JPH0451502B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a powder coating frit with excellent chemical resistance and hot water resistance, and a powder coating method using this frit. (Prior art) Conventional enamel frits are usually wet-pulverized together with clay to form a glaze, which is applied to the metal surface by dipping, spraying, etc., and then fired. Powder coating, which uses electrostatic voltage to attach metal to metal surfaces, is attracting attention. In this technique, a frit with a high electrical resistance value is used to improve the adhesion of the frit particles, and a powder coating frit whose surface is coated with an organic material with a high electrical resistance value such as alkoxysilane or organopolysiloxane is used. It is used. (for example,
JP-A-52-98721, JP-A-51-7005) (Problems to be Solved by the Invention) However, while such conventional frits for powder coating tend to have a mirror-like glazed surface,
Because of its extremely poor chemical resistance and hot water resistance, it was considered unsuitable for use in vessels used under harsh conditions, such as boilers, bathtubs, and sinks. Accordingly, there has been a need for a powder coating frit that has high adhesion suitable for powder coating and has excellent chemical resistance and hot water resistance, and a powder coating method using the frit. (Means for solving the problem) The present invention essentially contains _Al2O3 in a weight ratio of 4.5 _{to 12.0} %, and the total amount is 4.5 to 35.0% _,
In addition to R ₂ O ₃ components such as B ₂ O ₃ and Sb ₂ O ₃ , the total amount is 0.5~
_Na2O containing no more than 15.5% _Na2O at 30%,
R ₂ O components such as K ₂ O and Li ₂ O, MgO, CaO, ZnO,
RO components such as BaO and SrO, and SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ etc. that essentially contain SiO ₂ and _TiO 2 .
The first invention relates to a frit for powder coating characterized by comprising _two MO components and other subsidiary components added as necessary, and the frit of the first invention is powderized and then A second invention relates to a powder coating method characterized in that the powder coating is applied electrostatically to the surface of a metal substrate. Al ₂ O ₃ essentially contained in the first invention
is a component that increases the chemical resistance and hot water resistance of the frit. If it is less than 4.5%, the desired hot water resistance cannot be obtained, and if it exceeds 12.0%, acid resistance will deteriorate, so it should be in the range of 4.5 to 12.0%. There is a need.
In addition, R ₂ O ₃ components other than Al 2 O ₃ such as B ₂ O ₃ and Sb ₂ O ₃ have the same effect as Al ₂ O ₃ described above, but _the total amount of R ₂ O ₃ components is If it exceeds 35.0%, the acid resistance tends to deteriorate significantly, so the total amount should be reduced to 4.5%.
It needs to be ~35.0%. _Na2O , _K2O , _Li2O
The R ₂ O component is a component for facilitating melting of the frit and lowering the melting point, and it is desirable that the total amount is 0.5% or more. However, if the total amount exceeds 30%, the strength, chemical resistance, and hot water resistance will decrease, so the total amount of R ₂ O components should be in the range of 0.5 to 30%.
In addition, Na ₂ O in the R ₂ O component is a component that affects the electrical properties of the frit, and should be kept at 15.5% or less in order to give the frit stable chargeability and adhesion suitable for powder coating frits. .
RO components such as MgO, CaO, ZnO, BaO, and SrO are generally components to improve the melting properties of frits, but if the total amount exceeds 25%, hot water resistance tends to decrease, so it should be kept at 25% or less. It is preferable. SiO ₂ is the main oxide forming powder coating, and if it is less than 35%, the hot water resistance and acid resistance will deteriorate, and if it exceeds 65%, the frit will become poorly soluble, so it should be kept in the range of 35 to 65%. preferable. Furthermore, TiO ₂ is an essential component for improving acid resistance, and should be included as an essential component. Its preferred content is 3.5-16%. For the same reason, it is desirable that the total amount of _MO2 components such as _SiO2 , _TiO2 , _ZrO2 , _SnO2, etc. be 35 to 85%. In addition, the frit of the present invention contains 0.5 to 10%
F, 10% or less P ₂ O ₅ , 3% or less MoO ₃ etc.
Secondary ingredients including the species or species are added as necessary. F of 0.5% or more is effective in improving the meltability of the frit, but if it exceeds 10%, hot water resistance and acid resistance deteriorate. P ₂ O ₅ is effective in lowering the melting point and has little viscosity drop at high temperatures, so it is a preferred component for obtaining frits that can be fired at low temperatures and are difficult to burn out.
If it exceeds 10%, chemical resistance and hot water resistance will deteriorate. MoO ₃ is a component that improves acid resistance, but
If it exceeds 3%, foreign crystals will occur on the surface, so
% or less. In addition, CoO,
One or more of NiO, MnO ₂ , Cr ₂ O ₃ , Fe ₂ O ₃ , CuO, V ₂ O ₅ and the like is externally added in a total amount of 12% or less. The frit of the present invention having the above composition exhibits excellent adhesion when powder coated, as is clear from the examples described below, and has excellent chemical resistance and hot water resistance. By pulverizing it and electrostatically attaching it to the surface of a metal base, it is possible to obtain an excellent enamel product that can withstand harsh usage conditions. (Example) Raw materials were prepared to have the compositions of Examples 1 to 10 and Comparative Examples 11 to 24 in Table 1, melted at 1200 to 1300°C, and rapidly cooled to produce frits. These frits of Examples 1 to 30 and Comparative Examples 11 to 17 were treated with a coupling agent to make powder coating frits, and then applied to a steel plate on which a lower glaze had been baked using an electrostatic powder gun. It was glazed and fired by applying an electrostatic voltage of 100kV. On the other hand, the frits of Comparative Examples 18 to 24 included 100 parts by weight of the frit, 6 parts of clay, and 0.2 parts of potassium chloride.
45 parts of water were added and milled, and the slip of 50 c.c. was adjusted so that 5 g remained on a 200 mesh sieve.The slip was then glazed on a similar steel plate by spraying, dipping, etc., and dried. Fired. The acid resistance spot test, weight loss acid resistance test, weight loss resistance test, and weight loss hot water resistance test were conducted on each test piece obtained in this way. As shown in Table 2, the frits of Examples 1 to 12 were showed excellent properties. In addition, each test method is as follows.

