JP2007197639A - Normal temperature curable accelerator for japanese lacquer and normal temperature curable japanese lacquer clay composition using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suitable curable accelerator for Japanese lacquer by imparting water solubility to chitosan while retaining curing acceleration action on Japanese lacquer by leaving an amino group of chitosan as much as possible. <P>SOLUTION: The normal temperature curable accelerator is composed of a water-soluble chitosan in which parts of amino groups existing therein are neutralized with oxycarboxylic acid such as glycolic acid, lactic acid, α-oxylactic acid, malic acid, α-oxyglutaric acid, citric acid or glyceric acid. Pulp, kaolin, etc., is used as a filler. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a novel room temperature curing accelerator for lacquer and a room temperature curable lacquer clay composition obtained by blending it with a mixture of lacquer and filler.

  Lacquer is a liquid containing urushiol obtained from the secretions of sea urchin seeds as a main component and containing oxidase laccase, and by oxidative polymerization of urushiol by the catalytic action of laccase in the air with moisture, Since it is naturally dried to form a chemically stable and beautiful coating film, it is widely used as a natural paint exclusively for craft painting.

By the way, the action of the above laccase is strongly expressed under conditions of a temperature of 25 to 35 ° C. and a relative humidity (RH) of 70 to 80%. The higher the relative humidity, the faster the drying and the relative humidity is 60% or less. It is known that drying is slowed down, and that the drying speed decreases when the temperature is 20 ° C. or lower, and the lacquer does not dry when the temperature is 15 ° C. or lower.
For this reason, lacquer is dried in a temperature-controlled room with a high humidity atmosphere, but the drying speed is relatively slow even under such high humidity conditions. It usually takes months.

  For this reason, the drying time is usually shortened by adjusting the pH or adding a curing accelerator such as amines. Such curing accelerators have so far been protein hydrolysates (see Patent Documents 1 and 2), an amino group at the end of the main chain or branched chain of a hydrocarbon molecular chain, and a direct adjoining amino group. A compound having a reactive group having 2 or more chain carbon atoms (see Patent Document 3), a diamine compound having two amino groups at the end of a carbon chain composed of 2 or more carbon atoms (see Patent Document 4), etc. Has been.

  On the other hand, chitosan obtained by deacetylating chitin is a basic polysaccharide composed of glucosamine, which has many amino groups and is promising as a hardening accelerator for lacquer, but is insoluble in water, It cannot be used as it is. It is also known that the chitosan amino group can be easily dissolved in water if converted into a salt form of an organic acid (see Patent Document 5). When the acid is reacted, there is a problem that the free amino groups present are reduced and the hardening promoting action of lacquer is reduced.

JP-A-11-116896 (Claims and others) JP 11-256108 A (claims and others) JP 2002-3720 A (Claims and others) Japanese Patent Laying-Open No. 2003-238811 (Claims and others) JP-A-4-122702 (Claims and others)

  The present invention was made for the purpose of providing a suitable lacquer hardening accelerator by leaving as many amino groups of chitosan as possible while retaining the hardening accelerating action on lacquer and imparting water solubility to chitosan. Is.

  As a result of various studies on the modification of chitosan to water solubility, the present inventors have partially neutralized the amino group in chitosan with oxycarboxylic acid, thereby forming a plastic molding material based on lacquer. It was found that a water-soluble chitosan suitable as a room temperature curing accelerator was obtained, and the present invention was made based on this finding.

  That is, the present invention relates to a room temperature curing accelerator for lacquer composed of water-soluble chitosan in which some of the amino groups present therein are neutralized with oxycarboxylic acid, and (A) a lacquer base and (B) a filler, (C) The present invention provides a room temperature curable lacquer clay composition characterized by containing water-soluble chitosan in which a part of amino groups present therein is neutralized with oxycarboxylic acid.

