JPH11139847A - Frit for porcelain enamel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide frit for porcelain enamel, which is capable of being subjected to such low temp. firing as to be applicable to a plated steel sheet and an enameled product with which has excellent chemical durability and good surface performance. SOLUTION: This frit consists of P2 O5 , Sb2 O3 , Al2 O3 and B2 O3 and also contains: at least one compound selected from Na2 O, K2 O and Li2 O; at least one compound selected from ZnO, BaO, CaO and SrO; and at least one compound selected from TiO2 , SiO2 , and ZrO2 ; wherein the contents of the respective compounds in the frit are represented by the following composition A or composition B of the frit. The composition A comprises: 45 to 65 wt.% of P2 O5 ; 5 to 15 wt.% of Sb2 O3 ; 2 to 10 wt.% of Al2 O3 0.5 to 5 wt.% of B2 O3 ; Na2 O, K2 O and Li2 O in such a total content as to meet the formula 7 wt.%<(Na2 O+K2 O+Li2 O)<15 wt.%; ZnO, BaO, CaO and SrO in such a total content as to meet the formula 7 wt.%<=(ZnO+BaO+CaO+ SrO)<=20 wt.%; and TiO2 , SiO2 and ZrO2 in such a total content as to meet the formula 1 wt.%<=(TiO2 +SiO2 +ZrO2 )<=10 wt.%. The composition B comprises: 50 to 65 wt.% of P2 O5 ; 7 to 12 wt.% of Sb2 O3 ; 3 to 8 wt.% of Al2 O3 ; 0.5 to 4 wt.% of B2 O3 ; Na2 O, K2 O and Li2 O in such a total content as to meet the formula 11.5 wt.%<=(Na2 O+K2 O+Li2 O)<=13 wt.%; ZnO, BaO, CaO and SrO in such a total content as to meet the formula 11 wt.%<=(ZnO+BaO+ CaO+SrO)<=14 wt.%; and TiO2 , SiO2 and ZrO2 in such a total content as to meet the formula 1 wt.%<=(TiO2 +SiO2 +ZrO2 )<=8 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frit for enamel which can be baked at a low temperature and which has excellent chemical durability of the resulting enamel product.

[0002]

2. Description of the Related Art An enamel is generally obtained by baking inorganic glass powder as a glaze at a high temperature on a metal such as iron, and forming a glass coating having excellent surface performance on a metal substrate. Conventionally, the baking temperature of enamel is 800.
Since the temperature is as high as 900 ° C., there are the following problems (1) and (2), and an enamel frit that can be baked at a low temperature is required.

(1) When baking on a thin steel sheet, the dimensional accuracy of the product cannot be obtained because the deformation of the steel sheet due to heat increases. (2) When a plated steel sheet is used, the plating layer melts and flows down due to high temperatures. For this reason, in recent years, studies have been made on enamel frit that can be baked at a low temperature, and a firing temperature of 670 using an SiO ₂ frit has been studied.
° C or an aluminum-plated steel plate-enamel at a firing temperature of 500 to 540 ° C using a P ₂ O ₅ frit (see Japanese Patent Publication No. 6-43256). Thus, frit for enamel which can be baked even at low temperature has been developed.

The above SiO ₂ frit has a firing temperature of 67 ° C.
Since it can be fired at a lower temperature than 0 ° C and the conventional frit for enamel, the problem such as deformation of the steel plate can be improved.
With such a sintering temperature, problems such as run-down of the plating layer on the plated steel sheet cannot be avoided. For this reason,
Another frit for enamel is required to enable firing at a lower temperature.

On the other hand, in the case of the above-mentioned P ₂ O ₅ type frit, 50
Although enamels with excellent surface performance can be obtained even at a firing temperature as low as 0 to 540 ° C, chemical properties such as acid resistance and alkali resistance required for enamel products and resistance to weathering due to reaction with water, etc. can be obtained. The mechanical durability was not satisfactory.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and is a frit for enamel that can be used at low temperature and can be used for plated steel sheets. An object of the present invention is to provide a frit for enamel having excellent properties and excellent surface performance.

