Disk Roll and Base Material Thereof

Description

TECHNICAL FIELD

The invention relates to a disk roll and a disk roll base material thereof that may suitably be used to produce sheet glass.

BACKGROUND

Sheet glass is normally produced by continuously supplying molten glass to an apparatus, and downdrawing the molten glass from the apparatus in the shape of a strip to allow the molten glass to cool and solidify. Disk rolls, which function as a pair of tensile rolls, are used to hold and sending the molten glass.

A plurality of ring-shaped disk materials cut from a millboard (sheet-shaped product or base material) are normally attached (fitted) to a shaft to obtain a roll-shaped stack. The roll-shaped stack is pressed and secured from both ends via a flange. The outer circumferential surface of the disk materials serves as a molten glass transfer surface.

The disk roll that transfers strip-shaped molten glass is required to exhibit heat resistance, together with flexibility and hardness in order not to damage the surface of glass. For example, a disk roll that contains heat-resistant inorganic wool, mica, and clay has been known (see Patent Documents 1 to 3).

Patent Document 1: JP-T-2010-510956

Patent Document 2: JP-A-2009-132619

Patent Document 3: JP-A-2004-299980

SUMMARY OF THE INVENTION

However, mica may scratch glass. In view of variety and substitutability of raw materials, it is required to produce a disk roll which does not contain mica as an essential component. Further, disk rolls are produced by draining water from the aqueous slurry, and therefore, short drainage time has been required for efficient production of disk rolls.

An object of the invention is to provide a disk roll and a disk roll base material that does not contain mica as an essential component.

The invention provides the following disk roll base material and the like.

• 1. A disk roll base material comprising:

25 to 50 wt % of ceramic wool,

5 to 30 wt % of kibushi clay,

2 to 20 wt % of bentonite, and

25 to 45 wt % of a filler selected from alumina, wollastonite and calcined kaolin clay.

• 2. The disk roll base material according to 1, wherein the ceramic wool comprises 40 to 99 wt % of alumina, and 60 to 1 wt % of silica.
• 3. The disk roll base material according to 1 or 2, wherein the ceramic wool comprises 70 to 80 wt % of alumina, and 30 to 20 wt % of silica.
• 4. The disk roll base material according to any one of 1 to 3, wherein the filler is alumina.
• 5. The disk roll base material according to any one of 1 to 3, wherein the filler is wollastonite.
• 6. The disk roll base material according to any one of 1 to 3, wherein the filler is calcined kaolin clay.
• 7. The disk roll base material according to any one of 1 to 6, further comprising pulp and starch.
• 8. The disk roll base material according to 7, comprising 6 to 10 wt % of the pulp.
• 9. The disk roll base material according to 7 or 8, comprising 1 to 4 wt % of the starch.
• 10. A disk roll comprising the disk roll base material according to any one of 1 to 9.
• 11. A method of producing glass comprising:

transferring molten glass using the disk roll according to 10, and

cooling the molten glass.

The invention can provides a disk roll and a disk roll base material that does not contain mica as an essential component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating an example of a method of producing glass using disk rolls.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A disk roll base material according to the invention includes ceramic wool (alumina silicate wool and the like), kibushi clay, bentonite, and a filler selected from alumina, wollastonite, cordierite and calcined kaolin clay. The base material includes no mica.

The content of the ceramic wool in the base material is 25 to 50 wt %, preferably 25 to 45 wt %, and more preferably 30 to 40 wt %. If the content of the ceramic wool is less than 25 wt %, the heat resistance and thermal shock resistance of the base material may deteriorate. If the content of the ceramic wool exceeds 50 wt %, the bulk density of the disk material may become lower, as a result, the base material may become bulky so that the workability may deteriorate.

The ceramic wool include normally 40 to 99 wt %, preferably 40 to 80 wt %, more preferably 70 to 80 wt %, and further preferably 70 to 75 wt % of alumina. The ceramic wool also include normally 1 to 60 wt %, preferably 20 to 60 wt %, more preferably 20 to 30 wt %, and further preferably 25 to 30 wt % of silica. Heat resistance increases with increase of the amount of alumina. One kind or mixtures of two or more kinds of wool may be used.

