JPH0244850B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a polyester suitable for molding purposes, and more particularly to a method for producing a polyester whose molecular chain terminal is an alkali metal salt of a carboxylic acid. [Problems to be solved by the prior art and the invention] Polyethylene terephthalate (hereinafter referred to as
Despite having excellent physical properties, PET was not suitable as a molding resin. The reason is that the crystallization rate of PET is low, so when PET is injection molded in a normal mold that is heated with water and used at a temperature below 100℃, the
This is because the crystallization of PET does not proceed sufficiently, resulting in poor surface gloss and poor dimensional stability of the obtained molded product. If you use a molding machine capable of high-temperature molding and raise the mold temperature to 130℃ or higher using a heating medium such as oil, the crystallization of the molded product will proceed sufficiently, and the above problem with the molded product will be resolved. However, it is difficult to use such a mold temperature with a normal molding machine and is not practical. The reason for the low crystallization rate, which is a disadvantage of PET, is that the molecular structure of PET is quite rigid, so the activation energy for crystal nucleation when transitioning from the melt state to the crystal state is large, and the crystallization rate is slow. It is known that this is because a large degree of supercooling is required, and furthermore, in such a supercooled state, the mobility of the segments becomes low and the rate of crystal formation becomes slow. Research has been actively conducted to improve the crystallization rate of PET, and it is known that metal salts such as organic carboxylic acids, sulfonic acids, and phosphonic acids are effective as nucleating agents for PET crystallization. There is. However, with such externally added nucleating agents,
There is a limit to the ability to promote crystallization of PET, and it is difficult to lower the mold temperature during molding to below 100°C.
The reason for this is that even if such externally added nucleating agents are used, they cannot effectively nucleate at temperatures higher than the crystallization temperature at which spontaneous crystal nuclei are generated at a sufficiently high concentration. This is because the ratio that acts as a factor is extremely small. The present inventors have proposed a method for improving the crystallization rate of PET by generating a high concentration of crystal nuclei in a state with a smaller degree of supercooling, that is, in a state with greater molecular mobility. He expected that it would be possible to dramatically improve the crystallization speed of PET, and conducted intensive research on how to do so. As a result, it was found that by converting the ends of the molecular chains of PET into alkali metal salts of carboxylic acids, the above-mentioned objectives could be achieved and a rapidly crystallizing polyester could be obtained. Moreover, this polyester makes it possible to lower the molding temperature to below 100℃ while maintaining good crystallization properties.
Therefore, it was discovered that a water-heated mold can be used. Moreover, it has been found that such a method of introducing an alkali metal salt of a carboxylic acid at the end of a molecular chain is also effective in improving the crystallization rate of aromatic polyesters other than PET. [Means for solving the problem] That is, the present invention solves the problem by solving the general formula

A polyester with an intrinsic viscosity of 0.4 or more consisting of repeating units represented by the formula (R is a carboxyl group-free residue of an aromatic, alicyclic, or aliphatic dicarboxylic acid with a molecular weight of 300 or less, and (At least 90 mol% is a terephthalic acid residue. D is a residue not containing a hydroxyl group of an organic diol having 2 to 6 carbon atoms.) is reacted with a dicarboxylic acid, and then treated with a sodium or potassium compound. The present invention relates to a method for producing a polyester, which comprises producing a polyester whose molecular chain terminal is a sodium or potassium salt of a carboxyl group. General formula used as raw material in the present invention

