JPS5843402B2 - Manufacturing method of hydroxyethylcellulose - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hydroxyethylcellulose, and more particularly to a method for producing hydroxyethylcellulose of a purity high enough to be used as a binder for a phosphor suspension for manufacturing discharge tubes.

Hydroxyethylcellulose (hereinafter referred to as HEC) is a nonionic water-soluble polymer compound and has the following characteristics.

That is, the aqueous solution is viscous and stable in any pH range, and is also stable against salts.

In addition, the aqueous solution is stable at both low and high temperatures, and has excellent protective colloidal properties.

In addition, the HEC aqueous solution has excellent film-forming ability, and the resulting film is transparent, flexible, and completely free of stickiness.

These characteristics of the HEC aqueous solution are suitable for use as a vehicle for a phosphor suspension for manufacturing discharge tubes.In fact, when the phosphor is dispersed in the HEC aqueous solution, the phosphor is uniformly dispersed, and the dispersion is A uniform coating film can be easily obtained by applying H to a discharge tube, and H
It is possible to decompose and eliminate EC, thereby making it possible to substantially uniformly adhere the phosphor to the discharge tube.

However, HEC is manufactured by first making alkali cellulose from cellulose and an aqueous solution of caustic soda, reacting this with ethylene oxide, and removing the sodium component after the reaction is complete, so HEC always contains a small amount of sodium salts. These salts harm the phosphor and cause a decrease in the luminous flux of the finished lamp, which is not at all desirable.

Therefore, in order for HEC to be suitably used as a binder for a phosphor suspension for manufacturing discharge tubes, the amount of ash (sodium salts) contained in HEC must be 0.1% or less. is necessary.

To this end, various methods have been developed for reducing the content of sodium salts in HEC to obtain pure HEC.

One method is to dissolve the reaction product of alkali cellulose and ethylene oxide in water, and remove sodium ions from the resulting aqueous solution by dialysis using a large amount of water.
This method neutralizes the remaining alkali with acid to produce a product, but the sodium content is still insufficiently removed and about 20% by weight remains, making it impossible to use it as a binder for phosphor suspensions. Moreover, the manufacturing cost is high.

Another method is the method disclosed in Japanese Patent Publication No. 37-848.

In this method, the above reaction product is purified using a mixture of water and a hydrophilic organic solvent such as methanol, acetone, isopropyl alcohol, or jet-butyl alcohol (hydrophilic organic solvent: water -70 to 90:30 to 10). It's a method.

In this case, a method of directly purifying the reactant with such a mixed solution,
There is a method in which the alkali in the reaction product is neutralized with an organic or inorganic acid, and then the mixture is purified by squeezing the mixture.

However, either method requires a large amount of mixed liquid during purification, and no matter how large the mixed liquid is used, it is impossible to obtain HEC with a Na salt content of 0.1% or less. Therefore, it is difficult to use HEC obtained by such a method as a binder for a phosphor suspension for manufacturing discharge tubes.

As another method, a method is known in which the HEC obtained by the method of Japanese Patent Publication No. 37-848 is further dissolved in water and treated with an ion exchange resin (Japanese Patent Application Laid-Open No. 5083427).

This method is industrially extremely disadvantageous as it requires a two-step purification method and regeneration of the ion exchange resin is extremely difficult due to the viscous film of HEC coating the resin. The purity of the HEC obtained is also not satisfactory.

Furthermore, a method for purifying HEC by treating HEC with glyoxal in an acidic region and then washing it with water is known (Japanese Patent Publication No. 44-13159, British Patent No. 1142281, etc.).

However, even with this method, it is impossible to reduce the sodium salt content in HEC to 0.1% or less,
High purity HEC that can be used as a binder in phosphor suspensions for manufacturing discharge tubes cannot be produced.

The present inventor continued his research to develop an industrially advantageous method for producing HEC of high purity enough to be used as a binder for phosphor suspensions for manufacturing discharge tubes. The desired purpose can be achieved by an extremely simple operation of bonding in a hydrophilic organic solvent and then washing it with water at a temperature below 10°C, preferably below 5°C. When a mixture of a hydrophilic organic solvent and water at a specific mixing ratio is used instead, the desired purpose can still be achieved even if the temperature is below 20°C.1. The present invention has been completed based on this discovery.

HEC of glyoxalated HEC used in the present invention
Conventionally known components can be used as they are, and the method for producing them is not limited to any particular example.

For example, cellulose is converted into alkali cellulose by a conventional method, and also by a conventional method, for example, JP-A-49-1
The alkali cellulose is subjected to a hydroxylation reaction by the method of No. 7878, and the reaction product is neutralized.

