Glass lining, method for manufacturing glass lining and method for cleaning glass-lined articles

Abstract

A glass lining that has an excellent balance between a hydrophilic property and a hydrophobic property on its surface, that has less adhesion of dirt than a typical GL since having an excellent stain-proof property against both oily stains and aqueous stains, and that can maintain the stain-proof property and the self-cleaning performance for a long time after the glass lining is cleaned, leading to excellent cleaning performance and low dirt-adhesion. The glass lining includes a lining and a conductive inorganic compound contained in the lining. The glass lining is structured to have a plurality of hydrophilic concave portions and net-like hydrophobic convex portions connecting peripheries of the plurality of hydrophilic concave portions.

Claims

1. A glass lining comprising a lining and a conductive inorganic compound contained in the lining and having a structure comprising: a plurality of hydrophilic concave portions; and net-like hydrophobic convex portions connecting peripheries of the plurality of hydrophilic concave portions.

2. The glass lining according to claim 1, wherein the conductive inorganic compound is acicular conductive antimony-containing tin oxide.

3. The glass lining according to claim 1, wherein an average diameter of the concave portions ranges from 10 m to 60 m, and a difference in height between the concave portions and the convex portions ranges from 1 m to 3 m.

4. The glass lining according to claim 1, wherein a contact angle of water on the glass lining is 30 degrees or less.

5. A manufacturing method of the glass lining according to claim 1, the method comprising: providing a slip comprising a glass frit having a glass particle diameter ranging from 30 m to 70 m before the slip is used for a glass lining; and adding and mixing 3 parts by weight to 6 parts by weight of a conductive inorganic compound per 100 parts by weight of the glass frit after elapse of 40% to 75% of a total mill-grinding time.

6. A cleaning method of glass-lined equipment comprising the glass lining according to claim 1, the method comprising: irradiating the glass-lined equipment with an ultraviolet ray having an intensity ranging from 0.2 mW/cm.sup.2 to 10 mW/cm.sup.2.

Description

BRIEF DESCRIPTION OF DRAWING(S)

(1) FIG. 1 shows a test piece in Example 3, a surface of which is magnified 200 times.

(2) FIG. 2 shows the test piece in Example 3, the surface of which is magnified 500 times.

(3) FIG. 3 shows transition of contact angles of each of the test pieces after oily stains thereof is cleaned in Examples 1 to 3.

(4) FIG. 4 shows transition of contact angles of each of the test pieces after aqueous stains thereof is cleaned in Examples 1 to 3.

(5) FIG. 5 shows transition of contact angles of each of the test pieces after oily stains thereof is cleaned and irradiated with a small amount of ultraviolet ray in Examples 1 to 3.

DESCRIPTION OF EMBODIMENT(S)

(6) Exemplary embodiment(s) of the invention will be described in detail below by Examples. It should be noted that the invention is by no means limited to the Examples.

Example 1

(7) 50 parts by weight of H.sub.2O, 2.5 parts by weight of colloidal silica, 0.2 parts by weight of thickening polysaccharides, 0.2 parts by weight of sodium nitrite, and 1 part by weight of a white pigment (F-101: manufactured by Tokan Material Technology Co., Ltd.) were added per 100 parts by weight of a highly corrosion-resistant frit having a composition of 74.5 mol % of (SiO.sub.2+ZrO.sub.2), 20.2 mol % of (Li.sub.2O+Na.sub.2O+K.sub.2O), 3.2 mol % of (CaO+SrO), and 2.1 mol % of the residue. The obtained mixture was subjected to mill grinding. A surface of a plate formed of an SS400 material and having a 100-mm length and a 100-mm width was glazed with the ground mixture, dried and then fired for six minutes at a temperature from 780 degrees C. to 830 degrees C. Such a lining was repeated for a plurality of times until a thickness of the obtained lining reached 1 mm, so that a test piece of Example 1 was obtained.

Example 2

(8) A test piece of Example 2 was obtained in the same manner as that of Example 1, except that 5 parts by weight of ZrO.sub.2 (H4: manufactured by NITTO DENKO CORPORATION) and 5 parts by weight of SiO.sub.2 (pure silica powder: manufactured by Iwatsuki Kakou Co., Ltd.) were added per 100 parts by weight of the above highly corrosion-resistant frit and the obtained mixture was subjected to mill grinding.