The base material includes 5 to 30 wt %, preferably 5 to 25 wt %, and more preferably 5 to 20 wt % of kibushi clay. If the base material includes kibushi clay within the above range, good surface lubricity (smoothness) is obtained.

The base material includes 2 to 20 wt %, preferably 2 to 15 wt %, and more preferably 5 to 15 wt % of bentonite. If the base material does not include bentonite, drainage is insufficient due to insufficient fixation and coagulation. If the bentonite content is too high, drainage may deteriorate.

The base material according to the invention further includes alumina, wollastonite, cordierite or calcined kaolin clay as a filler. One kind or mixtures of two or more kinds of the filler may be used.

The base material includes 25 to 45 wt %, and preferably 28 to 42 wt % of the filler. If the base material includes less than 25 wt % of the filler, the surface lubricity (smoothness) of the resulting disk roll may deteriorate. If it includes more than 45 wt % of the filler, the disk may not be efficiently punched in the shape of a ring.

The base material according to the invention may further include a coagulant aid and an organic binder insofar as the advantages of the invention are not impaired.

Organic wool (pulp) and starch are preferable as the organic binder. The organic wool (pulp) provide the base material with compressibility. The content of the organic wool (pulp) in the base material may be 2 to 10 wt % or 6 to 10 wt %. Starch provides the base material with strength. The content of starch in the base material may be 1 to 10 wt % or 1 to 4 wt %.

The base material according to the invention may include ceramic wool, kibushi clay, bentonite, and filler as inorganic components in an amount of 90 wt % or more, 95 wt % or more, 98 wt % or more, 99 wt % or more, or 100 wt %.

If the base material according to the invention includes the above components within the above range, a disk roll that exhibits heat resistance, strength and hardness in a well-balanced manner without including mica can be obtained.

The base material can be produced by a papermaking method, a suction-dehydration method wherein a slurry is supplied to one surface of a metal mold such as a metal gauze while water is drained from another surface. Specifically, the base material may be produced by forming an aqueous slurry including given amounts of ceramic wool, kibushi clay, bentonite and a filler, optionally together with a coagulant aid, an organic binder, and the like into a board, and drying the resulting board. The thickness of the base material may be appropriately selected (normally 2 to 30 mm).

A method of producing a disk roll is described below. Normally, a plurality of ring-shaped disk materials cut from the base material are attached to a shaft made of a metal (e.g., iron) to obtain a roll-shaped stack. The roll-shaped stack is pressed from both ends via a flange thereon, and secured (fastened) using nuts or the like in a slightly compressed state. The resulting product is optionally fired. The outer circumferential surface of the disk materials are ground to have a given roll diameter to obtain a disk roll.

The disk roll may have a configuration in which the shaft is completely covered with the disk materials, a configuration in which only the parts of the shaft that come in contact with glass are covered with the disk materials, a single-axis configuration, or the like.

As shown in FIG. 1, molten glass 100 is transferred and cooled (solidified) between disk rolls 10 according to the invention to produce a glass sheet, for example.

EXAMPLES

[Disk Roll Base Material Containing Various Fillers]

Example 1

An aqueous slurry containing 30 wt % of fireproof inorganic wool (Mullite fiber including 70 wt % or more of alumina, and 30 wt % or less of silica), 32 wt % of alumina, 20 wt % of kibushi clay, 10 wt % of bentonite, 6 wt % of pulp and 2 wt % of starch was prepared. A disk roll base material (millboard) was produced by a suction-dehydration molding method such that the dimensions after drying were 200 mm×200 mm×6 mm.

The density of the disk roll base material thus obtained was measured, and the following properties (1) to (8) were evaluated. The results are shown in Table 1.

(1) Thermal Shrinkage Rate

A sample with a width of 30 mm and a length of 150 mm was cut from the disk roll base material, and heated at 900° C. for 3 hours. The dimensions in the longitudinal direction and the thickness direction were measured, and the thermal shrinkage rate was evaluated according to the following expression. Small thermal shrinkage rate in the thickness direction is preferable since separation between the disks may occur when degree of shrinkage is large.

