymerization were performed in the same manner as in Example 1 except that the intrinsic viscosity of the manufactured chip was changed by changing the solid phase polymerization time. The results are also shown in Table 1. Comparative Example 4 Melt polycondensation and solid phase polymerization were carried out in the same manner as in Example 1 in the case where the increment of crystal enthalpy of fusion did not satisfy the requirements of the present invention by changing the intrinsic viscosity of the prepolymer and the solid phase polymerization time. It was The results are also shown in Table 1.

[0013]

[Table 1]

Example 6 194 parts by weight of dimethyl terephthalate, 126 parts by weight of 1,4-butanediol and 1.21 parts by weight of titanium tetrabutoxide were subjected to a transesterification reaction in the same manner as in Example 1, and this was followed by heating at a temperature of 210 ° C. Transfer to another reactor, 1.0t in 1 hour
The pressure was reduced to orr, and at the same time, the reaction temperature was raised to 250 ° C. After continuing stirring at a pressure of 1.0 torr for 1.9 hours, 1.87 parts by weight of tridecyl phosphite was charged into the reaction system, and polymerization was further performed for 0.2 hours. The melt was extruded as a strand from the jet outlet to obtain a white, cylindrical prepolymer chip similar to that in Example 1. The resulting prepolymer had an intrinsic viscosity of 0.44. Next, this chip-shaped prepolymer was supplied to the same solid-phase reactor as in Example 1. The residence time was 15 hours, the polymer obtained had an intrinsic viscosity of 0.94, and the increase in the crystal melting enthalpy of the manufactured chips was
It was 18.1 J / g. The obtained manufactured chips were evaluated for crystallization rate and tensile strength in the same manner as in Example 1.
The results are shown in Table 2.

Example 7, Comparative Example 5 194 parts by weight of dimethyl terephthalate, 126 parts by weight of 1,4-butanediol and 1.21 parts by weight of titanium tetrabutoxide were transesterified in the same manner as in Example 1 and then this was reacted. Transfer to another reactor at a temperature of 210 ℃, 1.0t for 1 hour
The pressure was reduced to orr, and at the same time, the reaction temperature was raised to 250 ° C. After continuing stirring at a pressure of 1.0 torr for 1.9 hours, 1.87 parts by weight of tridecyl phosphite and boron nitride were placed in the reaction system.
0.2 parts by weight and 2.2 parts by weight of melted polyethylene wax (average molecular weight 5000) were added, and polymerization was further carried out for 0.2 hours. The melt was extruded as a strand from the jet outlet to obtain a white, cylindrical prepolymer chip similar to that in Example 1. The resulting prepolymer had an intrinsic viscosity of 0.45. Next, this chip-shaped prepolymer was used in Example 1.
It was fed to a solid phase reactor similar to. Dwell time is 14 hours,
The resulting polymer had an intrinsic viscosity of 0.94. The increase in the enthalpy of crystal fusion of the chips at this time was 14.5 J / g. The obtained manufactured chips were evaluated for crystallization rate and tensile strength in the same manner as in Example 1. On the other hand, for comparison, the prepolymer had an intrinsic viscosity of 0.85, and Example 7 was used.
Solid-state polymerization was carried out in the same manner as above to obtain an intrinsic viscosity of 0.94. The increase in enthalpy of crystal fusion at this time was 5.7 J / g. The evaluation values are also shown in Table 2.

[0016]

[Table 2]

Example 8, Comparative Example 6 170 parts by weight of dimethyl terephthalate, 24.0 parts by weight of dimethyl isophthalate, 126 parts by weight of 1,4-butanediol, and 1.21 parts by weight of titanium tetrabutoxide were transesterified in the same manner as in Example 1. The reaction is allowed to take place and this is followed by a temperature of 210 ° C.
Was transferred to another reactor of 1.0 torr and the reaction temperature was raised to 250 ° C. at the same time. After continuing stirring at a pressure of 1.0 torr for 2.0 hours, 1.87 parts by weight of tridecyl phosphite and 0.1 parts by weight of boron nitride were charged into the reaction system, and polymerization was further carried out for 0.2 hours. The melt was extruded as a strand from the ejection port to obtain a cylindrical prepolymer chip similar to that in Example 1. The resulting prepolymer had an intrinsic viscosity of 0.44. Next, this chip-shaped prepolymer was supplied to the same solid-phase reactor as in Example 1. It is deposited at a certain height in the vessel so as to maintain a certain residence time, extracted from the lower part, and dried 185 ° C nitrogen is supplied from the lower part and discharged from the upper part for continuous solid-phase polymerization under a nitrogen stream. went. The internal temperature of this reaction system was 185 ° C. in the upper part and 188 ° C. in the lower part, and the residence time was 20 hours. The obtained polymer had an intrinsic viscosity of 1.01, and the increment of crystal melting enthalpy during solid state polymerization was 12.1 J / g. On the other hand, for comparison, solid phase polymerization was carried out in the same manner as in Example 8 with the prepolymer having an intrinsic viscosity of 0.86 to obtain a product having an intrinsic viscosity of 1.00. The increase in crystal melting enthalpy of this product during solid state polymerization was 6.4 J / g. The evaluation values are also shown in Table 3. The crystallization rate in this case was evaluated by keeping the temperature at 184 ° C. and measuring the isothermal crystallization time.

[0018]

[Table 3]

Claims (4)

[Claims] 1. A product obtained by a transesterification reaction or an esterification reaction in producing a polyester from an acid component mainly containing terephthalic acid or a lower alcohol ester thereof and a diol component mainly containing 1,4-butanediol. The product is melt-polycondensed to a prepolymer with an intrinsic viscosity of 0.70 or less, and once solidified, the increase in the enthalpy of crystal fusion becomes 10 J / g or more in an inert gas stream or under reduced pressure, and A method for producing a polyester, which comprises subjecting a polyester to solid phase polymerization so that the viscosity is 0.70 or more and 1.05 or less. 2. The intrinsic viscosity of the prepolymer before the initiation of solid phase polymerization
The method for producing a polyester according to claim 1, which is 0.50 or less. 3. The method according to claim 1, wherein at least one phosphorus compound is added to the reaction system before the melt polycondensation is completed.
A method for producing the described polyester. 4. A molded product obtained by melt-molding a polyester or a composition thereof obtained by the method according to any one of claims 1 to 3.