JPH0597623A - Glass powder for glass ionomer cement and its production - Google Patents

Abstract

PURPOSE:To obtain the subject glass powder substantially extending operational time without having adverse effects on the physical properties of cured cement by mixing glass powder with a carboxylic acid in the presence of water followed by heat treatment. CONSTITUTION:Aluminosilicate glass powder to be used as a powder component for glass ionomer cement for dental use is incorporated with <=0.1 (pref. >=0.3)wt.% of a carboxylic acid (pref. tartaric acid) in the form of a 1-10wt./ vol.% aqueous solution. The mixture is then treated under heating at 100-400 (pref. 150-250) deg.C for 4-24hr. The resultant glass powder heat-treated is kneaded with a polyalkenic acid in the presence of water to carry out reaction and setting to prepare glass ionomer cement for dental use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminosilicate glass powder mainly used as a powder component of a dental glass ionomer cement.

[0002]

2. Description of the Related Art Dental glass ionomer cement is obtained by kneading aluminosilicate glass powder (hereinafter, glass powder) and polyalkenoic acid (hereinafter, polyacid) in the presence of water, and reaction-curing the mixture. This cured product has very little harming work to the pulp, and also has excellent adhesive strength to tooth substances such as enamel and dentin,
It is also excellent in long-term margin sealing. Furthermore, since a small amount of fluorine is continuously released from the hardened cement for a long period of time, the corrosion resistance is exhibited.

Thus, the glass ionomer cement has excellent characteristics, but in order to be actually accepted in the market, other properties such as crushing resistance, disintegration rate,
Scientific and engineering properties such as translucency, and further, easiness in clinical use, that is, operability is important with a specific gravity equal to or higher than these properties. Operability refers to the characteristics of the kneaded product from the start of kneading glass powder, polyacid and water until a certain time, in which the operating time, coagulation time, consistency, etc. are defined by JIS or BS. Has been done. In actual clinical practice, dental hygienists and doctors have a long working time in order to carry out their work with a sufficient margin, and on the other hand, cement that is rapidly hardened when loaded into the oral cavity is desired.

Therefore, many efforts have been made to satisfy the operability, in other words, both the operation time and the coagulation time. For example, a method of using tartaric acid or the like as a regulator (Japanese Patent Publication No. 55-8019), glass powder is washed with acid to remove soluble calcium and the like existing in the vicinity of the surface, and the curing reaction with polyacid is substantially delayed. (Japanese Patent Publication No. 59-5536), a method of adding an inorganic acid to a polyacid solution (Japanese Patent Publication No. 56-37964), and a method of finely pulverizing a glass lump in the presence of tartaric acid to perform surface treatment (JP-A-63-63). −
225567) has been proposed.

[0005]

As described above, many proposals have been made to improve the operability of glass ionomer cement, but it cannot be said to be sufficient. Especially since many clinicians have long been familiar with zinc phosphate cement, it seems that there is a shortage when compared with the operability of this cement,
This is one of the factors that prevent the spread of glass ionomer cement. In addition, the improvement of operability, especially the extension of operation time, can be applied not only to the field of dentistry but also to the field of surgery and industrial fields such as waterworks (leakage countermeasures) and construction work for interior construction. Expected to be. In addition, it is necessary to add a third component such as tartaric acid to improve the operability, and it is necessary to add a large amount to the glass powder or polyacid solution, which causes a decrease in the physical properties of the cured product, especially the crushing resistance. Cause.

[0006]

Means for Solving the Problems The present inventor has made the operability simple without causing a drastic change or expansion of the manufacturing process, and without causing a decrease in the physical property value of the hardened cement product due to the addition of a large amount of the third component. As a result of earnestly conducting research to improve it by various means, surprisingly, glass powder as a powder component of glass ionomer cement was mixed with carboxylic acid in the presence of water and heat-treated, so that the cement liquid component (polyalkene It was found that the operability in the kneading and curing reaction with (acid) was significantly improved. Usually, when the operation time is increased, the solidification (curing) time also becomes remarkably long, and the upper limit of the solidification time of JIS standard (T6602) often exceeds 8 minutes in many cases. However, according to the present invention, the operation time can be greatly extended while maintaining the coagulation time within the range of JIS standard by an extremely simple process.