[(Value measured before heating−value measured after heating)/value measured before heating]×100

(2) Bending Test of Raw Board (Flexural Strength and Flexural Modulus)

The disk roll base material was held in a heating furnace at 900° C. for 3 hours, and allowed to cool to room temperature. A specimen (width: 30 mm, length: 150 mm) was cut from the cooled base material, and the flexural strength and the flexural modulus of the specimen were evaluated using a tester “Autograph AG-100kND” (manufactured by Shimadzu Corporation) in accordance with JIS K 7171. Small flexural modulus is preferable since spalling resistance decreases in the case of large flexural modulus.

(3) Bending Test of Mounted Disk Material (Flexural Strength and Flexural Modulus)

A disk material (width: 30 mm, length: 150 mm) was cut from the disk roll base material, and compressed between stainless steel sheets such that the thickness was 10 mm and the density was 1.35 g/cm³. The compressed disk material was held in a heating furnace at 900° C. for 10 hours, and allowed to cool to room temperature. The compressive force was then released to obtain a measurement sample. The flexural strength and the flexural modulus of the measurement sample were evaluated using a tester “Autograph AG-100kND” (manufactured by Shimadzu Corporation) in accordance with JIS K 7171.

(4) Thermal Conductivity

A disk material (width: 50 mm, length: 100 mm) was cut from the disk roll base material, and compressed between stainless steel sheets such that the thickness was 10 mm and the density was 1.35 g/cm³. The compressed disk material was held in a heating furnace at 900° C. for 10 hours, and allowed to cool to room temperature. The compressive force was then released to obtain a measurement sample. The thermal conductivity of the surface of the sample was measured at room temperature using a thermal conductivity meter “QTM-500” (manufactured by Kyoto Electronics Manufacturing Co., Ltd.) in accordance with JIS R 2618 (unsteady-state hot wire method).

(5) Coefficient of Thermal Expansion

Disk materials (outer diameter: 60 mm, inner diameter: 20 mm) were cut from the disk roll base material, and roll-built around a stainless steel shaft such that the length was 100 mm and the density was 1.35 g/cm³, held in a heating furnace at 900° C. for 10 hours, and allowed to cool to room temperature. A measurement sample with dimensions of 5×5×20 mm was cut from the cooled sample. The measurement sample was heated from room temperature to 900° C. at 5° C./min in air using a thermomechanical analyzer “TMA8310” (manufactured by Rigaku Corporation) to measure the coefficient of thermal expansion. Large coefficient of thermal expansion is preferable since the disk material can follow changes in shaft dimensions.

(6) Restoration Rate After Compression and Heating

A disk material (width: 30 mm, length: 50 mm) was cut from the disk roll base material, and compressed between stainless steel sheets such that the thickness was 20 mm and the density was 1.35 g/cm³ to obtain a sample.

The sample was heated at 600° C. for 5 hours, and cooled to room temperature (25° C.). The length of the disk material measured after releasing the compressive force was divided by the original length to obtain the restoration rate. The disk roll obtained was heated at 900° C. for 10 hours, and the restoration rate was measured as described above. Large restoration rate after compression and heating is preferable in order that the disk material can follow thermal expansion of a shaft.

(7) Spalling Resistance

Disk materials (outer diameter: 60 mm, inner diameter: 20 mm) were cut from the disk roll base material, and roll-built around a stainless steel shaft (diameter: 20 mm) such that the length was 100 mm and the density was 1.35 g/cm³ to obtain a disk roll.

The disk roll was put in an electric furnace held at 900° C. for 15 hours, and then it was taken out from the electric furnace and quenched to room temperature at 25° C. The heating and quenching cycle was repeated until crack of the disk roll or disk separation occurred. The number of cycles at which the crack or disk separation occurred was counted. Large spalling resistance is preferable.

