JPH09165442A - Polycarbonate for optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polycarbonate which has a specified total nitrogen content to thereby reduce the occurrence of white spots by polymerizing a dihydric phenol with phosgene in the presence of a tert. amine catalyst and bringing the resultant org. layer into contact with an aq. alkali soln. followed by neutralization with phosphoric acid. SOLUTION: A polycarbonarte resin powder for an optical recording medium having a total nitrogen content of 10ppm or lower is obtd. by dissolving a dihydric phenol [e.g. 2,2-bis(4-hydroxyphenyl)propane] in an aq. alkali soln., adding a solvent (e.g. methylene chloride) to the resultant soln. under stirring, blowing thereinto a specified amt. of phosgene, vigorously stirring the soln. after the completion of the blowing to emulsify it, adding 0.02-0.05mol% tert. amine catalyst (e.g. triethylamine) to it to cause the polymn., separating the emulsion into an org. layer and a water layer after the completion of the polymn., stirring the org. layer with 0.1-3.0wt./vol.% aq. alkali soln. followed by neutralization with an aq. phosphoric acid soln., washing the layer with water until it becomes neutral, and pouring the resultant resin soln. into n- heptane, etc., to remove water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to compact discs, laser discs, optical cards, MO discs, MDs.
The present invention relates to a polycarbonate for an optical recording medium such as a disc or a PD disc, and more particularly to a highly reliable polycarbonate for an optical recording medium in which white spots on a disc substrate, which cause a signal reading error in a high temperature and high humidity environment, are significantly improved.

[0002]

2. Description of the Related Art Polycarbonate makes use of its characteristics such as transparency, heat resistance, hydrolysis resistance, and dimensional stability.
Recently, it has been widely used as a substrate material for optical recording media. However, there are some problems when using polycarbonate for the optical recording medium. Among them,
In a long-term reliability test under a high temperature and high humidity environment, there was a problem that minute white spots were generated on a polycarbonate disk substrate and a signal reading error occurred.

It has been found that this mechanism of white spot generation is caused by the hydrolysis of the polycarbonate due to impurities in the polycarbonate, and as a solution to this, the impurity metals of Group IA and Group VIII in the polycarbonate have been reduced. Material (JP-A-2-276037), material in which the amount of hydroxyl groups at the polycarbonate terminal end is reduced to 0.3 mol% or less (JP-A-3-100501), monomer in the polycarbonate is 10 ppm or less, and low molecular weight products 1 to 3 are 0.2. Materials have been developed that have been reduced to less than or equal to weight percent. Materials with these impurities reduced have already been used in commercially available polycarbonates for optical information media.

However, even in a disc substrate manufactured from a polycarbonate that satisfies these conditions, white spots may occur in a long-term reliability test, and the number of white spots is not always proportional to the amount of impurities. I found it wasn't. From these results, it was speculated that there were factors completely different from the above impurities in the occurrence of white spots.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides high reliability in a long-term reliability test in a high temperature and high humidity environment, in which no minute white spots are formed on a polycarbonate disk substrate and no signal reading error occurs. Another object of the present invention is to provide a polycarbonate for an optical recording medium.

[0006]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that there is a correlation between the amount of nitrogen contained in the polycarbonate and the occurrence of white spots. The inventors have found that the use of a material containing a limited amount of total nitrogen contained therein can suppress the generation of white spots in a hot and humid environment, and completed the present invention.

That is, the present invention relates to a polycarbonate for optical recording media in which the total amount of nitrogen contained in the polycarbonate is 10 ppm or less.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The nitrogen content contained in a polycarbonate is a nitrogen bonded to a molecular end of a polycarbonate, which is a tertiary amine of a polymerization catalyst mainly used in the production of an interfacial polymerization method and reacts with a urethane ( It exists in the form of a carbamate) structure. It is already known that if a large amount of urethane structure is contained as an impurity at this end, it will cause deterioration of the hue of the polycarbonate. For example, in JP-A-2-133425 and JP-A-3-199231, for the purpose of improving the hue, the polycarbonate terminal A method of reducing the urethane bonds present in the group is described.