Polyesters consisting of repeating units represented by [Formula] include polyethylene terephthalate, polypropylene terephthalate,
Examples include polybutylene terephthalate, polyhexamethylene terephthalate, and copolymers thereof. These polyesters were prepared using a 1:1 solution of phenol/tetrachloroethane (25
℃) has an intrinsic viscosity of 0.4 dl/g or more,
It is desirable that it is 0.6 dl/g or more. In the present invention, by reacting the above polyester with dicarboxylic acid to change the hydroxyl group at the end of the polyester to a carboxyl group, and then reacting with a sodium or potassium compound to change the carboxyl group at the end of the polyester to a sodium or potassium salt. , a polyester whose molecular chain ends are sodium or potassium salts of carboxylic acids is obtained. In the present invention, all the molecular chain ends of the polyester may be sodium or potassium salts of carboxylic acids. Examples of dicarboxylic acids to be reacted with polyester include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sepacic acid, maleic acid,
Examples include fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, and malic acid. Examples of sodium or potassium compounds used to convert carboxyl groups into sodium or potassium salts include alcoholates such as sodium methylate, sodium ethylate, and potassium butyrate, and weak acid salts such as sodium formate and potassium formate. However, potassium butyrate is preferred. The reason why the polyester obtained by the present invention has the property of rapidly crystallizing is that alkali metal salts of carboxylic acids generally have the property of forming liquid crystals, so it is likely that the terminal sodium or potassium salt of the carboxylic acid in the polyester is This is thought to be because the portion is forming liquid crystal or is in a state close to it, and this portion serves as a nucleus and crystal formation occurs. The polyester obtained by the present invention includes various fillers such as glass fiber, glass beads, aluminum silicate, asbestos, mica, carbon fiber, calcium carbonate, ferrite, silica, talc, metal powder, mold release agents, antioxidants, etc. A thermoplastic resin other than the polyester obtained by the invention can be blended to form a molding resin composition. As the filler, glass fiber, glass beads, and mica are preferably used. The amounts of these various compounding agents are as follows:
5 to 60% by weight, especially 20 to 50% by weight of the resin composition
It is preferable that it is in the range of . Furthermore, a plasticizer may be added to the resin composition blended with the polyester obtained according to the present invention in order to further improve moldability. Preferred plasticizers include aromatic carboxylic acids having at least one carboxyl group on the aromatic ring and having 7 to 11 carbon atoms and a compound of the formula (HOH ₂ C)- _x R ₁ (where x is 1 , 2 or 3, and R ₁ is a hydrocarbon group having 2 to 15 carbon atoms) or of the formula HO(-R ₂ -O)- _y R ₃ (wherein y is 1, 2
or 3, R ₂ is a hydrocarbon group having 2 to 15 carbon atoms, and R ₃ is a carbon atom or 2
It is a hydrocarbon group having ~20 carbon atoms. )
An organic ester selected from the reaction product with an alcohol selected from the alcohols represented by the formula;
R ₄ −O(−R ₅ −O)− _o R ₆ (wherein R ₄ and R ₆ are hydrogen atoms or hydrocarbon groups having 1 to 15 carbon atoms, and these hydrocarbon groups are oxygen atom, nitrogen atom, halogen atom, etc. _R5 is a hydrocarbon group having 2 to 22 carbon atoms, and the molecular weight is within the range of 100 to 100,000. Examples include polyether compounds. Specifically, neopentyl glycol dibenzoate, triethylene glycol dibenzoate, diethylene glycol dibenzoate, dipropylene glycol dibenzoate, tris-2-ethylhexyl trimellitate, phenyl benzoate, trimethylolethane tribenzoate, dioctyl phthalate, diisodecyl Examples include phthalate, polyethylene glycol, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polyethylene glycol glycidyl ether, polypropylene glycol, polybutylene glycol, polyneopentyl glycol, and the like. The appropriate amount of these plasticizers added is 0.05 to 15 parts by weight based on 100 parts by weight of the polyester obtained by the present invention. The resin composition containing the polyester obtained according to the present invention is produced by mixing each component by any known means. Neither the temperature nor the pressure during mixing are critical; for example, the components may be dry mixed in a suitable mixer or rotating machine,