In addition to the above, Shore D hardness of the disk material before subjecting to spalling resistance test, and hardness after occurrence of crack or disk separation (after spalling resistance test) were evaluated.

(8) Amount of Deformation Under Load

Disk materials (outer diameter: 60 mm, inner diameter: 20 mm) were cut from the disk roll base material, and roll-built around a stainless steel shaft (diameter: 20 mm) such that the length was 100 mm and the density was 1.35 g/cm³ to obtain a disk roll.

Each end of the shaft was supported using a mount, and the amount of deformation (at room temperature) when a compressing element applied a load of 10 kgf/cm to the roll surface formed of the disk materials at 1 mm/min was measured.

Further, the disk roll was held in a heating furnace at 900° C. for 10 hours, removed from the heating furnace, and cooled to room temperature, and the amount of deformation under load (at 900° C. for 10 hours) of the roll was measured in the same manner as described above. Large amount of deformation under load is preferable since it relates to softness.

Examples 2 and 3, and Reference Example 1

Disk roll base materials (millboards) having a composition shown in Table 1 in that calcined kaolin clay, wollastonite and cordierite were used respectively in place of alumina were produced in the same manner as in Example 1 by a suction-dehydration molding method. The properties (1) to (8) were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Reference Example 2

A disk roll base material (millboard) having a composition shown in Table 1 in that white mica was used in place of alumina, and ceramic wool (including 40 to 60 wt % of alumina, and 60 to 40 wt % of silica) as fireproof inorganic wool was used was produced by a papermaking method. The following properties (1) to (8) were evaluated in the same manner as in Example 1. The results are shown in Table 1. The base materials of Examples 1 to 3, and Reference Example 1 are equivalent to or superior to that of Reference Example 2 in the thermal shrinkage rate of raw board and other properties.

	TABLE 1
				Reference	Reference
	Example 1	Example 2	Example 3	Example 1	Example 2

Composition	Fireproof inorganic wool	30	30	30	30	30
[wt %]	White mica					32
	Alumina	32
	Wollastonite			37
	Cordierite				32
	Calcined kaolin clay		32
	Kibushi clay	20	20	15	20	20
	Bentonite	10	10	10	10	10
	Pulp	6	6	6	6	6
	Starch	2	2	2	2	2
Properties of	Density [g/cm3]	0.73	0.62	0.60	0.70	0.68

raw board	Thermal shrinkage rate	Longitudinal direction [%]	0.09	0.10	0.03	0.01	0.15
		Thickness direction [%]	0.24	0.23	0.40	0.68	1.63
	Bending test	Flexural strength [Mpa]	2.11	2.32	1.80	2.11	2.79
		Flexural modulus [Mpa]	832	757	603	653	1472

Properties of

Density [g/cm3]

1.35

1.35

1.35

1.35

1.25

mounted disk	Bending test	Flexural strength [Mpa]	1.66	3.08	1.53	1.54	3.51
material		Flexural modulus [Mpa]	230	501	277	211	816

Thermal conductivity [W/mK]

0.19

0.17

0.20

0.19

0.19

	Coefficient of thermal	Longitudinal direction [10−6 K]	5.73	5.04	7.84	3.69	4.71
	expansion	Diametrical direction [10−6 K]	5.65	4.93	5.56	4.85	3.79

Restoration

Density [g/cm3]

1.35

1.35

1.35

1.35

1.35

	Restoration rate after	600° C. × 5 hr [%]	24.9		40.4	38.1	1.1
	compression and heating	900° C. × 10 hr [%]	1.9		3.2	3.4	1.3

Properties of

Density [g/cm3]

1.35

1.35

1.35

1.35

1.25

roll	Spalling resistance	Number of cycles [times]	10	8	7	8	2
		Hardness before test	43	58	49	50	49
		Hardness after test	47	62	51	54	55
	Amount of deformation	Room temperature [mm]	0.28	0.17	0.21		0.15
	under load	900° C. × 10 hr [mm]	0.27	0.18	0.21		0.11

[Alumina-Containing Disk Roll Base Material]

Examples 4 and 5

The properties were evaluated for the disk roll base material of Example 1 varying the contents of inorganic wool and kibushi clay. Specifically, disk roll base materials (millboards) having a composition shown in Table 2 were produced by a suction-dehydration molding method. The properties (1) to (8) were evaluated in the same manner as in Example 1. The results are shown in Table 2. The base material containing alumina is particularly excellent in amount of deformation under load.