In the above method, it is necessary to delicately control the emulsified state and to significantly shift the addition time of the tertiary amine, which is not easy to control. In the present invention, a method in which control is easy and a sufficient effect is achieved, specifically, 0.02 to 0.05 mol% of a tertiary amine as a polymerization catalyst is used with respect to a raw material dihydric phenol of polycarbonate. And 0.4 to 1.0 mol% of a quaternary ammonium salt as a cocatalyst to carry out a polymerization reaction, and a tertiary amine of a polymerization catalyst to 0.1.
After the polymerization reaction using 02 to 0.05 mol%, the organic phase (resin phase) is separated from the aqueous phase, and the organic phase (resin phase) is washed with water to 0.1 to 3.0 wt / vol%. This is a method of contacting with a dilute alkaline aqueous solution (specifically, sodium hydroxide aqueous solution) for a short time, and the nitrogen content can be effectively reduced by using these methods together.

In the transesterification method, when a nitrogen compound is used as a transesterification reaction catalyst, it is difficult to remove the catalyst from the resin in a molten state, and nitrogen derived from the nitrogen compound of the catalyst remaining in the polymer is a problem. Becomes In the transesterification method, the nitrogen content can be reduced by using a catalyst other than a nitrogen compound as the catalyst, or by dissolving the molten resin obtained by the transesterification method in a solvent and performing extraction washing.

In the present invention, it is important that the total nitrogen content of the polycarbonate is 10 ppm or less. If it exceeds 10 ppm, it will be in a hot and humid environment (80 ° C, 9
0% 7H), the white spot generation amount of 50 μm or more increases,
This tends to cause an increase in read signal errors on the optical disc. Therefore, 10 ppm or less, and particularly 6 ppm or less, the occurrence of white spots is extremely reduced, which is preferable.

The polycarbonate in the present invention is a method known per se used for producing a polycarbonate from a dihydric phenol, for example, an interfacial polymerization method of a dihydric phenol and phosgene (phosgene method), or a dihydric phenol. It can be obtained by an ester exchange reaction (ether exchange method) between bisaryl carbonate and bisaryl carbonate, but the phosgene method, which is easy to remove impurities, is suitable for the production of polycarbonate for optical recording media.

In the former phosgene method, dihydric phenols and phosgene are usually reacted in the presence of an acid binder and a solvent. As the acid binder, for example, pyridine, sodium hydroxide, alkali metal hydroxide such as potassium hydroxide, or the like is used, and as the solvent,
For example, methylene chloride, chloroform, chlorobenzene, xylene, etc. are used. Further, a catalyst such as a tertiary amine such as triethylamine or a quaternary ammonium salt is used to accelerate the polycondensation reaction.

To control the degree of polymerization, phenol, pt
Monofunctional compounds such as alkylphenols such as -butylphenol, p-cumylphenol, long-chain alkyl-substituted phenols are used. If desired, a small amount of an antioxidant such as sodium sulfite or hydrosulfite or a branching agent such as phloroglysin or isatin bisphenol may be added.

The reaction is usually 0 to 150 ° C., preferably 5 to
A temperature in the range of 40 ° C is suitable. The reaction time depends on the reaction temperature, but is usually 0.5 minutes to 10 hours, preferably 1 minute to 2 hours. Also, during the reaction, p of the reaction system
It is desirable to keep H at 10 or more.

On the other hand, in the latter transesterification method,
The dihydric phenol and the bisaryl carbonate are reacted at high temperature under reduced pressure in the presence of a catalyst. As a catalyst, alkali metal, alkaline earth metal, quaternary ammonium salt,
Organic titanium, basic metal compounds, etc. are used. The reaction is usually carried out in the range of 150 to 350 ° C, preferably 200 to 300 ° C, and the degree of vacuum is finally preferably 1 m.
It is adjusted to mHg or less and the phenols generated by the reaction are distilled out of the system. The reaction is preferably carried out in an atmosphere of an inert gas such as nitrogen or argon, and if desired, an antioxidant may be added to carry out the reaction.

The polycarbonate of the present invention has an average molecular weight of 12,000 to 23, such as homo- or co-polycarbonate obtained by the above-mentioned production method, further branched one, and one having a long-chain alkyl group introduced at the terminal. It is about 000.