[0007]

Means for Solving the Problems The present inventors have studied and tested various compositions in order to solve the above-mentioned problems. As a result, the frit for enamel having the following composition has a firing temperature of 530 ° C.
The present inventors have found that the enamel is a frit for enamel which can be baked at a low temperature as described below and has excellent chemical durability and surface performance of the obtained enamel, and has reached the first invention described below.

That is, in the first invention, at least P ₂
O ₅ , Sb ₂ O ₃ , Al ₂ O ₃ and B ₂ O ₃ and Na ₂ O, K ₂ O and Li
_At least one selected from ₂ O, ZnO, BaO, CaO and Sr
A frit for enamel, comprising one or more selected from O ₂ and one or more selected from TiO ₂ , SiO ₂ and ZrO ₂ , wherein the components are contained at the following contents.

P ₂ O ₅ : 45 to 65 wt% Sb ₂ O ₃ : _{5 to} 15 wt% Al ₂ O ₃ : _{2 to} 10 wt% B ₂ O ₃ : 0.5 to 5 wt% 7 wt% ≦ Na ₂ O + K ₂ O + Li ₂ O <15 wt% 7 wt% ≦ ZnO + BaO + CaO + SrO ≦ 20 wt% 1 wt% ≦ TiO ₂ + SiO ₂ + ZrO ₂ ≦ 10 wt% Further, the present inventors have found that the deterioration of the design due to the change in appearance at the time of baking of the enamel on the plated steel sheet is also considered. To prevent this, it was found that the baking temperature had to be 520 ° C. or lower, and furthermore, the firing temperature was studied to be lower. As a result, the following second invention was reached.

[0010] That is, the second invention comprises at least P ₂
O ₅ , Sb ₂ O ₃ , Al ₂ O ₃ and B ₂ O ₃ and Na ₂ O, K ₂ O and Li
_It contains one or more selected from ₂ O, one or more selected from ZnO, BaO and CaO, and one or more selected from TiO ₂ , SiO ₂ and ZrO _2, and the components are contained at the following contents. It is a frit for enamel characterized by containing. P ₂ O ₅ : 50 to 65 wt% Sb ₂ O ₃ : 7 to 12 wt% Al ₂ O ₃ : _{3 to} 8 wt% B ₂ O ₃ : 0.5 to 4 wt% 11.5 wt% ≦ Na ₂ O + K ₂ O + Li ₂ O ≦ 13 wt % 11wt% ≦ ZnO + BaO + CaO ≦ 14wt% 1wt% ≦ TiO ₂ + SiO ₂ + ZrO ₂ ≦ 8wt%

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described as a first invention and a second invention.
The invention will be described in more detail in the order of the invention. [First invention:] The reason why the compounding ratios of the various oxides described above in the present invention are limited to the compounding ratios described above will be described.

First, P ₂ O ₅ constitutes the enamel glass of the present invention and is formed in a mesh. P ₂ O _5, from the viewpoint of enamel baked at low temperatures, it is necessary that the content is in the range of 45~65wt%. That is, the content of P ₂ O ₅ was 45 wt.
%, The baking temperature of the glass increases,
When the baking at a low temperature of not more than 65 ° C. becomes impossible, and when the amount exceeds 65 wt%, the solidification of the slip occurs during the ball mill pulverization in the production of the slip.

Since P ₂ O ₅ contains a simple double bond oxygen, P ₂ O ₅ has low chemical durability and high volatility as it is. For this reason, the properties required for the enamel can be exhibited by adding the following components. Sb ₂ O ₃ is a component that affects the chemical resistance of the enamel, and has a content of 5 to 15 wt%.
Must be within the range.

