JPH0472326A - Production of aromatic polycarbonate - Google Patents

Abstract

PURPOSE:To obtain the subject polycarbonate having excellent handleability and high quality on an industrial scale by carrying out solid-phase polymerization of a crystalline polycarbonate prepolymer using a vertical-type multi-stage polymerizer. CONSTITUTION:The objective polycarbonate is produced by the semi-continuous solid-phase polymerization of a crystalline polycarbonate prepolymer in an inert gas stream using a vertical-type multi-stage polymerizer 1. Preferably, the prepolymer is e.g. the one expressed by formula (p is number of recurring units; Ar<1> is bivalent aromatic residue) and the inert gas is nitrogen gas.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for producing aromatic polycarbonate.

More particularly, the present invention relates to a method for producing aromatic polycarbonates by solid state polymerization.

(Prior art) In recent years, aromatic polycarbonates have been improved in heat resistance, impact resistance,
It is widely used in many fields as an engineering plastic with excellent transparency. Various studies have been conducted on the production method of aromatic polycarbonate, including the combination of aromatic dihydroquine compounds such as 22-bis(4-hydroxyphenyl)bromonone (hereinafter referred to as bisphenol A) and phosgene. The interfacial polycondensation method has been industrialized.

However, in this interfacial polycondensation method using phosgene, toxic phosgene must be used;
There are problems such as corrosion of equipment due to by-produced chlorine-containing compounds such as hydrogen chloride and sodium chloride, and difficulty in separating impurities that adversely affect the physical properties of the polymer, such as sodium chloride mixed into the resin. Methylene chloride, which is commonly used as a reaction solvent, is a good solvent for polycarbonate and has an extremely high affinity for it. Therefore, methylene chloride inevitably remains in the produced polycarbonate, and as a result, molding The residual methylene chloride decomposes due to heating during the process and generates hydrogen chloride, which may lead to corrosion of the molding machine and deterioration of the quality of the polymer. Industrially reducing the amount of residual methylene chloride requires a great deal of expense, and it is almost impossible to completely remove the residual methylene chloride.

Furthermore, methylene chloride is a chemical substance that poses environmental and hygienic problems, and requires great care when handling; however, because its boiling point is extremely low at 40'C, it is difficult to manufacture aromatic polycarbonate. It would be very expensive to create a closed system in which the methylene chloride used could be completely recycled.

As described above, the phosgene method is accompanied by many problems when implemented industrially.

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. A method for producing polycarbonate by eliminating phenol through a reaction has been industrialized as the so-called transesterification method, also known as the melting method. however,
In this method, the degree of polymerization cannot be increased unless phenol and finally diphenyl carbonate are distilled off from the high viscosity polycarbonate melt, so it is usually carried out at a high temperature of 280 to 310"C. , and lm
It is necessary to react for a long time under high vacuum below mHg,
Therefore, (1) special equipment suitable for high temperature and high vacuum conditions and powerful stirring equipment are required due to the high viscosity of the product, and (2) due to the high viscosity of the product, the plastic industry The reactors and stirring type normally used in the industry can only produce polymers with a weight average molecular weight of about 30,000; (3) the reaction is carried out at high temperatures;
It has various disadvantages, such as side reactions (ζ) which tend to cause branching and crosslinking, making it difficult to obtain polymers of good quality, and (4) discoloration due to long-term residence at high temperatures (Mikio Matsugane). See also Plastic Materials Course (5) U Polycarbonate Resin J Published by Nikkan Kogyo Shimbunsha (1962), pp. 62-67].

Furthermore, it is known that polycarbonate obtained by this melting method structurally contains a large amount of hydroquinol end groups (-OHM), has a wide molecular weight distribution, and has many branched structures. For this reason, it has been pointed out that it has inferior physical properties compared to polycarbonate produced by the phosgene method, such as slightly inferior strength, particularly high brittle fracture, and non-Newtonian flow behavior. [Refer to "Komunshi" Vol. 27, p. 521 (1978)]. In particular, the fact that it contains a large amount of hydroxol groups as polymer terminal groups means that the polycarbonate obtained by this melting method is inferior in basic physical properties as an engineering plastic, such as heat resistance and hot water resistance. are doing.