Carbon-as the comonomer and the terminal stopper
Grafted polycarbonate obtained by grafting styrene on a modified polycarbonate obtained by using bisphenol or vinylphenol having a carbon unsaturated double bond, and a part obtained by using terephthalic acid chloride or isophthalic acid chloride as a part of phosgene. A modified polycarbonate having an ester bond, a modified polycarbonate obtained by graft-polymerizing a polycarbonate to a modified polystyrene obtained by using a phenolic hydroxyl group or the like as a comonomer, and the like are also used.

Specific examples of the dihydric phenol compound as a raw material for the polycarbonate in the present invention include bis (4-
Hydroxyphenyl) methane, bis (4-hydroxyphenyl) ether, bis (4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfoxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) ketone, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4
-Hydroxyphenyl) propane (bisphenol A;
BPA), 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) cyclohexane (bisphenol Z; BPZ), 2,2-bis (4-hydroxy-3,5) -Dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-
3-bromophenyl) propane, 2,2-bis (4-hydroxy-3-chlorophenyl) propane, 2,2-bis (4-hydroxy-3-methylphenyl) propane,
2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, bis (4-hydroxyphenyl) diphenylmethane, α, ω-bis [3- (O-hydroxyphenyl) propyl] polydimethylsiloxane, 1,1-bis (4-hydroxyphenyl) -3,
Examples include 3,5-trimethylcyclohexane, and these may be used in combination of two or more kinds. Among these, bisphenol A is particularly preferable.

In order to use the polycarbonate of the present invention as an optical disk substrate, it is necessary to use one that further reduces dust, which is an error inducing substance, in addition to reducing the nitrogen content. Specifically, 40,000 dust particles having a diameter of 0.5 to 1.0 μm contained in a polycarbonate molded product / g.
It is desirable that: As a dust reduction method,
For example, a method of filtering the resin solution after neutralization and washing with a membrane filter or centrifugal filtration can be used.

Further, halogen-based organic solvents, residual free chlorine, terminal chloroformates, terminal hydroxyl groups, residual alkali metals, which are substances that affect the increase in errors of optical disks,
It is preferable to reduce residual transition metals, monomers and low molecular weight substances as much as possible.

[0022]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the present invention.

Example 1 Dissolving 3.7 kg of sodium hydroxide in 42 liters of water and keeping it at 20 ° C., 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as “BPA”) 7.2
kg and 8 g of hydrosulfite were dissolved. Add 28 liters of methylene chloride to this, and stir while stirring.
-T-butylphenol (hereinafter referred to as "PTBP") 2
90 g were added and then 4.0 kg phosgene were bubbled in in 60 minutes. After the completion of blowing phosgene, the reaction solution was emulsified by vigorous stirring, and after emulsification, 1.5 g of triethylamine was added and stirring was continued for about 1 hour to polymerize.

After the reaction, the reaction mixture was separated into an aqueous phase and an organic phase, and the organic phase (resin phase) was contacted with 20 liters of a 0.5 wt / vol% sodium hydroxide aqueous solution for 20 minutes while stirring.
Then, after phosphoric acid was added to neutralize, the washing of the resin liquid was repeated until the washing liquid had a neutral pH and an electric conductivity of 10 μS / cm or less. Then, the resin solution was filtered through a 1.2 μm Teflon membrane filter. To the obtained resin liquid was added 7 liters of n-heptane, and the mixture was vigorously stirred at 45 ° C.
After being properly immersed in the pure water of 1 to obtain the resin powder, the aqueous solution containing the resin powder was boiled at 100 ° C. for 1 hour. The resin powder after boiling was filtered and then dried with a clean dryer to obtain a powdery polycarbonate having a viscosity average molecular weight of 15,2000 (hereinafter referred to as "P-1").

When the total amount of nitrogen contained in this polycarbonate was measured, it was 8 ppm. In addition, residual free chlorine, terminal chloroformate, terminal hydroxyl group content, Na
The amount, the amount of monomers, and the amount of methylene chloride were measured.

Example 2 The procedure of Example 1 was repeated, except that 72 g of benzyltriethylammonium chloride was added after the blowing of phosgene, and the amount of triethylamine was changed to 0.7 g after emulsification. The viscosity average molecular weight of the obtained powdery polycarbonate (hereinafter “P-2”) was 15,100. When the total amount of nitrogen contained in this polycarbonate was measured, it was 6 ppm.

