WO2000027772A1

WO2000027772A1 - Glass surface protective-treating method and glass cleaning agent

Info

Publication number: WO2000027772A1
Application number: PCT/US1999/026831
Authority: WO
Inventors: Hideaki Kiniwa; Shoji Ouchi
Original assignee: S. C. Johnson Commercial Markets, Inc.
Priority date: 1998-11-12
Filing date: 1999-11-12
Publication date: 2000-05-18

Abstract

To provide a novel glass surface protective-treating method that can long maintain the beauty and durability of the glass surface having been cleaned. A treating method by which the glass surface can be protected over a long period of time without a possibility of recontamination is provided, which comprises the first step of cleaning a glass surface with a hydrogen fluoride type cleaning agent and the second step of coating the cleaned glass surface with a silicon type coating agent. A new acid ammonium fluoride glass cleaning agent to remove blackening from glass is also disclosed.

Description

GLASS SURFACE PROTECTIVE-TREATING METHOD AND GLASS

CLEANING AGENT

FIELD OF THE INVENTION

This invention relates to a glass surface protective-treating method that can long maintain the beauty and durability of the glass surface having been cleaned.

BACKGROUND OF THE INVENTION

Exterior glass including front-faceted glass and show window glass of commercial facilities such as hotels, restaurants and department stores, special glass for atrium top light, glass of office buildings and public institutions, and bath room glass of hotels and golf club houses is used everywhere. Compared with interior glass, such exterior glass tends to become contaminated, and also is difficult to clean. This is presumed to be due to the following.

Chief components constituting the glass originate from silica sand (SiO₂), soda ash (Na₂O) and lime (CaO). Water comes to adhere to the glass surface over a long period of time, where the water diffuses gradually to the interior of glass to hydrolyze soda ash and remains as an alkali solution on the glass surface.

Chemical Formula 1

SiO₂ + Na₂O + (x+2)H₂O → H₂SiO₃ xH₂O + 2NaOH

If this component is washed away immediately, the state of glass surface does not change so much conspicuously. However, upon repetition of drying and wetting in this state and further occurrence of chemical action caused by carbon dioxide (CO₂), sulfur oxides (SO_x) and nitrogen oxides (NO_x) in the atmosphere, the following chemical reaction takes place. Chemical Formula 2

2NaOH + CO₂ → Na₂CO₃ + H₂O

These products (NaOH and Na₂CO₃) gradually affect the structure of silicon, the chief component of glass, to cause chemical changes on the glass surface, such as gelation of silicon.

As a result, there may occur "white clouding", which is a state where the gloss of glass has decreased to become cloudy, or fish scales "scale covering" under conditions where the cycle of adhesion of water (moisture content), its evaporation and surface drying is frequently repeated. Also, "rainbow appearance" may occur, in which the glass surface looks rainbow-colored because of interference light caused when a thin film is formed thereon. Recently, "blackening" may also be seen, which is caused by dust, exhaust gas and sulfur trioxides especially at the hearts of the cities, in the vicinity of principal roads having a lot of traffic and around factories and incinerators.

These phenomena are generally referred to as weathering of glass, and commonly as "burning" and "fur" . Likewise applicable is an instance where metal components such as calcium contained in water sticks to the glass surface to lower the transparency of glass. Such burning of glass often occurs on i) glass present at places always splashed with drops of water in the vicinities of, e.g., fountains, ponds or man-made falls, ii) glass present at places wetted with dew or splashed with water under conditions of high temperature and high humidity as in bath rooms, pools and greenhouses, iii) glass present at places where water may remain after the sweeping of a garden by sprinkling water on garden plants, iv) exterior glass of buildings near to the seashore, v) glass having not been cleaned for a long period of time, vi) glass used in constructions where contaminants having adhered to outer walls or substances flowing out of such contaminants or out of outer- wall materials may flow onto glass surface together with rain water, and vii) glass facing the north. Once the burning has occurred, the glass tends to cause the fixing of water (moisture content) at the part where it has occurred, and simultaneously comes to attract contaminants and also dust in the air. Contamination (burning) arouses contamination (burning) to cause the glass to damage acceleratively. From the glass surface having been thus contaminated, it is difficult for the contaminants to be removed with ordinary cleaning agents, and physical means of removing them by polishing with a polishing agent or diamond pad is used. Such means, however, makes it necessary to bring a polishing assembly to the field and also requires a long operating time, resulting in a low operation efficiency. Also, fine scratches may remain on the glass surface to accelerate the adhesion of contaminants, and hence it is difficult to maintain the beauty for a long period of time. In order to overcome this disadvantage in operability, a method is employed in which the contaminated surface is subjected to chemical etching with a hydrogen fluoride type cleaning agent. However, there is a disadvantage that the glass surface once cleaned in this way is again contaminated in a relatively short time. In addition, for the surface again contaminated it becomes difficult to be easily restored to the original beautiful surface by using the hydrogen fluoride type cleaning agent repeatedly. Thus, any method by which the contamination of exterior glass surface can effectively be removed and the effect after cleaning can long be maintained has not been developed at present.