Neutralization can be carried out by any conventionally known method (or directly with an organic acid such as formic acid, acetic acid, propionic acid, or a mixture of an organic acid and a hydrophilic organic solvent).

It is even better to neutralize by using an organic acid ester and utilizing the saponification reaction of the ester.

In the present invention, first, glyoxal is bound to neutralized HEC.

Specifically, 0.3 to 10 parts by weight of glyoxal is dissolved in a hydrophilic organic solvent and added to 100 parts by weight of HEC, stirred at 40 to 80°C for 0.5 to 3 hours, and then added to 100 parts by weight of HEC.
It may be dried at 80°C.

Examples of the hydrophilic organic solvent include methanol, ethanol, acetone, and a mixed solvent thereof.

By this treatment, glyoxalated HEC in which glyoxal is bound in a ratio of 0.3 to 10 parts by weight per 100 parts by weight of HEC can be obtained.

If the amount of glyoxal bound is less than 0.3 parts by weight, HEC tends to become pasty and purification is insufficient, and conversely, if it exceeds 10 parts by weight, water solubility, which is the original property of HEC, decreases. undesirable.

In the present invention, the glyoxalated HEC is then washed with water at a temperature of 10°C or lower, particularly 5°C or lower.

Due to this treatment, extremely pure HE
C is obtained.

At this time, if the HEC is washed with water at a temperature higher than 10°C, the HEC becomes pasty and washing becomes insufficient.

In addition, if the temperature is 5° C. or lower, the time required for the washing operation is long, which is preferable in terms of operation.

As the washing liquid at this time, pure water is used, and examples include deionized water and distilled water.

In the case of deionized water, its pm is usually about 5.0 to 6.5.

In addition, in the present invention, there is a method in which a mixture of water and a hydrophilic organic solvent is used instead of water during the above-mentioned washing. The temperature of the cleaning solution is 20°C or lower, especially 15°C.
The following are desirable.

At this time, if the proportion of the hydrophilic organic solvent in the mixture of pure water and hydrophilic organic solvent is high, the liquid temperature may be close to 20'C, but the liquid temperature needs to be lowered as the ratio of water increases. There is.

At this time, it goes without saying that the higher the ratio of water, the better the removal of Na salts.

The amount of washing solution is preferably 10 times that of HEC, and 1
If the test is carried out three times using 0 times the amount of water, the objective is achieved, and the amount of Na salt as ash becomes undetectable by chemical analysis.

After completion of purification, it is dried and crushed to become a pure HEC product.

In addition, without drying the purified product, add a specified amount of water to the temperature at 20°C.
When heated above, it dissolves and becomes a transparent viscous liquid, which can also be used as it is as a binder for a phosphor suspension.

The present invention will be specifically explained below with reference to Examples. In the following Examples, parts and % refer to parts by weight and % by weight.

Example 1 HEC treated with glyoxal [100 parts of HEC was reacted with 5 parts of glyoxal.

That is, 100 parts of HEC, 5 parts of glyoxal, 6 parts of methanol, and 4 parts of acetone were mixed in a stainless steel blender, stirred at 50°C for 2 hours, and then air-dried at 70°C.

Moisture 5%, ash 10%, viscosity 1000 cps (2%
Aqueous solution, measured at 20°C)] 100P was poured into 1 liter of pure water cooled to 5°C, stirred gently for 5 minutes, and then
C is precipitated and the supernatant liquid is removed.

After repeating this operation three times, it is filtered and dried to form a product 7.
Obtained 0P.

The product had a moisture content of 3% and no ash was detected (0.
05% or less).

Further, this product was dissolved in distilled water (pH 6.8) to make a 2% aqueous solution, and the viscosity and pH of the aqueous solution were measured at 20°C, and the viscosity was 2000 cps and the pH was 6.9.

Example 2 Glyoxal-treated HECl used in Example 1
ooP was poured into a separately prepared mixture of 300 rrll of methanol cooled to 15° C. and 700 ml of pure water, and the purification operation as in Example 1 was repeated three times.

It was filtered and dried to obtain 78 g of product. This product has a moisture content of 2%
and no ash was detected (0.05% or less).

In addition, this product was dissolved in distilled water (pI (6,8) and 2%
The viscosity and pH of the aqueous solution were measured at 20°C, and the viscosity was 1900 cps, and the pH was 6.9.

Example 3 HEC1 treated with glyoxal used in Example 1
00f? was poured into a separately prepared mixture of 1,501 rL of acetone cooled to 12°C and 850 ml of pure water, and as in Examples 1 and 2, this purification operation was performed three times, filtered,
Product 821 was obtained by drying.

The product had a moisture content of 2% and no ash was detected (0.
05% or less).

The viscosity was 1850 cps and the pH was 6.9 (
Measured in the same manner as in Example 1).