By the way, the most common condensation polymers, such as polyhexamethylene adipamide (nylon 66) and polyethylene terephthalate (PET), are usually polymerized by melt polymerization to a molecular weight that has sufficient mechanical properties for plastics and fibers. However, solid phase polymerization is carried out by heating the high molecular weight polymer thus produced under reduced pressure or under a flow of dry nitrogen to a temperature at which it can maintain a solid phase state, and then It is already known that it is possible to increase the degree of polymerization.

In this solid phase polymerization, it is thought that dehydration condensation progresses as a terminal carboxyl group reacts with a nearby terminal amino group or terminal hydroxol group in the solid polymer. In addition, in the case of polyethylene terephthalate, some condensation reactions due to removal of ethylene glycol also occur.

In this way, the reason why it is possible to increase the degree of polymerization of nylon 66 and polyethylene terephthalate through solid phase polymerization is that these polymers have high melting points (265°C and 265°C, respectively).
This is because it is an originally crystalline polymer having a temperature of 60°C) and can sufficiently maintain its solid state at the temperature at which solid state polymerization proceeds (for example, 230 to 250°C). More importantly, the compound to be eliminated must be a substance with a small molecular weight and a relatively low boiling point, such as water or ethylene glycol, so that it can easily move through the solid polymer and exit the system as a gas. This is because it can be removed.

However, no attempt has been made to produce aromatic polycarbonate, which is a substantially non-grade polymer based on dihydroxydiarylalkane such as bisphenol A, by solid-state polymerization of a relatively low molecular weight prepolymer. There wasn't. This means that bisphenol A polycarbonate has a glass transition temperature (Tg) of
This is because it was considered impossible to carry out solid phase polymerization because it is an inferior polymer with a temperature of 149 to 150°C.

In other words, in order to make solid phase polymerization possible for boat fishing, it is necessary for the polymer to maintain a solid phase state without causing fusion at temperatures above the glass transition temperature. This is because, in the case of the polycarbonate, fusion and the like occur at temperatures of 150° C. or higher, making solid phase polymerization virtually impossible as it is.

The present inventors discovered that such an aromatic polycarbonate is
A new method for manufacturing by solid phase polymerization was discovered and an application was filed earlier (Japanese Patent Application Laid-open No. 1-158033).

This method involves crystallizing a substantially non-grade polycarbonate prepolymer having terminal hydroxyl groups and terminal aryl carbonate groups, and then solid-state polymerizing the crystalline polycarbonate prepolymer. We discovered for the first time that it is possible to produce high-quality aromatic polycarbonate.

In the invention, for solid phase polymerization, nitrogen, argon,
It was disclosed that the polymerization reaction can be advantageously carried out by introducing an inert gas such as helium or carbon dioxide, and entraining it with by-produced aromatic monohydroxy compounds and diaryl carbonates.

(Problems to be Solved by the Invention) The present invention overcomes various drawbacks of the conventional phosgene method and melting method, and produces high-quality aromatic polycarbonate that does not contain chlorine compounds by reducing the amount of inert gas used. The object of the present invention is to provide an industrially advantageous production method using a solid phase polymerization method, which is easy to handle and has a small amount of oxidation.

(Means for Solving the Problem) The present inventors conducted intensive research on a method for producing aromatic polycarbonate with a high degree of polymerization by solid-phase polymerizing a crystalline polycarbonate prepolymer under inert gas flow. As a result, we discovered that the above problems could be solved by performing semi-continuous polymerization using a vertical multi-stage polymerization apparatus,
Based on this knowledge, we have completed the present invention.

The method of the invention will be explained with the help of figures.

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

In the figure, 1 is a vertical multistage polymerization apparatus divided into a first chamber 9 to an Nth chamber 11 by gas distribution plates 6 (first stage) to 8 (Nth stage) (N is the number of stages). show.

). Inert gas is supplied from 4 and exhausted from 5.