In the present specification, the operating time is the British standard "dental glass ionomer cement" BS60.
39 (1981).

The present invention is widely applicable to glass for glass ionomer cement, that is, aluminosilicate glass powder used as a powder component of glass ionomer cement. This glass powder is usually silica (Si
O ₂ ), alumina (Al ₂ O ₃ ), calcium (CaO)
As a main component, and further includes a fluorine component (F) and a phosphorus component (P
₂ O ₅ ), sodium component (Na ₂ O) and the like are contained. For example, Japanese Examined Patent Publications 50-24328 and 59-553.
See 6. However, it is not intended to be limited to these, as long as the operability improving effect of the present invention is obtained,
It includes aluminosilicate glass powders of various compositions. The glass for glass ionomer cement is manufactured, for example, as follows, according to a usual method. That is, the raw materials are weighed at a predetermined weight ratio, sufficiently mixed, and then melted at a high temperature of 1100 ° C. or higher. The homogeneously melted melt is rapidly cooled into a glass frit. The glass frit is finely pulverized by an ordinary pulverizing method, for example, a ball mill, a jet mill, a vibration mill, etc., and the particle size of the glass powder is 50 μm or less at the maximum, preferably 40 μm or less, and particularly 25 μm or less when used for coalescence. Is desirable. On the other hand, if the amount of fine powder of 1 μm or less increases, the physics and engineering characteristics improve, but the operability and the like decrease. Then, the glass powder thus obtained is subjected to the predetermined heat treatment of the present invention.

The glass powders suitable for the present invention are finely pulverized and untreated (without the treatment according to the invention),
When kneaded with a conventional polyacid solution, for example, British Standard (B
S) 6039, the operation time is 3 minutes or less, preferably 2 minutes or less, more preferably 1 minute or less, and the coagulation time is 7 minutes or less, preferably 5 minutes or less, more preferably 4 minutes or less. The effect is particularly remarkably exerted on the glass powder exhibiting early properties.

As the carboxylic acid used in the present invention, the operability is improved by delaying the curing reaction between the glass powder and the polyacid at the beginning (early) stage, while adversely affecting the cement hardened product characteristics. Select the one that does not reach. Carboxylic acid has a carboxyl group (-COO in the molecule).
H) is an organic acid having a carboxyl group 1
Lactic acid, acetic acid, gluconic acid, salicylic acid, 2 oxalic acid, malic acid, succinic acid, tartaric acid, maleic acid, 3 citric acid, 4 ethylenediaminetetraacetic acid (E
DTA) and the like, most preferred are d, l,
(Dl) Tartaric acid. Also, a mixture of these may be used. Whether it is solid or liquid, it is preferably water-soluble. Many of the above carboxylic acids are solid (powder) at room temperature. In the case of powder, the particle size is small, and it is advantageous that the particle size is fine in order to quickly achieve a uniform mixed state with glass powder.