(9) The above-obtained glass is excellent in a balance between a hydrophobic oxide and a hydrophilic oxide which are uniformly dispersed over a GL surface, and is also excellent in stain-proof property against both oily stains and aqueous stains.

Example 3

(10) A test piece of Example 3 was obtained in the same manner as that of Example 1 except that: a glass particle diameter in a slip before glass lining was determined in a range from 30 m to 70 m; 5 parts by weight of the acicular antimony-containing tin oxide was added per 100 parts by weight of the above highly corrosion-resistant frit after 60% of a mill-grinding time was elapsed and the obtained mixture was subjected to mill grinding; and the plate was glazed with the ground mixture, dried and fired at a temperature from 800 degrees C. to 860 degrees C. for 7.5 minutes that was longer by about 20% than in Example 1.

(11) The test piece of Example 3, which is conductive, prevents dirt adhesion caused by static electricity and exhibits an excellent dissolution in the glass and an excellent surface gloss.

(12) FIGS. 1 and 2 show images of the surface of the test piece in Example 3 taken at 200 times and 500 times magnifications using a microscope.

(13) It is understood from FIGS. 1 and 2 that a tin oxide is dissolved in the glass in a network and a fine concave-convex surface (an average diameter of concave portions is in a range from 20 m to 50 m and a height difference between the concave portions and convex portions is in a range from 1 m to 3 m) is formed. The concave portions have a hydrophilic property due to a high glass concentration while the convex portions have a hydrophobic property due to a high concentration of the tin oxide. With this arrangement, it is considered that the surface of the glass lining is excellent in the balance between the hydrophilic property and the hydrophobic property and is also excellent in the stain-proof property and the cleaning performance against both oily stains and aqueous stains.

(14) Test 1 (Oily Stains Repeating Test)

(15) With respect to the test pieces of Examples 1 to 3, each surface was smeared with a vegetable oil, subsequently cleaned with a running water and a running ethanol in this sequential order, irradiated with a short-wavelength ultraviolet ray (UVC) having a wavelength from 240 nm to 270 nm at an intensity of 1 mW/cm.sup.2 for 120 hours, and left still at a temperature of 20 degrees C.5 degrees C. and a humidity of 5010% for 100 hours in a room.

(16) Subsequently, 5 L of water drops (ion-exchange water) was dripped over each surface of the test pieces and a contact angle (an initial value) of each surface was measured within one minute. At the measurement of the contact angle, the temperature was 20 degrees C.5 degrees C. and the humidity was 5010%.

(17) Next, after the respective surfaces of the test pieces were smeared with a vegetable oil, the test pieces were cleaned with a running ion-exchange water and then with a running ethanol at normal temperature, and irradiated with a short-wavelength ultraviolet ray (UVC) having a wavelength from 240 nm to 270 nm at an intensity of 2 mW/cm.sup.2 for 21 hours. A contact angle of each surface was measured in the same manner and conditions as described above at a temperature of 20 degrees C.5 degrees C. and a humidity of 5010%. For comparison, the test piece in Example 1 was also subjected only to cleaning with a running water and a running ethanol without being irradiated with ultraviolet ray. A contact angle of the surface of the test piece in Example 1 was measured in the same manner and conditions as described above. This cycle was repeated 10 times. FIG. 3 shows transition of the thus obtained contact angles of each of the test pieces.

(18) It is understood from FIG. 3 that the initial contact angle in Example 1 was the largest, that in Example 2 is the second largest, and that in Example 3 is the smallest. It is also understood that, among the contact angles after 10 cycles of oily stains, cleaning and ultraviolet ray irradiation in Examples 1 to 3, the contact angle in Example 1 without ultraviolet ray irradiation was the largest, the contact angle in Example 1 with ultraviolet ray irradiation was the second largest, and the contact angles in Examples 2 and 3, which were equal to each other, were smaller than the contact angle in Example 1 with ultraviolet ray irradiation. It is also understood that the contact angles in Examples 2 and 3 were particularly as small as 10 degrees or less in an ultra-hydrophilic region.

(19) Test 2 (Aqueous Stains Adhesion Test)

(20) With respect to the test pieces of Examples 1 to 3, each surface was smeared with a vegetable oil, subsequently cleaned with a running water and a running ethanol in this sequential order, irradiated with a short-wavelength ultraviolet ray (UVC) having a wavelength from 240 nm to 270 nm at an intensity of 1 mW/cm.sup.2 for 120 hours, and left still at a temperature of 20 degrees C.5 degrees C. and a humidity of 5010% for 100 hours in a room.