SUMMARY OF THE INVENTION

As a result of extensive studies made in order to solve such problems, the present inventors have found out a treating method in which the contaminants on the glass surface are removed with a fluoride type cleaning agent and thereafter the glass surface is treated with a silicon type coating agent so that the glass surface can be protected over a long period of time without a possibility of recontamination. DET AILED DESCRIPTION OF THE INVENTION

More specifically, the present invention is a glass surface protective- treating method comprising (1) the first step of cleaning a glass surface with a hydrogen fluoride type cleaning agent and (2) the second step of coating the cleaned glass surface with a silicon type coating agent.

The hydrogen fluoride type cleaning agent used in the first step of the glass surface protective-treating method in the present invention is produced using hydrogen fluoride, hydrofluoric acid, hydrofluoric acid solution or acid ammonium fluoride as a material and adding to it a conventionally know surface-active agent and further an inorganic acid such as sulfur ic acid, hydrochloric acid, nitric acid or phosphoric acid or a low-molecular weight organic acid. Usually, those produced using acid ammonium fluoride and a surface-active agent with addition of an acidic substance are commonly available. A particularly preferred glass surface cleaning agent discovered by the present inventors which can be used to advantage in step 1 of the method of the present invention is an aqueous composition comprising from 10 to 30% by weight of acid ammonium fluoride, from 0.5 to 10% by weight of a surface-active agent and from 5 to 40% by weight of at least one of an organic acid and an inorganic acid. This preferred glass cleaner is effective to clean blackened glass whether or not the subsequent protective step of the present method is used. As the silicon type coating agent next used in the second step, a solution is used which is prepared by dissolving a cured film forming agent containing a conventionally known silicon-containing polymer and a conventionally known catalyst for combining silanol groups, in a low-boiling solvent such as isopropanol or a hydrocarbon type solvent such as methylene chloride. The silicon- containing polymer commonly includes mefhylhydrogenpolysiloxane and dimethylsiloxane; and the catalyst for combining silanol groups, dibutyltin diacetate. As those composed chiefly of methylhydrogenpolysiloxane, preferred are "KF-99", trade name, available from Shin-Etsu Silicone Co., Ltd. and "SH-11107", trade name, available from Toray Silicone Co., Ltd., and, as those composed chiefly of dimethylsiloxane, "KF-96", trade name, available from Shin-Etsu Silicone Co., Ltd., and "SH-200", trade name, available from Toray Silicone Co., Ltd.

In the first step of cleaning a glass surface with the hydrogen fluoride type cleaning agent in the present invention, a cloth or sponge is soaked with the above hydrogen fluoride type cleaning agent, and then the cleaning agent is uniformly applied to the glass surface to be cleaned and is kept being held thereon for 10 to 30 seconds. Thereafter, the glass surface is wiped up with a wet towel or waste and the water is removed by squeegee, thus the first step is completed. Next, in the second step of coating the cleaned glass surface with a silicon type coating agent, the glass surface is left for 30 minutes to 1 hour and, after making sure that it has dried, a dried towel or waste is soaked with the above silicon type coating agent, and the coating agent is thin spread over the glass surface. Here, the silicon type coating agent may preferably be used in an amount of 10 ml per square meter of glass treatment area and be coated in a thickness of about 10 μm as the thickness of the silicon type coating agent.

A particularly preferred glass surface cleaning agent discovered by the present inventors which can also be used in step 1 of the present method is an aqueous composition comprising from 10 to 30% by weight of acid ammonium fluoride, from 0.5 to 10% by weight of a surface-active agent and from 5 to 40% by weight of at least one of an organic acid and an inorganic acid.