A predetermined amount of such solid or liquid carboxylic acid is added to glass powder and mixed. In this case, the operability is hardly improved by simply dry and mechanically mixing with a ribbon type or V type mixer. The effect can be recognized only when added in a large amount, for example, in an amount exceeding 5% by weight of the glass powder, but as described above, the properties of the cured product are significantly deteriorated. However, by mixing the carboxylic acid in the glass powder in the presence of water and then heat-treating it, the effect of improving the operability is clearly recognized even if the addition amount of the carboxylic acid is small. That is, 0.1 wt% or more, preferably 0.3 wt% or more with respect to the glass powder has a sufficient effect, and addition of 2% may be sufficient depending on the heat treatment conditions. When about 4% is added, the curing time tends to be too long, and 5% or less is usually sufficient.
Almost all the cement sets (packs) on the market contained tartaric acid as a chelating agent in a large amount of 3 to 15% in the glass powder or the polyacid solution for curing, and when used (at the time of kneading). Since it is added, it is not preferable to add a larger amount of carboxylic acid thereto. A small amount can exert a sufficient effect that the carboxylic acid dissolves in water and becomes an ion, and reaches the surface of the glass powder rapidly and well, and a monovalent to trivalent cation particularly calcium present on the surface, This is probably because it efficiently and selectively reacts with divalent alkaline earth metal ions such as barium and strontium to suppress the reaction with polyacid. Even when the carboxylic acid is a liquid (for example, acetic acid: melting point 17 ° C.), the presence of water similarly makes it possible to exert a sufficient effect with a small amount of the carboxylic acid.

Further, as a means for detecting the formation of calcium salt or the like on the glass surface, Fourier transform infrared spectroscopy (DRFT-IR) by the diffuse reflection method from the viewpoint of a small amount of production and production on the powder surface. Is suitable, and the state change of organic substances such as carboxylic acid can be measured.

Water may be added as an aqueous solution of a carboxylic acid by a method of uniformly spraying it onto glass powder by a small amount if it is a small amount, or by adding it to a paste or slurry when it is large. In this case, the concentration of the aqueous solution may be adjusted appropriately, but is usually 1 to 10 wt / vol% (g of carboxylic acid /
It is recommended to use about 100 ml of water. Alternatively, water may be added after previously mixing the glass powder and the carboxylic acid. The mixture of glass powder, carboxylic acid, and water may be dried, for example, at 90 to 95 ° C to remove excess water once. However, the drying step is not essential, and the mixture of glass powder, carboxylic acid, and water may be subjected to the next heat treatment without being dried. This mixture is then transferred to an oven and above 100 ° C to 400 ° C.
Heat treatment is performed at the following temperature. If the temperature is lower than 100 ° C, the effect of the addition of carboxylic acid is not sufficiently exerted
If the temperature exceeds 0 ° C., the glass powder becomes gray to black due to thermal decomposition of carboxylic acid or the like even for a relatively short time, the commercial value is significantly impaired, and the coagulation time tends to be too long. The treatment temperature and the holding time may be appropriately selected depending on the composition of the glass powder, the type of carboxylic acid, the purpose of use of the cement, etc., but a heat treatment temperature of 150 ° C to 250 ° C is usually preferable, and the higher the temperature, the longer the operating time. .. The treatment time is too short at 0.1 hours, preferably 4 hours to 2 hours.
4 hours. As with temperature, the longer the time, the greater the effect.

[0014]

EXAMPLE 1 Fluoroaluminosilicate glass powder (raw material composition (wt%) S having an average particle size of 4.7 μm by X-ray transmission method)
_{iO 2: 31, Al 2 O} 3,: 28, CaO: 9, Ba
O: 11, F: 12, P 2 O 5: 7, ZnO: 2) 100
100 parts of a 1.0 wt / vol% aqueous solution of d-tartaric acid (1 g of tartaric acid / 100 ml of water) was added to parts by weight (hereinafter referred to as "parts") to form a slurry, which was dried at 92 ° C for 24 hours to remove water. Subsequently, the dried product was transferred to an oven at a predetermined temperature, held for 8 hours to be heat-treated, and then left to cool in a desiccator. The glass powder heat-treated in this way and a commercially available polyacid solution (Matsufuze Co., Ltd., Hybond C registered trademark)
A polyacrylic acid-based copolymer and tartaric acid (containing about 8%) were kneaded at a powder / liquid ratio (= P / L) of 1.5 / 1 by weight to examine operability and various physical and engineering properties of the hardened cement. .. The operation time is BS6039, and the coagulation time, crushing resistance, and film thickness are JI
It was determined according to S6602. The results are shown in Table 1.
In addition, Comparative Example Sample 1 is a glass powder that has not been subjected to any treatment (one that has not been treated with a carboxylic acid solution and heat treatment), and Comparative Example Sample 2 is a glass powder that has been dried at 92 ° C. (a carbon powder in the presence of water). This is an example of using a product which has been treated with an acid but has not been heat treated.

