JPH0139451B2 - - 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 structure, but it stands out among all resins in terms of heat resistance. Among them, wholly aromatic polyesters produced from terephthalic acid, isophthalic acid, parahydroxybenzoic acid or its derivatives, and 4,4'-dihydroxydiphenyl or its derivatives are injection moldable and have various physical properties, such as 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 and electronic It is used in various fields such as 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. Furthermore, since high molding temperatures are required, there are problems such as polymer deterioration and coloring during molding, and from these points as well, improvement in moldability has been desired. In addition, such wholly aromatic polyesters have the property of being easily oriented during injection molding, and the shrinkage rate that occurs during molding may vary in the machine axis direction (MD) and the direction perpendicular to the machine axis (TD) of the molded product. There tends to be a difference. Such anisotropy in molding shrinkage rate is unfavorable from the viewpoint of dimensional stability of the molded article. As mentioned above, the problems of fully aromatic polyesters include poor moldability (fluidity);
Various methods have been used to solve problems such as easy orientation during injection molding and anisotropy in shrinkage rate. As a method for improving moldability, 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, 4,4'-
When mixing, granulating, and molding a fully aromatic polyester obtained from dihydroxydiphenyl or the like with polyethylene terephthalate or polycarbonate, if each step is performed in the temperature range where the fully aromatic polyester is homogenized, it will be thermally stable at this temperature. Polyethylene terephthalate and polycarbonate, which have poor properties, are prone to thermal decomposition, and if these resins are treated in a temperature range where they can be stabilized and homogenized, the temperature is insufficient for the flow of fully aromatic polyester, so the entire system of the composition will not be uniform. It does not become a 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. Alternatively, in order to lower the molding temperature of wholly aromatic polyester, a wholly aromatic polyester with a low molecular weight can be mixed, granulated, and molded with a resin that has excellent moldability, as described above. Although it is possible to do this, the various excellent properties of wholly aromatic polyesters will be degraded. A blending method using a solution is also considered, but
In the case of wholly aromatic polyester, a solvent that can uniformly dissolve it without decomposition has not yet been found, and it can be said that it is 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 non-uniform. As mentioned above, it can be said that it is difficult to improve the moldability of the above-mentioned wholly aromatic polyester using the usual blending method. A completely different method is to use copolymerization instead of blending. For polymers with rigid main chains such as wholly aromatic polyesters, a flexible unit such as an aliphatic segment such as ethylene glycol is copolymerized for the purpose of imparting fluidity. However, with this method, there is no non-uniformity seen in blends;
Although the fluidity is improved and the moldability is improved, it is preferable because of the many excellent properties that wholly aromatic polyesters inherently have, especially the reduction in heat resistance. The second problem with wholly aromatic polyesters, the anisotropy between orientation and molding shrinkage, can be suppressed to a certain extent by adjusting injection molding conditions. Molding conditions such as injection pressure and injection speed are selected to control orientation. However, it goes without saying that such a method has its limitations, and that the resin itself needs to be improved. A commonly used method is to use a filler. The fillers are mainly inorganic materials such as glass fiber, graphite, quartz, tin oxide, titanium oxide, and talc. The usual purpose of using fillers is to improve mechanical strength, and the rigidity of materials such as polyethylene terephthalate and polyamide (nylon) can be greatly improved by filling them with glass fibers and the like. It may also be used to take advantage of the characteristics of other fillers, or as a filler. In the case of wholly aromatic polyester, orientation can be suppressed by filling several tens of percent of a filler such as glass fiber. However, the strength (rigidity) is actually lower when filled with polyethylene terephthalate and polyamide (nylon) because the orientation is suppressed.
