JPH0786138B2 - Aromatic polycarbonate manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an aromatic polycarbonate.

More specifically, the present invention relates to a method for producing aromatic polycarbonate by solid phase polymerization.

(Prior Art) In recent years, aromatic polycarbonate has been improved in heat resistance, impact resistance, and
It is widely used in many fields as an engineering plastic with excellent transparency. Various studies have been conducted on the production method of this aromatic polycarbonate, and among them, aromatic dihydroxy compounds such as 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as bisphenol A) and phosgene have been investigated. The interfacial polycondensation method has been industrialized.

However, in this interfacial polycondensation method using phosgene, toxic phosgene must be used,
There are problems that the equipment will be corroded by chlorine-containing compounds such as hydrogen chloride and sodium chloride that are by-produced, and that it will be difficult to separate impurities such as sodium chloride mixed in the resin that adversely affect the physical properties of the polymer. Since methylene chloride which is usually used as a reaction solvent is a good solvent for polycarbonate and has an extremely high affinity,
In the generated polycarbonate, the methylene chloride is unavoidably left behind, and as a result, due to heating during molding,
The residual methylene chloride is decomposed to generate hydrogen chloride, which may lead to corrosion of the molding machine and deterioration of polymer quality.
It is very costly to industrially reduce the amount of residual methylene chloride, and it is almost impossible to completely remove the residual methylene chloride.

In addition, methylene chloride is a chemical substance that has environmental and hygiene problems, and it must be handled with care, but its boiling point is very low at 40 ° C, so it is used during the production of aromatic polycarbonate. It is very expensive to make a closed system that can completely recycle the methylene chloride.

As described above, the phosgene method involves many problems when it is industrially implemented.

On the other hand, a method for producing an aromatic polycarbonate from an aromatic dihydroxy compound and a diaryl carbonate has also been known for a long time, and for example, phenol is eliminated by a transesterification reaction between bisphenol A and diphenyl carbonate in a molten state to give a polycarbonate. The manufacturing method has been industrialized as a so-called transesterification method or another name melting method. However,
In this method, from the melt of high-viscosity polycarbonate, since the degree of polymerization does not increase unless phenol and finally diphenyl carbonate are distilled off, usually at a high temperature of 280 to 310 ° C, And it is necessary to react for a long time under a high vacuum of 1 mmHg or less, therefore,
(1) Requires a special device suitable for high temperature and high vacuum, and a strong stirring device due to the high viscosity of the product,
(2) Due to the high viscosity of the product, the reactor and stirring type usually used in the plastics industry can obtain only a polymer having a weight average molecular weight of about 30,000. (3) At high temperature Since the reaction is carried out, there are various drawbacks such as branching and cross-linking easily occurring due to side reactions, it is difficult to obtain a good quality polymer, and (4) color retention is unavoidable due to long-term retention at high temperature. Mikio Matsugane et al., Plastic material course [5] "Polycarbonate resin", published by Nikkan Kogyo Shimbun (Showa 44), pages 62-67].

Furthermore, it is known that the polycarbonate obtained by this melting method structurally contains a large number of hydroxyl end groups (-OH groups), has a wide molecular weight distribution, and has many branched structures. Therefore, compared with polycarbonate produced by the phosgene method, for example, it is pointed out that it is inferior in physical properties such as slightly inferior in strength, particularly large brittle fracture property, non-Newtonian flow behavior, etc. "[Polymer] Vol. 27, 521 (1
978))]. In particular, containing a large amount of hydroxyl groups as polymer end groups means that the polycarbonate obtained by the melting method is inferior in basic physical properties as an engineering plastic such as heat resistance and hot water resistance. ing.

By the way, polyhexamethylene adipamide (nylon 66) and polyethylene terephthalate (PET), which are the most common condensation polymers, are usually polymerized by the melt polymerization method up to a molecular weight that has sufficient mechanical properties for plastics and fibers. However, the high-molecular weight polymer produced in this manner is subjected to solid phase polymerization by heating at a temperature capable of maintaining a solid phase state under reduced pressure or under the flow of dry nitrogen or the like, and It is already known that it is possible to increase the degree of polymerization.

In this solid phase polymerization, it is considered that in the solid polymer, the terminal carboxyl group reacts with the terminal amino group or terminal hydroxyl group existing in the vicinity to cause dehydration condensation. Further, in the case of polyethylene terephthalate, a condensation reaction due to deethylene glycol also partially occurs.