[0015]

[Table 1]

According to Table 1, as compared with the glass powder which has not been treated at all (Comparative sample 1), each glass powder prepared by adding d-tartaric acid (Example samples 1 to 7, Comparative sample) Example sample 2) has extended operating time. And glass powder simply treated at room temperature (RT) (Comparative sample 2)
It can be seen that the glass powder heat-treated at each temperature of 100 ° C. or higher (Example samples 1 to 7) can further extend the operation time, as compared with Example 1. Although the coagulation time is extended, most of the examples are within 8 minutes of JIS standard. However, when the heat treatment temperature is 400 ° C. or higher, the solidification time is significantly extended and the physical properties of the cured product are considerably deteriorated (Example sample 7). Therefore, the heat treatment temperature is 400 ° C. under the conditions of this example. It can be seen that less than is preferable. By the way,
The thinner the coating thickness, the higher the adhesive strength, the longer the life and the less discomfort, which is preferable, and the glass powder of this example is also extremely excellent in this respect.

[0017]

Example 2 A predetermined amount of d-tartaric acid (solid) was added to 100 parts of the fluoroaluminosilicate glass powder of Example 1, and the mixture was dry-mixed in a dairy bee for 30 minutes. To this, 35 parts of water was added dropwise to form a paste, which was then dried at 90 ° C. for 16 hours. Then, after heat treatment at 200 ° C. for 8 hours, it was left to cool. Then, in the same manner as in Example 1 above, each characteristic was examined by kneading and curing with a commercially available polyacid solution. The results are shown in Table 2. In addition, the comparative sample 1 is a glass powder which is only heat-treated without adding tartaric acid, and the comparative sample 2,
No. 3 is an example using glass powder to which tartaric acid was added but which was kept at room temperature (RT) but not heat-treated.

[0018]

[Table 2]

According to Table 2, the amount of tartaric acid added was only 0.
Even with 25 parts (Example sample 8), it can be seen that the operation time can be considerably extended when the heat treatment is performed. Also, in terms of film thickness, all of the samples of this example are significantly superior to the sample of comparative example 3. However, when the amount of tartaric acid added was 4.0 parts, the coagulation time exceeded the upper limit of 8 minutes according to the JIS standard, and the crushing resistance also considerably decreased (Example sample 12). It is understood that less than 4.0 parts is preferable under the condition of.

[0020]

Example 3 Fluoroaluminosilicate glass powder having an average particle size of 4.3 μm (raw material composition SiO ₂ : 28 wt%, A
_{l 2 O 3: 19%,} AlPO 4: 10%, CaF 2: 25
_{%, AlF 3: 12%,} Na 3 AlF 6: 6%) to 8 wt / vol% aqueous solution of l- tartaric acid 100 parts, 100 parts of glass powder to uniformly sprayed with a spray such that the part tartrate sufficient The surface of the glass powder was wetted. This 8
It was dried at 5 ° C. for 20 hours, then heat-treated at 200 ° C. for a predetermined time and then left to cool. Then, in the same manner as in Example 1 above, each characteristic was examined by kneading and curing with a commercially available polyacid solution. The results are shown in Table 3. Incidentally, Comparative Example Sample 1 used glass powder which was not subjected to any treatment, and Comparative Example Sample 2 used glass powder which was added with 1 part of 1-tartaric acid and dry-mixed in dairy bees for 30 minutes but not subjected to heat treatment. Here is an example.

