JP4033824B2 - Method for producing polybutylene terephthalate - Google Patents

Description

  The present invention is remarkably effective in reducing molecular weight due to thermal deterioration during molding and blending and heating, and preventing coloration, improving productivity, heat resistance, hue (particularly color b value), mechanical strength, and molding. The present invention relates to a method for producing polybutylene terephthalate having excellent properties.

  Polyesters, especially polyethylene terephthalate, polyethylene naphthalate, polytrimethylene terephthalate and polybutylene terephthalate are superior in their mechanical, physical and chemical properties, so that Widely used in molded products.

  In particular, polybutylene terephthalate is an engineering plastics that has a high crystallization speed, heat resistance, and strong strength, and is widely used as a fiber, sheet, and film, including various molded products. in use. However, since this polybutylene terephthalate-based polyester is inferior in heat resistance when compared with polyethylene terephthalate, it has a problem that the molecular weight is decreased due to thermal decomposition during polymerization and coloration tends to occur.

In order to solve such a problem, it is generally performed to suppress yellowishness by adding a cobalt compound to polyester to suppress yellowishness or by adding an additive such as an antioxidant. Indeed Hue (b value) of the polyester by adding a cobalt compound to improve can, but reduces the melt heat stability of the polyester by adding a cobalt compound, a polymer - is also liable to occur in the thermal decomposition There is a problem of becoming.

  In addition, for molecular weight reduction due to heat degradation during heat melting, in order to ensure the molecular weight required after heat melting, the molecular weight of the pellet before heat melting is increased in advance in anticipation of the molecular weight decrease that occurs during heat melting. Although there is a method to keep it, it is not necessarily efficient from the viewpoint of productivity such as energy.

In order to solve such problems, a product obtained by reacting a titanium compound with trimellitic acid (see, for example, Patent Document 1), or obtained by reacting a titanium compound with a phosphite. It is disclosed that each product is used as a reaction catalyst for polyester (see, for example, Patent Document 2). Certainly, according to this method, the melt heat stability of the polyester can be improved to some extent. But still obtained polymer - color phase is not sufficient. Thus to suppress the heat deterioration, and polymer over the color phase is desired good polybutylene terephthalate.
Japanese Examined Patent Publication No.59-46258 JP 58-38722 A

  The object of the present invention is to eliminate the problems of the prior art described above, to significantly reduce the molecular weight reduction due to thermal degradation during heating and melting, and to deteriorate the hue (color b value), productivity, heat resistance, An object of the present invention is to provide polybutylene terephthalate which is excellent in mechanical strength and moldability and used for fibers, various molded articles, sheets and films.

  As a result of intensive studies in view of the above prior art, the present inventors have completed the present invention. That is, it can be achieved by bringing polybutylene terephthalate into contact with an aqueous solution of alkali metal salt and / or alkaline earth metal salt having a concentration of 1 ppm to 10 wt%.

  Polyethylene terephthalate obtained by the treatment method of the present invention is remarkably effective in reducing molecular weight and preventing coloration due to thermal degradation that occurs during heating and melting during molding, blending, etc., improving productivity, heat resistance, hue ( In particular, polybutylene terephthalate having excellent color b value), mechanical strength, and moldability can be provided.

  Hereinafter, the present invention will be described in detail. The main repeating unit of the polybutylene terephthalate used in the present invention is butylene terephthalate. Copolymerized polybutylene terephthalate obtained by copolymerizing a third component other than butylene terephthalate may also be used. The third component (copolymerization component) may be a dicarboxylic acid component, a glycol component, or an aromatic diol component. Further, “main” represents 70 mol% or more of all repeating units.

  Specific components preferably used as the third component include 2,6-naphthalenedicarboxylic acid, isophthalic acid, phthalic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylketone as the dicarboxylic acid component. Aromatic dicarboxylic acids such as dicarboxylic acid, sodium-sulfoisophthalic acid or dibromoterephthalic acid, aliphatic dicarboxylic acids such as malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid or decanedicarboxylic acid, cyclohexanedicarboxylic acid Acid, decalin dicarboxylic acid, alicyclic dicarboxylic acid such as hexahydroterephthalic acid, etc., or ester bond-forming derivatives thereof can be raised. Here, the ester bond-forming derivative is a compound that easily forms an ester bond by a chemical reaction, and specifically includes an acid halide, a lower alkyl ester, and a lower aromatic ester. These can be used alone or in combination of two or more.