When the content of Sb ₂ O ₃ is less than 5% by weight, the baking temperature of the enamel becomes high, and low-temperature baking below 530 ° C. cannot be performed. Conversely, when the content exceeds 15% by weight, the chemical resistance of the enamel decreases. Not demonstrated. Also, Al ₂ O ₃ is a mechanical property of enamel,
A component that affects chemical resistance and has a content of 2
It must be in the range of 10 wt%.

That is, when the content of Al ₂ O ₃ is less than 2 wt%, the mechanical properties and chemical resistance of the enamel are not exhibited,
Conversely, if it exceeds 10 wt%, the baking temperature of the enamel will increase,
Low-temperature baking below 530 ° C is not possible. Next, B ₂ O ₃
Is a component that has an effect on lowering the baking temperature of the enamel and on the gloss. Its content must be in the range of 0.5 to 5% by weight.

That is, when the content of B ₂ O ₃ is less than 0.5 wt%, the gloss of the enamel is reduced, and the baking temperature is increased, so that low-temperature baking at 530 ° C. or less cannot be performed.
If it exceeds wt%, the acid resistance is poor, and the chemical resistance deteriorates. Na ₂ O, K ₂ O and Li ₂ O are components that affect the lowering of the enamel baking temperature, gloss and chemical resistance, and are selected from Na ₂ O, K ₂ O and Li ₂ O. It is necessary that the total content of one or more of the components is not less than 7 wt% and less than 15 wt%.

That is, when the total content of the above three components is less than 7% by weight, the gloss of the enamel is reduced, and the baking temperature is increased, so that low-temperature baking at 530 ° C. or less cannot be performed. If so, the chemical resistance of the enamel will decrease. Next, ZnO, BaO, CaO, and SrO are components that affect the chemical resistance, mechanical properties, and coefficient of thermal expansion of the enamel, and a total content of at least one selected from ZnO, BaO, CaO, and SrO. It is necessary that the rate be 7 wt% or more and 20 wt% or less.

That is, if the total content of the above four components is less than 7% by weight, the enamel cannot exhibit its chemical resistance and mechanical properties. Conversely, when the total content of the above four components exceeds 20 wt%, the baking temperature of the enamel increases,
Low-temperature baking at 530 ° C. or lower becomes impossible, and the thermal expansion coefficient of the enamel is increased, and a crack is generated in the enamel due to a difference from a linear expansion coefficient of a metal plate such as a steel plate.

[0019] Finally, TiO _2, SiO _2, ZrO ₂ is chemical resistant enamel, are components that influence the mechanical properties, TiO _2,
The total content of at least one selected from SiO ₂ and ZrO ₂ is 1
It is necessary that the content is not less than wt% and not more than 10 wt%. That is, when the total content of the above three components is less than 1 wt%,
The enamel's chemical resistance and mechanical properties are not exhibited.
If it exceeds wt%, the baking temperature of the enamel becomes high, 530 ℃
The following low-temperature baking cannot be performed.

[Second invention:] By the first invention, which can be baked at a low temperature of 530 ° C. or less, it is possible to prevent the plating layer from flowing down during the enamel baking on the plated steel sheet and to prevent the adhesion of the plating from lowering. However, there were cases where the appearance changed during baking and the design property was reduced.

The present inventors have conducted various experiments to prevent the above-mentioned change in the plating layer, and as a result, have found that it is necessary to set the baking temperature of the enamel on the plated steel sheet to 520 ° C. or less. As a result of repeated tests, it was found that an enamel frit having the following composition can be baked at a low temperature of 520 ° C. or less, and that the resulting enamel has excellent chemical durability and excellent surface performance. Invented the invention.

The reason why the mixing ratios of the various oxides described above in the present invention are limited to the above-described mixing ratios will be described. In the following second invention, a second embodiment described later is used.
As shown in the figure, the softening temperature of the frit for enamel, which is a representative characteristic value of the baking temperature, is used as the representative characteristic value of chemical durability. Explanation will be made using acid resistance which is a rate.

