JPS5814384B2 - Anhydrite composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to anhydrous gypsum compositions suitable for use as various gypsum-based building materials, particularly as plaster for poured floors.

BACKGROUND ART Conventionally, calcined gypsum obtained by calcining gypsum hemihydrate, such as dihydrate gypsum, which is a by-product from various chemical and iron manufacturing processes, has been used as a raw material for manufacturing gypsum plaster, gypsum board, and the like.

Although hemihydrate gypsum has the advantage of high water availability and fast setting speed (short setting time), the strength of the hardened material obtained by hydration and setting is lower than that of cement hardened material, and the water resistance is also low. This is a major obstacle to expanding demand for gypsum.

On the other hand, for anhydrite, by-product dihydrate is fired at high temperature (600
~1000C); by-product anhydrite produced in large quantities from the manufacturing process of hydrofluoric acid, titanium, etc.; and other naturally occurring natural type anhydrite, etc.; When used alone, it has an extremely slow setting rate and is difficult to form into a dihydrate, so it is of little practical use, and only a small portion of it is used as Keens cement or anhydrite plaster. The reality is that most raw anhydrite is simply discarded.

Furthermore, there is almost no demand for calcined type 1 anhydrite, and production on an industrial scale has not yet been carried out.

However, it is a well-known fact that type 2 anhydrite has a hardened product strength so great that it surpasses that of a cement hardened product, and has water resistance.

Therefore, the setting time of anhydrite can be shortened and become comparable to that of hemihydrate. Since it became possible to handle it in the same way as anhydrite, and its hardened product has high strength and water resistance, the scope of industrial use of anhydrite was significantly expanded, and its industrial value increased dramatically. .

Conventionally, a method has been proposed in which soluble sulfates, such as sulfates of sodium, ammonium, magnesium, aluminum, iron, etc., are added to anhydrite in order to shorten the setting time of anhydrite and increase the strength of the hardened gypsum. There is.

Due to the addition of this soluble sulfate, the strength of the hardened anhydrite gypsum one day after hardening is greater than that of hemihydrate gypsum and comparable to that of Bortland cement hardened material, but it is still compared to hemihydrate gypsum. The setting rate is slow, and the initial strength of the hardened product is slow.

Therefore, in order to further shorten the setting time of anhydrite and accelerate the initial strength development of the hardened product, a method has been used in which alkaline substances such as caustic alkali, water glass, and lime are added to anhydrite together with soluble sulfate. However, even with this method, it is still not possible to make the setting time of anhydrite comparable to that of hemihydrate, and the initial strength of the hardened product cannot be sufficiently accelerated. If a substance containing sodium atoms, such as caustic potash, is used, an efflorescence phenomenon will occur on the surface of the cured product, which will fatally impair its practicality.

In view of these circumstances, the inventors of the present invention have attempted to significantly shorten the water use and setting time of anhydrite compared to the past, so that it is almost comparable to that of hemihydrate gypsum, and to make the initial strength of the hardened material sufficiently rapid. As a result of various studies, it was found that an anhydrite composition suitable for the purpose can be obtained by blending a specific amount of potassium sulfate, one or more alkaline substances that do not contain sodium atoms, and gypsum hemihydrate with anhydrite. The workability of such anhydrite composition is very good because no breathing occurs when it is watered and set to produce a cured product, and the obtained cured product does not exhibit birch color, and It has been found that because of its extremely high strength, it can be suitably used for various building materials, especially cast flooring materials.

The present invention was made based on this knowledge, and
The gist is that 100 parts by weight of anhydrite, 0.2 to 5.0 parts by weight of potassium sulfate, and 0.2 to 5.0 parts by weight of one or more alkaline substances that do not contain sodium atoms.
5 to 10.0 parts by weight and 5.0 to 23.0 parts by weight of gypsum hemihydrate
parts by weight, and if necessary, a known setting retarder,
An anhydrite composition containing appropriate amounts of antifoaming agents, dispersants, admixtures, etc.

The anhydrite composition of the present invention is produced by adding and mixing predetermined amounts of each of the above components to anhydrite.

The anhydrite used in the anhydrite composition of the present invention is hydrated and
Any type of anhydrite can be used as long as it is capable of setting, such as anhydrite produced as a by-product from the manufacturing process of hydrofluoric acid, titanium, etc.; calcined anhydrite obtained by high-temperature firing of gypsum dihydrate or gypsum hemihydrate; : Natural anhydrite is a typical example.

Some by-product anhydrite gypsum, such as hydrofluoric acid by-product gypsum, contains acid as an impurity, but when using such gypsum as a raw material, it must first be treated with an alkaline substance that does not contain sodium atoms, such as slaked lime, quicklime, etc. It is necessary to add a similar alkali to the raw gypsum to neutralize the acid content.

