Ink composition for water-based ballpoint pen

Patent metadata

Field	Value
Publication number	US-12441899-B2
Application number	US-202017759825-A
Country	US
Kind code	B2
Filing date	Jan 30, 2020
Priority date	Jan 30, 2020
Publication date	Oct 14, 2025
Grant date	Oct 14, 2025

Abstract

An ink composition for a water-based ballpoint pen and a water-based ballpoint pen, which have stable ink flowability even in a so-called fine ballpoint pen, have excellent luster of drawn lines, and do not cause a ball to fall off. The ink composition for a water-based ballpoint pen according to the present invention contains at least an aluminum pigment and 8 to 25 mass % of solid urethane particles with an average particle size of 0.3 to 10 μm. In addition, a water-based ballpoint pen according to the present invention is provided with the ink composition for a water-based ballpoint pen that has the above composition.

First claim

The invention claimed is:

1. A water-based ballpoint pen, comprising:
a ballpoint pen tip having a ball with a ball diameter of 0.5 mm or less; and
an ink composition suitable for a water-based ballpoint pen,
wherein the ink composition comprises an aluminum pigment, having an average particle size in a range of from 5 to 20 μm, in a range of from 0.1 to 20 mass % and solid urethane particles, having an average particle size in a range of from 0.3 to 10 μm, in a range of from 8 to 25 mass %.

2. The water-based ballpoint pen of claim 1 , wherein the ink composition comprises the solid urethane particles in a range of from 10 to 18 mass %, and
wherein the solid urethane particles have an average particle size in a range of from 0.5 to 8 μm.

3. The water-based ballpoint pen of claim 1 , wherein the urethane particles have a 10% strength of 30 MPa or less, calculated by equation (II), as measured by a micro compression test:
C ( x )=(2.48× P )/(π× d 2 )  (II),

wherein C(x) is 10% strength in MPa, P is a test force at 10% displacement of particle size in N, and d is particle size in mm.

4. The water-based ballpoint pen of claim 1 , wherein the urethane particles are not colored.

5. The water-based ballpoint pen of claim 1 , wherein the solid urethane particles have an average particle size in a range of from 1 to 6 μm.

6. The water-based ballpoint pen of claim 2 , wherein the solid urethane particles have an average particle size in a range of from 1 to 6 μm.

7. The water-based ballpoint pen of claim 1 , wherein the solid urethane particles comprise, in polymerized form, hexamethylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, isophorone diisocyanate, and/or an isocyanate prepolymer.

8. The water-based ballpoint pen of claim 1 , wherein the solid urethane particles comprise, in polymerized form, a triol adduct of hexamethylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and/or isophorone diisocyanate.

9. The water-based ballpoint pen of claim 1 , wherein the solid urethane particles comprise, in polymerized form, an isocyanurate-modified product of hexamethylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and/or isophorone diisocyanate.

10. The water-based ballpoint pen of claim 1 , wherein the ball diameter of the ball is 0.3 mm or less.

11. The water-based ballpoint pen of claim 1 , wherein the ball diameter of the ball is 0.29 mm or less.

12. The water-based ballpoint pen of claim 1 , wherein the ball diameter of the ball is in a range of from 0.1 to 0.5 mm.

13. The water-based ballpoint pen of claim 1 , wherein the ball diameter of the ball is in a range of from 0.1 to 0.3 mm.

14. The water-based ballpoint pen of claim 1 , wherein the ball diameter of the ball is in a range of from 0.1 to 0.29 mm.

15. The water-based ballpoint pen of claim 1 , wherein the solid urethane particles comprise, in polymerized form, an adduct of hexamethylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and/or isophorone diisocyanate with trimethylolpropane.

16. The water-based ballpoint pen of claim 3 , wherein the urethane particles have a 10% strength in a range of from 5 to 30 MPa.

17. The water-based ballpoint pen of claim 1 , wherein the value of X calculated by equation (I) is in a range of from 27 to 37:
X =( L/D )×100  (I)

wherein B is ball diameter, and L is maximum ball exposure, which is a sum of ball exposure and clearance.

Assignees

• Mitsubishi Pencil Co

Inventors

• Hirayama Akiko
• Ogura Kousuke

Classifications

• C09D11/17

  characterised by colouring agents · CPC title

• B43K7/02

  Ink reservoirs; Ink cartridges (B43K7/01 takes precedence) · CPC title

• B43K1/086

  with resilient supporting means for the ball, e.g. springs · CPC title

• C09D11/18 Primary

  specially adapted for ball-point writing instruments · CPC title