Dispersion plates 6 (1st stage) to 8 (Nth stage) are provided with a large number of pores that allow inert gas from the bottom to pass through, but do not allow polymer particles to pass through.6 Crystalline polycarbonate prepolymer is
After being polymerized in the first chamber 9 for a predetermined period of time, it is transferred to the second chamber 10 and further polymerized. Possible transfer methods include rotating the dispersion plate (FIG. 2), opening the dispersion plate downward (third circle), and dropping the dispersion plate using a connecting pipe (FIG. 4).

After the polymer in the first chamber 9 has been transferred to the second chamber 10, fresh crystalline prepolymer is fed 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,
Fresh crystalline prepolymer is fed from 2. By repeating this operation, the polymer is sequentially transferred to the lower stage. The lower the polymer, the higher the molecular weight, and the polymer that is polymerized in the N chamber and reaches the target molecular weight is discharged from 3.

The number of stages in the multistage polymerization apparatus of the present invention is two or more.

It has become clear that by using two or more stages, a high molecular weight aromatic polycarbonate can be obtained with a smaller amount of inert gas used than in the case of one stage.

According to the method of the present invention, 1 kg of aromatic polycarbonate
The amount of inert gas used when manufacturing is! Normally 1.5~2O
It is in the range of Nm. Further, there is no particular restriction on the upper limit of the number of stages, but it is preferably 20 stages or less from the point of view of equipment cost.

In the present invention, the polymer polymerized in 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 polymerization in a fixed bed state, it is possible to prevent polymers from fusing together, for example, by intermittently increasing the flow rate of an inert gas.

The flow rate of the inert gas in the present invention is selected within a range that does not cause the polymer to scatter. Although it varies depending on the particle size of the polymer, it is usually in the range of 0.01 to 5 m/sec.

The inert gas used in the present invention includes nitrogen neon,
Examples include gases of organic compounds such as argon, CO2, and lower hydrocarbons that do not adversely affect the reaction. Nitrogen is particularly preferred from the viewpoint of easy availability.

The solid phase polymerization of the present invention is carried out at a temperature above the glass transition temperature and below the melting point of the crystalline polycarbonate prepolymer,
Usually in the range of 150'C to 260'C.

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

There is no particular restriction on the shape of the pores in the dispersion plate provided in the multistage polymerization apparatus of the present invention, and any shapes such as circular, oval, irregular shapes, etc. are possible. The cross-sectional area of the pore is 7×10-mrr! ~7
0mn? A range of is preferred. In addition, the aperture ratio, i.e.
The area ratio of the openings to the area of the dispersion plate is set so that the pressure loss of the dispersion plate is in the range of 2 to 30%, preferably in the range of 4 to 20%, relative to the pressure loss of the flowing powder layer. . Usually, the aperture ratio is in the range of 0.01 to 0.30.

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

The crystalline polycarbonate prepolymer referred to in the present invention is represented by the formula; be.

Such aromatic residues include, for example, phenylene (various types), naphthylene (various types), biphenylene (various types), pyridazine (various types), and general formulas.

A divalent aromatic group represented by Ar2-Z-Ar' --... (U) can be mentioned.

Here, Ar' and Ar3 are divalent aromatic groups which may be the same or different, such as phenylene (various), naphthylene (various), biphenylene (various), pyridazine (various). represents a group such as

Z is a simple bond or -○-1-CO-1-8S○2-
1-CO2-1-CON (R')-R2R2R' Represents a divalent group.

(Here, R', R', R3, and R' may be the same or different, and include a hydrogen atom, a lower alkyl group,
Represents a lower alkokene group or a socroalkyl group, k is 3 to
Represents an integer of 11. ) Furthermore, such divalent aromatic groups (i.e., Ar
', or Ar2, Ar'), one or more hydrogen atoms may be substituted with other substituents that do not adversely affect the reaction, such as a halogen atom, a lower alkyl group, a lower alkokino group, a phenyl group, a fenoquino group, a vinyl group. , an ano group, an ester group, an amide group, a nitro group, or the like.

Examples of such aromatic groups include (R5).

A substituted or relatively substituted phenylene group represented by: A substituted or relatively substituted biphenylene group represented by: Also, the crystalline polycarbonate prepolymer of the present invention contains about 0.01 to 3 mol % based on the entire Ar' A trivalent aromatic group may be included within this range.

