JP2001031646A - Purification of pentaerythritol poly(thioglycolate) - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain pentaerythritol poly(thioglycolate) at a low polymerization rate without coloring and to provide a method for purification by which the pentaerythritol poly(thioglycolate) is industrially and readily supplied in high yield at a low cost. SOLUTION: Pentaerythritol poly(thioglycolate) is washed with an aqueous solution of an alkali metal carbonate to thereby afford the pentaerythritol poly(thioglycolate) with <=0.30 wt.% content of thioglycolic acid useful for a polyurethane-based plastic lens. The alkali metal carbonate is preferably sodium carbonate or potassium carbonate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a purified pentaerythritol poly (thioglycolate) useful as a monomer for a plastic lens, a raw material for a polyurethane resin, an epoxy curing agent, a paint curing agent, a vulcanizing agent for a synthetic resin, and the like. The present invention relates to a purification method, a plastic lens using purified pentaerythritol poly (thioglycolate), and a method for producing the same.

[0002]

2. Description of the Related Art Normally, pentaerythritol poly (thioglycolate) is produced by a dehydration esterification reaction between thioglycolic acid and pentaerythritol. In many cases, unreacted thioglycolic acid is present as an impurity in products. Will remain.

[0003] As a purification method for removing thioglycolic acid, which is an impurity, washing with sufficient water or high temperature (1
60 ° C.), distillation under high vacuum (0.13 kPa) (US Pat. No. 3,144,422), neutralization with aqueous sodium hydroxide solution, and repeated washing with water (US Pat.
r1195522), a method of washing with alcohol (Japanese Patent Publication No. 3-20390), and the like are known.
When the removal of thioglycolic acid was attempted by the same method, there were problems that thioglycolic acid was not sufficiently removed, the obtained product was colored yellow, and the yield was low.

[0004] As another method, a method using a thioglycolic acid ester instead of thioglycolic acid as an impurity (Japanese Patent Publication No. 63-58824) is known.

According to the present method, it appears that a product containing no thioglycolic acid can be obtained at first glance. However, in practice, water is added in the presence of an acidic catalyst to cause a reaction with the alkyl thioglycolate and pentaerythritol. The raw material thioglycolic acid ester is hydrolyzed, and eventually thioglycolic acid remains.

[0006] Further, a major problem of the present method is that the alkyl thioglycolate as a raw material must be produced from thioglycolic acid, and almost no alcohol-water mixture is distilled off during the esterification. In the case of, it is impossible to separate to form an azeotrope, and not only can it be recycled, but also the processing cost is required.Only methanol does not form an azeotrope, but a very high number of distillation stages for separation There is a point that a tower is required and the equipment cost is enormous, which results in an increase in cost.

[0007] Therefore, it cannot be said that this method is industrially preferable, and practically, a method using thioglycolate is hardly used.

On the other hand, as a method for producing a plastic lens using pentaerythritol poly (thioglycolate), Japanese Patent Publication No. 8-30762 and Japanese Patent Publication No. 6-53
No. 23, and the like.

For example, pentaerythritol tetrakis (thioglycolate) and m-xylylene diisocyanate are mixed and homogenized, defoamed, poured into a glass mold, and cured by heating.

However, when pentaerythritol poly (thioglycolate) produced by a conventional purification method is polymerized with a general-purpose general-purpose polyisocyanate to produce a polyurethane-based plastic lens, the polymerization speed is high and the molding rate is extremely high. Not only is it difficult, but in some cases, before the resin is injected into the mold, the mixture becomes resinous in a very short time, making it impossible to produce a plastic lens.

[0011]

Therefore, pentaerythritol poly (thioglycolate), which has no coloration and a low polymerization rate, and a purification method for providing it industrially, easily, with high yield and at low cost. Development was strongly desired.

[0012]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present inventors have solved the problem of the polymerization rate when the content of thioglycolic acid is 0.3 wt% or less, so that a polyurethane-based plastic lens can be used. It has been found that it can be suitably used as a monomer.

Furthermore, it has been found that the content of thioglycolic acid can be reduced to 0.3 wt% or less extremely easily and efficiently by washing pentaerythritol poly (thioglycolate) with an aqueous alkali metal carbonate solution. Was.