First, P ₂ O ₅ constitutes the enamel glass of the present invention and is formed in a mesh. We have:
As a result of various examinations and experiments, the content of P ₂ O ₅ was reduced to 50 wt%.
As described above, it was found that as the content increased, both the softening temperature of the frit for enamel and the weight reduction rate after immersion of the frit for enamel after baking in an acidic solution decreased.

On the contrary, if the P ₂ O ₅ content exceeds 65 wt%, the solidification of the slip occurs during the ball mill pulverization in the production of the slip. In other words, in order to obtain the enamel having excellent acid resistance may been possible low temperature sintering, in the present invention, defining the P ₂ O ₅ content of the 50~65wt%. Next, FIG.
The relationship between the content of Sb ₂ O ₃ , the softening temperature of the frit for enamel, and the weight reduction rate after the acid resistance test of the frit for enamel after firing is shown.

As shown in FIG. 1, when the content of Sb ₂ O ₃ is large, the frit for enamel can be fired at a low temperature, but the acid resistance does not satisfy the target value. The acid resistance was supplemented by the component adjustment described below, and the Sb ₂ O ₃ content was specified to be 7 to 12 wt% as a component composition that can be fired at a low temperature and has excellent acid resistance. In particular, if the Sb ₂ O ₃ content is in the range of 8 wt% or more and 9.5 wt% or less, it can be fired at low temperature and exhibits acid resistance.

Sb ₂ O ₃ for lowering the firing temperature described above
To compensate for the decrease in acid resistance with the increase in the content, Al ₂ O ₃
Is specified as 3 wt% or more. Al ₂ O ₃ content 3wt
%, The acid resistance is not satisfied. Conversely, if the Al ₂ O ₃ content exceeds 8 wt%, the firing temperature of the enamel increases,
Baking at 520 ° C becomes impossible.

That is, in order to obtain an enamel that can be fired at a low temperature and has excellent acid resistance, in the present invention, Al is used.
_{The 2} O ₃ content was specified as ₃ to 8 wt%. In particular, if the Al ₂ O ₃ content is in the range of 4% by weight or more and 6% by weight or less, low-temperature sintering is possible and acid resistance is exhibited. Next, the B ₂ O ₃ content is 0.
It needs to be in the range of 5 to 4% by weight.

That is, if the B ₂ O ₃ content is less than 0.5, the firing temperature of the enamel becomes high, and firing at 520 ° C. becomes impossible. On the contrary, if it exceeds 4 wt%, the acid resistance is not satisfied. In particular, when the B ₂ O ₃ content is in the range of 0.5 wt% or more and 2 wt% or less, the composition can be fired at a low temperature and exhibits acid resistance. Also,
It is necessary that the total content of at least one selected from Na ₂ O, K ₂ O and Li ₂ O is in the range of 11.5 wt% or more and 13 wt% or less.

If the amount is less than 11.5% by weight, the firing temperature of the enamel becomes high, so that the firing at 520 ° C. becomes impossible. On the other hand, if it exceeds 13% by weight, the acid resistance is not satisfied. Next, ZnO, BaO and
The total content of at least one selected from CaO is 11 wt% or more,
It is necessary to be in the range of 14 wt% or less. That is,
If it is less than 11 wt%, the firing temperature of the enamel becomes high, and 520 ℃
Sintering cannot be performed. Conversely, if it exceeds 14% by weight, the acid resistance is not satisfied.

Finally, it is necessary that the total content of at least one selected from TiO ₂ , SiO ₂ and ZrO ₂ is in the range of 1 wt% to 8 wt%. If the amount is less than 1% by weight, the acid resistance is not satisfied. On the other hand, if it exceeds 8% by weight, the sintering temperature of the enamel becomes high, and the sintering at 520 ° C. becomes impossible.
In particular, if the total content of at least one selected from TiO ₂ , SiO ₂ and ZrO ₂ is in the range of 3% by weight or more and 6% by weight or less, it can be fired at a low temperature and exhibits acid resistance.