If an alkaline substance containing sodium-Jium atoms, such as caustic soda or soda ash, is used during this neutralization, when the anhydrite composition of the present invention is hydrated and coagulated to produce a hardened body, the surface of the hardened body will be It is not preferred because it causes efflorescence.

There is no problem in using raw gypsum with different crystal shapes, crystal porosity, etc., and there is no need for special pulverization; normally, gypsum with a particle size of 1 m or less is suitable for use, so it can be used commercially. The powder can be used as is.

The anhydrite composition of the present invention mainly contains potassium sulfate as a component that promotes water utilization and setting rate of anhydrite.

Conventionally, soluble sulfates such as potassium alum and aluminum sulfate have been commonly used as setting accelerators for anhydrite. corrodes the species.

Therefore, when these sulfates are used as a setting accelerator, it is necessary to neutralize the gypsum slurry using an alkali in order to prevent corrosion of metals, but when potassium sulfate is used as a setting accelerator, Since the gypsum slurry is usually neutral or weakly alkaline, in this case there is no need for an alkali to neutralize the slurry, which is economical.

In addition, when potassium alum, aluminum sulfate, etc. are added to anhydrous gypsum together with alkali, aluminum hydroxide precipitates are formed in the gypsum slurry, impairing workability during the production of hardened products. When added to gypsum, workability is good not only when it is used alone but also when it is used in combination with an alkali because no hydroxide is generated in the gypsum slurry.

For these reasons, potassium sulfate can be said to be particularly suitable as a setting accelerator for anhydrite.

The amount of potassium sulfate used in the anhydrite composition of the present invention is 0.2 to 5.0 parts by weight based on 100 parts by weight of anhydrite.

If the amount of potassium sulfate used is less than 0.2 parts by weight, the setting speed of anhydrite is extremely slow, and even if it is used in a large amount exceeding 5.0 parts by weight, the setting speed of anhydrite will not be so fast, and will instead become unfavorable. It's the economy.

Merely adding potassium sulfate to anhydrite is still insufficient to shorten the setting time of anhydrite, and the initial strength of the hardened product is slow to develop.In order to improve this, the anhydrite composition of the present invention contains an alkaline substance, especially an alkaline substance not containing Na-J-cum atoms.

Examples of the types of alkaline substances that can be used include slaked lime, quicklime, Bortland cement, and dolomite, but the present invention is not limited to these, and these alkalis can be used not only alone but also in combination of two types. A mixture of the above can also be used.

In the present invention, the amount of the alkaline substance not containing sodium atoms used is 0.5 to 100 parts by weight of anhydrite.
It is 10.0 parts by weight.

If the amount used is less than 0.5 parts by weight, it cannot be expected to shorten the setting rate of anhydrite or to accelerate the development of the initial strength of the hardened gypsum, and if it is used in an amount exceeding 10.0 parts by weight, the hardened product will actually deteriorate. strength decreases.

When a hardened material is produced by adding soluble sulfate and an alkaline substance containing sodium atoms to anhydrite and allowing it to coagulate under water, efflorescence occurs on the surface of the hardened material as described above, but potassium sulfate and When an alkaline substance that does not contain sodium atoms is added to anhydrite and allowed to hydrate and coagulate, no efflorescence phenomenon is observed on the surface of the cured product.

This is the greatest effect of using an alkaline substance that does not contain sodium atoms in the present invention.

By adding potassium sulfate and an alkaline substance that does not contain sodium atoms to anhydrite, the setting time of anhydrite is considerably shortened compared to when potassium sulfate alone is added, and the initial strength of the hardened product is also faster. The setting speed of anhydrite is still considerably slower than that of hemihydrate, and the initial strength development of the hardened product cannot be said to be fast enough for practical use.

Additionally, anhydrite to which potassium sulfate and alkaline substances that do not contain sodium atoms are added causes breathing during hydration and coagulation, which not only worsens workability during the production of hardened products, but also causes bleeding during the production of hardened products. When this occurs, the setting speed of anhydrite is significantly delayed and the strength of the cured product is reduced.

In the present invention, in order to correct these points, gypsum hemihydrate is included in the anhydrite composition.

Types of hemihydrate gypsum used in the present invention include α-type hemihydrate gypsum, β-type hemihydrate gypsum, and the like.

These gypsum hemihydrates may have different crystal shapes and crystal voids, and there is no need for special pulverization, and commercially available powder products can be used as they are.

The amount of gypsum hemihydrate used in the present invention is 5.0 to 23.0 parts by weight per 100 parts by weight of anhydrite.

