# US 7,611,606 B2 · Low-density neutral paper

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- Number: US 7,611,606 B2
- Document ID: US7611606B2
- Status: Granted
- Kind: B2
- Application number: 10/599,135
- Filed: 2005-03-15
- Published: 2007-09-27
- Granted: 2009-11-03
- Earliest claimed: 2004-03-30
- Assignees: Nippon Paper Industries Co., Ltd.
- Inventors: Kazunari Soga; Dai Nagahara; Kazuyuki Fujita; Takashi Ochi; Koji Kutsuwa; Katsumasa Ono
- Web page: https://patentgrep.com/patent/US7611606B2

## CPC

- D21H 17/69: modified, e.g. by association with other compositions prior to incorporation in the pulp or paper
- C09C 1/024: {Coating}
- D21H 17/675: {Oxides, hydroxides or carbonates}
- C01P 2004/61: Micrometer sized, i.e. from 1-100 micrometer
- C01P 2004/62: Submicrometer sized, i.e. from 0.1-1 micrometer
- C01P 2004/80: Particles consisting of a mixture of two or more inorganic phases
- C01P 2006/12: Surface area
- C01P 2006/19: Oil-absorption capacity, e.g. DBP values
- C01P 2006/60: Optical properties, e.g. expressed in CIELAB-values
- D21H 21/52: Additives of definite length or shape
- Y10T 428/253: Cellulosic [e.g., wood, paper, cork, rayon, etc.]
- D21H: PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- C09C: TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES (treatment of materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone C04B14/00, C04B18/00, C04B20/00); PREPARATION OF CARBON BLACK {; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS}
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

The present invention provides a low-density neutral paper offering excellent opacity, opacity after printing and other advantageous printability properties despite high bulk, by containing, as a filler, precipitated calcium carbonate-silica composite having an average particle size of 30 μm or less and produced by neutralizing a mixture of precipitated calcium carbonate and alkaline silicate to pH 7 to 9, wherein the ratio of precipitated calcium carbonate to silica (precipitated calcium carbonate/silica) is 30/70 to 70/30 in solid content by weight and the surface of precipitated calcium carbonate particles is covered with silica. In particular, the present invention provides a low-density printing paper, or an electrophotographic transfer paper offering excellent stiffness and copier suitability, by means of adjusting the filler content in paper to a range of 1 to 25 solid content percent by weight, or provides a neutral newsprinting paper by means of adjusting the filler content in paper to a range of 0.1 to 25 solid content percent by weight.

## Claims

### Claim 1

A low-density neutral paper characterized by containing as a filler a precipitated calcium carbonate-silica composite wherein a surface of precipitated calcium carbonate particles is covered with silica and a ratio of precipitated calcium carbonate to silica (precipitated calcium carbonate/silica) is 30/70 to 70/30 in solid content by weight.

### Claim 2 (depends on 1)

A low-density neutral paper according to claim 1, characterized in that the low-density neutral paper is any of a printing paper, neutral newsprinting paper, or electrophotographic transfer paper.

### Claim 3 (depends on 2)

A low-density neutral paper according to claim 2, characterized in that the average particle size of the precipitated calcium carbonate-silica composite is 30 μm or less.

### Claim 4 (depends on 2)

A low-density neutral paper according to claim 2, characterized in that the precipitated calcium carbonate particles used to produce the precipitated calcium carbonate-silica composite are constituted by rosette-calcite precipitated calcium carbonate where spindle-shaped primary particles agglutinate with one another to form secondary particles.

### Claim 5 (depends on 1)

A low-density neutral paper according to claim 1, characterized in that the low-density neutral paper is a printing paper or electrophotographic transfer paper containing the precipitated calcium carbonate-silica composite at a filler content in paper of 1 to 25 solid content percent by weight.

### Claim 6 (depends on 5)

A low-density neutral paper according to claim 5, characterized in that the average particle size of the precipitated calcium carbonate-silica composite is 30 μm or less.

### Claim 7 (depends on 5)

A low-density neutral paper according to claim 5, characterized in that the precipitated calcium carbonate particles used to produce the precipitated calcium carbonate-silica composite are constituted by rosette-calcite precipitated calcium carbonate where spindle-shaped primary particles agglutinate with one another to form secondary particles.

### Claim 8 (depends on 1)

A low-density neutral paper according to claim 1, characterized in that the low-density neutral paper is a neutral newsprinting paper containing the precipitated calcium carbonate-silica composite at a filler content in paper of 0.1 to 25 solid content percent by weight.

### Claim 9 (depends on 8)

A low-density neutral paper according to claim 8, characterized in that the average particle size of the precipitated calcium carbonate-silica composite is 30 μm or less.

### Claim 10 (depends on 8)

A low-density neutral paper according to claim 8, characterized in that the precipitated calcium carbonate particles used to produce the precipitated calcium carbonate-silica composite are constituted by rosette-calcite precipitated calcium carbonate where spindle-shaped primary particles agglutinate with one another to form secondary particles.

### Claim 11 (depends on 1)

A low-density neutral paper according to claim 1, characterized in that the average particle size of the precipitated calcium carbonate-silica composite is 30 μm or less.

### Claim 12 (depends on 11)

A low-density neutral paper according to claim 11, characterized in that the precipitated calcium carbonate particles used to produce the precipitated calcium carbonate-silica composite are constituted by rosette-calcite precipitated calcium carbonate where spindle-shaped primary particles agglutinate with one another to form secondary particles.

### Claim 13 (depends on 1)

A low-density neutral paper according to claim 1, characterized in that the precipitated calcium carbonate particles used to produce the precipitated calcium carbonate-silica composite are constituted by rosette-calcite precipitated calcium carbonate where spindle-shaped primary particles agglutinate with one another to form secondary particles.

### Claim 14

A low-density neutral paper which is a printing paper, neutral newsprinting paper, or electrophotographic transfer paper, comprising:
pulp; and
a filler comprising a composite of precipitated calcium carbonate-silica wherein precipitated calcium carbonate particles are coated with precipitated silicic acid component, if the in an amount of 0.1 to 25 solid content percent by weight to the paper if,
wherein a ratio of precipitated calcium carbonate to silica (precipitated calcium carbonate/silica) in the composite of precipitated calcium carbonate-silica is 30/70 to 70/30 in solid content by weight.

### Claim 15 (depends on 14)

The low-density neutral paper according to claim 14, wherein the composite of precipitated calcium carbonate-silica has an average particle size of 30 μm or less.

### Claim 16 (depends on 14)

The low-density neutral paper according to claim 14, wherein the precipitated calcium carbonate particles are constituted by rosette-calcite precipitated calcium carbonate where spindle-shaped primary particles agglutinate with one another to form secondary particles.

### Claim 17 (depends on 14)

The low-density neutral paper according to claim 14, wherein the filler comprises the composite of precipitated calcium carbonate-silica in an amount of 1 to 25 solid content percent by weight to the paper.