Example 3 As in Example 1, except that the resin solution was contact-stirred with 20 liters of a 2 wt / vol% sodium hydroxide aqueous solution for 20 minutes before neutralizing the resin solution with phosphoric acid, and then neutralized and purified. went. The obtained powdery polycarbonate (hereinafter referred to as "P-
3 ”) had a viscosity average molecular weight of 15,000. When the total amount of nitrogen contained in this polycarbonate was measured, it was 2 ppm.

Example 4 Example 3 was repeated except that the amount of triethylamine used during the polymerization was changed to 4.8 g. The viscosity average molecular weight of the obtained powdery polycarbonate (hereinafter “P-4”) was 15,000. When the total amount of nitrogen contained in this polycarbonate was measured, it was 9 ppm.

Comparative Example 1 3.7 kg of sodium hydroxide was dissolved in 42 liters of water and kept at 20 ° C. while keeping 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as “BPA”) 7.2.
kg and 8 g of hydrosulfite were dissolved. Add 28 liters of methylene chloride to this, and stir while stirring.
-T-butylphenol (hereinafter referred to as "PTBP") 2
90 g were added and then 4.0 kg phosgene were bubbled in in 60 minutes. After the completion of blowing phosgene, the reaction solution was emulsified by vigorous stirring. After emulsification, 2.0 g of triethylamine was added and the mixture was stirred for about 1 hour to polymerize.

After the reaction, the reaction mixture is separated into an aqueous phase and an organic phase, and the organic phase (resin phase) is neutralized by adding phosphoric acid. The pH of the washing solution is neutral and the conductivity is 10 μS / Washing of the resin solution with water was repeated until it became less than or equal to cm. After that, add 1.2
It was filtered through a μm Teflon membrane filter. After 7 liters of n-heptane was added to the obtained resin liquid and the mixture was immersed in vigorously stirred pure water at 45 ° C. to obtain a resin powder,
The aqueous solution containing the resin powder was boiled at 100 ° C. for 1 hour.
The resin powder after boiling was filtered and then dried with a clean dryer to obtain a powdery polycarbonate having a viscosity average molecular weight of 15,2000 (hereinafter referred to as "P-5"). When the total amount of nitrogen contained in this polycarbonate was measured, it was 13 ppm.

Comparative Example 2 Comparative Example 1 was repeated except that the amount of triethylamine used during the polymerization was changed to 4.8 g. The viscosity average molecular weight of the obtained powdery polycarbonate (hereinafter "P-6") is 1
5,100. When the total amount of nitrogen contained in this polycarbonate was measured, it was 26 ppm.

Comparative Example 3 The procedure of Comparative Example 1 was repeated except that the amount of triethylamine used during the polymerization was changed to 8.0 g. The viscosity average molecular weight of the obtained powdery polycarbonate (hereinafter “P-7”) is 1
5,100. When the total amount of nitrogen contained in this polycarbonate was measured, it was 50 ppm.

Table 1 shows the total nitrogen content in the polycarbonates obtained in the above Examples and Comparative Examples.

[0034]

[Table 1] Example Viscosity average nitrogen free chlorine free Na terminal OH terminal Cl monomer residual solvent Comparative example Molecular weight ppm ppm ppm ppm ppm ppm ppm ppm Actual 1 15,200 8 0.14 ND 180 0.04 ND 0.3 Actual 2 15,100 6 0.15 ND 156 0.04 ND 0.2 Actual 3 15,000 2 0.12 ND 195 0.01 ND 0.5 Actual 4 15,000 9 0.09 ND 212 0.02 ND 0.4 Ratio 1 15,200 13 0.15 ND 158 0.03 ND 0.3 Ratio 2 15,100 26 0.14 ND 171 0.03 ND 0.3Ratio 3 15,100 50 0.11 ND 189 0.05 ND 0.4 (Actual: Example, ratio: Comparative example)

Viscosity average molecular weight: 20 ° C., 0.5 w / v% dichloromethane solution was used to measure the intrinsic viscosity [η], and the formula [η] = 1.23 × 10
^{-4 Calculated} from M ^0.83 .

Nitrogen: The total amount of nitrogen contained in the polycarbonate was measured by a total nitrogen measuring device manufactured by Mitsubishi Chemical Corporation.

Free chlorine: Chlorine ions were extracted from a 10% dichloromethane solution of polycarbonate with ultrapure water and measured with an ion chromatograph manufactured by Dionex.