If the amount of gypsum hemihydrate used is less than 0.5 parts by weight, the curing speed of anhydrite will not increase significantly, and if it is used in excess of 23.0 parts by weight, the curing speed of anhydrite will be too fast, making it difficult to handle the gypsum slurry. It becomes difficult.

Up until now, attempts have been made to add small amounts of gypsum hemihydrate or gypsum dihydrate to anhydrite and use these as seed crystals to promote the conversion of anhydrite into dihydrate (water utilization/condensation). However, simply adding gypsum hemihydrate or gypsum dihydrate to anhydrite in the required amount as seed crystals does not significantly shorten the setting time of anhydrite, and also accelerates the development of initial strength of the hardened material. In addition, it is hardly expected to increase the strength of the cured product.

On the other hand, in the present invention, gypsum hemihydrate is contained in the anhydrite composition of the present invention in an amount exceeding that normally required as a seed crystal, and this unexpectedly causes a mutual effect with other components. Not only does this significantly accelerate the setting speed of anhydrite, but it also homogenizes the density of the gypsum slurry so that no breathing occurs at all during the production of the hardened product.The absence of this breathing further accelerates the setting speed of anhydrite. The setting time of the anhydrite composition of the present invention is almost comparable to that of gypsum hemihydrate, the initial strength of the cured product is faster, and the strength of the cured product is also increased. It has been found that various excellent effects can be obtained by varying the anhydrite, such as being able to arbitrarily control the setting time of anhydrite and improving the dimensional stability of the cured product.

As is clear from the above description, in the anhydrite composition of the present invention, three components, potassium sulfate, an alkaline substance not containing sodium, and gypsum hemihydrate, are used to produce a hardened product by irrigating and coagulating the anhydrite composition. The anhydrite composition of the present invention contains these substances, which interact with anhydrite to improve workability during the production of cured products and improve the performance of the cured products. In addition to the three components, in order to improve the workability during the production of the cured product and the performance of the cured product, any known additives conventionally commonly used in this type of composition, such as setting retarders, may be added as necessary. Appropriate amounts of antifoaming agents, admixtures, etc. can be added.

Commonly preferred setting retarders include citric acid, sodium tripolyphosphate, polypeptone, etc.
In particular, when polypeptone is used, the strength of the cured product decreases less than when other setting retarders are used, and the setting time of the anhydrite composition can be controlled arbitrarily even if only a small amount is used. It's advantageous.

When producing a lightweight gypsum molded body from the anhydrite composition of the present invention, it is not necessary to use a defoaming agent, but when trying to obtain a high-strength molded body, alcohol A fatty acid ester, silicone, etc. Preferably, antifoaming agents are added to the anhydrite compositions of the present invention.

When producing a gypsum molded body, the fluidity of the gypsum slurry is an important factor in the work, and it is preferable for the gypsum slurry to exhibit good fluidity depending on the intended use in order to improve workability.

Anhydrous gypsum has a standard water content that varies widely from 25 to 65% (based on gypsum weight%) due to differences in type and manufacturing conditions.
Generally, it is advantageous to increase the amount of water mixed in because it improves the fluidity of the gypsum slurry, but if the amount of water mixed in is too large, breathing will occur, setting time will be delayed, and a long curing time will be required. Moreover, the strength of the obtained molded product is also low, making it impractical.

Therefore, it is possible to add a dispersant, a viscosity modifier, etc. to the anhydrite composition of the present invention, which can improve the fluidity of the gypsum slurry even when the amount of mixed water is reduced.

Examples of the type of dispersant used include nignosulfonate, naphthalenesulfonate, polyalkylarylsulfonate, melamine-formalin condensate, and the like.

In particular, a polyalkylaryl sulfonate and a melamine-formalin condensate are preferred dispersants because they have a large water-reducing effect and do not cause a decrease in the strength of the molded article.

Types of admixtures (aggregates) that can be added to the anhydrite composition of the present invention include wood flour, perlite, fibers such as shirasu balloons, lightweighting materials, fillers, as well as sand, cement, etc. It is used depending on the purpose.

In addition, a foaming agent, a water retention agent, an anti-wear material, a polymeric substance, etc. may be added to the anhydrite composition of the present invention, if necessary.

Next, the configuration and effects of the present invention will be specifically explained using Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Comparative Example Various setting accelerators and various alkaline substances were added to 100 parts by weight of by-product anhydrite in amounts shown in Tables 1 and 2 and mixed well.

Next, 33 parts by weight of water was added to 100 parts by weight of the obtained mixture, and the mixture was stirred and kneaded.