In this way, nylon 66 and polyethylene terephthalate can be highly polymerized by solid phase polymerization because these polymers are originally crystalline polymers having high melting points (265 ° C and 260 ° C, respectively), This is because the solid state can be sufficiently maintained at the temperature at which solid phase polymerization proceeds (for example, 230 to 250 ° C.). More importantly, the compound to be desorbed is a substance having a small molecular weight such as water and ethylene glycol and a relatively low boiling point, and they easily move in a solid polymer and are discharged as a gas out of the system. It can be removed.

However, no attempts have been made to produce aromatic polycarbonates, which are substantially amorphous polymers based on dihydroxydiarylalkanes such as bisphenol A, by solid state polymerization of relatively low molecular weight prepolymers. There wasn't. This means that bisphenol A polycarbonate has a glass transition temperature (Tg) of 14
This is because it was considered impossible to perform solid phase polymerization because it is an amorphous polymer at 9 to 150 ° C.

That is, in general, in order to enable solid phase polymerization, it is necessary that the polymer can maintain a solid state at a temperature equal to or higher than the glass transition temperature without causing fusion and the like. This is because in the case of the polycarbonate, fusion bonding and the like occurred at a temperature of 150 ° C. or higher, and solid phase polymerization was substantially impossible as it was.

The present inventors have found that such an aromatic polycarbonate is
A new method that can be produced by solid-state polymerization was found and filed previously (Japanese Patent Application Laid-Open No. 1-158033).

This method involves crystallizing a substantially amorphous polycarbonate prepolymer having terminal hydroxyl groups and terminal aryl carbonate groups and then solid-phase polymerizing the crystalline polycarbonate prepolymer. For the first time, it has been found that a quality aromatic polycarbonate can be produced.

In the invention, for solid phase polymerization, nitrogen, argon,
It has been disclosed that an inert gas such as helium or carbon dioxide is introduced and is allowed to accompany with an aromatic monohydroxy compound or a diaryl carbonate produced as a by-product to advantageously proceed the polymerization reaction.

(Problems to be Solved by the Invention) The present invention overcomes various drawbacks of the conventional phosgene method and melting method, and uses a high-quality aromatic polycarbonate containing no chlorine compound in an amount of an inert gas. The present invention provides a method for producing by an industrially advantageous solid-phase polymerization method, which has a small amount and is easy to handle.

(Means for Solving the Problems) The inventors of the present invention have earnestly studied a method for producing a high-polymerization aromatic polycarbonate by solid-phase polymerizing a crystalline polycarbonate prepolymer having a specific structure under an inert gas flow. As a result of research, it was found that the above problems can be solved by semi-continuously polymerizing using a vertical multi-stage polymerization apparatus, and the present invention has been completed based on this finding.

The method of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of an apparatus suitable for carrying out the method of the present invention.

In the figure, 1 is a vertical multistage polymerization apparatus divided into first chamber 9 to Nth chamber 11 by gas dispersion plates 6 (first stage) to 8 (Nth stage) (N is the number of stages). Show.). The inert gas is supplied from 4 and discharged from 5. Dispersion plate 6 (first stage) ~
The 8th (Nth stage) is provided with a large number of pores through which the inert gas from the lower portion passes and the polymer particles do not pass. The crystalline polycarbonate prepolymer is supplied from 2
After being polymerized in the chamber 9 for a predetermined time, it is transferred to the second chamber 10 and further polymerized. As a method of transfer, a method of rotating the dispersion plate (Fig. 2) and a method of opening the dispersion plate downward (No. 3)
(Fig.), A method of providing a connecting pipe and dropping it (Fig. 4) and the like are possible.

After the polymer in the first chamber 9 is transferred to the second chamber 10, new crystalline prepolymer is supplied from 2. After being polymerized in the first chamber 9 and the second chamber 10 for a predetermined time, the polymer in the second chamber is transferred to the third chamber, the polymer in the first chamber is transferred to the second chamber, and the new crystalline prepolymer from 2 is transferred. Supplied. By repeating this operation, the polymer is sequentially transferred to the lower stage. The lower the polymer is, the higher the molecular weight is, and the polymer polymerized in the N chamber to reach the target molecular weight is discharged from 3.

The multistage polymerization apparatus of the present invention has two or more stages. It has been clarified that by using two or more stages, a high molecular weight aromatic polycarbonate can be obtained by using a small amount of inert gas as compared with the case of one stage.

According to the method of the present invention, the amount of the inert gas used when producing 1 kg of the aromatic polycarbonate is usually in the range of 1.5 to 20 Nm ³ . The upper limit of the number of stages is not particularly limited, but it is preferably 20 or less from the viewpoint of equipment cost.