Example 4 HEC treated with glyoxal [100 parts of HEC was reacted with 3 parts of glyoxal.

That is, 100 parts of HEC, 3 parts of glyoxal, 3.6 parts of methanol, and 2.4 parts of acetone were mixed in a stainless steel blender, stirred at 50°C for 2 hours, and then heated to 70°C.
Air-dried.

Moisture: 6%, ash: 8%, viscosity: 400 cps (2% aqueous solution, measured at 20°C)
Added to the mixed solution of
Repeated several times.

was overdried to obtain product 8o1. The product has a moisture content of 2%, no ash (less than 0.05%), and a viscosity of 750 cps.
The pH was 6.9 (measured in the same manner as in Example 1).

Example 5 HECloo treated with glyoxal used in Example 4
tert cooled to 15°C, prepared separately in advance.
- Pour into a mixture of 2 ooml of butyl alcohol and 800 ml of pure water, repeat the purification operation twice as in Examples 1 to 4,
Next, pure water cooled to 5℃ lI! The washing operation was carried out in the same manner as in Example 1, and then after removing the supernatant, about half of the sample was taken for analysis, and 1 liter of pure water was added to the remainder, which was heated with gentle stirring until it reached 50°C. At this point, it completely dissolved and became transparent.

After stirring for an additional 30 minutes, the temperature was adjusted to 20°C and the viscosity was measured to be 10,000 cps.

Analysis of the sample collected earlier revealed that the moisture content was 3%, the ash content was not detected (less than 0.05%), and the viscosity was 700 cps.
The pH was 6.9 (measured in the same manner as in Example 1).

Example 6 All treatments were carried out in the same manner as in Example 1 except that the temperature during washing was changed from 5°C to 10°C.

I got exactly the same result.

Next, the results will be shown when HEC obtained by the method of the present invention and HEC obtained by a conventionally known method are used for manufacturing a discharge tube.

Usage example: HEC obtained in Example 1 above (ash content 0.05% or less)1.
52 was added to 100 rnl of pure water (deionized water) and stirred gently for 1 hour, completely dissolving it to form a transparent solution.

White calcium halophosphate phosphor powder 1001 was added to this aqueous solution at 4200° and stirred for 10 minutes to disperse it in the liquid to prepare a phosphor suspension.

Next, this suspension was applied to the inner surface of a glass bulb for a 40 watt fluorescent lamp in a conventional manner and dried by blowing hot air at 90°C.

The dried coated bulb was then heated and baked in air at 400°C to completely decompose and volatilize the binder HEC.

The bulb was further constructed into a 40 watt fluorescent lamp in the conventional manner.

The resulting fluorescent lamp has an extremely smooth thick skin of the fluorescent film, and the adhesion strength of the fluorescent film is also high, so the fluorescent film does not peel or fall off during lamp manufacturing, transportation, and lighting. There were none.

Furthermore, the luminous flux of the fluorescent lamp obtained was 13401 m.
Met.

Comparative Example A 40 watt fluorescent lamp was manufactured in the same manner as above using HEC (ash content 0.15%) obtained by a conventionally known method.

The obtained fluorescent lamp has a smooth surface of the fluorescent film, but
It was slightly yellowish and the adhesion strength of the fluorescent film was poor, so peeling or falling off of the fluorescent film was observed during lamp manufacture, transportation, and lighting.

Furthermore, the lamp luminous flux of the fluorescent lamp obtained was 7001rr.
L, which was about 1/2 compared to the lamp luminous flux of a fluorescent lamp manufactured using HEC obtained by the method of the present invention.

Claims (1)

[Claims] 1. 0.3 to 10 parts by weight of glyoxal dissolved in a hydrophilic organic solvent is added to 100 parts by weight of hydroxyethyl cellulose, stirred at 40 to 80°C for 0.5 to 3 hours, and then Dry at 50 to 80°C, and further dilute the obtained glyoxalated hydroxyethyl cellulose with water at 10°C.
A method for producing hydroxyethyl cellulose, which comprises washing at the following temperature to obtain hydroxyethyl cellulose having an ash content of 0.1 or less. 2 Add 0.3 to 10 parts by weight of glyoxal dissolved in a hydrophilic organic solvent to 100 parts by weight of hydroxyethyl cellulose, stir at 40 to 80°C for 0.5 to 3 hours, and then dry at 50 to 80°C. Then, the glyoxalated hydroxyethyl cellulose obtained is further treated at a temperature of 20°C or less with a mixture of a hydrophilic organic solvent and water, the mixture containing at least 70% by weight of water. A method for producing hydroxyethylcellulose, which comprises washing to obtain hydroxyethylcellulose having an ash content of 0.1% or less.