Free Na: 1 g of polycarbonate was mic wave ashed, extracted into a dilute hydrochloric acid aqueous solution, and measured with an atomic absorption spectrophotometer manufactured by Shimadzu Corporation. Detection limit 0.05ppm.

Terminal OH: The amount of terminal hydroxyl groups of the polycarbonate was measured by a titanium tetrachloride colorimetric method.

Residual solvent: The amount of methylene chloride in the polycarbonate was measured by the ECD gas chromatography method.

Terminal Cl: Polycarbonate was ashed by a dry ashing method, extracted with water, and chlorine ion was measured by an ion chromatograph. The residue obtained by subtracting chlorine of free chlorine and methylene chloride from this chlorine ion amount is the terminal C
It was set to 1 value.

Monomer: Measured using GPC manufactured by Waters. Detection limit 10 ppm. (Note): Polycarbonate material was used for viscosity average molecular weight, and pellets were used for other analysis.

The polycarbonate powders obtained in the above Examples and Comparative Examples were heated at 250 ° C. in a clean room.
Was pelletized by an extruder with a 20 mm vent, and an injection molding machine (resin temperature 300 ° C.) was used to obtain an injection molded product of 90 mm × 50 mm × 3 mm. About this molded product, 85 ℃, 90% R
Diameter 50μ after being left in H for 1000 hours and 2000 hours
The results of measuring the number of white spots of m or more with an optical microscope are shown in Table 2.

[0044]

Table 2 Examples Number of white spots generated during environmental test Comparative example 1000 hours 2000 hours Example 1 0 1 Example 2 0 0 Example 3 0 0 Example 4 0 1 Comparative Example 1 1 5 Comparative Example 2 3 17 Comparative Example 3 7 39

[0045]

The optical disk using the polycarbonate of the present invention suppresses the generation of minute white spots due to hydrolysis under a high temperature and high humidity environment, reduces errors due to white spots, and has high reliability as a recording medium.

Front page continuation (72) Inventor Katsuji Kusakabe 2-12, Shinshu-cho, Toyonaka City, Osaka Prefecture Mitsubishi Gas Chemical Co., Ltd. Osaka Plant

Claims (7)

[Claims] 1. A polycarbonate for an optical recording medium, wherein the total amount of nitrogen contained in the polycarbonate resin is 10 ppm or less. 2. The total amount of nitrogen is 6 ppm or less.
A polycarbonate for an optical recording medium as described above. 3. The polycarbonate for an optical recording medium according to claim 1, wherein the polycarbonate resin is a resin produced by a reaction of a dihydric phenol and phosgene by an interfacial polymerization method. 4. The polycarbonate for an optical recording medium according to claim 1, wherein the dihydric phenol is 2,2-bis (4-hydroxyphenyl) propane. 5. A method for producing a polycarbonate by an interfacial polymerization method, wherein 0.03 to 0.05 mol% of a tertiary amine as a polymerization catalyst is used with respect to a raw material dihydric phenol.
After the polymerization reaction using, the organic phase (resin liquid)
The total amount of nitrogen is 10 which is characterized by being contacted with an alkaline aqueous solution of 3.0 wt / vol% and then neutralized with an aqueous phosphoric acid solution.
A method for producing a polycarbonate for an optical recording medium, which has a content of ppm or less. 6. A method for producing a polycarbonate by an interfacial polymerization method, wherein 0.02-0.05 mol% of a tertiary amine as a polymerization catalyst and quaternary ammonium salt as a cocatalyst are used with respect to a raw material dihydric phenol. 0.4-1.0
A method for producing a polycarbonate for an optical recording medium, wherein the total nitrogen content is 10 ppm or less, which is characterized by using mol%. 7. A method for producing a polycarbonate by an interfacial polymerization method, wherein 0.02 to 0.05 mol% of a tertiary amine as a polymerization catalyst and quaternary ammonium salt as a cocatalyst are used with respect to a raw material dihydric phenol. 0.4-1.0
After the polymerization reaction using mol%, the organic phase (resin liquid) is contacted with an alkaline aqueous solution of 0.1 to 3.0 wt / vol% and then neutralized with a phosphoric acid aqueous solution. The following is a method for producing a polycarbonate for an optical recording medium.