  Specific glycol components preferably used as the third component include aliphatic glycol components such as ethylene glycol, diethylene glycol, triethylene glycol, trimethylene glycol, hexagonal. Methylene glycol, polyethylene glycol, polytetramethylene glycol, cyclohexane dimethanol, 2,2-bis [4- (2-hydroxyethoxy) phenyl] propane, etc. are used as alicyclic diols. For example, cyclohexanediol as the component, glycolic acid, hydroacrylic acid, 3-oxypropionic acid, etc. as the aliphatic oxycarboxylic acid component, and asacic acid, quinova as the alicyclic oxycarboxylic acid component. Acids etc. as aromatic oxycarboxylic acid components such as salicylic acid, m-oxybenzoic acid , P-oxybenzoic acid, mandelic acid, atrolactic acid and the like. These can be used alone or in combination of two or more. Further, as aromatic diol components, for example, hydroquinone, catechol, naphthalene diol, resorcin, 4,4'-dihydroxy-diphenylsulfone, bisphenol A [2,2'-bis (4-hydroxyphenyl) Propane], tetrabromobisphenol A and the like. These can be used alone or in combination of two or more.

  Further, a polyfunctional compound having a valence of 3 or more, such as glycerin, trimethylolpropane, pentaerythritol, trimellitic acid, trimesic acid, pyrol within the range in which the polymer chain constituting polybutylene terephthalate is substantially linear. Mellitic acid, tricarballylic acid, gallic acid or the like may be copolymerized, and a monofunctional compound such as o-benzoylbenzoic acid or naphthoic acid may be added as necessary.

  What is necessary is just to manufacture the said polybutylene terephthalate using the manufacturing method of a conventionally well-known polybutylene terephthalate. For example, an esterification reaction is performed using terephthalic acid and butanediol, or a transesterification reaction is performed using a lower alkyl ester of terephthalic acid (for example, dimethyl ester) and butanediol. Further, it can be produced by a polycondensation reaction.

  It is preferable to use a transesterification catalyst, a polymerization catalyst, a stabilizer and the like when producing polybutylene terephthalate by these techniques. As these catalysts and stabilizers, those known as known polybutylene terephthalate catalysts and stabilizers can be used. For example, as the catalyst used, titanium compounds such as tetraisopropoxy titanium, tetrapropoxy titanium, tetra-n-butoxy titanium, tetraethoxy titanium, tetraphenoxy titanium, octaalkyl trititanate, hexaalkyl dititanate, etc. , Or dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethylditin oxide, cyclohexahexylditin oxide, didodecyltin oxide, triethyltin hydroxide, triphenyltin hydroxide, triisobutyltin acetate, dibutyltin diacetate , Diphenyltin dilaurate, monobutyltin trichloride, dibutyltin dichloride, tributyltin chloride, dibutyltin sulfide The organic tin compounds such as butyl hydroxy tin oxide, monoalkyl tin compound among them is preferably used. There is no problem even if these catalysts are used in combination of not only one type but also two or more types.

  If necessary, other additives such as colorants, antioxidants, ultraviolet absorbers, antistatic agents, flame retardants and the like may be used.

  Further, after polybutylene terephthalate obtained in the melt polymerization step is pelletized, it may be polycondensed in the solid phase polymerization step for further increase in molecular weight or reduction of impurities such as tetrahydrfuran, if necessary. Any known method may be adopted as a method for carrying out solid phase polymerization.

  In the present invention, it is necessary to directly contact the polybutylene terephthalate obtained by the above method with an aqueous solution of an alkali metal salt and / or an alkaline earth metal salt.

  The alkali metal salt used in the present invention is not particularly limited as long as it is water-soluble. Specifically, potassium chloride, potassium alum, potassium formate, tripotassium citrate, dipotassium hydrogen citrate, Potassium dihydrogen citrate, potassium gluconate, potassium succinate, potassium butyrate, dipotassium oxalate, potassium hydrogen oxalate, potassium stearate, potassium phthalate, potassium hydrogen phthalate, potassium metaphosphate, potassium malate, phosphoric acid Tripotassium, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium nitrite, potassium benzoate, potassium hydrogen tartrate, potassium bioxalate, potassium biphthalate, potassium bitartrate, potassium bisulfate, potassium nitrate, potassium acetate, water Potassium oxide, potassium carbonate, potassium carbonate Sodium, potassium bicarbonate, potassium lactate, potassium sulfate, potassium hydrogen sulfate, sodium chloride, sodium formate, trisodium citrate, disodium hydrogen citrate, sodium dihydrogen citrate, sodium gluconate, sodium succinate, sodium butyrate, Disodium oxalate, sodium hydrogen oxalate, sodium stearate, sodium phthalate, sodium hydrogen phthalate, sodium metaphosphate, sodium malate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, nitrous acid Sodium, sodium benzoate, sodium hydrogen tartrate, sodium bioxalate, sodium biphthalate, sodium bitartrate, sodium bisulfate, sodium nitrate, sodium acetate, sodium hydroxide, sodium carbonate Sodium, sodium bicarbonate, sodium lactate, sodium sulfate, sodium hydrogen sulfate, lithium chloride, lithium formate, trilithium citrate, dilithium hydrogen citrate, lithium dihydrogen citrate, lithium gluconate, lithium succinate, lithium butyrate, Lithium oxalate, lithium hydrogen oxalate, lithium stearate, lithium phthalate, lithium hydrogen phthalate, lithium metaphosphate, lithium malate, trilithium phosphate, dilithium hydrogen phosphate, lithium dihydrogen phosphate, nitrous acid Lithium, lithium benzoate, lithium hydrogen tartrate, lithium heavy oxalate, lithium biphthalate, lithium bitartrate, lithium bisulfate, lithium nitrate, lithium acetate, lithium hydroxide, lithium carbonate, lithium hydrogen carbonate, lithium lactate, lithium sulfate , Sulfuric acid Examples include lithium hydrogen, and among them, sodium acetate, potassium acetate, dipotassium carbonate, potassium bicarbonate, disodium carbonate, sodium bicarbonate, potassium sodium carbonate, lithium acetate, dilithium carbonate, lithium bicarbonate Can be preferably used, preferably lithium salt, sodium salt, potassium salt, more preferably sodium salt, potassium salt, particularly preferably potassium salt. On the other hand, when viewed from the anion species side, acetates and / or carbonates are preferred among these, and acetates are particularly preferred.