[0021]

[Table 3]

According to Table 3, as compared with the glass powder which was not subjected to any treatment (Comparative Example Sample 1), each glass powder obtained by adding 1-tartaric acid and heat treatment (Example Samples 14 to 1).
8, Comparative Example Sample 2) has an extended operation time, and it can be seen that the longer the heat treatment time, the longer the operation time. Further, the glass powder (Example sample 16) treated with an aqueous solution of tartaric acid and heat-treated, as compared with the glass powder which was dry-mixed with tartaric acid but not heat-treated (Comparative sample 2). It can be seen that the operating time can be significantly extended, and the operating time can be extended even if the heat treatment time is shortened (Comparative sample 2 vs. Example samples 14 and 15). Although the coagulation time was extended, the samples of all Examples were within the JIS standard upper limit of 8 minutes. Also, in terms of the film thickness, all of the samples 14 to 18 of this example are superior to the samples 1 and 2 of the comparative examples.

[0023]

Example 4 As shown in Table 4, fluoroaluminosilicate glass powders A and B having different chemical compositions and average particle diameters.
And C were prepared.

[0024]

[Table 4]

To 100 parts of these glass powders A, B and C, d
-1 part tartaric acid and 100 parts water were added to make a uniform slurry. It is dried at 90 ° C. for 15 hours, then 200
Heat treatment was performed at 8 ° C. for 8 hours. This heat treated glass powder 1.
5 parts were kneaded with 1 part of an aqueous solution of polyacid (acrylic acid-maleic acid copolymer, containing 11% tartaric acid), and the operation time and coagulation time were examined. The results are shown in Table 5. Comparative Samples 1, 2 and 3 are examples using glass powders A, B and C which have not been subjected to any treatment as they are pulverized.

[0026]

[Table 5]

Table 5 shows that the operating time can be extended when various fluoroaluminosilicate glass powders are heat treated by adding tartaric acid and water.
Also in these samples 19 to 21 of this example, the solidification time is within the upper limit of 8 minutes according to the JIS standard. On the other hand, in Comparative Examples 1, 2, and 3 in which the treatment of the present invention is not performed, the operation time is 1 minute or less, which is extremely short. Incidentally, the glass powder A has a high viscosity from the beginning and hardens gradually, the glass powder B hardens immediately when mixed with the polyacid solution, and the glass powder C hardens rapidly, though not as much as the powder B. ..

[0028]

Example 5 To 100 parts of fluoroaluminosilicate glass powder similar to that of Example 1, 50 parts of an aqueous solution in which various carboxylic acids were dissolved or dispersed at a predetermined addition amount was added to obtain a uniform slurry. This is dried at 97 ℃ for 10 hours,
Then, heat treatment was performed at 200 ° C. for 8 hours. This heat-treated glass powder was treated with the same polyacid solution as in Example 1 to give a powder / liquid ratio.
Kneaded at 1.5 / 1. The results are shown in Table 6. In addition, Comparative Example Sample 1 uses a glass powder that is simply heat-treated without adding a carboxylic acid aqueous solution, and Comparative Example Samples 2 and 3 are glass powders that are simply adding a carboxylic acid aqueous solution and not heat-treated. It is an example.

[0029]

[Table 6]

According to Table 6, as compared with the glass powder which was simply heat-treated without adding the carboxylic acid aqueous solution (Comparative Example Sample 1), a glass powder obtained by adding various carboxylic acids and heat-treating (implementation) It can be seen that in Examples 22 to 34), the operation time can be sufficiently extended even when the amount of carboxylic acid added is only about 0.5 to 2.0 parts. This extension of the operation time is recognized regardless of the type of carboxylic acid. Also, regarding the coagulation time, except when adding 1.0 part of oxalic acid,
All of the example samples fall within the JIS standard upper limit of 8 minutes, and most of the example samples fall within the more preferable coagulation time of 6 minutes.