That is, according to the present invention, a pentaerythritol poly (thioglycolate) having a thioglycolic acid content of 0.3 wt% or less, and a thioglycolic acid content of 0.3 wt% by washing with an aqueous alkali metal carbonate solution. The purification method described below, and the content of thioglycolic acid was 0.1.
A polyurethane-based plastic lens obtained by reacting 3 wt% or less of pentaerythritol poly (thioglycolate) with a polyisocyanate, and a method for producing the same.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The pentaerythritol poly (thioglycolate) according to the present invention refers to an ester compound formed by a dehydration esterification reaction between pentaerythritol and thioglycolic acid, such as pentaerythritol mono (thioglycolate) and pentaerythritol (Thioglycolate), pentaerythritol tris (thioglycolate), pentaerythritol tetrakis (thioglycolate), pentaerythritol mono (mercaptomethylcarbonylthioglycolate) tris (thioglycolate), pentaerythritol di (mercaptomethylcarbonylthio) (Glycolate) di (thioglycolate) and the like, and also a mixture thereof.

The amount of thioglycolic acid in pentaerythritol poly (thioglycolate) is preferably as small as possible, but in practice, it is preferably at most 0.30 wt%, more preferably at most 0.25 wt%. 0wt
% Is most preferred.

As a method for removing residual thioglycolic acid, washing with an aqueous alkali metal carbonate solution is easy,
Be effective and efficient. Examples of the alkali metal carbonate include sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate and the like. Among them, sodium carbonate and potassium carbonate are particularly preferred.

When washing is carried out with a strongly basic aqueous solution represented by sodium hydroxide, potassium hydroxide, aqueous ammonia, etc., the product flows into the wastewater and the yield is extremely reduced. Conversely, when a weakly basic aqueous solution such as an aqueous solution of sodium phosphate, an aqueous solution of potassium phosphate, or an aqueous solution of sodium acetate, or water is used, it is difficult to efficiently purify pentaerythritol poly (thioglycolate).

The washing of pentaerythritol poly (thioglycolate) with an aqueous solution of an alkali metal carbonate may or may not be used, but the use of a solvent provides better liquid separation and yield. In some cases, a solvent is used because it may be expensive.

The type of the solvent is preferably a solvent which does not adversely affect the quality of the obtained product, has good liquid separation properties, and has a high yield. For example, aromatic hydrocarbon solvents such as benzene, toluene and xylene, and halogen solvents such as dichloromethane and dichloroethane are exemplified.

The washing with the aqueous alkali metal carbonate is usually performed once, but may be performed several times if necessary.

After washing with the alkali metal carbonate water, necessary operations such as washing with water are usually performed several times as necessary.

The pentaerythritol poly (thioglycolate) solution thus obtained is usually heated under reduced pressure to remove the solvent.

The degree of pressure reduction is approximately 300 to 1 torr (40
~ 0.1 kPa) and 200-5 torr (27
-0.7 kPa) is more preferable.

The heating temperature is about 20 to 150 ° C. and 40
It is more preferable that the temperature is in the range of to 120C.

The obtained pentaerythritol poly (thioglycolate) is usually converted into a product through a filtration step, and this filtration can be carried out by filtration under reduced pressure or filtration under pressure.

Usually, pressure filtration using nitrogen is used, and pressure is often applied at about 0.1 to 0.3 MPa (gauge pressure).

Usually, the filtration is carried out at room temperature. However, since pentaerythritol poly (thioglycolate) has a high viscosity at room temperature, in some cases, the filtration is carried out at a temperature higher than room temperature within a range without any problem. There are things.

The thus obtained purified pentaerythritol poly (thioglycolate) having a thioglycolic acid content of 0.3 wt% or less has a low polymerization rate and is easy to mold. It can also be suitably used for a wide variety of applications such as raw materials for polyurethane resins, epoxy curing agents, paint curing agents, and vulcanizing agents for synthetic resins.

Next, a method for producing a polyurethane plastic lens according to the present invention will be briefly described.

The purified pentaerythritol poly (thioglycolate) of the present invention and polyisocyanate, and if necessary, other monomers and additives are mixed and homogenized, and defoaming is performed by stirring under reduced pressure or the like.

Thereafter, the defoaming liquid is poured into a glass mold mainly composed of a glass mold and a resin gasket or tape, and cured mainly by heat.

The heating condition is such that the temperature is gradually increased from a low temperature to a high temperature in a temperature range of about 0 to 200 ° C., and the heating is completed in about 1 to 100 hours.

When a radiation polymerizable monomer is used as the other monomer, radiation irradiation may be used in combination. When irradiating radiation, ultraviolet rays of 400 nm or less are mainly used. Irradiation conditions of ultraviolet rays are approximately 1 to 1000 mJ.
In many cases, irradiation is performed for 1 to 7200 sec at an intensity of / sec, and sometimes cooling or irradiation is performed several times before irradiation for the purpose of heat removal or obtaining an optically uniform molded product. There is also.