The mixing ratios of the various oxides according to the first and second inventions of the present invention and the reasons for limiting them have been described above. As the required characteristics for the frit for enamel,
In addition to low softening temperature, variable surface gloss, and chemical resistance (acid resistance and alkali resistance), a low coefficient of thermal expansion and excellent mechanical properties are essential. If you use an enamel frit that satisfies the composition range,
Problems such as peeling and cracking of the enamel do not occur.

[Raw material and method for producing an enamel frit of the present invention:] A composition constituting an enamel glaze that can be baked at a low temperature according to the first and second inventions (both are hereinafter collectively referred to as the present invention). Any material may be used as long as it produces the above-mentioned various oxides or a mixture of these oxides by firing.

For example, ammonium monohydrogen phosphate, sodium monohydrogen phosphate, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, aluminum oxide, antimony oxide, (anhydrous) boric acid, sodium carbonate, sodium silicate, potassium carbonate , Lithium carbonate, zinc oxide, barium carbonate, calcium carbonate, strontium carbonate, titanium oxide, (anhydrous) silicic acid, zirconium oxide, zircon, and the like.

Next, a method for producing an enamel frit capable of low-temperature baking according to the present invention will be described. That is, the frit for enamel that can be baked at a low temperature according to the present invention is manufactured, for example, as follows. (1) appropriately selecting and weighing the raw materials from the raw materials exemplified above,
They are sufficiently crushed and mixed.

(2) The mixture is heated and fired in a furnace to be melted. In the steps (1) and (2),
The blended raw materials may be melted without pulverization. (3) In the final stage of melting, at a temperature of 800 to 1200 ° C, 30
The melting is performed at a temperature of 1000 to 1150 ° C. for 30 minutes to 2 hours.

In this case, if necessary, stirring may be carried out on the way. (4) Pre-firing may be performed as necessary when melting. That is, when performing the above-mentioned pre-firing, for example,
When an ammonium salt such as ammonium monohydrogen phosphate is used, it is first thoroughly mixed at room temperature. Then 150-500
The reaction is carried out at a temperature of 30 ° C. for 30 minutes to 3 hours to degas ammonia.

The solid obtained as described above is subsequently pulverized, and the above-mentioned (3) is melted. If you do this,
Since degassing hardly occurs at the time of melting, the work can be performed safely without the raw material spilling out of the crucible, and a frit for enamel having a predetermined composition can be accurately produced. Except for the case where an ammonium salt is used as the above-mentioned raw material, for the same reason as above, when a powder containing water or a carbonate is used as a raw material, the above-mentioned pre-baking treatment (4) is performed before melting. Is preferred.

(5) The obtained melt is thrown into water or poured onto a thick iron plate and rapidly cooled at once. This is because quenching results in a pulverized glass-like frit, which facilitates pulverization in the next step. (6) The obtained frit is finely pulverized using a ball mill, a pot mill, a vibration mill, a crusher or the like.

Thus, the desired low melting point frit for enamel is obtained. [Method of coating enamel frit of the present invention on metal plate:] Next, a method of coating the metal plate with the enamel frit obtained as described above will be described. That is, the frit for enamel that can be baked at a low temperature obtained as described above is added to frog-eye (gairome) clay, bentonite, ammonium alginate, sodium hexametaphosphate, sodium tripolyphosphate, sodium pyrophosphate, tripotassium phosphate, and hydrogen phosphate. Additives such as various phosphates such as disodium, a coloring pigment, and water are added to produce a slip by, for example, ball milling.

The obtained slip is glazed on a metal plate using a dipping method, a flow coating method, a spray method, an electrostatic spraying method or the like.
Bake at a temperature of not more than 520 ° C, more preferably at most 520 ° C. In this case, there is no effect on the characteristics and appearance of the enamel whether or not a drying step is performed between the glaze and the firing.

