JPH024608B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing aromatic polyester. Fully aromatic polyester has excellent properties based on its production, but it stands out among all resins in terms of heat resistance. Among these, wholly aromatic polyesters produced from terephthalic acid, isophthalic acid, parahydroxybenzoic acid or its derivatives, and 4,4'-dihydroxydiphenyl or its derivatives can be injection molded and have various physical properties, namely mechanical properties. In addition to having excellent electrical properties and thermal stability, it also has many excellent properties such as high heat resistance, chemical resistance, oil resistance, radiation resistance, and dimensional stability, making it suitable for mechanical parts, electrical・Used in various fields such as electronic parts and automobile parts. However, such wholly aromatic polyesters have the drawbacks of high melt viscosity and poor moldability due to their high softening temperatures. In addition, since high molding temperatures are required, thermal deterioration of the polymer during molding may occur.
There are problems such as coloring, and from these points as well, improvement in moldability has been desired. As a conventionally known method for solving such problems, there is a method of blending with a resin having better fluidity (good moldability). For example, it is blended with polyethylene terephthalate, polycarbonate, etc. and molded. However, the aforementioned terephthalic acid, isophthalic acid, parahydroxybenzoic acid,
When mixing, granulating, and molding a fully aromatic polyester obtained from 4,4'-dihydroxydiphenyl or the like with polyalkylene terephthalate or polycarbonate, each step is performed in a temperature range where the fully aromatic polyester is homogenized. At this temperature, polyalkylene terephthalate and polycarbonate, which have poor thermal stability, are prone to thermal decomposition, and if these resins are processed in a temperature range where they can be stabilized and homogenized, the temperature is insufficient for the flow of fully aromatic polyester. , the entire composition system does not become a homogeneous dispersion. In order to homogenize the entire system, it is possible to lengthen the residence time of the resin in each process such as mixing, granulation, and molding, but this is far from achieving uniform dispersion, and it takes a large amount of time to achieve this state. This is not realistic. A blending method using a solution may also be considered, but in the case of wholly aromatic polyesters, no solvent has been found so far that can uniformly dissolve the polyester without decomposition, and this would be extremely difficult. If the dispersibility is insufficient, parts of the resin or molded product may deteriorate when exposed to solvents or reagents, variations may occur from shot to shot during molding, or the strength of the molded product may be uneven. As mentioned above, from the normal blending method,
It can be said that it is difficult to improve the moldability of the above-mentioned wholly aromatic polyester. In view of the current situation, the inventors of the present invention have conducted intensive studies to improve the moldability of wholly aromatic polyester without the disadvantages caused by deterioration of physical properties or poor dispersion that are seen in blends. It has been found that these objects can be achieved by allowing polyalkylene terephthalate to be present in a certain proportion during the polymerization of the polyester, and by carrying out the polymerization in bulk in the absence of substantially any solvent. Polymerization methods for aromatic polyester include solution polymerization, in which the polymer is dissolved in an organic solvent, and suspension polymerization, in which the polymer is precipitated from the solvent used for polymerization. Bulk polymerization methods that do not use solvents are known. In the case of fully aromatic polyesters produced from terephthalic acid, isophthalic acid, parahydroxybenzoic acid, and 4,4'-dihydroxydiphenyl, a solvent that can dissolve them has not been found to date, so solution polymerization is used. is difficult to employ. High-boiling point solvents such as hydrogenated terphenyl, diphenyl ether, and diphenyl mixtures are used in the suspension polymerization method, but the process is complicated, including removal and recovery of these solvents, and washing of the polymer. It has the economic disadvantage of low production volume. Bulk polymerization is the most economically advantageous polymerization method, but it has not been widely applied to the production of aromatic polyesters. The reason for this is that aromatic polyesters have a higher melting point than aliphatic polyesters such as polyethylene terephthalate, and require high temperatures to maintain the molten state, which significantly reduces the value of the polymer as a product. It is from. If this problem of color deterioration can be solved, it will have great industrial significance as a process that can satisfy both polymer quality and economic efficiency. The present inventors have found that when polymerizing the fully aromatic polyester, polyalkylene terephthalate is present and the polymerization is carried out in a bulk polymerization method in the absence of a substantial solvent. Compared to fully aromatic polyester obtained without the presence of terephthalate or aromatic polyester obtained by other methods (e.g. suspension polymerization) even when polyalkylene terephthalate is present, it has better moldability and physical properties. The present invention was based on the discovery that it is also excellent. That is, the present invention involves adding polyalkylene terephthalate to the polymerization reaction system at a rate of 5 to 20% by weight of the final polymer when producing an aromatic polyester consisting of repeating structural units represented by the following formulas (A), (B), and (C). %, and the polymerization is carried out by a bulk polymerization method substantially in the absence of a solvent. (In the above formula, X is an alkylene group having 1 to 4 carbon atoms, -