As the acid ammonium fluoride useful in the preferred glass cleaner, those produced using as materials hydrofluoric acid and from 0.5 to 1 mole of ammonia gas per mole of the former may usually be used. As the surface-active agent, any of anionic surface-active agents, nonionic surface active agent and amphoteric surface-active agents may be used. In particular, anionic surface-active agents are preferred in view of their compatibility with the acid ammonium fluoride or stability of the aqueous composition. As for the organic acid and the inorganic acid, those having a good compatibility with the acid ammonium fluoride may be used. As the organic acid, those having 5 or less carbon atoms, having a hydroxyl group or carboxyl group, are preferred, as exemplified by oxalic acid, citric acid and glycolic acid. As the inorganic acid, commonly known inorganic acids may be used, which may include, e.g., hydrochloric acid, sulfur ic acid and phosphoric acid. These organic acid and inorganic acid are each used alone or in combination. In the aqueous composition for glass surface treatment, the acid ammonium fluoride, surface-active agent and also at least one of the organic acid and the inorganic acid may be used in the range of from 10 to 30% by weight, and preferably from 15 to 25% by weight, for the acid ammonium fluoride; in the range of from 0.5 to 10% by weight, and preferably from 1 to 4% by weight, for the surface-active agent; in the range of from 5 to 40% by weight, and preferably from 10 to 30% by weight, for the inorganic acid.

As a method of cleaning the glass surface by using the aqueous composition for glass surface treatment described above, a waste may be soaked with the aqueous composition for glass surface treatment, and the aqueous composition may uniformly be applied to the target glass surface and may be kept being held thereon for 15 seconds. Thereafter, the glass surface may be wiped up with a wet waste, and then the water may be removed by squeegee.

The object of the present invention can be achieved by the two step treatment described above. To obtain a more preferable result, the step of removing residual components of the hydrogen fluoride type cleaning agent with a cleaning agent containing a conventionally know surface-active agent and a conventionally known low-boiling solvent may be provided between the first step and the second step. Providing this step makes it unnecessary to take the time of from 30 seconds to 1 hour provided for the drying of glass surface after the first step is completed, bringing about advantages that the step of treatment with the silicon type coating agent can be taken immediately and that the beauty and durability of the glass surface having been cleaned can be improved. In this embodiment, the treatment is completed through three steps of (1) the first step of cleaning a glass surface with the fluoride type cleaning agent, (2) the second step of removing a residual component remaining in the first step, with the cleaning agent containing a surface- active agent and a low-boiling solvent and (3) the third step of coating the cleaned glass surface with the silicon type coating agent. It is presumed that the adhesion of the silicon type coating agent to the glass surface is improved by providing the second step, to bring about an improvement of durability. As a preferred low- boiling solvent used in the second step, methanol, ethanol or isopropanol may be used. Incidentally, it is also preferable to provide, before the first step, a preliminary cleaning step of cleaning the glass surface with a cleaning agent making use of a conventionally know surface-active agent.

Examples Preferred examples of the present invention are shown below.

In order to manifest the effect attributable to the glass surface protective-treating method of the present invention, exterior glass having long been used and having caused blackening was picked out in a building located adjacently to a road having a relatively lot of traffic in Kawasaki City. On the surface of this glass, an area seen to have uniformly been contaminated was divided into six equal parts, which were then cleaned with six types of cleaning methods according to Examples 1 to 4 and Comparative Examples 1 and 2 shown below. The appearance of each glass surface before cleaning, immediately after cleaning, after the lapse of one month, after the lapse of six months and when the surface was further again cleaned was visually evaluated according to the following criteria.

1. A state where contamination (blackening or scales) appears clearly on the whole glass surface; evaluated as X X .

2. A state where contamination (blackening or scales) appears partly on the whole glass surface; evaluated as X . 3. A state where no contamination remains but traces of cleaning remain; evaluated as Δ .

4. A state of substantially the same level as that of new glass; evaluated as O. Results obtained are shown in Table 1 together. Example 1

(1) A waste was soaked with a hydrogen fluoride type cleaning agent 1 comprised of 20% by weight of acid ammonium fluoride, 25% by weight of phosphoric acid, 2% by weight of an anionic surface-active agent and 53% by weight of water, and the cleaning agent was uniformly applied to the glass surface and was kept being held thereon for 15 seconds. Thereafter, the glass surface was wiped up with a wet waste, and then the water was removed by squeegee.