There are no particular limitations on the degree of crystallinity of the crystalline polycarbonate prepolymer of the present invention, but it is usually preferably 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 2.0
00 to 200.000.

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

There are no particular limitations on the shape of the crystalline polycarbonate prepolymer of the present invention. It may be in the form of irregularly shaped powders or granules, but columnar, pellet-shaped, tablet-shaped, etc. shaped by various known methods such as extrusion granulation and compression molding are particularly preferred.

The method for obtaining the crystalline polycarbonate prepolymer used in the present invention is usually to first synthesize an amorphous polycarbonate polymer, and then to crystallize this non-quality polycarbonate prepolymer.

There are no particular limitations on the method of synthesizing the non-grade polycarbonate prepolymer (it can be synthesized by the various methods described below).

That is, a method in which bisphenol such as bisphenol A is synthesized by melt polymerization of diaryl carbonate by a transesterification method, and an interfacial MEfJ synthesis method in which biphenol and phosgene are synthesized in the presence of an aromatic monohydroquine compound such as phenol or t-butylphenol as a terminal termination side. A method in which a condensate of biphenol and diaryl carbonate with a molar ratio of 1:2 is synthesized in advance, and this and biphenol are melt-polymerized.In interfacial polycondensation, excess phosgene and phenol are added to the biphenol. Examples include a method in which biphenol is newly added to a phenyl carbonate-terminated polycarbonate oligomer obtained by the reaction and melt polymerized.

In the present invention, an aromatic polycarbonate substantially free of chlorine compounds can be obtained.

For example, when using non-grade polycarbonate obtained by transesterification, there are no chlorine compounds in the raw material, so
Aromatic polycarbonate containing no chlorine can be produced.

Furthermore, even when a non-grade polycarbonate prepolymer is produced using phosgene or the like, it is easy to remove chlorine from a low molecular weight non-grade prepolymer. aromatic polycarbonate can be obtained.

There are no particular restrictions on the method for crystallizing the non-quality polycarbonate prepolymer, but solvent treatment and heating crystallization are usually preferably used.

The former solvent treatment method is a method in which a prepolymer is crystallized using an appropriate solvent, and specifically, an amorphous prepolymer is dissolved in a solvent, and then a crystalline prepolymer is precipitated from this solution. Using a method or a solvent with low dissolving power for the prepolymer, the prepolymer is dissolved in a liquid state for a period of time necessary for the solvent to penetrate into the non-crystalline prepolymer and crystallize the amorphous prepolymer. A method of contacting with a solvent or solvent vapor is preferably used.

Solvents that can be used for solvent treatment of such amorphous prepolymers include, for example, chloromethane, methylene chloride, chloroform, carbon tetrachloride, chloroethane, dichloroethane (various types), trichloroethane (various types), trichloroethylene, tetrachloroethane ( Aromatic halogenated hydrocarbons such as chloroenzene and dichloroenzene; Ethers such as tetrahydrofuran and dioxane; Esters such as methyl acetate and ethyl acetate; Ketones such as acetone and methyl ethyl ketone Examples include aromatic hydrocarbons such as benzene, toluene, and xylene. Halogen-free solvents are particularly preferred in order to obtain high quality polymers. These solvents may be used alone or in combination of two or more.

On the other hand, the heating 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 starts to melt. It is. This method can be carried out industrially very easily since the prepolymer can be crystallized simply by holding it under heat.

The number average molecular weight of the aromatic polycarbonate obtained by solid phase polymerization has a higher degree of polymerization than that of the crystalline polycarbonate prepolymer used as a raw material,
Usually 6,000 to 200,000.

Although solid-phase polymerization can be carried out in the presence or absence of a catalyst, non-catalytic polymerization is preferred because the resulting polymer has much better color, heat resistance, and hot water resistance.

As the polymerization catalyst, there can be used various known transesterification catalysts such as polycarbonate or polyester (L=l2). Examples include alkali metal salts of bisphenol A, compounds of tin, and lead.

(Example) Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited in any way by these examples.

Note that the molecular weight is a number average molecular weight measured by gel permeation chromatography (GPC).