O-, _-SO2- , -S- or -CO-, m,
n is 0 or 1. The ratio of (A):(B) is from 1:1
It is in the range of 10:1, and the ratio of (B):(C) is from 9:10
It is in the 10:9 range. Furthermore, the substituents on the aromatic ring in the above formula are in para or meta positions with respect to each other. ) The aromatic polyester obtained by polymerization in the presence of polyalkylene terephthalate has significantly improved moldability compared to the case of polymerization in the absence of polyalkylene terephthalate. Compared to the above, the surface and interior of the molded product are uniform and well-dispersed. In addition, results were obtained in which there was less deterioration in various physical properties, especially in thermal stability and mechanical strength, as seen in blended products.
The cause of this is not clear at present, but some manufacturing changes may occur in the polyalkylene terephthalate during polymerization of the wholly aromatic polyester. (For example, generation of a new structure by cleavage and recombination of the polymer main chain by transesterification is also considered.) In this case,
The aromatic polyester finally obtained is considered to be "uniform" so to speak. On the other hand, when polyalkylene terephthalate is simply blended with aromatic polyester, there is no bonding reaction between the two, or even if it occurs, it is minimal, so there is more "heterogeneity." Dew. Considering that the non-uniformity (insufficient dispersion) due to blending as mentioned above may have a negative effect on the physical properties of the polymer, it is necessary to make the aromatic polyester (polyalkylene terephthalate) of the present invention present during polymerization. It can also be seen that the moldability of the products (obtained by the above methods) is improved, and the deterioration of various physical properties is small. In addition, by polymerizing in the presence of polyalkylene terephthalate, an aromatic polyester with little color deterioration can be obtained even if a bulk polymerization method is used.
In addition, a method for producing aromatic polyester that is satisfactory in both economy and polymer quality has been discovered due to improved moldability. The reduction in color deterioration during bulk polymerization is thought to be due to the reduction in melt viscosity due to polyalkylene terephthalate. Monomer components used in the production of the wholly aromatic polyester used in the present invention include, for example, parahydroxybenzoic acid, metahydroxybenzoic acid, terephthalic acid, isophthalic acid, hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, ,4′−
Dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxybenzophenone, 4,4'-dihydroxydiphenylmethane, etc. Derivatives can be used. Among these combinations, combinations of parahydroxybenzoic acid or its ester, terephthalic acid or its ester, and 4,4'-dihydroxydiphenyl or its ester are particularly preferred. Further, examples of the polyalkylene terephthalate that is present during polymerization when producing a wholly aromatic polyester include polyethylene terephthalate and polybutylene terephthalate. The amount of polyalkylene terephthalate used during the polymerization of the fully aromatic polyester should be between 5 and 20% by weight of the final polymer. Below this range, the effect will not be sufficient, and above this range, the resulting aromatic polyester will not have sufficient thermal and mechanical properties. Note that as the amount of polyalkylene terephthalate is increased, the thermal properties will deteriorate, so the amount must be selected in consideration of the relationship between desired physical properties and composition. As the polymerization method, a bulk polymerization method is used. Any generally known bulk polymerization method may be used. For example, first, a compound for forming a wholly aromatic polyester consisting of repeating structural units represented by formulas (A), (B), and (C) and polyalkylene terephthalate are simultaneously charged into a reaction tank. There is a way. Thereafter, the polymerization reaction is carried out by heating, and the polymerization reaction is carried out at about 200 to 400°C, preferably 250 to 350°C, under normal pressure or reduced pressure, and in an insoluble gas atmosphere. It is also possible to proceed with the polymerization using a catalyst whose residue does not adversely affect the physical properties of the polymer or whose activity can be rendered inactive by simple treatment. A more preferable bulk polymerization method is to proceed with the polymerization by constantly applying a shearing force to the polymer produced by polymerization at the polymerization temperature so that the polymer does not solidify, and to form a solid polydisperse system without solidifying the polymer. This is a method in which polymerization is carried out until substantially all of the solid phase is obtained in a state of The limit is to initially carry out the condensation at a relatively low temperature and to increase the temperature as the condensation progresses.