The polyisocyanate used as a monomer for a plastic lens is an organic compound having two or more isocyanate groups in a molecule, and examples thereof include the following compounds.

For example, m-xylylene diisocyanate, α, α, α ', α'-tetramethyl-m-xylylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, isophorone diisocyanate, bis (4-isocyanatocyclohexyl) methane, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, bis (isocyanatomethyl) norbornane, bis (isocyanatomethylthio) methane and the like. In addition, this invention is not limited only to these listed compounds.

Examples of other monomers added as needed include polythiols other than pentaerythritol poly (thioglycolate), (meth) acrylic compounds, allyl or vinyl compounds, and (thio) epoxy compounds.

Examples of polythiols other than pentaerythritol poly (thioglycolate) include, for example, pentaerythritol poly (3-mercaptopropionate),
4- (mercaptomethyl) -3,6-dithiaoctane,
1,8-dithiol, 4,8-bis (mercaptomethyl) -3,6,9-trithiaundecane-1,11-dithiol, 2,5-bis (mercaptomethyl) -1,4
-Dithiane, trithioglycerin, 1,1,3,3-tetrakis (mercaptomethyl) -2-thiapropane and the like. In addition, this invention is not limited only to these listed compounds.

As the (meth) acrylic compound, for example, ethylene glycol di [(meth) acrylate],
Diethylene glycol di [(meth) acrylate], butanediol di [(meth) acrylate], neopentyl glycol di [(meth) acrylate], trimethylolpropane tris [(meth) acrylate], pentaerythritol tris [(meth) acrylate] Pentaerythritol tetrakis [(meth) acrylate], dipentaerythritol hexa [(meth) acrylate], 2,2-bis [(meth) acryloylethoxyethoxyphenyl] propane, 2,2-bis [(meth) acryloylethoxyphenyl ] Propane, bis [(meth) acryloylethoxyethoxyphenyl] methane, bis [(meth) acryloylethoxyphenyl]
Methane, bis [(meth) acryloylmethyl] tricyclodecane, 2-hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, ethanedithioldi [(meth) acrylate ], 3-thiaheptane-1,5-dithioldi [(meth) acrylate], 2,5-bis [(meth) acryloylthiomethyl] -1,4-dithiane, and the like. In addition, this invention is not limited only to these listed compounds.

Examples of the allyl or vinyl compound include, for example, diethylene glycol bis (allyl carbonate), diallyl sulfide, styrene, isopropenylbenzene, divinylbenzene, vinylcyclohexene oxide, diisopropenylbenzene, 3-isopropenyl-α, α-dimethyl Benzyl isocyanate and the like. In addition, this invention is not limited only to these listed compounds.

As the (thio) epoxy compound, for example, bisphenol A diglycidyl ether, bisphenol A bis [3-glycidyloxy-2-hydroxy-1-propyl ether], 3,4-epoxycyclohexylcarboxylic acid 3,4- Epoxycyclohexylmethyl ester, 1,4-butanedicarboxylic acid di3,4-epoxycyclohexylmethyl ester, vinylcyclohexene dioxide, diglycidyl sulfide, bis (epithiopropyl) sulfide, bis (epithiopropyl) disulfide and the like. . In addition, this invention is not limited only to these listed compounds.

In the production of the plastic lens of the present invention, if necessary, a thermal catalyst, a photocatalyst, an ultraviolet absorber, an internal mold release agent, an antioxidant, a polymerization inhibitor, an oil-soluble dye, a filler, a plasticizer And other known additives may be added.

Further, the obtained transparent resin, transparent optical material,
In addition, plastic lenses have surface polishing, antistatic treatment, hard coating, etc. to improve anti-reflection, high hardness, abrasion resistance, chemical resistance, anti-fog, or fashion, if necessary. Physical or chemical treatment such as treatment, anti-reflection coating treatment, and light control treatment can be performed.

[0044]

The present invention will be described below in more detail with reference to examples and comparative examples. The refractive index, Abbe number, and degree of coloring of the obtained plastic lens were evaluated by the following test methods.

Refractive index, Abbe number: Measured at 20 ° C. using a Pulfrich refractometer.