In the present invention, the polymer polymerized at each stage may be in a fixed bed state or a fluidized bed state. Polymerization in a fluidized bed is an advantageous method in that fusion between polymers is less likely to occur. Even in the case of polymerizing in a fixed bed state, it is possible to prevent fusion between polymers by a method of, for example, intermittently increasing the flow rate of the inert gas.

The flow rate of the inert gas of the present invention is selected within the range where the polymer does not scatter. Usually depends on the particle size of the polymer,
It is in the range of 0.01 to 5 m / sec.

As the inert gas used in the present invention, nitrogen neon,
Examples of the gas include organic compounds such as argon, CO ₂ and lower hydrocarbons that do not adversely affect the reaction. Nitrogen is particularly preferable in terms of ease of manpower.

The solid phase polymerization of the present invention is performed at a temperature not lower than the glass transition temperature of the crystalline polycarbonate prepolymer and not higher than the melting point,
It is usually in the range of 150 ° C to 260 ° C.

The pressure of the solid phase polymerization is not particularly limited, and it can be carried out under reduced pressure, normal pressure or increased pressure.

The shape of the pores of the dispersion plate provided in the multi-stage polymerization apparatus of the present invention is not particularly limited, and any shape such as a circle, an oval, or an irregular shape is possible. Sectional area of the pores is in the range of 7 × 10 ^-3 mm ² ~70mm ² is preferred. The opening ratio, that is, the area ratio of the opening to the area of the dispersion plate, is such that the pressure loss of the dispersion plate is in the range of 2 to 30% with respect to the pressure loss of the flowing powder layer, preferably 4 to 20
It is set to be in the range of%. Normally, the aperture ratio is 0.01
It is in the range of ~ 0.30.

In the present invention, the polymerization time at each stage varies depending on the number of stages and the polymerization conditions and is not particularly limited, but is usually in the range of 0.5 to 5 hours.

The crystalline polycarbonate prepolymer used as a starting material in the present invention has the formula: (In the formula, P represents a repeating number. Ar ¹ represents a divalent aromatic residue.

X is -H- or Alternatively, it is --Ar ¹ --OH. R ¹ represents hydrogen, an alkyl group, an aralkyl group or an alkoxy group. ) Specific examples of R ¹ include —H, —CH ₃ , Etc.

It is represented by.

Examples of such an aromatic residue include phenylene (various), naphthylene (various), biphenylene (various) pyridylene (various), and a general formula: -Ar ² -Z-Ar ³ -... (II) The divalent aromatic group represented is mentioned.

Here, Ar ² and Ar ³ are the same or different divalent aromatic groups, such as phenylene (various), naphthylene (various), biphenylene (various) and pyridylene (various). ) Represents a group such as.

Z is a mere bond, or -O-, -CO-, -S-, -SO ₂
−, −CO ₂ −, −CON (R ¹ ) −, Represents a divalent group such as.

(Here, R ¹ , R ² , R ³ and R ⁴ may be the same or different and each represents a hydrogen atom, a lower alkyl group, a lower alkoxy group or a cycloalkyl group, and k is 3 to 11). Represents an integer, the above formula The hydrogen atom of may be substituted with a lower alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkoxy group, a halogen atom or the like. ) Furthermore, such divalent aromatic groups (ie A
r ¹ or Ar ² , Ar ³ ), one or more hydrogen atoms are
Other substituents that do not adversely affect the reaction, for example, halogen atom, lower alkyl group, lower alkoxy group, phenyl group, phenoxy group, vinyl group, cyano group, ester group,
It may be substituted with an amide group, a nitro group, or the like.

Specific examples of the aromatic residue Ar ¹ include, for example, A substituted or specific substituted phenylene group represented by: A substituted or specific substituted biphenylene group represented by: (R ² and R ³ in the formula are each a hydrogen atom, a halogen atom,
A lower alkyl group having 1 to 4 carbon atoms, a lower alkoxy group having 1 to 4 carbon atoms, a cycloalkyl group or a phenyl group, which may be the same or different from each other, and m and n are R ² may be different from each other when m is 2 or more, and n is 2
In the above cases, R ³ may be different from each other) and a substituted or unsubstituted divalent aromatic group and the like can be mentioned.

As Ar ¹ in these structures, Is preferred.

further, It is preferred that the content of the repeating unit is 85 mol% or more.

Further, the crystalline polycarbonate prepolymer of the present invention,
A trivalent aromatic group may be contained within a range of about 0.01 to 3 mol% with respect to the entire Ar ¹ .

The crystallinity of the crystalline polycarbonate prepolymer of the present invention is not particularly limited, but usually in the range of 5 to 55% (X-ray analysis method).