First at a temperature of 180~250℃, then raised to 250~
Polymerization is carried out at a temperature of 380°C, preferably from 300 to 360°C, under normal pressure or reduced pressure. Once it becomes a solid polydispersion, it is possible to raise the temperature while taking into consideration its fusion temperature and decomposition temperature, such as 300 to 400℃,
Preferably it is 310 to 370°C, but as long as it is below the decomposition temperature and below the fusion temperature, the higher the temperature, the faster the reaction rate. Alternatively, as another method, formula (A),
A compound for constituting a wholly aromatic polyester consisting of repeating structural units represented by (B) and (C) and polyalkylene terephthalate are simultaneously charged,
A method of producing a prepolymer by polycondensation, transferring it to a second reaction tank, and increasing the molecular weight is also used.
The prepolymer produced in the first reaction tank is taken out in a molten state, pulverized and homogenized, and then
The molecular weight may be increased in the second reaction tank, or the prepolymer may be pelletized using an extruder and the molecular weight may be increased in the second reaction tank. Alternatively, as another method, instead of charging polyalkylene terephthalate from the beginning, it can be added sequentially during the polymerization reaction of a wholly aromatic polyester consisting of repeating structural units represented by formulas (A), (B), and (C). There are ways to go. If this method is carried out in two-stage polymerization using a first and second reaction tank, it is more preferable to add the compound sequentially during polymerization in the first reaction tank. The aromatic polyester thus obtained is a polymer with little coloring, excellent moldability, and excellent heat resistance and mechanical properties. The aromatic polyester obtained according to the present invention can contain additives commonly added to plastics, such as stabilizers, colorants, fillers, etc., to the extent that they do not impair the properties of the polymer. Fillers include, for example, silica, powdered quartz or sand, fumed silica, silicon carbide, aluminum oxide, glass fibers, tin oxide, iron oxide, zinc oxide, carbon, graphite, and as pigments titanium dioxide and other inorganic materials and heat-resistant materials. organic pigments can be used. The polymer obtained by the present invention can be molded into molded products, films, sheets, etc. by methods such as press molding, injection molding, and extrusion molding, such as mechanical parts, electrical/electronic parts, automobile parts, various containers, and packaging. It is widely used in fields that require high performance as engineering plastics, such as materials. The present invention will be explained below with reference to Examples and Comparative Examples, but these are illustrative and not limiting. Example 1 756 g (5.48 mol) of parahydroxybenzoic acid and terephthalic acid were placed in a polymerization tank that had an anchor-type stirring blade and had a small clearance between the tank wall and the stirring blade.
453 g (2.73 moles), 508 g (2.73 moles) of 4,4'-dihydroxydiphenyl, 169 g of polyethylene terephthalate (PET RT-560 manufactured by Toyobo Co., Ltd.) (corresponding to 10% by weight of the final polymer), and 1337 g of acetic anhydride. (13.1 mol) was added. 150 in 1 hour while stirring under nitrogen gas atmosphere
The mixture was heated to 0.degree. C. and refluxed at this temperature for 3 hours. Thereafter, while raising the temperature, acetic acid produced as a result of the reaction was distilled off, and the temperature was raised to 330°C under high shear.
Polymerization was further continued for 2 hours with strong stirring, and then the mixture was gradually cooled down to 200°C, and strong stirring was continued, and then the polymerized product was taken out of the tank. The amount recovered was 1,570g (93.1% of the amount of rinsing). After pulverizing this, it was transferred to an aluminum rotary oven and heated under a nitrogen stream.
320° while rotating the entire system and thoroughly stirring the powder.
The temperature was gradually increased to 320℃ for 6 hours, and the temperature reached 320℃.