[0031]

Example 6 SiO ₂ : 26 wt% (hereinafter simply referred to as%), A
l ₂ O ₃ : 15%, CaF ₂ : 23%, AlF ₃ : 12%,
ZnO: 12%, AlPO ₄ : 12%, 100 parts of glass powder having an average particle size of 3.7 μm, various carboxylic acids and 50 parts of water were added, and the mixture was put directly in an oven kept at 190 ° C. Heat treated for 12 hours. This treated powder is a commercially available polyacid solution
The effect of heat treatment was investigated by kneading with Fuji ionomer I) at a powder / liquid ratio of 1.5 / 1 (Table 7).

[0032]

[Table 7]

According to Table 7, the glass powder (Example samples 35 to 39) obtained by adding the carboxylic acid and water and heat-treating the glass powder of the present composition without the drying step was:
It can be seen that the operation time can be sufficiently extended even when the amount of carboxylic acid added is only about 0.5 to 2.0 parts.

[0034]

Example 7 SiO ₂ : 30 wt% (hereinafter simply referred to as%), A
_{l 2 O 3: 24%,} SrF 2: 33%, AlPO 4: 12
%, Na ₂ O: 1%, 1 part of tartaric acid was added to 100 parts (by weight) of glass powder having various average particle sizes, 40 parts of water was further added and mixed, and then dried at 95 ° C. for 10 hours. This was treated in the same manner as in Example 6 below, and the effect of heat treatment was examined (Table 8).

The comparative samples 1 to 4 are glass powders having the average particle diameters corresponding to the example samples 40 to 43, respectively, which are heat-treated without adding tartaric acid.

[0036]

[Table 8]

Table 8 shows that even when glass powders of various particle sizes are heat treated by adding tartaric acid and water, the operating time can be remarkably extended while keeping the coagulation time within 8 minutes of JIS standard. ..

[0038]

Example 8: a) Tartaric acid (purity of 98% or more), b) Glass powder (having the composition of Sample 1 of Example 1), and c) Glass powder to which tartaric acid and water were added (Sample 1 of Example 1). Having a composition of 5 parts, including 5 parts of tartaric acid and adding water to form a paste, and dried at 90 degrees for 16 hours),
Before and after the heat treatment at 200 ° C. for 8 hours, the diffuse reflection Fourier transform infrared spectroscopic analysis (DR-FT-IR) spectrum was examined. The results are shown in FIGS.

That is, FIG. 1 shows a) tartaric acid (at room temperature, before heat treatment), FIG. 2 a) tartaric acid (after heat treatment), FIG. 3 b) glass powder (before heat treatment: the same after heat treatment), and FIG. FIG. 5 is a DRFT-IR spectrum diagram of c) glass powder to which tartaric acid and water were added (before heat treatment), and FIG. 5 is c) glass powder to which tartaric acid and water were added (after heat treatment). 4 and 5
As is clear from the comparison with FIG. 3, in Sample c) according to the example, a clear absorption peak is observed between 1700 and 1600 cm ⁻¹ . By the way, in JP-A-63-225567 (where carboxylic acid is added during grinding but no heat treatment is applied), tartaric acid of about 3400 to 3300 is added at 1% or more.
Although a sharp absorption peak was shown at cm ^-1, it did not appear in the sample according to this example.

[0040]

[Example 9] a) Tartaric acid, and c) Example 1 Glass powder having the composition of Sample 1 was mixed with 5 parts of tartaric acid and water to form a paste, which was dried at 90 ° C for 16 hours, and then dried in air. The state change (weight, heat generation, decomposition, etc.) when heated to 300 ° C. at a rate of 5 ° C./min was examined by a weight / differential thermal analysis method (TG-DTA).

FIG. 6 a) TG-DTA for tartaric acid
It is a curve. From FIG. 6, there is a change in the vicinity of 172 ° C. that is consistent with the melting of tartaric acid, and decomposition and evaporation of tartaric acid is observed at temperatures above this. On the other hand, FIG. 7 is a TG-DTA curve for glass powder to which c) tartaric acid and water were added. From FIG. 7, no change due to the state change of tartaric acid alone as shown in FIG. 6 is observed. That is, the tartaric acid added reacts with the glass powder to form a stable compound,
According to the G line, it is recognized that the compound remains even at 300 ° C. Incidentally, TG-D for pure glass powder
No change was observed in the TA curve.