(2) Next, the glass surface was left for 30 minutes and, after making sure that it had dried, a waste was soaked with a silicon type coating agent comprised of 12% by weight of methylhydrogenpolysiloxane, 57% by weight of isopropanol, 30% by weight of a hydrocarbon type solvent and 1 % by weight of dibutyltin diacetate, and the coating agent was coated in a thickness of 10μm.

Example 2 (1) A waste was soaked with the same hydrogen fluoride type cleaning agent as that in Example 1, and the cleaning agent was uniformly applied to the glass surface and was kept being held thereon for 15 seconds. Thereafter, the glass surface was wiped up with a wet waste, and then the water was removed by a squeegee. (2) Subsequently, a waste was soaked with a cleaning agent comprised of 63 % by weight of isopropanol, 1 % by weight of an anionic surface- active agent, 1 % by weight of a nonionic surface-active agent and 35 % by weight of water, and the glass surface was wiped with it. Then the water was removed by squeegee. (3) Next, a waste was soaked with the same silicon type coating agent as that in Example 1 , and the coating agent was coated in a thickness of 10 μm.

Example 3

(1) Using KRINSTON (trade name) as a hydrogen fluoride type cleaning agent, 2, a waste was soaked with it, and the cleaning agent was uniformly applied to the glass surface and was kept being held thereon for 15 seconds. Thereafter, the glass surface was wiped up with a wet waste, and then the water was removed by squeegee.

(2) Subsequently, a waste was soaked with a cleaning agent comprised of 63 % by weight of isopropanol, 1 % by weight of an anionic surface- active agent, 1 % by weight of a nonionic surface-active agent and 35% by weight of water, and the glass surface was wiped with it. Then the water was removed by squeegee.

(3) Next, a waste was soaked with the same silicon type coating agent as that in Example 1 , and the coating agent was coated in a thickness of 10 μm.

Example 4

(1) A waste was soaked with a hydrogen fluoride type cleaning agent 3 comprised of 6% by weight of hydrofluoric acid, 4% by weight of oxalic acid, 4% by weight of citric acid, 4% by weight of an anionic surface-active agent and 82% by weight of water, and the cleaning agent was uniformly applied to the glass surface and was kept being held thereon for 15 seconds. Thereafter, the glass surface was wiped up with a wet waste, and then the water was removed by squeegee. (2) Subsequently, a waste was soaked with a cleaning agent comprised of 63% by weight of isopropanol, 1 % by weight of an anionic surface- active agent, and 35% by weight of water, and the glass surface was wiped with it. Then the water was removed by squeegee.

(3) Next, a waste was soaked with the same silicon type coating agent as that in Example 1, and the coating agent was coated in a thickness of 10 μm.

Comparative Example A

(1) Using the hydrogen fluoride type cleaning agent 2 of Example 3, the cleaning agent was uniformly applied to the glass surface and was kept being held thereon for 15 seconds. Thereafter, the glass surface was wiped up with a wet waste, and then the water was removed by squeegee.

Comparative Example B

Using the hydrogen fluoride type cleaning agent 2 of Example 3, the cleaning agent was uniformly applied to the glass surface and was kept being held thereon for 15 seconds. Thereafter, the glass surface was wiped up with a wet waste, and then the water was removed by squeegee.

Table 1

Immedi¬

Immediately ately after

Before after After After second

Cleaning cleaning 1 month 6 month cleaning

Example:

1 X X O O Δ O

2 X X O O O O

3 X X O O O O

4 X X O O O O

Comparative Examples:

A X X O X X X Δ⁽*)

B X X O X X X Δ(*)

(*) Traces of wiping remain unevenly on the glass surface.

As can be seen from the results shown in Table 1 , by the use of the glass surface protective-treating method of the present invention any tough contamination having occurred on exterior glass can be removed with ease. Moreover, once it has been removed, the glass surface can be kept from being again contaminated, and its beauty can be maintained over a long period of time.

The preferred glass cleaner discovered by the present inventors can be illustrated by the following examples.

Example 5

An aqueous solution comprised of 20% by weight of acid ammonium fluoride, 25% by weight of phosphoric acid, 2% by weight of an anionic surface- active agent and 53 % by weight of water was prepared.

Example 6

An aqueous solution comprised of 20% by weight of acid ammonium fluoride, 10% by weight of glycolic acid, 2% by weight of an anionic surface-active agent and 68% by weight of water was prepared.