The number average molecular weight of the crystalline polycarbonate prepolymer used in the present invention is 1,500 or more, preferably 2,000 to 20,0.
00.

The terminal group of the crystalline polycarbonate prepolymer is composed of a hydroxyl group and an aryl carbonate group. The ratio of the hydroxyl group to the aryl carbonate group is not particularly limited, but from the viewpoint of the polymerization rate, it is preferably in the range of 10:90 to 90:10, particularly 20:80 to 80:20.

The shape of the crystalline polycarbonate prepolymer of the present invention is not particularly limited. Although it may be in the form of irregular powder or granules, it is particularly preferable that it has a columnar shape, a pellet shape, a tablet shape or the like formed by various known methods such as an extrusion granulation method and a compression molding method.

As a method for obtaining the crystalline polycarbonate prepolymer used in the present invention, a method of first synthesizing an amorphous polycarbonate prepolymer and then crystallizing the amorphous polycarbonate prepolymer is usually used.

The method for synthesizing the amorphous polycarbonate prepolymer is not particularly limited, and the amorphous polycarbonate prepolymer can be synthesized by the following various methods.

That is, by a transesterification method, a method of synthesizing a bisphenol such as bisphenol A by melt polymerization with a diaryl carbonate, an aromatic dihydroxy compound and phosgene in the presence of an aromatic monohydroxy compound such as phenol or t-butylphenol as a terminal stopper. Is synthesized by interfacial polycondensation, a condensation product of aromatic dihydroxy compound and diaryl carbonate in a molar ratio of 1: 2 is previously synthesized, and melt polymerization of this and aromatic dihydroxy compound is performed. Examples include a method in which an aromatic dihydroxy compound is newly added to a phenyl carbonate-terminated polycarbonate oligomer obtained by reacting excess phosgene and phenol with respect to the group dihydroxy compound, and melt polymerization is performed.

In the present invention, an aromatic polycarbonate containing substantially no chlorine compound can be obtained.

For example, when using the amorphous polycarbonate obtained by the transesterification method, since there are no chlorine compounds in the raw material,
An aromatic polycarbonate containing no chlorine can be produced.

Further, even when an amorphous polycarbonate prepolymer is produced using phosgene or the like, it is easy to remove chlorine from the low molecular weight amorphous prepolymer. It is possible to obtain a non-aromatic polycarbonate.

The method for crystallizing the amorphous polycarbonate prepolymer is not particularly limited, but usually a solvent treatment method and a heat crystallization method are preferably used.

The former solvent treatment method is a method of crystallizing a prepolymer using an appropriate solvent. Specifically, after dissolving an amorphous prepolymer in a solvent, a crystalline prepolymer is precipitated from this solution. The method or a solvent having a low dissolving power for the prepolymer is used, and the solvent is permeated into the amorphous prepolymer, and the prepolymer is kept in a liquid state for a time required for crystallizing the amorphous prepolymer. A method of contacting with a solvent or solvent vapor is preferably used.

Examples of the solvent that can be used for solvent treatment of such an amorphous prepolymer include chloromethane, methylene chloride, chloroform, carbon tetrachloride, chloroethane, dichloroethane (various), trichloroethane (various), trichloroethylene, tetrachloroethane ( Aliphatic halogenated hydrocarbons such as various); aromatic halogenated hydrocarbons such as chlorobenzene and dichlorobenzene; ethers such as tetrahydrofuran and dioxane; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone Kinds; aromatic hydrocarbons such as benzene, toluene, xylene and the like can be mentioned. Halogen-free solvents are particularly preferred for obtaining high quality polymers. These solvents may be used alone or in combination of two or more.

On the other hand, the heat crystallization method is a method in which the prepolymer is crystallized by heating at a temperature above the glass transition temperature of the target aromatic polycarbonate and below the temperature at which the prepolymer begins to melt. is there. This method can be carried out extremely easily industrially because the prepolymer can be crystallized simply by holding it under heating.

The number average molecular weight of the aromatic polycarbonate obtained by solid-state polymerization is one having a higher degree of polymerization than the crystalline polycarbonate prepolymer used as a raw material,
It is usually 6,000 to 200,000.

The solid-phase polymerization can be carried out in the presence or absence of a catalyst, but the non-catalytic polymerization is preferable because the color, heat resistance and hot water resistance of the polymer obtained are remarkably excellent.

As the polymerization catalyst, various known catalysts such as transesterification catalysts used for polycarbonate or polyester can be used. Examples thereof include alkali metal salts of bisphenol A, tin and lead compounds.

(Examples) Next, the present invention will be described in more detail with reference to Examples.
The invention is in no way limited by these examples.