The mixture can be melt extruded or other components can be mixed during the polyester synthesis stage and melt extruded after synthesis. The resin composition thus obtained can be molded into various shapes (block, rod, sheet, film, etc.) by various known molding methods. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. In addition, all parts in the examples mean parts by weight unless otherwise specified. Example 1 300 parts of nitrobenzene was added to 20 parts of polyethylene terephthalate having an intrinsic viscosity of 0.73 dl/g (phenol/tetrachloroethane 1:1, 25°C), and the mixture was heated to 210°C under a nitrogen gas stream to form polyethylene terephthalate. Completely dissolved. next
After cooling to 175°C, 0.4 part of succinic anhydride was added and reacted for 3 hours, and then cooled to room temperature to precipitate the polymer. This precipitate was separated with a filter and washed several times with nitrobenzene. The carboxyl group of the obtained polymer was quantified using a 0.01N NaOH solution and found to be 79 μeq/g. Then back into the polymer
300 parts of nitrobenzene was added and the temperature was raised to 210°C to dissolve the polymer. Then cool to 120℃,
Potassium/t-butyrate solution (potassium concentration
After adding 5.3 parts of 2.8 g/dl) and reacting for 10 minutes, the mixture was cooled to room temperature, and the polymer was precipitated and separated. Next, after washing with methanol several times, it was vacuum dried at 100°C for 48 hours to obtain a polyester with potassium succinate bonded to the terminals. The intrinsic viscosity of the obtained polyester is 0.75 dl/g
The carboxyl group content was 13 μeq/g. The average molecular weight was calculated from the intrinsic viscosity, and the total number of end groups was calculated to obtain a value of 93.0 μeq/g. The following equation was used as the relational expression between the intrinsic viscosity [η] and the average molecular weight n: [η]=2.1×10 ⁻⁴ n ⁰ 〓 ⁸² . From the above results, carboxyl group
Of the 93μeq/g, 66μeq/g becomes potassium salt,
Carboxylic acid potassium salt terminal is 66/93× of all terminal groups
It can be seen that 100 = 71%. In order to measure the crystallization rate of the obtained polyester, we used a differential scanning calorimeter (UNIX-H model manufactured by Rigaku Denki) to measure the crystallization rate when the polyester was cooled from a molten state at 290°C at a rate of 20°C/min. The exothermic peak temperature (hereinafter referred to as Tc) due to crystallization was determined.
That is, the higher the Tc, the higher the crystallization rate. The polyester obtained by the above operation had a Tc of 218°C, which was higher than that of polyethylene terephthalate, which was 176°C, and crystallized rapidly. Furthermore, when potassium propionate was examined for the presence or absence of liquid crystal formation using a polarizing microscope equipped with a heating stage, it was found that liquid crystal was formed at temperatures below approximately 350°C.
It is thought that the ends of the polyester described above also form liquid crystals in a melt state. Example 2 300 parts of nitrobenzene was added to 20 parts of the same polyethylene terephthalate used in Example 1,
After heating to 217°C to completely dissolve, the mixture was cooled to 150°C, 10 parts of tri-n-butylamine was added, and further cooled to 130°C. Sebacic acid chloride
Add 4.5 parts, react for 30 minutes, then cool to room temperature.
The reaction solution was transferred into 1000 parts of n-hexane to precipitate the polymer, which was separated. The precipitate was washed with acetone, water, and acetone in this order, and dried under vacuum. The carboxyl group content of the obtained polymer was 85 μeq/g. Then add 200 parts of nitrobenzene to 10 parts of polymer powder.
After heating to 210℃ and melting, heat to 120℃
After cooling to room temperature, add 3.7 parts of potassium t-butyrate solution and react for 10 minutes.
of methanol, and the resulting polymer was
Vacuum drying was performed at 100°C for 48 hours. The intrinsic viscosity of the obtained polyester was 0.74 dl/
g, and the carboxyl group content was 15 μeq/g.