The end groups in the prepolymer were analyzed by high performance liquid chromatography or NMR.

Crystallinity was determined by powder X-ray diffraction according to JP-A-1-158033.
It was determined by the method described in the publication.

Example 1 A non-quality prepolymer polymerized by the melt method using bisphenol A and diphenyl carbonate as raw materials was crystallized with acetone, and the number average molecular weight was 3800, the terminal hydroxyl group was 29%, the terminal phenyl carbon 2-to group was 71%, and the crystallization result was A crystalline polycarbon 7-Tobre polymer with a degree of 25% was obtained. This was molded using a rotary granulator to obtain pellets with a diameter of about 2 mm and a length of about 3 mm.

Solid phase polymerization of the pellets was carried out using a six-stage, vertically shaped polymerization apparatus. The polymerization device is SUS 3 with an inner diameter of 200+ nm.
It is divided into 6 chambers by 6 rotatable distribution plates made of 04.

12 kg of the above pellets were supplied to the first chamber, and polymerization was carried out in a fluidized bed state by flowing heated nitrogen 6ON/Hr at 210"C from the bottom. After 1 hour, the dispersion plate was rotated and the Drop a pellet in the second chamber, and a new pellet 7 in the first chamber.
) 12 kg was supplied. Thereafter, the pellets were sequentially transferred downward and new pellets were supplied every hour. After 6 hours, pellets began to be discharged from the bottom of the polymerization apparatus. The number average molecular weights of the pellets discharged after 10 hours, 15 hours, and 20 hours were 13 and 2, respectively.
00.13, 300.13.200, and it can be seen that polymerization was carried out steadily from 10 hours to 20 hours. The amount of nitrogen used per 1 kg of pellets is 5Nr.
It was rr.

Comparative Example 1 Solid phase polymerization was carried out using the same pellets and fluidized bed apparatus as in Example 1. However, only the topmost dispersion plate was used, and the remaining five dispersion plates were left open. Pelleno (16 kg) was placed in the smallest stage and heated to 210°C with 6 ON of nitrogen.
When solid phase polymerization was performed by supplying m/Hr from the bottom,
After 6 hours, the number average molecular weight reached 13.200. The amount of nitrogen used per 1 kg of pellets is 22.5 Nm,
This was more than four times that of Example 1.

Examples 2 to 4 Solid phase polymerization was performed using the same pellets and polymerization apparatus as in Example 1. However, the number of stages used, the amount of pellets per stage, the residence time of pellets per stage, the amount of heated nitrogen, and the temperature were varied.

The results are summarized in Table 1. In all cases, the amount of nitrogen used per 1 kg of pellets was 15 Nm/Hr or less.

Example 5 Solid phase polymerization was carried out in the same manner as in Example 1, except that the same pellets as in Example 1 were used, the amount of pellets per stage was 2 kg, and the flow rate of heated nitrogen was 7 Npo/Hr. Each stage of pellets was polymerized in a fixed bed. The number average molecular weight of the pellets discharged after 15 hours was 12.500.

Example 6 After synthesizing bisphenol A and phosgene by interfacial polycondensation in the presence of phenol, a number average molecular weight of 3,400, a terminal hydroquine group of 38%, and a terminal phenyl capo group were obtained by a solvent crystallization method using acetone. A crystalline polycarbonate prepolymer having a crystallinity of 62% and a crystallinity of 25% was formed into pellets 7) in the same manner as in Example 1, and solid phase polymerization was performed. 2
The number average molecular weight of the pellets discharged from the bottom of the fluidized bed apparatus after 0 hours was 13.000.

(Effects of the Invention) The present invention is an industrially advantageous solid phase polymerization process that can produce high quality aromatic polycarbonate with a relatively small amount of inert gas used.

[Brief explanation 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. FIGS. 2 to 4 are schematic diagrams showing various forms of the dispersion plate that transports the polymer produced at each stage. 1st bolt Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In producing aromatic polycarbonate with a high degree of polymerization by solid-phase polymerizing a crystalline polycarbonate prepolymer under inert gas flow, the process is characterized by semi-continuous polymerization using a vertical multi-stage polymerization apparatus. , aromatic polycarbonate manufacturing method.