This is different from the case of ordinary thermoplastic resins. When a filler such as glass fiber is used for the purpose of suppressing orientation, there is a problem in addition to such a decrease in strength (rigidity) that it may damage the molding machine. Alternatively, depending on the use of the molded article, it may be preferable to have no filler (that is, only resin), and so far no method has been found for wholly aromatic polyesters to suppress the orientation of the resin itself. In view of the current situation, the present inventors have conducted intensive studies to improve the moldability (fluidity) of wholly aromatic polyester and to suppress the orientation during molding. By making a certain type of polyester exist in a specific proportion in the reaction system and carrying out the polymerization using a bulk polymerization method in which substantially no solvent is present, the above objectives can be achieved without reducing the excellent performance of wholly aromatic polyesters. The inventors have discovered that this can be achieved and have arrived at the present invention. That is, the present invention comprises the following repeating units [],
When producing a wholly aromatic polyester composed of [] and [] (hereinafter referred to as wholly aromatic polyester A or wholly aromatic polyester represented by general formula A), the following repeating unit [] is added to the polymerization reaction system. A polyester composed of and [ ] (hereinafter referred to as polyester B or aromatic polyester represented by general formula B) is present in a proportion of 5 to 50% by weight of the final polymer, and the polymerization is carried out. The present invention relates to a method for producing an aromatic polyester, which is characterized in that it is carried out by a bulk polymerization method in which substantially no solvent is present. (In the above formula, X is a C ₁ to C ₄ alkyl group, -O-, -SO ₂
-, -S- or -CO-, and m and n are 0 or 1. []: [] ratio is 1:1 to 10:
1, and the ratio of []:[] is from 9:10.
It is between 10:9. Furthermore, the substituents on the aromatic ring in the above formula are in para or meta positions with respect to each other. ) (Of the structure of [] and [], [] occupies 80 mol% or more. Also, the sum of the polymerization degrees of [] and [] is in the range of 10 to 1000.) When polymerization was carried out in the presence of polyester B during production, orientation was significantly suppressed, the appearance of the molded product was good, and the anisotropy of shrinkage rate was small even without a filler. Furthermore, the mechanical properties and heat resistance were not only comparable to those in the absence of polyester B, but also the fluidity (moldability) was improved. As a result, effects such as a significant improvement in the strength of the weld portion of the molded product were also observed. The cause of such an effect due to polymerization in the presence of polyester B is not clear, but the polymerization temperature of the aromatic polyester and the molding temperature of the obtained polymer when polymerized in the presence of polyester B are not clear. Polyester B is lower than the melting point of Polyester B and has a similar ester structure, so Polyester B acts as a kind of "good wettability" filler and is uniformly distributed in wholly aromatic polyester A. It is also thought that the orientation is suppressed by dispersing and acting as a filler. Alternatively, it is also conceivable that polyester B is incorporated into the main chain of wholly aromatic polyester A by transesterification during the polymerization reaction (though it is considered that only a portion of it is considered in view of the melting point and polymerization temperature). And this will also cause good wetting of polyester B and wholly aromatic polyester A. Polyester B must be present during the polymerization of wholly aromatic polyester A. Polyester B
Simply blending the polyester A with the fully aromatic polyester A did not improve the moldability or orientation problems. This is thought to be due to poor uniform dispersibility. Furthermore, the molecular weight of polyester B must also be within a certain range. When the degree of polymerization of polyester B is less than 10, the effect is less than when it is 10 or more. If the molecular weight is low, it may be sufficiently incorporated into the main chain through transesterification during the polymerization reaction and may not be effective as a "good wettability" filler. The molecular weight of polyester B is a value determined by the terminal group quantitative method, but when the degree of polymerization exceeds 1000, the quantitative accuracy decreases, and it is difficult to understand how it corresponds to the effect. The amount of polyester B used during the polymerization of the wholly aromatic polyester should be 5 to 50% by weight of the final polymer. Below this range, the effect will not be sufficient, and above this range, the resulting polyester will not have sufficient mechanical properties. Further, the polymerization must be carried out by a bulk polymerization method in which substantially no solvent is present. Methods for producing aromatic polyester include solution polymerization, in which the produced polymer is dissolved in an organic solvent as the polymerization solvent, suspension polymerization, in which the produced polymer is precipitated from the solvent used for polymerization, and bulk polymerization, in which no solvent is used. Polymerization methods are known. In the case of fully aromatic polyesters produced from terephthalic acid, isophthalic acid, parahydroxybenzoic acid, 4,4'-dihydroxydiphenyl, etc., no solvent has been found to date that can dissolve them. Legal is difficult to adopt. Suspension polymerization methods include hydrogenated terphenyl, diphenyl ether,