  Further, the alkaline earth metal salt used in the present invention is not particularly limited as long as it is water-soluble, but specifically, calcium chloride, calcium formate, calcium succinate, calcium butyrate, calcium oxalate , Calcium stearate, calcium phosphate, calcium nitrate, calcium acetate, calcium hydroxide, calcium carbonate, calcium lactate, calcium sulfate, magnesium chloride, magnesium formate, magnesium succinate, magnesium butyrate, magnesium oxalate, magnesium stearate, magnesium phosphate, Examples thereof include magnesium nitrate, magnesium acetate, magnesium hydroxide, magnesium carbonate, magnesium lactate, magnesium sulfate, etc. Among them, magnesium acetate, calcium acetate, magnesium carbonate Siumu, it is preferable to use calcium carbonate. Preferably, calcium salt and magnesium salt are used, and more preferably calcium salt is used. On the other hand, when viewed from the anion species side, among these, acetates and / or carbonates are preferred.

  In the present invention, one of the above alkali metal salts and / or alkaline earth metal salts may be selected and used as an aqueous solution, or a mixture of two or more may be used as an aqueous solution.

  The aqueous solution of the alkali metal salt and / or alkaline earth metal salt needs to be in a concentration range of 1 ppm to 10 wt%. When the concentration is less than 1 ppm, the molecular weight reduction (decrease in intrinsic viscosity) due to thermal degradation that occurs during heating and melting such as molding and blending, and the effect of preventing coloring are not sufficient. If it exceeds 10 wt%, the cost increases. A preferable range of the concentration is 10 ppm to 5 wt%, and more preferably 100 ppm to 2 wt%.

  In addition, the contact method between the pellet and the aqueous solution of the salt may be either a batch type or a continuous type. When the batch type is used, an alkali metal salt and / or alkaline earth metal salt aqueous solution and What is necessary is just to carry out the method etc. which put the butylene terephthalate pellet and contact, and in the case of a continuous type, supply the aqueous solution of an alkali metal salt and / or alkaline-earth metal salt by a counter current or a parallel flow, and a pellet. The method of making it contact with can be illustrated.

  The form of polybutylene terephthalate to be contacted with an aqueous solution of the alkali metal salt and / or alkaline earth metal salt is not particularly limited. A person skilled in the art normally assumes a chip, but is not limited to a chip, and may be, for example, a sheet. In this case, for example, a method of continuously introducing a sheet into a continuous processing apparatus and bringing it into contact with an aqueous solution of the alkali metal salt and / or alkaline earth metal salt can be exemplified. Further, the temperature at which the aqueous solution and polybutylene terephthalate are brought into contact with each other is not particularly limited. The contact time is usually 10 minutes to 10 hours, preferably 1 to 6 hours. Among these, it is preferable in that processing can be easily performed in the form of a chip.

  The above-mentioned treatment conditions are different from the appropriate immersion treatment time depending on the concentration, temperature, etc. of the alkali metal salt and / or alkaline earth metal salt solution, as well as the intrinsic viscosity, hue, and molecular weight of the polybutylene terephthalate to be treated. What is necessary is just to select suitably according to the magnitude | size etc. of a pellet, and when supplying the aqueous solution of the above-mentioned alkali metal salt and / or alkaline-earth metal salt continuously, also about the flow volume of an aqueous solution, whether it is a countercurrent or a parallel flow, What is necessary is just to select suitably.