After crosstalk, the obtained gypsum slurry was heated to 40H (high; g) x 4
It was poured into a mold with dimensions of 0B (width) x 160 mmL (length 5) and left indoors to harden.

The compressive strength of the molded product obtained in this way was determined according to JIS-R
It was measured according to the test method of No. 5201.

pH of gypsum slurry > Setting time according to the method of JIS-R9112: Presence or absence of breathing: Presence or absence of efflorescence in the obtained cured product; Measurement results of compressive strength, etc. are shown in Tables 1 and 2.

As is clear from Experiments A1 to 8 in Table 1, when a setting accelerator such as soluble sulfate is simply added to anhydrite, the setting rate of anhydrite and the initial strength development of the hardened product are both very slow. .

Furthermore, as is clear from Experiment A9 in Table 1, when a hardened body is produced by adding gypsum hemihydrate to anhydrite, no breathing occurs during the manufacturing process, and no efflorescence phenomenon is observed in the hardened body. However, both the setting speed and the initial strength development of the cured product are slow.

Furthermore, as seen in Experiments A2, 4, and 8 in Table 1, Nikka was observed in all of the hardened bodies obtained when sulfate containing Na atoms was added as a setting accelerator to anhydrite. .

Next, the experimental breaths 10, 11, 12, 1314, 1 in Table 2
5, 17, and 18, when a setting accelerator that does not contain Na atoms and an alkaline substance that contains Na atoms are added to anhydrite in combination, efflorescence occurs in the hardened product, but As seen in Nos. 19, 20, and 21, when a setting accelerator that does not contain Na atoms and an alkaline substance that does not contain Na atoms are used together, efflorescence does not occur in the cured product.

In addition, as is clear from AIO~21 in Table 2, when a setting accelerator and an alkaline substance are added together to anhydrite, the setting rate and initial strength of anhydrite are lower than when the setting accelerator is used alone. Both of them develop faster, but both are still slower than hemihydrate gypsum and cannot be treated in the same way as hemihydrate gypsum.

Example 1 To 100 parts by weight of anhydrite, potassium sulfate, various Na atom-free alkaline substances, and gypsum hemihydrate were added in amounts as shown in Table 3, and mixed well to form the anhydrite composition of the present invention. I made it.

Next, using this composition, a gypsum molded body was manufactured according to the same method as in the comparative example, and the same test was conducted.

The results obtained are shown in Table 3.

For comparison, when a setting accelerator other than potassium sulfate was used for anhydrite, or when no setting accelerator was used,
The results obtained when an alkaline substance containing Na atoms was not used, when gypsum hemihydrate was not used, etc. are also listed in Table 3 as a control.

As is clear from Table 3, when the anhydrite composition of the present invention to which the three components of potassium sulfate, an alkaline substance not containing Na atoms, and gypsum hemihydrate are added, the setting speed is sufficient. It is fast, does not cause bleeding, efflorescence, etc., and the initial strength of the obtained cured product is sufficiently fast. or when an anhydrite composition lacking any one of the three components specified in the present invention is irrigated and solidified, the excellent effects brought about by the anhydrite composition of the present invention can be obtained. I can't.

Example 2 Potassium sulfate, an alkaline substance not containing Na atoms, and gypsum hemihydrate were added to 100 parts by weight of anhydrite in amounts shown in Table 4, and mixed well to prepare an anhydrite composition of the present invention. .

Next, using this composition, a gypsum molded body was manufactured according to the same method as in the comparative example, and the same test was conducted.

The results obtained are shown in Table 4.

As is clear from Table 4, in the anhydrite composition of the present invention, by varying the amount of setting accelerator and alkaline substance C used, water use and setting time can be adjusted as desired. Also, there is no breathing flame generation during the production of the molded product, and the initial strength of the obtained molded product is developed sufficiently quickly.

Example 3 Potassium sulfate, slaked lime and α-hemihydrate gypsum were added to 100 parts by weight of by-product anhydrite in amounts shown in Table 5 and mixed well to prepare an anhydrite composition of the present invention.

Next, a gypsum slurry and a molded body were produced from this composition according to the same method as in Comparative Examples 1 and 2, and the same tests were conducted.

The results obtained are shown in Table 5.

As is clear from experimental results 52, 53 and 54 in Table 4, the setting time can be arbitrarily adjusted in the anhydrite composition of the present invention by varying the content of hemihydrate.

Furthermore, as is clear from Experiments 555 and 56 in the same table, the setting time of the anhydrite composition of the present invention can be adjusted using a known setting retarder.Example 4 Anhydrite composition of the present invention An example of application to manufacturing building materials using the pouring method is shown below.