High-boiling point solvents such as diphenyl mixtures are used, but the process of removing these solvents, recovering them, and washing the polymer is complicated, and there is an economic disadvantage in that the amount of polymer produced per unit batch is low. . 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 their molten state, which can significantly reduce the value of the polymer as a product. This is because it will be done. 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 producing the fully aromatic polyester, polyester B is present in the polymerization reaction system, and the polymerization is carried out by a bulk polymerization method in which substantially no solvent is present, whereby an aromatic polyester with less color deterioration can be obtained. In addition, compared to fully aromatic polyesters obtained by polymerization without the presence of polyester B, or even when polyester B is present, compared to aromatic polyesters obtained by other methods (for example, suspension polymerization method). It has been found that a polymer with excellent moldability and fluidity, less orientation, and excellent physical properties can be obtained. Examples of the components of the wholly aromatic polyester used in the present invention include parahydroxybenzoic acid, metahydroxybenzoic acid, terephthalic acid, isophthalic acid, hydroquinone, resorcinol, 4,4'-dihydroxy-diphenyl, and 4,4'-dihydroxydiphenyl. Enyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxybenzophenone, and derivatives thereof 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. Polyester B used in the polymerization of wholly aromatic polyester is obtained from parahydroxybenzoic acid, metahydroxybenzoic acid, or derivatives thereof. This polyester can also be obtained by suspension polymerization or bulk polymerization, but those obtained by bulk polymerization are preferred. A bulk polymerization method is used as the method for polymerizing the aromatic polyester of the present invention. Any generally known bulk polymerization method may be used. One example is a method in which a compound for forming a wholly aromatic polyester represented by the general formula A and an aromatic polyester represented by the general formula B are simultaneously charged into a reaction tank. 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, in an inert 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 as not to solidify the polymer, and to form a solid polydisperse system without solidifying the polymer. In this method, polymerization is carried out until substantially all of the solid phase is obtained. The maximum temperature that can be used depends on the monomer used,
It depends in part on the boiling point and decomposition point of the oligomer or polymer. The condensation is initially carried out at a relatively low temperature and the temperature is increased as the condensation progresses. Polymerization is carried out initially at a temperature of 180 to 250°C, then at an increased temperature of 250 to 380°C, preferably at 300 to 360°C, under normal pressure or reduced pressure. Once it becomes a solid polydispersion, it is possible to raise the temperature while considering the fusion temperature and decomposition temperature, and it is possible to raise the temperature to 300 to 400 °C, preferably 310 to 370 °C.
Polymerization is carried out at °C. Further, as long as this polymerization temperature is below the decomposition temperature and below the fusion temperature, the higher the polymerization temperature is, the faster the reaction rate will be. In addition, as another method, the general formula A is added to the first reaction tank.
There is also a method in which a compound capable of constituting a wholly aromatic polyester represented by the formula B and an aromatic polyester represented by the general formula B are simultaneously charged, a prepolymer is produced by polycondensation, and the prepolymer is transferred to a second reaction tank to increase the molecular weight. used. The prepolymer produced in the first reaction tank may be taken out in a molten state, pulverized and homogenized, and then made to have a high molecular weight in the second reaction tank, or the prepolymer may be pelletized using an extruder to form a The molecular weight may be increased in the second reaction tank. Alternatively, as yet another method, instead of charging the aromatic polyester represented by the general formula B from the beginning, there is a method in which the aromatic polyester represented by the general formula B is added sequentially during the polymerization reaction of the wholly aromatic polyester represented by the general formula A. If this method is carried out in two-stage polymerization using first and second reaction vessels, it is preferable to add the compound sequentially during polymerization in the first reaction vessel. The aromatic polyester thus obtained is a polymer with little coloring, excellent moldability, and excellent heat resistance, mechanical properties, etc. Although the aromatic polyester obtained by the present invention sufficiently satisfies mechanical properties and other physical properties without adding fillers, if necessary,
Stabilizers, colorants, various fillers and other additives commonly added to plastics can be added 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 produced into mechanical parts, electrical/electronic parts, automobile parts, various containers, packaging, etc. in the form of molded products, films, sheets, etc. by methods such as press molding, injection molding, and extrusion molding. It is widely used as an engineering plastic in fields that require high performance. The present invention will be explained below using Reference Examples, Examples, and Comparative Examples, but these are illustrative and are not limited thereto. Reference Example 1 2072 g (15 mol) of parahydroxybenzoic acid and 1685 g of acetic anhydride are placed in a polymerization tank that has an anchor-type stirring blade and has a small clearance between the tank wall and the stirring blade.