After processing for a period of time, it was cooled and the powder was taken out at 200°C. The powder obtained weighed 1539 g. This polymer was processed using a single-screw extruder manufactured by Tanabe Plastic Machinery VS-
30-28 (screw diameter 30mm, L/D ~ 28), cylinder temperature 320℃, screw rotation speed
After granulation at 50 rpm, injection molding was performed using a Neomattu N47/28 injection molding machine manufactured by Sumitomo Heavy Industries. The bar flow length was measured at various molding temperatures. The results are shown in Table 1. It can be seen that the molding temperature range is wider than in Comparative Examples 1 and 2 described below, and molding can be performed at a relatively low temperature. Comparative Example 1 Polymerization and post-treatment were carried out in the same manner as in Example 1, except that polyethylene terephthalate was not used at all, and 1412 g (93.0% of the theoretical amount) of a wholly aromatic polyester was obtained. . This product was granulated and injection molded in the same manner as in Example 1. The results are shown in Table 1. Compared to Example 1, the molding temperature range is narrower and a higher molding temperature is required. Comparative Example 2 900 g of the wholly aromatic polyester obtained in Comparative Example 1 was mixed with 100 g of the polyethylene terephthalate used in Example 1 using a super mixer. The obtained polymer was granulated and injection molded in the same manner as in Example 1. The results are shown in Table 1. Although the molding temperature range is slightly wider than that of Comparative Example 1, it is narrower than that of Example 1 and requires a higher molding temperature. In addition, the molded product was burnt at temperatures above 360°C, and the surface of the molded product was not uniform. Comparative Example 3 900 g (5 moles) of paraacetoxybenzoic acid, 415 g (2.5 moles) of terephthalic acid, 675 g (2.5 moles) of 4,4'-dihydroxydiphenyl diacetylate,
Polyethylene terephthalate (PET manufactured by Toyobo Co., Ltd.)
RT-560) 154g (10% by weight of the final polymer
) and Santotherm as a high-boiling solvent.
66 (Mitsubishi Monsanto Chemical Co., Ltd.) was placed in a reactor and the mixture was heated to 180°C in 1 hour under constant stirring in a nitrogen gas atmosphere.
It was once raised to 320 degrees Celsius for 10 hours. Stirring was continued for another 16 hours at 320°C, followed by heating at 340°C for 3 hours to form a slurry. The reaction mixture was allowed to cool and then 1000g of Santotherm 66 was added to 70°C.
And so. 1920 g of acetone was added and the slurry was filtered, and the powder was extracted with acetone using a Soxhlet to remove Santotherm 66. Heat this powder to 110℃
The mixture was dried under reduced pressure to obtain 1328 g (86.0% of the theoretical amount) of aromatic polyester. This powder was transferred to an aluminum rotary oven and kept at 200°C for 10 hours while thoroughly stirring the powder by rotating the entire system under nitrogen flow.
The temperature was gradually raised to 300°C for 6 hours, kept at this temperature for 2 hours, and then cooled to 200°C and the powder was taken out. This polymer was granulated in the same manner as in Example 1,
Injection molded. The results are shown in Table 1. Although the molding temperature range is slightly wider than that of Comparative Example 1, it is narrower than that of Example 1 and requires a higher molding temperature. In addition, orientation was observed on the surface of the molded product, and some burns occurred, so the surface of the molded product was not uniform.

[Table] Example 2 400 g of glass fiber was added to 600 g of each of the polymers obtained in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3.
g each to be mixed and dispersed almost uniformly. These were granulated in the same manner as in Example 1 to obtain pellets. A dumbbell-shaped test piece, an Izot impact strength test piece, and a weld strength test piece were injection molded using various molds, and the physical properties of each were measured. The results are shown in Table 2.

[Table] When the polymer of Example 1 was used, the physical property values had a small dependence on molding temperature, and all showed higher values than when the polymers of Comparative Examples 1, 2, and 3 were used. In particular, the difference in strength at the weld part is large. The physical properties of the polymer of Comparative Example 1 are slightly inferior to those of the polymer of Example 1. The molding temperature dependence is also somewhat large. The polymer of Comparative Example 2 has extremely low physical property values. Comparative example 3
The polymer has high tensile strength and tensile modulus, but
This is thought to be due to the orientation observed on the surface of the molded product. Furthermore, the molding temperature dependence is also greater than that of the polymer of Example 1. Example 3 Into the same apparatus as in Example 1, 756 g (5.48 mol) of parahydroxybenzoic acid and 453 g (2.73 mol) of terephthalic acid were added.
mole), 4,4'-dihydroxydiphenyl 410g
(2.20 mol), hydroquinone 59.4g (0.54 mol),
Polyethylene terephthalate (PET manufactured by Toyobo Co., Ltd.)