  Although the pellets processed by these methods need to be dried before being subjected to the molding process, a commonly used drying method for polybutylene terephthalate can be used.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention does not receive any limitation by this. In addition, each value in an Example was calculated | required with the following method. In Examples and Comparative Examples, “parts” represents parts by weight.
1) Intrinsic viscosity:
According to a conventional method, the measurement was performed at 35 ° C. using an orthochlorophenol solvent.
2) color phase (Kara -L value and color -b value):
The polybutylene terephthalate pellets were measured using a Z-1001DP quick color difference meter manufactured by Nippon Denshoku. The L value indicates the lightness, and the larger the value, the higher the lightness. The b value indicates the greater the yellowness, the greater the value.
3) Heat melting treatment:
The heat-melting treatment was performed by drying polybutylene terephthalate pellets at 160 ° C. for 5 hours, and then using an injection molding machine Dynamelter-M-100DM manufactured by Meiki Seisakusho at a cylinder temperature of 275 ° C. and a molding cycle of 30 seconds. The intrinsic viscosity of the obtained molded body (the flat plate having a thickness of 5 mm), the color phase (Col-b), by comparing the values before and after the molding, and evaluate the degree of thermal degradation due to heating and melting.

[Example 1]
In a mixture of 100 parts of dimethyl terephthalate and 70.5 parts of 1,4-butanediol, 0.0526 parts of tetra-n-butyl titanate are provided with a stirrer, rectifying column and methanol distillation condenser. The transesterification reaction was carried out while distilling out the methanol produced as a result of the reaction while gradually raising the temperature from 140 ° C. The internal temperature reached 190 ° C. 3 hours after the start of the reaction. Subsequently, the obtained reaction product is transferred to another reactor equipped with a stirrer and a glycol distillation condenser, and gradually heated from 210 ° C. to 250 ° C., and from a normal pressure to a high vacuum of 70 Pa. The polymerization reaction was carried out while reducing the pressure. While tracing the melt viscosity of the reaction system, the polymerization reaction was terminated when the intrinsic viscosity reached 0.69 dl / g.

  The molten polymer was extruded in the form of a strand from the bottom of the reactor into cooling water, and was cut into pellets using a strand cutter.

  The obtained pellets were pre-crystallized at 120 ° C. for 4 hours, charged into a tumbler type solid-phase polymerization apparatus, heated to 200 ° C. in a nitrogen atmosphere, and then solid-phased at a high vacuum of 70 Pa for about 14 hours. Polymerization reaction was performed to obtain polybutylene terephthalate pellets having an intrinsic viscosity of 0.875 dl / g.

  Subsequently, 1 kg of the polybutylene terephthalate pellets was placed in a 5 liter treatment apparatus containing 2.5 kg of a 0.5 wt% potassium acetate aqueous solution at 25 ° C. and contacted for 4 hours. After removal, the film was dried at 160 ° C. for 5 hours under a nitrogen stream. The results are shown in Table 1.

[Examples 2 to 22]
In Example 1, the same operation was performed except that the type, concentration and treatment conditions of the metal salt used as the aqueous solution were changed. The results are shown in Table 1.

[Comparative Example 1]
In Example 1, the same operation was performed except that the contact treatment and the drying treatment were not performed. The results are shown in Table 1 [Comparative Example 2]
In Example 1, the same operation was performed except that water was put into the treatment apparatus as a contact treatment liquid. The results are shown in Table 1.

  Polyethylene terephthalate obtained by the treatment method of the present invention is extremely effective in reducing molecular weight (decrease in intrinsic viscosity) due to thermal degradation that occurs during heating and melting during molding, blending, etc., and preventing coloring, improving productivity. , Polybutylene terephthalate having excellent heat resistance, hue (particularly color b value), mechanical strength, and moldability can be provided. The resulting polybutylene terephthalate can be suitably used for fibers, various molded articles, sheets and films.

Claims (11)

  A method for producing polybutylene terephthalate, comprising bringing polybutylene terephthalate into contact with an aqueous solution of an alkali metal salt and / or an alkaline earth metal salt having a concentration of 1 ppm to 10 wt%.   The process according to claim 1, wherein the alkali metal salt is a potassium salt.   The production method according to claim 2, wherein the potassium salt is acetate and / or carbonate.   The process according to claim 1, wherein the alkali metal salt is a sodium salt.   The process according to claim 4, wherein the sodium salt is acetate and / or carbonate.   The process according to claim 1, wherein the alkali metal salt is a lithium salt.   The process according to claim 6, wherein the lithium salt is acetate and / or carbonate.   The process according to claim 1, wherein the alkaline earth metal salt is a calcium salt.   The production method according to claim 8, wherein the calcium salt is acetate and / or carbonate.   The process according to claim 1, wherein the alkaline earth metal salt is a magnesium salt.   The production method according to claim 10, wherein the magnesium salt is acetate and / or carbonate.