【table】

【table】

【table】

[Table] (1) Acid resistance spot test A 10% citric acid solution was applied to a 3-ply filter paper of 3 x 3 cm placed on a test piece using a method similar to the room-temperature spot test method using citric acid in JIS R 4301 5.9.1. Drop it from above with a dropper to sufficiently moisten the filter paper, leave it at room temperature for 15 minutes, and evaluate the change in surface gloss. (2) Mass loss acid resistance test Using a test device based on ISO-2733, the test piece was placed in 450 ml of a 6% citric acid solution and kept in a boiling state for 6 hours, and then the weight loss value of the enamel layer (liquid phase test piece) was measured. Measure. The measured value is the average value of three test pieces and is expressed in units of g/m ² . (3) Mass loss hot water resistance test Using the same test equipment as in (2), the test piece was placed in 450 ml of pure water and kept in a boiling state for 48 hours, then the weight loss value of the enamel layer of the liquid phase test piece and the gas phase test piece was determined. Measure. The measured value is the average value of 3 test pieces, g/m ² /
Shown in units of day. The numerator is the data for the liquid phase test piece, and the denominator is the data for the gas phase test piece. (4) Weight loss resistance test Using a test device based on ISO-2734, place the test piece in a 5% sodium pyrophosphate solution at 90℃±
The weight loss value of the enamel layer (liquid phase test piece) is measured after being kept in a constant temperature bath at 1° C. for 6 hours. The measured value is 3
The average value of the specimens is taken and expressed in g/m ² . (5) Adhesion evaluation Powdered frit is 100mm x 100mm x 1.2tmm
The frit was electrostatically attached to a steel plate for enameling, and an impact of 0.28 kg/cm ² was applied without firing, and the amount of the frit falling was measured, and the percentage of the frit that did not fall was expressed as a percentage. (Effects of the Invention) As is clear from the explanation of the above examples, the powder coating frit of the present invention has excellent adhesion suitable for powder coating, and has excellent chemical resistance and hot water resistance. Therefore, according to the powder coating method using this frit, it is possible to produce an enamel product having an enamel layer with excellent chemical resistance and hot water resistance. Therefore, according to the present invention, it is possible to easily enamel boilers, bathtubs, sinks, etc., to which powder coating methods could not be used in the past, using powder coating methods. Therefore, the present invention eliminates the problems of the prior art and greatly contributes to the development of industry.

Claims (1)

[Claims] 1. Al ₂ O ₃ , B ₂ O ₃ , which essentially contains 4.5 to 12.0% Al ₂ O ₃ by weight, and the total amount is 4.5 to 35.0%;
In addition to _R2O3 components such _{as Sb2O3} , the total amount is 0.5-30% _.
Na2O , _K2O containing up to 15.5% _Na2O ,
R ₂ O components such as Li ₂ O, MgO, CaO, ZnO, BaO,
RO components such as SrO, MO ₂ components such as SiO _{2 ,} TiO ₂ , ZrO ₂ , SnO ₂ that essentially contain SiO 2 and TiO ₂ , and other secondary components added as necessary. A frit for powder coating, characterized by comprising: 2 The total amount of RO components is 25% or less, and MO ₂
The total amount of components is 35-85%, containing 35-65% _SiO2 , and the secondary components are 0.5-10% F and 10
% or less of P ₂ O ₅ and 3% or less of MoO ₃ . 3 As pigments, CoO, NiO, MnO ₂ , Cr ₂ O ₃ ,
The frit for powder coating according to claim 1 or 2, wherein one or more of Fe ₂ O ₃ , CuO, and V ₂ O ₅ is externally added in a total amount of 12% or less. 4 Al2O3, _B2O3 , which essentially contains 4.5 to _12.0 % _Al2O3 by weight, _and the total amount is 4.5 to _35.0 % _;
In addition to _R2O3 components such _{as Sb2O3} , the total amount is 0.5-30% _.
Na2O , _K2O containing up to 15.5% _Na2O ,
R ₂ O components such as Li ₂ O, MgO, CaO, ZnO, BaO,
RO components such as SrO, MO ₂ components such as SiO _{2 ,} TiO ₂ , ZrO ₂ , SnO ₂ that essentially contain SiO 2 and TiO ₂ , and other secondary components added as necessary. A powder coating method characterized by pulverizing a powder coating frit made of powder and then electrostatically adhering it to the surface of a metal substrate.