[0042]

The operation time of the glass powder for glass ionomer cement can be remarkably extended by the extremely simple treatment of mixing the carboxylic acid in the presence of water and heat-treating it, with almost no adverse effect on the physical properties of the hardened cement. .. Further, the operating time and the coagulation time of the glass ionomer glass powder can be easily adjusted by changing the kind and amount of the carboxylic acid, the existing state of water or the heating temperature and time according to the application.

[Brief description of drawings]

FIG. 1 DRFT-IR spectrum diagram (tartaric acid: at room temperature, before heat treatment)

FIG. 2 DRFT-IR spectrum diagram (tartaric acid: after heat treatment)

FIG. 3 is a DRFT-IR spectrum diagram (glass powder: the same before and after heat treatment)

FIG. 4 DRFT-IR spectrum diagram (tartaric acid and water-added glass powder: before heat treatment)

FIG. 5: DRFT-IR spectrum diagram (tartaric acid and water-added glass powder: after heat treatment)

FIG. 6 TG-DTA curve (tartaric acid)

FIG. 7 TG-DTA curve (tartaric acid and water-added glass powder)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiko Shibata No. 1-36-36 Noritake Shinmachi, Nishi-ku, Nagoya, Aichi Prefecture Noritake Company Limited Limited (72) Inventor Hideki Nonogawa 3-chome, Noritake Shin-cho, Nishi-ku, Aichi Prefecture No.36 Noritake Company Limited (72) Inventor Eiichi Masuhara 2-5-11 Honkomagome, Bunkyo-ku, Tokyo (72) Inventor Shigeo Komiya 3-7-10 Minamiurawa, Urawa-shi, Saitama (72) Invention Person Tetsuya Nakamura 2-20-3 Kasuga, Tsukuba City, Ibaraki Prefecture (72) Inventor Yoshitaka Goto 2-24-5 Umezono, Tsukuba City, Ibaraki Prefecture (72) Inventor Masayo Nakayama 1132-9 Nagakuni, Tsuchiura City, Ibaraki Prefecture

Claims (12)

[Claims] 1. A glass powder for glass ionomer cement, wherein the surface of the glass powder is heat-treated with a carboxylic acid. 2. The glass powder according to claim 1, wherein the carboxylic acid for heat treatment is a carboxylic acid having 1 to 4 carboxyl groups in the molecule. 3. The glass powder before treatment has an operating time of 2 minutes or less,
The glass powder according to claim 1, having a coagulation time of 5 minutes or less. 4. The glass powder according to claim 1, wherein the heat-treated glass powder exhibits a clear absorption peak between 1700 and 1600 cm ^{−1 by} a diffuse reflection Fourier transform infrared spectroscopic analysis. 5. A method for producing glass powder for glass ionomer cement, which comprises mixing glass powder with carboxylic acid in the presence of water and heat-treating the mixture. 6. The method according to claim 5, wherein the carboxylic acid for heat treatment is a carboxylic acid containing 1 to 4 carboxyl groups in the molecule. 7. The glass powder before treatment has an operating time of 2 minutes or less,
The production method according to claim 5, wherein the coagulation time is within 5 minutes. 8. The method according to claim 5, wherein 0.01 to 5.0 wt% of carboxylic acid is added based on the weight of the glass powder. 9. The manufacturing method according to claim 5, wherein an aqueous carboxylic acid solution is added to the glass powder. 10. The production method according to claim 5, wherein carboxylic acid and water are added to the glass powder. 11. The method according to claim 5, wherein the glass powder is mixed with a carboxylic acid in the presence of water, the water is removed by drying, and then the heat treatment is performed. 12. The manufacturing method according to claim 5, wherein the heat treatment temperature is in the range of 100 ° C. to 400 ° C.