From this, it was found that 74% of all end groups were potassium salts of carboxylic acids. Also, Tc is
The temperature was 219℃, and potassium pelargonate formed liquid crystals up to 295℃. Example 3 In the same manner as in Example 2, a potassium terephthalate salt-terminated polyester was synthesized using 3.85 parts of terephthaloyl chloride in place of sebacyl chloride. In the obtained polyester, 77% of the ends were potassium salts of carboxylic acids, and the Tc was 219°C. Furthermore, potassium benzoate remained in a liquid crystal state up to 450°C. Reference Example 1 20 parts of polyester obtained in Example 1, 50 parts of polyethylene terephthalate with an intrinsic viscosity of 0.73 dl/g
and 30 parts of glass fiber were mixed in a Henschel mixer and melt-kneaded at 270°C in a single-screw extruder to obtain pellets. The pellets were fed into a 4-ounce in-line screw type injection molding machine and injection molded at a cylinder temperature of 260-280°C, a mold temperature of 98°C, and a cycle time of 60 seconds. Molding was carried out smoothly, and the entire molded product obtained was uniformly crystallized. Reference Example 2 Without using the polyester obtained in Example 1,
Pellets were prepared in the same manner as in Reference Example 1, except that 70 parts of polyethylene terephthalate was used, and molding was carried out under the same conditions as in Reference Example 1, except that the mold temperature was 110°C. The resulting molded product did not release smoothly from the mold, was not completely cured immediately after being taken out of the mold, and had irregularities on its surface after curing. Reference Example 3 2 parts of the polyester obtained in Example 2, polyethylene terephthalate 60 with an intrinsic viscosity of 0.73 dl/g
Pellets were prepared in the same manner as in Reference Example 1 using 35 parts of glass fiber and molding was carried out under the same conditions as in Reference Example 1 except that the mold temperature was 110°C. The molding was carried out almost smoothly, and the molded product obtained was uniformly crystallized, but the surface gloss was slightly inferior to that obtained in Reference Example 1. Reference Example 4 Molding was carried out in the same manner as Reference Example 3 except that 0.5 part of the polyester obtained in Example 2 was used.
The molded product did not release smoothly from the mold, was not completely cured immediately after being taken out of the mold, and had uneven surfaces after being cured. Reference Example 5 5 parts of the polyester obtained in Example 3, polyethylene terephthalate 60 with an intrinsic viscosity of 0.73 dl/g
Reference Example 1 using 5 parts of dimethoxypolyethylene glycol with an average molecular weight of 1000 and 30 parts of glass fiber.
Pellets were made in the same manner. This pellet was injection molded using the same injection molding machine as in Reference Example 1 at a cylinder temperature of 260 to 280°C, a mold temperature of 90°C, and a cycle time of 20 seconds. Molding was carried out smoothly, and the molded product obtained was uniformly crystallized throughout and had good surface gloss. Reference Example 6 Injection molding was carried out in the same manner as Reference Example 5 except that 5 parts of neopentyl glycol dibenzoate was used instead of dimethoxypolyethylene glycol. Molding was carried out smoothly, and the molded product was uniformly crystallized. The above results are summarized in Table 1.

〔Effect of the invention〕

The polyester obtained by the production method of the present invention maintains good crystallization properties while maintaining the molding temperature.
The temperature can be lowered to 100°C or less, and molded products can be molded industrially advantageously.

Claims (1)

[Scope of Claims] 1 A polyester having an intrinsic viscosity of 0.4 or more and consisting of repeating units represented by the general formula [Formula] [However, R in the above structural formula is an aromatic, alicyclic, or aliphatic dicarbonate having a molecular weight of 300 or less. It is a residue that does not contain an acid carboxyl group, and at least 90 mol% of R is a terephthalic acid residue. Further, D is a residue of an organic diol having 2 to 6 carbon atoms that does not contain a hydroxyl group. ] A method for producing a polyester, which comprises reacting a dicarboxylic acid with a dicarboxylic acid and then reacting with a sodium or potassium compound to produce a polyester in which the molecular chain terminal of the polyester is a sodium or potassium salt of a carboxyl group. 2. The method for producing a polyester according to claim 1, wherein the polyester having an intrinsic viscosity of 0.4 or more and consisting of repeating units represented by the general formula [Formula] is polyethylene terephthalate.