As the metal plate, not only an uncoated metal plate such as a normal steel plate and an aluminum plate, but also a plated steel plate such as an aluminum-plated steel plate, an aluminum-zinc alloy-plated steel plate, and a zinc-iron alloy-plated steel plate can be used. The above description has been given of an example in which an enamel product is manufactured by coating a metal plate with an enamel frit that can be baked at a low temperature, but the enamel frit of the present invention is applied to a base made of a material other than the metal plate. Coating is, of course, possible.

As described above, the frit for enamel of the present invention (the frit for enamel of the first invention and the frit for enamel of the second invention) which can be baked at a low temperature has a baking temperature.
Since it is very low at 530 ° C. or less, according to the present invention, when baked on a thin steel sheet, almost no thermal deformation of the steel sheet occurs, and an enamel product with high dimensional accuracy can be manufactured. Also,
The frit for enamel that can be baked at a low temperature according to the present invention has a very low baking temperature of 530 ° C. or less, so that even when baked on a galvanized steel sheet such as a galvanized steel sheet, the problem due to melting of the plating layer can be avoided.

Further, the frit for enamel of the present invention which can be baked at a low temperature does not contain harmful substances such as heavy metals.
No harm or recycling problems. Further, as shown in the following examples, by using the frit for enamel of the present invention, the resulting enamel product is excellent in chemical durability, which is defined as a quality standard of the enamel product, particularly excellent in acid resistance. The above-mentioned object of the present invention has been solved.

Further, according to the frit for enamel according to the second invention, since the baking temperature is very low at 520 ° C. or less, it is possible to avoid a change in the plating layer when the enamel is baked on the plated steel sheet. As a result, it is possible to prevent the design of the enameled steel plate from deteriorating due to a change in appearance.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. [Example 1] (First invention) Ammonium monohydrogen phosphate, aluminum oxide, antimony oxide, boric anhydride, sodium carbonate, potassium carbonate, lithium carbonate, zinc oxide, barium carbonate, calcium carbonate, strontium carbonate, titanium oxide , Silicic anhydride, and zirconium oxide as raw materials, the following (1) →
In the manufacturing process of (5), enamel frits having various compositions shown in Table 1 were manufactured (Examples 1 to 8 of the present invention and Comparative Examples 1 to 8).

(1) Raw materials were selected, weighed, and blended so as to obtain a target composition from the above-mentioned raw materials, and thoroughly mixed at room temperature. (2) The obtained mixture was reacted at a temperature of 350 ° C. for 2 hours to remove ammonia. (3) The obtained solid was pulverized, heated and fired in a furnace, melted and stirred.

In the final stage of melting, at a temperature of 1100 ° C.,
Melted for 1 hour. (4) The obtained melt was poured into water, rapidly cooled, and a glassy frit in a crushed state was obtained. (5) The obtained frit was finely pulverized using a pot mill to obtain a frit for enamel.

Next, based on 100 parts by weight of the enamel frit having the composition shown in Table 1, 20 parts by weight of rutile-based titanium oxide was blended as a titanium pigment as a main component.
A slip was prepared by adding 1 part by weight of a dispersant (: sodium pyrophosphate) and 35 parts by weight of water. Each slip was glazed on the surface of the galvannealed steel sheet and fired at 530 ° C. to form an enamel layer having a thickness of 50 μm.

The performance of the obtained enamel product was evaluated based on the following performance evaluation method. [Performance Evaluation Method:] (Appearance;) The state of the enamel layer of the enamel product was visually observed and evaluated according to the following criteria. ：: Enamel layer surface has sufficient gloss ×: Enamel layer surface has insufficient gloss (acid resistance;) Room temperature spot test with citric acid specified in JIS-R 4301-1978 “Enamel product quality standards”
10% citric acid, 15 minutes spot), the surface erosion degree was determined by the same test method AA class, A class, B class, C class,
Judgment was made in five stages of D class.

(Alkali resistance;) Based on the alkali resistance test (10% sodium carbonate, 15 minute spot) specified in JIS-R 4301-1978 "Enamel product quality standards"
The degree of surface erosion was determined based on the following criteria. ：: Neither discoloration nor a pencil line mark was observed.