(16.5 mol) was added. 150 in 1 hour while stirring under nitrogen gas atmosphere
℃ and refluxed at this temperature for 3 hours. Thereafter, the acetic acid produced as a result of the reaction was distilled off while raising the temperature, and the temperature was raised to 330°C under high shear. Polymerization was further continued for 1 hour with strong stirring, then gradually cooled, and after continuing strong stirring until 200°C, the polymerized product was taken out of the tank. The amount recovered was 1740g (theoretical amount)
96.7%). After pulverizing the powder, it was transferred to an aluminum rotary oven, and the entire system was rotated under a nitrogen stream to thoroughly stir the powder and the temperature was raised to 370℃.
The temperature was gradually increased over a period of time and the mixture was treated at 370°C for 3 hours, then cooled and the powder was taken out at 200°C. The amount of powder obtained was 1680 g. The number average degree of polymerization of this polyester was determined to be 85 by the terminal group determination method. Reference Example 2 In a device similar to Reference Example 1, 1926 g (9.0 mol) of phenyl parahydroxybenzoate and metahydroxy-
214 g (1.0 mol) of phenyl benzoate was charged.
The temperature was raised while stirring in a nitrogen gas atmosphere, the phenol produced as a result of the reaction was distilled off, and polycondensation was carried out in the same manner as in Reference Example 1, yielding 1120 g of polymer (theoretical amount).
93.3%). The number average degree of polymerization of this polyester was determined to be 25 by the terminal group determination method. Example 1 In a device similar to Reference Example 1, 910.8 g (6.6 mol) of parahydroxybenzoic acid and 547.8 g of terephthalic acid were added.
(3.3 mol), 4,4'-dihydroxydiphenyl
613.8 g (3.3 mol), 458.7 g (corresponding to 20% by weight of the final polymer) of the polymer obtained in Reference Example 1, and 1613.2 g (15.8 mol) of acetic anhydride were charged. 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, the acetic acid produced as a result of the reaction was distilled off while raising the temperature, and the temperature was raised to 310°C under high shear. Polymerization was continued for 2 hours with further strong stirring, and then heated to 200°C.
The mixture was cooled to 2,163 g (94.3% of the theoretical amount) of a polymer. After pulverizing this, it was transferred to an aluminum rotary oven, the entire system was rotated under a nitrogen stream, the powder was thoroughly stirred, and the temperature was gradually raised to 320°C for 6 hours, and then the temperature was gradually raised to 320°C for 3 hours. cool down
The powder was taken out at 200°C. This polymer was extruded using a single-screw extruder VS-30-28 manufactured by Tanabe Plastic Machinery (screw diameter 30 mm, L/D ~
28) at a cylinder temperature of 350°C and screw rotation speed of 50 rpm, and then injection molded using an injection molding machine Neomatsu N47/28 manufactured by Sumitomo Heavy Industries.
A dumbbell-shaped test piece, an Izot impact strength test piece, a weld part strength test piece, etc. were molded using various molds, and the physical properties of each were measured. The results are shown in Table 1. The surface orientation of the molded product is suppressed and the appearance is smooth. It is also thought that the strength of the weld portion is increased and the fluidity is improved. The results of Comparative Examples 1 to 3 are also shown. Comparative Example 1 In Example 1, polymerization and post-treatment were carried out in the same manner as in Example 1, except that the polyester obtained in Reference Example 1 was not used at all.
1745 g (95.1% of theory) was obtained. This product was granulated and injection molded in the same manner as in Example 1. Table 1 shows the results.
Shown below. Orientation was observed, and the strength of the weld portion was low, making it inferior to Example 1. Furthermore, the high tensile strength and Izot impact value are considered to be due to the orientation. Comparative Example 2 800 g of the polyester obtained in Comparative Example 1 and 200 g of the polyester obtained in Reference Example 1 were mixed and stirred using a super mixer. The obtained polymer was granulated and molded in the same manner as in Example 1. Table 1 shows the results.