Example 7

An aqueous solution comprised of 20% by weight of acid ammonium fluoride, 20% by weight of glycolic acid, 2% by weight of an anionic surface-active agent and 58% by weight of water was prepared.

Example 8

An aqueous solution comprised of 20% by weight of acid ammonium fluoride, 30% by weight of glycolic acid, 2% by weight of an anionic surface-active agent and 48 % by weight of water was prepared.

Comparative Example C

An aqueous solution comprised of 20% by weight of acid ammonium fluoride and 80% by weight of water was prepared, and this was designated as Comparative Cleaning Agent 1. Comparative Example D

An aqueous solution comprised of 20% by weight of acid ammonium fluoride, 25 % by weight of phosphoric acid, 10% by weight of glycolic acid and 45% by weight of water was prepared.

Comparative Example E

An aqueous solution comprised of 20% by weight of acid ammonium fluoride, 2% by weight of an anionic surface-active agent and 78% by weight of water was prepared.

Comparative Example F

An aqueous solution comprised of 6% by weight of hydrofluoric acid and 94% by weight of water was prepared.

Comparative Example G

A cleaning agent available from Krinston Co. under the trade name "KRINSTON", was used as Comparative Cleaning Agent 5.

Using the foregoing cleaning agents of Examples 5 to 8 and Comparative Examples C to G, their cleaning effect was examined in the following way.

Exterior glass having long been used and having caused blackening was picked out in a building located adjacently to a road having a relatively lot of traffic in Kawasaki City. On the surface of this glass, an area seen to have uniformly been contaminated was divided into nine equal parts, and their surfaces were cleaned with the cleaning agents of Examples 5 to 8 and the comparative cleaning agents of Comparative Examples C to G. As a method of cleaning, a waste was soaked with each cleaning agent, and the cleaning agent was applied to the target glass surface and was kept being held thereon for 15 seconds 1. A state where contamination "blackening" remains clearly; evaluated as 1.

2. A state where contamination "blackening" remains partly; evaluated as 2.

3. A state where the contamination "blackening" remains more or less; evaluated as 3.

4. A state where the contamination "blackening" remains slightly; evaluated as 4.

5. A state where the contamination "blackening" does not remain at all; evaluated as 5.

Results obtained are shown in Table 1 together.

Table 1

Degree of contamination of glass surface

Cleaning Agents Before Cleaning After Cleaning

Cleaning agent used in:

Example 5 1 5

Example 6 1 5

Example 7 1 5

Example 8 1 5

Comparative Example C 1 2

Comparative Example D 1 3

Comparative Example E 1 3

Comparative Example F 1 5

Comparative Example G 1 1

Claims

1. A glass surface protective-treating method comprising (1) the first step of cleaning a glass surface with a hydrogen fluoride type cleaning agent and (2) the second step of coating the cleaned glass surface with a silicon type coating agent.

2. The method according to claim 1 wherein the silicon type coating agent comprises a silicon-containing polymer, a catalyst for confining silanol groups and an alcohol or hydrocarbon solvent.

3. The method according to claim 2 wherein said polymer is selected from the group consisting of methylhydrogen polysiloxane, dimethylsiloxane or mixtures thereof.

4. A glass surface protective-treating method comprising (1) the first step of cleaning a glass surface with a hydrogen fluoride type cleaning agent, (2) the second step of removing a residual component remaining in the first step, with a cleaning agent containing a surface-active agent and a low-boiling solvent and (3) the third step of coating the cleaned glass surface with a silicon type coating agent.

5. The method according to claim 4 wherein the silicon type coating agent comprises a silicon-containing polymer, a catalyst for confining silanol groups and an alcohol or hydrocarbon solvent.

6. The method according to claim 5 wherein said polymer is selected from the group consisting of methylhydrogen polysiloxane, dimethylsiloxane or mixtures thereof.

7. An aqueous composition for glass surface treatment comprising from 10 to 30% by weight of acid ammonium fluoride, from 0.5 to 10% by weight of a surface-active agent and from 5 to 40% by weight of at least one of an organic acid and an inorganic acid.

8. A composition according to claim 7 wherein said organic acid is selected from the group consisting of oxalic acid, citric acid, glycolic acid and mixtures thereof.

9. A composition according to claim 7 wherein said inorganic acid is selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid and mixtures thereof.

10. A composition according to claim 7 wherein said surface active agent is anionic.