Aqueous dispersion of polyester resin, production method of the same, and aqueous coating composition

• US 6,818,699 B2
• Filed: 09/25/2001
• Issued: 11/16/2004
• Est. Priority Date: 09/28/2000
• Status: Expired due to Fees

• Current Assignee: Unitika Limited
• Original Assignee: Unitika Limited
• Inventors: Tanaka, Toru, Kokuryo, Sachiko, Kajimaru, Hiroshi, Shirasawa, Daisuke
• Primary Examiner(s): Yoon, Tae H.
• Application Number:
  US09/961,412
• Publication Number:
  US 20020061959A1
• Time in Patent Office: 1,148 Days
• Field of Search: 524/845, 524/601, 524/604, 528/308, 528/501
• US Class Current: 524/845
• CPC Class Codes: C08J 2367/00 Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain of polyester-amides C08J2377/12; of polyester-imides C08J2379/08; Derivatives of such polymers
• CPC Class Codes: C08J 3/03 in aqueous media
• CPC Class Codes: C09D 167/00 Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain based on polyester-amides C09D177/12; based on polyester-imides C09D179/08; Coating compositions based on derivatives of such polymers

Abstract

The present invention is to provide an aqueous dispersion of polyester resin with an excellent molecular weight stability, its production method, and an aqueous coating composition. An aqueous dispersion of polyester resin having an acid value of 8 to 40 mg KOH/g and a weight average molecular weight of 9,000 or more contains an organic solvent less than 0.5% by mass. A method for producing the aqueous dispersion of polyester resin comprising a step of at first obtaining an aqueous dispersion of polyester resin containing not lower than 0.5% by mass of an organic solvent by adding the polyester resin and a basic compound to an aqueous medium to make the resulting mixture aqueous and a step of removing the organic solvent from the aqueous dispersion. An aqueous coating composition can be obtained by adding a curing agent to the foregoing aqueous dispersion of polyester resin.

Claims

1. An aqueous dispersion of polyester resin having an acid value of 8 to 40 mg KOH/g and a weight average molecular weight of 9,000 or more,

wherein the aqueous dispersion contains an organic solvent less than 0.5% by mass;

the polyester is formed of dicarboxylic acid as a dicarboxylic acid component among constitutional acid components;

wherein said dicarboxylic acid is at least one dicarboxylic acid selected from the group consisting of

terephthalic acid, isophthalic acid, orthopthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid,

oxalic acid, succinic acid, succinic anhydride, adipic acid, azelaic acid, sebasic acid, dodecanedioic acid, hydrogenated dimer acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, dimer acid,

1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 2,5-norbornenedicarboxylic acid, an anhydride of 2,5-norbornenedicarboxylic acid, tetrahydrophthalic acid and an anhydride of tetrahydrophthalic acid;

the polyester contains aromatic polybasic acids as a constituent acid component at a ratio of 70% by mole or higher; and

the polyester may contain as the constituent acid component a tri- or more carboxylic acid and/or a monocarboxylic acid.

2. The aqueous dispersion of polyester resin according to either claim 1, wherein the polyester resin contains mainly neopentyl glycol and ethylene glycol as constituent alcohol components.

3. The aqueous dispersion of polyester resin according to either claim 1, wherein the polyester resin contains mainly 1,2-propanediol and ethylene glycol as constituent alcohol components.

4. A method for producing the aqueous dispersion of polyester resin according to claim 1 comprising a first a step of obtaining an aqueous dispersion of polyester resin containing not lower than 0.5% by mass of an organic solvent by adding the polyester resin and a basic compound to an aqueous medium to make the resulting mixture aqueous and then a step of removing the organic solvent from the aqueous dispersion.

5. A method for producing the aqueous dispersion of polyester resin according to claim 2 comprising at first a step of obtaining an aqueous dispersion of polyester resin containing not lower than 0.5% by mass of an organic solvent by adding the polyester resin and a basic compound to an aqueous medium to make the resulting mixture aqueous and then a step of removing the organic solvent from the aqueous dispersion.

6. A method for producing the aqueous dispersion of polyester resin according to claim 3 comprising at first a step of obtaining an aqueous dispersion of polyester resin containing not lower than 0.5% by mass of an organic solvent by adding the polyester resin and a basic compound to an aqueous medium to make the resulting mixture aqueous and then a step of removing the organic solvent from the aqueous dispersion.

7. An aqueous coating composition being obtained by adding a curing agent to the aqueous dispersion of polyester resin according to claim 1.

8. An aqueous coating composition being obtained by adding a curing agent to the aqueous dispersion of polyester resin according to claim 2.

9. An aqueous coating composition being obtained by adding a curing agent to the aqueous dispersion of polyester resin according to claim 3.

10. The aqueous dispersion of polyester resin of claim 1, wherein said weight average molecular weight is 14,000 or more.

11. The aqueous dispersion of polyester resin of claim 1, wherein said acid value is 8 to 25 mg KOH/g.

12. The aqueous dispersion of polyester resin of claim 1, wherein the glass transition temperature of said polyester resin is 0°

C. to 100°

C.

13. The aqueous dispersion of polyester resin of claim 1, wherein said aqueous dispersion further comprises a compound having a protective colloidal function.

14. The aqueous dispersion of polyester resin of claim 1, wherein said aqueous dispersion further comprises an ingredient selected from the group consisting of leveling agent, defoaming agent, bubbling preventing agent, pigment dispersing agent, UV absorbing agent, pigment and dye.