Shown below. Compared to Example 1, the physical properties are lower and the surface of the molded product is non-uniform. Comparative Example 3 This comparative example was carried out using the suspension polymerization method. 900 g (5.0 mol) of paraacetoxybenzoic acid, 415 g (2.5 mol) of terephthalic acid, 675 g (2.5 mol) of 4,4'-dihydroxydiphenyl diacetylated product, 347.5 g of polyester obtained in Reference Example 1
(corresponding to 20% by weight of the final polymer) and 1,400 g of Santotherm 66 (manufactured by Mitsubishi Monsanto Chemical Co., Ltd.) as a high boiling point solvent were placed in a reactor, and the mixture was stirred constantly in a nitrogen gas atmosphere for 1 hour. It was heated to 180℃ and then raised to 320℃ for another 8 hours. Continue stirring at 320℃ for 16 minutes.
A slurry was formed by heating at 340° C. for 3 hours. The reaction mixture was allowed to cool, and 1000 g of Santotherm 66 was added to the mixture to bring the temperature to 70°C. 1920 g of acetone was added, the slurry was filtered, and the powder was Soxhlet extracted with acetone to remove Santotherm 66. This powder was dried under reduced pressure at 110℃ for 5 hours to obtain 1543g of polymer (theoretical amount).
88.8%). This powder was transferred to an aluminum rotary oven, the entire system was rotated under a nitrogen stream, and the powder was kept at 200°C for 10 hours while stirring thoroughly.Then, the temperature was gradually raised to 300°C for 6 hours. After being kept at 200°C for 2 hours, the powder was cooled to 200°C and taken out. This polymer was granulated and injection molded in the same manner as in Example 1. The results are shown in Table 1. The molded product showed orientation, and its physical properties were lower than those of Example 1.

[Table] Example 2 In the same manner as in Example 1, the polymer obtained in Reference Example 1 was used as the final polymer 10, 20, 30, 40,
Each polymer was obtained by polymerization in a proportion of 50% by weight. These were granulated and molded in the same manner as in Example 1 to obtain various physical property values.
The results are shown in Table 2. For comparison, cases where the polymer present was 0.60% by weight are also shown. The molding shrinkage rate was determined as the shrinkage rate (%) in the machine axis direction (MD) and in the direction perpendicular to the machine axis (TD) by molding a shrink plate and measuring its dimensions. The molding temperature for each polymer in the table represents the optimum molding temperature (molding temperature considered to be optimal in view of the balance of characteristic values).

[Table] The presence of polyester improves the appearance and significantly improves the strength of the weld portion. Furthermore, the anisotropy of molding shrinkage (MD and TD)
(difference between the two) has also become smaller, and it is thought that the orientation has been relaxed. At 60%, mechanical strength is poor. Example 3 An aromatic polyester was obtained by carrying out the subsequent operations in the same manner as in Example 1, except that the polymer obtained in Reference Example 2 was present in a proportion that was 20% by weight of the final polymer. This product was granulated and molded, and various physical properties were measured. Table 3 shows the results.

【table】

Claims (1)

[Claims] 1. The following repeating units [], [] and []
When producing a wholly aromatic polyester composed of, a polyester composed of the following repeating units [] and [] is present in the polymerization reaction system in a proportion of 5 to 50% by weight of the final produced polymer, A method for producing an aromatic polyester, characterized in that the polymerization is carried out by a bulk polymerization method in the absence of substantially any solvent. (In the above formula, X is a C ₁ to C ₄ alkyl group, -O-, -SO ₂
-, -S- or -CO-, and m and n are 0 or 1. []: [] ratio is 1:1 to 10:
1, and the ratio of []:[] is from 9:10.
It is between 10:9. Furthermore, the substituents on the aromatic ring in the above formula are in para or meta positions with respect to each other. ) (In the structure of [] and [], [] occupies more than 80 mol%. Also, the sum of the polymerization degrees of [] and [] is in the range of 10 to 1000.)