(21) Subsequently, 5 L of water drops (ion-exchange water) was dripped over each surface of the test pieces and a contact angle (an initial value) of each surface was measured within one minute. At the measurement of the contact angle, the temperature was 20 degrees C.5 degrees C. and the humidity was 5010%.

(22) Subsequently, 5 L of water drops (ion-exchange water) was dripped over each surface of the test pieces and a contact angle (an initial value) of each surface was measured within one minute. At the measurement of the contact angle, the temperature was 20 degrees C.5 degrees C. and the humidity was 5010%.

(23) Next, the test pieces were exposed to an outside at an about 15 degrees inclination while tap water was sprayed over the test pieces once every other day unless it rained. At every elapse of a predetermined time, the test pieces were cleaned with a running ion-exchange water and then with a running ethanol at normal temperature, and irradiated with a short-wavelength ultraviolet ray (UVC) having a wavelength from 240 nm to 270 nm at an intensity of 2 mW/cm.sup.2 for 21 hours. A contact angle of each surface was measured in the same manner and conditions as described above at a temperature of 20 degrees C.5 degrees C. and a humidity of 5010%. This cycle was repeated seven times. FIG. 4 shows transition of the thus obtained contact angles of each of the test pieces.

(24) Such a tendency is understood from the transition of the contact angles after the outside exposure shown in FIG. 4 that the contact angle in Example 1 is larger than the contact angle in Example 2 and the contact angle in Example 2 is larger than the contact angle in Example 3 immediately after the long-time exposure (i.e., before the cleaning). In particular, even the largest one of the contact angles in Example 3 was maintained at about 20 degrees in a hydrophilic region.

(25) It is also observed that, every time after the cleaning and the ultraviolet ray irradiation, the contact angles in Examples 2 and 3 were decreased to about 10 degrees in the ultra-hydrophilic region, whereas some of the contact angles in Example 1 were decreased at most to 20 degrees.

(26) Test 3 (Small Amount Ultraviolet Test)

(27) With respect to the test pieces of Examples 1 to 3, each surface was smeared with a vegetable oil, subsequently cleaned with a running water and a running ethanol in this sequential order, irradiated with a short-wavelength ultraviolet ray (UVC) having a wavelength from 240 nm to 270 nm at an intensity of 1 mW/cm.sup.2 for 120 hours, and left still at a temperature of 20 degrees C.5 degrees C. and a humidity of 5010% for 100 hours in a room.

(28) Subsequently, 5 L of water drops (ion-exchange water) was dripped over each surface of the test pieces and a contact angle (an initial value) of each surface was measured within one minute. At the measurement of the contact angle, the temperature was 20 degrees C.5 degrees C. and the humidity was 5010%.

(29) Next, after the respective surfaces of the test pieces were smeared with a vegetable oil, the test pieces were cleaned with a running ion-exchange water and then with a running ethanol at normal temperature, and irradiated with a short-wavelength ultraviolet ray (UVC) having a wavelength from 240 nm to 270 nm at an intensity of 0.2 mW/cm.sup.2 for 6 hours to 168 hours. A contact angle of each surface was measured in the same manner and conditions as described above at a temperature of 20 degrees C.5 degrees C. and a humidity of 5010%. FIG. 5 shows transition of the thus obtained contact angles.

(30) FIG. 5 reveals the transition of the contact angles obtained after the surface was smeared with a vegetable oil and was subjected to water cleaning, ethanol cleaning, and irradiation of a small amount of the ultraviolet ray (0.2 mW/cm.sup.2). Since the contact angle in Example 3 was smaller than 15 degrees after the ultraviolet ray irradiation for about 24 hours, it was confirmed that the contact angle in Example 3 was superior to those in Examples 1 and 2 even when irradiated with the small amount of the ultraviolet ray.

(31) In light of the above, it is found that, after use of the glass-lined equipment including the lining of the invention exhibiting excellent stain-proof property and self-cleaning performance, subjecting the glass-lined equipment to a typical cleaning such as water cleaning and solvent cleaning and the irradiation with a short wavelength ultraviolet ray (UVC) for a predetermined time can refresh a surface of the glass-lined equipment every batch to recover an inherent performance of the surface, thereby allowing the surface to maintain the stain-proof property and the self-cleaning performance for a long period of time.