Neutral gray glass

(74) Agent: Cabinet Malémont, 103, rue de Miromesnïl, Paris (8).

New neutral gray glass.

72) Invention of; Shigeki Kato and Takeshi Yamamoto.

33) (32) (31

Conventional priority: Patent application filed in Japan on December 11, 1969, No. 99.056 / 1969 in the name of the applicant.

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The present invention relates to a neutral gray glass and relates, more particularly, to a glass of this kind absorbing heat, which can be used as glass in construction and in the automobile industry and having a low excitation purity.

Attempts have already been made to produce a glass which absorbs an appreciable fraction of the heat of the solar radiation, a glass the use of which reduces the load imposed on the air conditioning installations used to regulate the temperature inside buildings and vehicles. .

Classic heat-absorbing glass has a blue-green color due to the presence of iron oxide. In order to produce a heat-absorbing glass having a neutral gray color, a suitable quantity of Fe 2 O 4 is incorporated into the standard glass NaQ-CaO-SiC 4 as a heat-absorbing component and a proportion is added to this composition. suitable for CoO, NiO and Se to neutralize the green color of the glass. An example of the composition of a conventional neutral gray glass for windows is as follows:

<td>Si0₂</td><td> 72,5 % &lt;</td>

<td>Al „û„</td><td> 1,6 %</td>

<td> 2 3</td><td></td>

<td>CaO</td><td> 7,0 %</td>

<td>MgO</td><td> 3,9 %</td>

<td>so₃</td><td> 0,2 %</td>

<td>N / A₂0</td><td> 14,5 %</td>

<td>^Fe2°3</td><td> 0,23%</td>

<td>NiO</td><td> 0,009%</td>

<td>CoO</td><td> 0,005%</td>

<td>Se</td><td> 0,001%</td>

To manufacture conventional neutral gray glasses, it is necessary to control the properties of heat absorption and transmission by acting on the properties of the four colored components, so that it is sometimes difficult to adjust this degree of absorption and this coloring.

In the process for manufacturing flat glasses which consists in polishing a ribbon of glass by sliding it over the surface of a bath of molten tin protected by a reducing atmosphere, a process known as the flotation process, it is easy to completely reduce certain components of glass to a metallic state.

In this process, most of the nickel oxide, NiO, in the glass is reduced to nickel, so that many black spots appear in the glass. Consequently, it is not possible to produce a neutral gray heat-absorbing glass by this flotation process. In addition, it is also preferable to produce a neutral gray glass having a low excitation purity.

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The object of the present invention is to produce a neutral gray heat-absorbing glass which depends on the balance of three components which are Fe ^ O ^, CoO and Se.

Another object of the invention is to provide a neutral gray heat-absorbing glass having a high resistance to weathering, a lower tendency to devitrification and a low excitation purity.

The neutral gray heat-absorbing glass according to the invention has essentially the composition indicated in Table I, where the percentages are given by weight:

<td colspan="3">TABLE I</td>

<td>Components</td><td>Range of values</td><td>Range of values</td>

<td>I) Basic component</td><td>eligible</td><td>favorite</td>

<td>_Sio₂</td><td> 68-75</td><td> 70-74</td>

<td>^A12°3</td><td> 0-5</td><td> 1-2</td>

<td>CaO</td><td> 5-15</td><td> 5-10</td>

<td>MgO</td><td> 0-10</td><td> 1-5</td>

<td>(CaO + MgO)</td><td> 6-15</td><td> 8-12</td>

<td>Na 0</td><td> 10-18</td><td> 11-15</td>

<td>K₂0</td><td> 0-5</td><td> 0-1</td>

<td>(N / A₂0 + K₂0)</td><td> 10-20</td><td> 12-16</td>

<td>II) Colored components</td><td></td><td></td>

<td>B 0</td><td> 0,1-0,5</td><td> 0,18-0,22</td>

<td> 2 3</td><td></td><td></td>

<td>CoO</td><td> 0,003-0,02</td><td> 0,0031-0,0040</td>

<td>NiO</td><td> 0- 0,002</td><td> 0-0,0004</td>

<td>Se</td><td> 0,0005-0,001</td><td> 0,0006-0,0009</td>

<td>III) Sub-components</td><td></td><td></td>

<td>TiO</td><td> 0-0,5</td><td> 0-0,5</td>

<td>SO₃</td><td>0τ0.5</td><td> 0-0,5</td>

<td>^Sb2°3</td><td>σ-σ, 5</td><td> 0-0,5</td>

<td>^AS2°3</td><td> 0-0,5</td><td> 0,0,5</td>

<td>Cl</td><td> 0-0,5</td><td> 0-0,5</td>

<td>ZnO</td><td> 0-0,5</td><td> 0-0,5</td>

<td>Sn0₂</td><td> 0,0,1</td><td> 0-0,1</td>

The main components include Si0₂, ^^{es ox}yd^es of alkali metals, alkaline earth oxides and A ^ O ^,

The proportion of these substances used in the composition of glass has a great influence on its melting, on its forming properties, its viscosity, its devitrification properties and its resistance to weathering.

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The allowable limits for each component were determined based on the following considerations:

The weather resistance of the glass becomes poor when the proportion of SiO 3 is less than 68%, while devitrification of the glass easily occurs when the SiO 3 content exceeds 75%.