	TABLE 2
	Example 4	Example 5

Composition	Fireproof inorganic wool	35	40
[wt %]	Alumina	32	32
	Kibushi clay	15	10
	Bentonite	10	10
	Pulp	6	6
	Starch	2	2
Properties of	Density [g/cm3]	0.73	0.66

raw board	Thermal	Longitudinal direction [%]	0.06	0.04
	shrinkage rate	Thickness direction [%]	0.70	0.60
	Bending test	Flexural strength [Mpa]	2.49	1.60
		Flexural modulus [Mpa]	1093	680

Properties of

Density [g/cm3]

1.35

1.35

mounted disk	Bending test	Flexural strength [Mpa]	1.12	0.79
material		Flexural modulus [Mpa]	162	125

Thermal conductivity [W/mK]

0.18

0.17

	Coefficient of	Longitudinal direction [10−6 K]	6.87	7.19
	thermal	Diametrical direction [10−6 K]	5.47	5.85
	expansion

Restoration

Density [g/cm3]

1.35

1.35

	Restoration	600° C. × 5 hr [%]	39.0	56.7
	rate after	900° C. × 10 hr [%]	4.1	4.7
	compression
	and heating

Properties of

Density [g/cm3]

1.35

1.35

roll	Spalling	Number of cycles [times]	10	10
	resistance	Hardness before test	43	43
		Hardness after test	45	43
	Amount of	Room temperature [mm]	0.27	0.28
	deformation	900° C. × 10 hr [mm]	0.25	0.24
	under load

[Wollastonite-Containing Disk Roll Base Material]

Examples 6 to 8

The properties were evaluated for the disk roll base material of Example 3 varying in that the contents of inorganic wool, kibushi clay and pulp. Specifically, disk roll base materials (miliboards) having a composition shown in Table 3 were produced by a suction-dehydration molding method. The properties (1) to (8) were evaluated in the same manner as in Example 1. The results are shown in Table 3.

	TABLE 3
	Example 6	Example 7	Example 8

Composition	Mullite fiber	35	40	35
[wt %]	Wollastonite	37	37	37
	Kibushi clay	10	5	13
	Bentonite	10	10	10
	Pulp	6	6	3
	Starch	2	2	2
Properties of	Density [g/cm3]	0.59	0.51	0.58

raw board	Thermal shrinkage	Longitudinal direction [%]	0.03	0.04	0.01
	rate	Thickness direction [%]	0.08	−0.49	0.26

Properties of

Density [g/cm3]

1.35

1.35

1.35

mounted disk	Bending test	Flexural strength [Mpa]	1.48	0.97	1.85
material		Flexural modulus [Mpa]	282	221	413

	Thermal conductivity [W/mK]	0.19	0.19	0.202
Restoration	Density [g/cm3]	1.35	1.35	1.35

	Restoration rate	600° C. × 5 hr [%]	48.6	64.1	46.8
	after compression	900° C. × 10 hr [%]	3.3	3.4	3.3
	and heating

Properties of

Density [g/cm3]

1.35

1.35

—

roll	Spalling resistance	Number of cycles [times]	9	10	—
		Hardness before test	45	44	—
		Hardness after test	47	45	—

Amount of abrasion [mm]

9.4

9.8

—

	Amount of	Room temperature [mm]	0.18	0.19	—
	deformation under	900° C. × 10 hr [mm]	0.19	0.22	—
	load

INDUSTRIAL APPLICABILITY

The disk roll according to the invention can be used to produce sheet glass, particularly glass for liquid crystal displays and plasma displays.

Although only some exemplary embodiments and/or examples of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments and/or examples without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.

The documents described in the specification are incorporated herein by reference in their entirety.