Δ: Either discoloration or a pencil line mark is seen. X: Both discoloration and a pencil line mark are seen. The performance evaluation results of the obtained enamel product are shown in Table 1 together with the composition of the frit for enamel used (Examples 1 to 8 of the present invention and Comparative Examples 1 to 8). As is clear from Table 1, the enamel products of the comparative examples manufactured using the enamel frit that does not satisfy the composition range of the first invention have poor appearance and poor acid resistance or poor acid resistance. The enamel products of the examples manufactured using the frit for enamel which satisfies the composition range of the present invention are all excellent in appearance, acid resistance and alkali resistance, and are sufficiently excellent even at low temperature baking at 530 ° C. It can be seen that an enamel product of high quality can be obtained.

Since the enamel frit of the present invention is particularly excellent in the acid resistance of the enamel product obtained, it can be used for the production of enamel products in various fields including the field of enamel products requiring acid resistance of A class or higher. It can be used as a frit for enamel.

[0053]

[Table 1]

Example 2 (Second Invention) In this experiment, the following simple experiment method was employed to determine the composition of the frit for enamel. this is,
This is because the ordinary enamel experiment described above requires a long process as shown in FIG. 2, requires a long period of time and many trial production costs, and allows the experiment to proceed efficiently in a short period of time.

The frit obtained in the same manner as in Example 1 was finely pulverized using a pot mill to obtain enamel frit having the composition shown in Table 2 (Examples 9 to 29 of the present invention and Comparative Examples 9 to 2).
8). The obtained frit for enamel was evaluated based on the following performance evaluation method. [Performance evaluation method:] (Measurement of softening temperature;) A frit for enamel was pulverized, and a powder on a sieve having a mesh size of 44 µm was used under a sieve having a mesh size of 74 µm.

A test cone was prepared from the above powder in accordance with JIS R 2204, “Testing method for fire resistance of refractory bricks”. The temperature at which the tip of the test cone contacted the cradle by heating was defined as the "softening temperature". From various butting experiments prior to this test, it was found that the softening temperature should be 480 ° C. or less to enable enamel firing at 520 ° C. or less.

(Measurement of Chemical Resistance) The prepared frit for enamel was baked into pellets and immersed in an acidic solution (18% hydrochloric acid aqueous solution) or an alkaline solution (20% sodium hydroxide aqueous solution) for 1 hour, before and after the test. Was evaluated by the rate of weight loss of the pellets. In addition, from various butting tests prior to this test, in order to make the surface erosion resistance (remaining gloss ratio) in the normal temperature spot test with citric acid specified in JIS R 4301-1978 above AA class or higher. Indicates that the weight loss rate of the pellet before and after the immersion in the acidic solution is 2%.
% Or less.

The frit for enamel of the present invention had a weight reduction rate of 1% or less when immersed in an alkaline solution. That is, the frit for enamel of the present invention shows no decrease in gloss in the alkali resistance test. The performance evaluation results of the obtained enamel frit are shown in Table 2 together with the composition of the enamel frit (Examples 9 to 29 of the present invention and Comparative Example 9).
~ 28).

The target softening temperature is 480 ° C. or lower as described above, and the target chemical resistance (acid resistance,
The weight loss rate in the (alkali resistance) test is 2% or less. As is clear from Table 2, in the case of the frit for enamel of the comparative example which does not satisfy the composition range of the second invention, the softening temperature is higher than the target value of 480 ° C. or the weight of the pellet before and after immersion in the acidic solution. The reduction rate is higher than 2% of the target value.

On the other hand, in the examples satisfying the composition range of the second invention, these target values were all achieved, and an enamel product which sufficiently satisfies the enamel properties even at a low baking temperature of 520 ° C. It can be seen that it can be obtained. In particular, in Examples 20, 21, 23, 26, and 27 of the present invention, the softening temperature was 480 ° C. or less, and the weight loss rate of the pellet before and after immersion in the acidic solution was 1% or less.