The molecular weight is the number average molecular weight measured by gel permeation chromatography (GPC).

The terminal groups in the prepolymer were determined by high performance liquid chromatography analysis or NMR analysis.

The crystallinity was determined by powder X-ray diffraction according to the method described in JP-A-1-158033.

Example 1 Amorphous prepolymer polymerized by a melting method using bisphenol A and diphenyl carbonate as raw materials was crystallized with acetone to give a number average molecular weight of 3,800, a terminal hydroxyl group of 29%, a terminal phenyl carbonate group of 71%, and a degree of crystallinity.
25% of crystalline polycarbonate prepolymer was obtained. This was molded by a rotary granulator to obtain pellets having a diameter of 2 mm and a length of about 3 mm.

Solid-state polymerization of these pellets was performed using a vertical 6-stage polymerization apparatus. The polymerization apparatus is made of SUS304 having an inner diameter of 200 mm and is divided into six chambers by six rotatable dispersion plates.

12 kg of the above pellets are supplied to the first chamber, and heated nitrogen at 210 ° C 6
Polymerization was carried out in a fluidized bed by flowing 0 Nm ³ / Hr from the bottom.
After 1 hour, the dispersion plate was rotated to drop pellets from the first chamber to the second chamber, and 12 kg of new pellets were supplied to the first chamber. Hereafter, the pellets are sequentially transferred downward every hour,
And supplied new pellets. After the 6th hour, pellets came to be discharged from the lower part of the polymerization apparatus. The number average molecular weights of the pellets discharged after 10 hours, 15 hours, and 20 hours were 13,200, 13,300, and 13,200, respectively, and it can be seen that the polymerization is constantly performed from 10 hours to 20 hours. The amount of nitrogen used per 1 kg of pellets was 5 Nm ³ .

Comparative Example 1 Solid phase polymerization was carried out using the same pellet and fluidized bed apparatus as in Example 1. However, as the dispersion plate, only the uppermost one layer was used, and the remaining five layers were used while being left open. 16 kg of pellets were charged in the uppermost stage, and 60 Nm ³ / Hr of 210 ° C. heated nitrogen was supplied from the bottom to carry out solid-phase polymerization. After 6 hours, the number average molecular weight reached 13,200. The amount of nitrogen used per 1 kg of pellets was 22.5 Nm ³ , which was more than four times that of Example 1.

Examples 2 to 4 Solid-state polymerization was carried out using the same pellet and polymerization apparatus as in Example 1. However, the number of stages used, the amount of pellets per stage, the residence time per stage of pellets, the amount of heated nitrogen and the temperature were changed.

The results are summarized in Table 1. In each case, the amount of nitrogen used per 1 kg of pellets is 15 Nm ³ / Hr or less.

Example 5 Solid-state polymerization was performed in the same manner as in Example 1 except that the same pellets as in Example 1 were used and the amount of pellets per stage was 2 kg and the flow rate of heated nitrogen was 7 Nm ³ / Hr. The pellets in each stage are
Polymerized in a fixed bed. The number average molecular weight of the pellet discharged after 15 hours was 12,500.

Example 6 Bisphenol A and phosgene were synthesized by interfacial polycondensation in the presence of phenol and then obtained by a solvent crystallization method with acetone. The number average molecular weight was 3,400 and the terminal hydroxy group was 38.
%, 62% of terminal phenyl carbonate groups and 25% of crystallinity, a crystalline polycarbonate prepolymer was pelletized by the same method as in Example 1 and solid phase polymerization was carried out. The number average molecular weight of the pellet discharged from the lower part of the fluidized bed apparatus after 20 hours was 13,000.

(Effect of the Invention) The present invention is an industrially advantageous solid-state polymerization process capable of producing a high-quality aromatic polycarbonate with a relatively small amount of inert gas used.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a vertical multistage polymerization apparatus suitable for carrying out the method of the present invention. 2 to 4 are schematic views showing various forms of the dispersion plate for transferring the polymer produced in each stage.

Claims (1)

[Claims] 1. A formula: (In the formula, P represents the number of repetitions. Ar ¹ represents a divalent aromatic residue, and X represents —H— or Alternatively, it is —O—Ar ¹ —OH. R ¹ is hydrogen, an alkyl group,
Represents an aralkyl group or an alkoxy group. ) And a crystalline polycarbonate prepolymer having a molecular weight of 1500 or more is solid-phase polymerized under an inert gas flow to produce an aromatic polycarbonate having a high degree of polymerization, and semi-continuous using a vertical multistage polymerization apparatus. A method for producing an aromatic polycarbonate, characterized in that the aromatic polycarbonate is polymerized.