Na ^ O and K ^ O are fluxing agents and, consequently, the weather resistance of glass becomes poor when the percentage of Na ^ O exceeds 18% or when the content of Na 0 + KO exceeds 20 7 ,, while that the melting properties of the glass are affected by a content of less than 10 7 in Na ^ O or less than 10 7 in Na ^ O + K ^ O. In addition, when the K ^ O content exceeds 5 7, the melting point becomes too high and the glass is not economical, since ^ 0 is expensive compared to Na ^ O. CaO and MgO are added as fluxes to improve weather resistance. The weather resistance of glass is poor when the CaO content is less than 5 7, or when that of CaO + MgO is less than 6 7, while glass devitrifies easily when the proportion of CaO exceeds 15 7 "or when that of MgO exceeds 10% or that the CaO + MgO content is greater than 15 7.

The A ^ Og is used to adjust viscosity and improve weather resistance. The melting properties of glass are poor when the content of A ^ Og exceeds 5 7.

The preferred limits of the proportions of said substances are indicated in the right column of Table I.

As regards the coloring components, Fe ^ O ^ is used to impart predetermined heat-absorbing properties to said glass, while, on the other hand, the CoO and Se are mixed with the to give a neutral gray coloring to the resulting glass.

The glass has a green color when the content of Τ ^ θβ exceeds 0.5%, while the heat-absorbing properties of the latter are poor when the proportion of Fe ^ O ^ ^East less than 0.17 ,.

The transparency coloring of the glass can be neutralized by adding 0.003 to 0.02 7_O of CoO and 0.005 to 0.001 7 of Se. On the other hand, it is preferable that the percentage of NiO is negligible in the flotation process, this proportion having, preferably, to be kept lower than 0.002 7, of NiO and, preferably, lower than 0.0004 7. One does not note no defect in the glass produced by the flotation process when the proportion of NiO is less than 0.0004 7 ,.

Since NiO is an impurity present in the raw materials used to make glass or which comes from the surface of the device, it is preferable to avoid contamination by NiO.

The preferred proportions of the coloring substances are: 0.18 to 0.22 7

44251 ⁴ 2074983 F ^ O, 0.031 to 0.0040% CoO, 0.006 to 0.009% Se and 0 to 0.0004 7, NiO. Between these limits, a neutral gray glass is obtained having, under a thickness of 5 mm, a light transmission coefficient of 57 to 63 7c, a solar energy transmission coefficient of 57 to 63 7₀, a dominant wavelength less than 580m) u and an excitation purity less than 1.5 7 °.

As shown in Table I, SO ^, Sb₂O₃, the Ace₂0₃ and Cl can be added as refining agents, Ti0₂, ZnO and Sn0₂ can also be added as color adjusting agents or as stabilizing agents.

In addition, other secondary components can be added. However, each upper limit is shown in Table I.

The glass comprising said components can be produced by the conventional method according to which these are mixed according to the composition of the glass to be produced, then are melted, formed and annealed.

The examples which follow, which of course have no limiting character, will make the particular features of the invention better understood.

EXAMPLES I and II

The table below indicates the proportion of the various components and the physical properties of the resulting glass.

<td>Components</td><td>I</td><td>II</td>

<td>If °₂</td><td>72.2% by weight</td><td>72.5% by weight</td>

<td>^A12°3</td><td> 1,74 </td><td> 1,70 </td>

<td>CaO</td><td> 6,97</td><td> 6,93</td>

<td>MgO</td><td> 3,88</td><td> 3,88</td>

<td>Na 0</td><td></td><td></td>

<td></td><td> 14,8</td><td> 14,5</td>

<td>_v not</td><td></td><td></td>

<td> 2</td><td></td><td></td>

<td>^Fe2°3</td><td> 0,204</td><td> 0,222</td>

<td>NiO</td><td> 0,0014</td><td> -</td>

<td>CoO</td><td> 0,0035</td><td> 0,0034</td>

<td>Se</td><td> 0,00081</td><td> 0,00077</td>

<td>^S°3</td><td> 0,20</td><td> 0,22</td>

<td>Ti0₂</td><td> 0,02</td><td> 0,03</td>

<td colspan="3">Properties</td>

<td>Transmission coefficient of</td><td></td><td></td>

<td>light</td><td>62.4 T,</td><td>62.8 7c</td>

<td>Transmission coefficient of</td><td></td><td></td>

<td>solar energy</td><td>60.2 7c</td><td>57.5 T,</td>

<td>Dominant wavelength</td><td>519 m μ</td><td>542.5 m μ</td>

<td>Purity of excitement</td><td>0.577c</td><td>0.5 7c</td>

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The spectral transmission curves of samples I and II (based on a thickness of 5 mm) are indicated respectively in the drawing, the wavelengths being plotted on the abscissa and the transmission coefficient on the ordinate. It can be seen that these samples have a practically uniform light transmission coefficient between 440 and 660 m and each have a neutral gray coloring.

A ribbon of flat glass is produced from each of samples I and II by the flotation process and no black spot is observed.

It can therefore be seen that the invention makes it possible to produce a heat-absorbing glass having a neutral gray color which has great resistance to weathering, which has less tendency to devitrification, which has a low excitation purity and which has a coefficient of light transmission in one form.

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