Next, using the enamel frit of Examples 9 to 29 of the present invention, a Zn-Al alloy-plated steel sheet containing 55% of aluminum was enameled to evaluate its characteristics. The enameling conditions in this evaluation experiment were as follows. That is, as a main component, 20 parts by weight of rutile-based titanium oxide is blended as a titanium pigment with respect to 100 parts by weight of an enamel frit, 1 part by weight of a dispersant (: sodium pyrophosphate), and 35 parts by weight of water. Was added and slipping was performed by ball mill pulverization.

Next, each slip was glazed on the surface of the Zn-Al alloy-plated steel plate and baked at 480-520 ° C. to form an enamel layer having a thickness of 30-40 μm. Next, as a result of evaluating the characteristics of the obtained enamel-plated steel sheet, the enamel-plated steel sheet had properties at least equivalent to those of a normal enamel-plated steel sheet.

[0063]

[Table 2]

[0064]

[Table 3]

[0065]

The frit for enamel of the present invention can be baked at a low temperature and can be applied to plated steel sheets. Further, the resulting enamel product has excellent chemical durability, especially excellent acid resistance, and good surface performance. Also, since it does not contain harmful substances such as Pb, it exhibits excellent performance as an enamel frit for enamel products in various fields.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the content of Sb ₂ O ₃ , the softening temperature of an enamel frit, and the weight loss rate of an enamel frit after firing after an acid resistance test.

FIG. 2 is an explanatory view showing steps of an enamel experiment.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masato Kumagai 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Corp. (72) Kyoko Hamahara 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki (72) Inventor Toshihide Suzuki 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Pref. (72) Inventor Koji Watanabe 2-18-13 Higashi-Narashino, Narashino-shi, Chiba (72) Inventor Hiroshi Nagaishi 2-18-13 Higashi-Narashino, Narashino-shi, Chiba Pref.Institute of Technology (72) Inventor Fusao Togashi 2-18-13, Higashi-Narashino, Narashino-shi, Chiba Construction Materials Co., Ltd.

Claims (2)

[Claims] At least one of P ₂ O ₅ , Sb ₂ O ₃ , Al ₂ O ₃ and B ₂ O ₃ , at least one selected from Na ₂ O, K ₂ O and Li ₂ O, ZnO, BaO A frit for enamel, comprising at least one selected from CaO and SrO, and at least one selected from TiO ₂ , SiO ₂ and ZrO ₂ , and containing these components at the following contents. Note P ₂ O ₅ : 45 to 65 wt% Sb ₂ O ₃ : _{5 to} 15 wt% Al ₂ O ₃ : _{2 to} 10 wt% B ₂ O ₃ : 0.5 to 5 wt% 7 wt% ≦ Na ₂ O + K ₂ O + Li ₂ O <15 wt % 7wt% ≦ ZnO + BaO + CaO + SrO ≦ 20wt% 1wt% ≦ TiO ₂ + SiO ₂ + ZrO ₂ ≦ 10wt% 2. At least one selected from P ₂ O ₅ , Sb ₂ O ₃ , Al ₂ O ₃ and B ₂ O ₃ , at least one selected from Na ₂ O, K ₂ O and Li ₂ O, ZnO, BaO And one or more selected from CaO and Ti
Containing at least one selected from O ₂ , SiO ₂ and ZrO ₂ ,
A frit for enamel, comprising the following components: Note P ₂ O ₅ : 50 to 65 wt% Sb ₂ O ₃ : 7 to 12 wt% Al ₂ O ₃ : _{3 to} 8 wt% B ₂ O ₃ : 0.5 to 4 wt% 11.5 wt% ≦ Na ₂ O + K ₂ O + Li ₂ O ≦ 13wt% 11wt% ≦ ZnO + BaO + CaO ≦ 14wt% 1wt% ≦ TiO ₂ + SiO ₂ + ZrO ₂ ≦ 8wt%