Reference Example 1 [Production of pentaerythritol tetrakis (thioglycolate)] In a 2-liter reaction flask, 1105.4 g (12.0 mol) of thioglycolic acid, 408.4 g (3.0 mol) of pentaerythritol, p -8.4 g of toluenesulfonic acid / monohydrate and 250 ml of toluene were charged, and heated and stirred for azeotropic dehydration (9
3-124 ° C) for 6 hours. The amount of product water extracted was 209.9 g (96.7% by weight / theoretical amount).

After the reaction solution was cooled to room temperature, it was washed five times with 500 ml of water. The obtained lower organic layer was desolvated at 60 ° C. under reduced pressure. When almost no solvent was distilled off, the degree of vacuum was increased (0.4 to 0.7 kPa), and topping was performed as it was. Finally, the residue was filtered to obtain 1273.4 g (crude yield = 98.1%) of slightly yellowish transparent pentaerythritol tetrakis (thioglycolate).

The hue of the obtained product is APHA15,
The H value is 8.49 meq / g (theoretical 9.25 meq / g).
g), the thioglycolic acid content determined by HPLC (internal standard method) was 0.90 wt%.

Example 1 310.1 g of pentaerythritol tetrakis (thioglycolate) of Reference Example 1 was dissolved in 1200 g of benzene, and then washed with 820 g of 5 wt% aqueous potassium carbonate.
The lower aqueous layer was separated and discarded.

The obtained organic layer was washed five times with 500 ml of water, desolvated, topped and filtered in the same manner as in Reference Example 1 to obtain 264.8 g of pentaerythritol tetrakis (thioglycolate) (purification yield: 85 .4%).

The thioglycolic acid content of the obtained product was 0.10 wt% (internal HPLC method).

COMPARATIVE EXAMPLE 1 Instead of washing with potassium carbonate in Example 1, complicated neutralization (pH 7.5) with 1 wt% aqueous ammonia was carried out, and the lower aqueous layer was discarded. Otherwise, the same purification as in Example 1 was performed.

The thioglycolic acid content of the obtained product was 0.60 wt% (internal HPLC method).

COMPARATIVE EXAMPLE 2 Instead of neutralizing and washing with ammonia water of Comparative Example 1, 5
The substrate was washed with 820 g of wt% aqueous ammonia for 30 minutes at 25 ° C. Otherwise, the same operation as in Comparative Example 1 was performed.

As a result, pentaerythritol tetrakis (thioglycolate) was not obtained at all.

Example 2, Comparative Examples 3 and 4 (Comparison of Polymerization Rate-1) 33.0 g of m-xylylene diisocyanate (0.17 g)
5 mol), 12.7 g of hexamethylene diisocyanate
(0.076 mol), 2- (2′-
Preparation of 50 mg (500 ppm) of hydroxy-5'-t-octylphenyl) benzotriazole and 150 mg (1500 ppm) of di (1,4,7-trimethyl-3,6,9-trioxatridecyl) phosphoric acid as an internal release agent Immediately after, the pentaerythritol tetrakis (thioglycolate) of Example 1, Reference Example 1, or Comparative Example 1 was added to the mixture.
54.3 g (0.126 mol) of each was separately added, and the mixture was stirred while measuring the viscosity sequentially in a water bath at a water temperature of 20 ° C., and the time required for each mixture to reach 100 cps was measured. went. Table 1 shows the results.

[0057]

[Table 1] PETG; pentaerythritol tetrakis (thioglycolate)

Example 3 Thioglycolic acid 147 was added to a 3 liter reaction flask.
3.8 g (16.0 mol), pentaerythritol 54
4.6 g (4.0 mol), 44.0 g of p-toluenesulfonic acid monohydrate and 700 ml of dichloroethane were charged,
A heating and stirring azeotropic dehydration reaction (83 to 95 ° C.) was performed for 8 hours. The amount of product water extracted is 279.0 g (95.4 w
t% / theoretical production amount).

After cooling the reaction solution to room temperature, 2 wt% hydrochloric acid 6
00g, 600 g of water, and 600 g of 16.7 wt% sodium carbonate water in that order, and the lower organic layer obtained was washed with
Further washing was performed four times with water (600 g) (total 2,400 g). Subsequently, the obtained organic layer was desolvated at 60 ° C. under reduced pressure. When almost no solvent was distilled off, the degree of vacuum was increased (0.4 to 0.7 kPa), and topping was performed as it was. Finally, the residue was cooled to room temperature and filtered to obtain 1602.7 g (crude yield = 92.6%) of colorless and transparent pentaerythritol tetrakis (thioglycolate).

The hue of the obtained product is APHA10,
The H value is 8.63 meq / g (theoretical 9.25 meq / g).
g), thioglycolic acid content determined by HPLC (internal standard method) was 0.25 wt%.