18 parts by weight of alpha hemihydrate, 1.0 parts by weight of potassium sulfate, and 1.0 parts by weight of slaked lime were added to ioo parts by weight of by-product anhydrite and mixed well.

On the other hand, 33 parts by weight of water was prepared, and the above mixture was added thereto and stirred and kneaded.

After kneading, the obtained slurry was poured into the same mold as used in the comparative example and left indoors to coagulate and harden.

The gypsum slurry solidified in 20 minutes to the same level as hemihydrate gypsum, and was able to be removed from the mold within an hour.

The compressive strength of the molded product after 3 hours after being poured into the mold is 123
It developed fQ/crI and a surprising initial intensity.

Generally, after hydrating and setting gypsum hemihydrate, excess water is forcibly dried and removed in order to speed up the strength development of the hardened material.
The amount of heat required to remove this excess water is enormous.

On the other hand, when the anhydrite composition of the present invention is irrigated and solidified, there is no need to forcibly remove excess water, and the hardened product develops a strength that can be easily handled in a short period of time.

Example 5 An example in which the anhydrite composition of the present invention is applied to the construction of cast gypsum flooring is shown below.

100 parts by weight of by-product anhydrite, 1.0 parts by weight of potassium sulfate, 10 parts by weight of alpha hemihydrate, 0.9 parts by weight of slaked lime, 0.2 parts by weight of polyalkylaryl sulfonate, and 0.0 parts by weight of a silicone antifoaming agent. 02 parts by weight were added and mixed well.

On the other hand, a predetermined amount of water was prepared, and the above mixture was poured into the water and stirred and mixed.

After mixing, the viscosity, fluidity, coagulation time, etc. of the obtained slurry were measured.

The viscosity was measured using a B-type viscometer, and the fluidity was measured by flowing the slurry down onto a glass plate using a glass funnel (the distance between the glass plate and the bottom end of the funnel leg was 2511 mm, and the inner diameter of the funnel leg was 8 mm).
mm, slurry volume 44 ml), and its spread width was taken as the flow value.

Also, the same gypsum slurry is 40H x 40B x 160Lm
The mixture was poured into a mold with dimensions of −m and left indoors to solidify and harden.

Then, after 24 hours, the compressive strength and residual native water of the cured molded body were measured.

The results obtained are shown in Table 6.

For comparison, the results of a test similar to the above using a commercially available α-hemihydrate gypsum composition for cast flooring instead of the anhydrite composition of the present invention are also shown in Table 6 as a control example.

As is clear from Table 6, when the anhydrous gypsum composition of the present invention is applied to the production of cast flooring, there is no darkening compared to when commercially available cast flooring is used; in fact, it is superior. There are many points.

Example 6 An example in which the anhydrite composition of the present invention is applied to gypsum plaster for boards is shown below.

1.0 parts by weight of potassium sulfate, 10 parts by weight of β-hemihydrate gypsum, 2.0 parts by weight of slaked lime, and 200 parts by weight of standard sand were added to 10 parts by weight of natural anhydrite and mixed well.

On the other hand, a predetermined amount of water was prepared, and the above mixture was poured into the water and stirred and kneaded.

After kneading, the obtained slurry is 20HX20BX80Lm
．． The mixture was poured into a mold with dimensions of m and left indoors to solidify and harden.

After 24 hours, the bending strength of the molded body was measured according to JIS-A69.
It was measured according to the test method of No. 04.

The results obtained are shown in Table 7.

For comparison, the results of a test similar to the above using a commercially available β-hemihydrate gypsum plaster for boards in place of the anhydrite composition of the present invention are also listed in Table 7 as a control example.

As is clear from Table 7, when the anhydrous gypsum composition of the present invention is applied to gypsum glass for boards, it is handled in the same way as when commercially available gypsum plaster for boards is used, and the strength of the product is reduced. It can be improved significantly.

Incidentally, the gypsum board produced from the anhydrite composition of the present invention did not exhibit any efflorescence phenomenon even after 3 months had passed.

Claims (1)

[Claims] 1. 100 parts by weight of anhydrite and 0.2 to 0.2 to 100% potassium sulfate
5.0 parts by weight, 0.5 to 10.0 parts by weight of one or more alkaline substances that do not contain sodium atoms, and 5.0 to 23.0 parts by weight of gypsum hemihydrate, as necessary. Anhydrous gypsum composition containing appropriate amounts of known setting retarders, antifoaming agents, dispersants, admixtures, etc. 2. The anhydrite composition according to claim 1, wherein the alkaline substance containing no sodium atoms is slaked lime, quicklime, caustic potash, Bortland cement, or dolomite.