RT-560) 269g (20% by weight of the final polymer
corresponds to ) and 1337 g (13.1 mol) of acetic anhydride were added. The subsequent operations were carried out in the same manner as in Example 1 to obtain a polymer. 400 g of the glass fiber used in Example 2 was mixed with 600 g of this polymer, dispersed almost uniformly, and then granulated and injection molded. The results are shown in Table 3.

[Table] The molding temperature range is wide, and the dependence of physical properties on molding temperature is small. Example 4 Into the same apparatus as in Example 1, 828 g (6.00 mol) of parahydroxybenzoic acid and 332 g (2.00 mol) of terephthalic acid were added.
mole), 4,4'-dihydroxydiphenyl 376g
(2.02 mol), polyethylene terephthalate (PET RT-560 manufactured by Toyobo Co., Ltd.) 338 g (corresponding to 20% by weight of the final polymer), acetic anhydride 1122 g
(11.0 mol) was added. Polymerization was carried out in the same manner as in Example 1 to obtain a polymer. The yield of polymer is 1665
g, corresponding to 98.5% of the theoretical yield. This polymer was pulverized into particles of 0.5 mm or less using a pulverizer, heated in a nitrogen stream, and solid-phase polymerized at 280° C. for 6 hours.
The flow temperatures before and after solid state polymerization are 224℃ and 315℃, respectively.
It was warm at ℃. The flow temperature was measured using a Shimadzu flow tester using a nozzle with a diameter of 1 mm and a length of 10 mm, and when the temperature was raised at a rate of 4°C/min under a pressure of 100 kg/cm ² , the melt viscosity of the polymer reached 48,000 poise. The temperature is shown and used as a guide for molecular weight and molding temperature. Thermal stability of the obtained polymer (280℃
Table 4 shows the physical properties of the molded product obtained by injection molding (cylinder temperature: 340°C, mold temperature: 120°C). It can be seen that the example of the present invention is superior to Comparative Example 4. The tensile test was conducted in accordance with ASTM D-638 at a gauge distance of 40 mm and a tensile speed of 5 mm/min, and the heat distortion temperature measurement was conducted at a pressure of 18.6 in accordance with ASTM D-648.
Kg/cm ² , and the Izot impact strength was measured with a notch according to ASTM D-256. Comparative Example 4 Parahydroxybenzoic acid was added to the same apparatus as in Example 4.
414g (3.00mol), 581g (3.50mol) terephthalic acid, 655g 4,4'-dihydroxydiphenyl
(3.52 mol), 366 g (corresponding to 20% by weight of the final polymer) of polyethylene terephthalate (same as in Example 4), and 1122 g (11.0 mol) of acetic anhydride were polymerized under the same conditions as in Example 4. The yield of polymer was 1779 g, corresponding to 97.1% of the theoretical yield. The flow temperatures before and after solid state polymerization are respectively
The temperatures were 231℃ and 318℃. Table 4 shows the thermal stability of the obtained polymer and the physical properties of the molded product obtained by injection molding.

【table】

Claims (1)

[Scope of Claims] 1. When producing an aromatic polyester consisting of repeating structural units represented by the following formulas (A), (B) and (C), polyalkylene terephthalate is added to the polymerization reaction system as 5 to 50% of the final polymer. A method for producing an aromatic polyester, characterized in that the aromatic polyester is present in a proportion of 20% by weight, and the polymerization is carried out by a bulk polymerization method in which substantially no solvent is present. (In the above formula, X is an alkylene group having 1 to 4 carbon atoms, -
O-, _-SO2- , -S- or -CO-, m,
n is 0 or 1. The ratio of (A):(B) is from 1:1
It is in the range of 10:1, and the ratio of (B):(C) is from 9:10
It is in the 10:9 range. Furthermore, the substituents on the aromatic ring in the above formula are in para or meta positions with respect to each other. )