Example 4, Comparative Example 5 (Comparison of polymerization rate
2) bis (isocyanatomethyl) norbornane 51.4 g
(0.249 mol), 4- (mercaptomethyl) -3,
6-dithiaoctane-1,8-dithiol 21.7 g
(0.083 mol), 2- (2′-
Preparation of 50 mg (500 ppm) of hydroxy-5'-t-octylphenyl) benzotriazole and 150 mg (1500 ppm) of di (1,4,7-trimethyl-3,6,9-trioxatridecyl) phosphoric acid as an internal release agent Immediately after, add the mixture of Example 3 or a commercially available product (manufactured by Yodo Chemical Co., Ltd.)
Of pentaerythritol tetrakis (thioglycolate) was separately added, and the mixture was stirred and stirred at an internal temperature of 20 ° C. while measuring the viscosity successively. The time reached was measured. Table 2 shows the results.

[0062]

[Table 2] PETG: pentaerythritol tetrakis (thioglycolate)

Reference Example 2 (Production of Plastic Lens) 26.9 g (0.062 mol) of pentaerythritol tetrakis (thioglycolate) of Example 3 and 51.4 g (0.24 g) of bis (isocyanatomethyl) norbornane
9 mol), 21.7 g of 4- (mercaptomethyl) -3,6-dithiaoctane-1,8-dithiol (0.083
Mol), 40 mg of dibutyltin dichloride as a catalyst
(400 ppm), 50 mg (500 ppm) of 2- (2′-hydroxy-5′-t-octylphenyl) benzotriazole as an ultraviolet absorber, and di (1,4,7-trimethyl-3,6,6) as an internal release agent. 150 mg (1500 ppm) of 9-trioxatridecyl) phosphoric acid was mixed and dissolved, and mixed and defoamed under reduced pressure.

After the defoaming was completed, the mixture was poured into a molding mold prepared in advance, gradually heated from room temperature to 120 ° C., and cured by heating for 20 hours. The injection work into the mold was easily performed.

After cooling, the lens obtained by releasing the mold was colorless and transparent, and had a refractive index Nd = 1.594 and an Abbe number νd = 42.

By comparing Example 1, Example 3, Reference Example 1, and Comparative Example 1, thioglycolic acid can be removed up to 0.30 wt% or less by washing with aqueous potassium carbonate and sodium carbonate. It is understood that thioglycolic acid cannot be sufficiently removed by washing with water or neutralization. ○ According to Comparative Example 2, it was found that the purification yield was significantly reduced by washing with ammonia water. -Comparison between Example 2, Comparative Example 3, and Comparative Example 4, and further comparison between Example 4 and Comparative Example 5 show that when the amount of thioglycolic acid decreases, the polymerization rate decreases. -Reference Example 2 shows that pentaerythritol poly (thioglycolate) obtained by the purification method of the present invention can be suitably used as a monomer for plastic lenses.

[0067]

According to the present invention, it is possible to provide pentaerythritol poly (thioglycolate) from which thioglycolic acid has been removed up to 0.30% by weight or less. Use of thioglycolate) slows down the polymerization rate and facilitates the production of polyurethane plastic lenses.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C08L 75:04 (72) Inventor Yoshinobu Kanamura 30 Asamuta-cho, Omuta-shi, Fukuoka Mitsui Chemicals, Inc. F-term (reference) 4F071 AA53 AH19 BB12 BC07 4H006 AA02 AD16 BB31 BE12 TA04 TB35 TB54 4J034 BA02 CA02 CA04 CA32 CB05 CB08 CC07 DK02 DK05 DK08 HA01 HA07 HB03 HC03 HC07 HC12 HC17 HC22 HC46 HC61 HC64 HC67 Q71 HC71 Q

Claims (5)

[Claims] 1. A thioglycolic acid content of 0.30 w
pentaerythritol poly (thioglycolate) for polyurethane-based plastic lens, which is not more than t%. 2. A method for purifying pentaerythritol poly (thioglycolate), comprising washing pentaerythritol poly (thioglycolate) with an aqueous alkali metal carbonate solution. 3. The method according to claim 2, wherein the alkali metal carbonate is sodium carbonate or potassium carbonate. 4. A polyurethane plastic lens obtained by reacting the pentaerythritol poly (thioglycolate) according to claim 1 with a polyisocyanate. 5. The method for producing a polyurethane plastic lens according to claim 4, wherein the pentaerythritol poly (thioglycolate) according to claim 1 is reacted with a polyisocyanate.