In the present invention, examples of the oxycarboxylic acid used for neutralizing a part of the amino group in chitosan include glycolic acid, lactic acid, hydroacrylic acid, α-oxy-butyric acid, β-oxy-butyric acid, α-oxyiso Monooxymonocarboxylic acids such as butyric acid, α-oxy-n-valeric acid, monooxydicarboxylic acids such as tartronic acid, malic acid, α-oxyglutaric acid, β-oxyglutaric acid, and citric acid And dioxymonocarboxylic acids such as monooxytricarboxylic acid and glyceric acid.
Neutralization of the amino group of chitosan with these oxycarboxylic acids should be carried out at a rate at which 30 to 60%, preferably 40 to 50% of the amino groups present in the chitosan are neutralized. If the neutralization rate is less than 30%, chitosan is not sufficiently dissolved in water, and if the neutralization rate is more than 60%, the hardening acceleration effect of lacquer decreases.

  The neutralization reaction of the amino group in chitosan is performed, for example, by dispersing chitosan powder in water, adding an amount of oxycarboxylic acid corresponding to a desired neutralization rate, and stirring. This neutralization reaction proceeds sufficiently even at room temperature, but can be carried out by heating to a temperature of 50 to 80 ° C. if desired.

  The curing accelerator thus obtained is usually added at a ratio of 0.01 to 20% by mass with respect to the lacquer base, but more may be used if desired. If this addition amount is less than 0.01% by mass, a sufficient curing accelerating effect cannot be obtained.

Next, the room temperature curable lacquer clay composition of the present invention contains (A) a lacquer base, (B) a filler, and (C) the curing accelerator.
As the lacquer base of the component (A), refined lacquer (sugurome lacquer) from raw lacquer removed at low temperature to remove water, black lacquer (Kuroro lacquer) purified by adding iron hydroxide, etc., various pigments Any of the colored lacquer blended and colored can be used.

  In addition, as the filler of the component (B), either an inorganic filler or an organic filler may be used. Examples of the inorganic filler include porcelain clay, talc, glass powder, ceramic powder, metal powder, shirasu balloon, and carbon black. Examples of the organic filler include synthetic resin powder and cellulose powder, and natural fibers such as pulp are particularly preferable.

These fillers can be used in a mass ratio of 7: 3 to 3: 7 with respect to the lacquer base, but can be appropriately increased or decreased as long as the plastic formability is not lost.
If desired, alcohols, aromatic hydrocarbons, turpentine oil, and the like can be added to the room temperature curable lacquer clay composition.

  The room temperature curable lacquer clay composition of the present invention is suitable as various modeling materials.

  According to the present invention, there is provided a curing accelerator for lacquer that has good compatibility with lacquer and exhibits an excellent curing acceleration effect.

  Next, the best mode for carrying out the present invention will be described by way of examples. However, the present invention is not limited to these examples.

  By dispersing 2 g of chitosan powder in 100 ml of water and adding glycolic acid in an amount corresponding to 0.5 equivalent to the amino groups in chitosan and stirring at room temperature for 1 hour, 50 amino acids of chitosan were added. An aqueous solution of water-soluble chitosan neutralized with glycolic acid was prepared.

  In place of glycolic acid in Example 1, lactic acid was used in an amount corresponding to 0.5 equivalent to the amino group in chitosan, and the same operation as in Example 1 was carried out, and 50% of the amino group of chitosan was lactic acid. An aqueous solution of neutralized water-soluble chitosan was prepared.

  Instead of glycolic acid in Example 1, malic acid was used in an amount corresponding to 0.6 equivalents relative to the amino group in chitosan, and 60% of the amino group of chitosan was malic acid by operating in the same manner as in Example 1. An aqueous solution of water-soluble chitosan neutralized with 1 was prepared.

The aqueous chitosan aqueous solution obtained in Example 1 was added to a mixture of 200 g of lacquer, 100 g of paper pulp and 20 g of shirasu balloon, and kneaded for 1 hour to obtain a room temperature curable lacquer clay composition. When differential scanning calorimetry (DSC) was performed on this composition, the total calorific value for curing at 30 ° C. for 72 hours was 75.08 mJ / mg. This is almost 4 times as much as when the raw chitosan solid was added, indicating that the room temperature curing acceleration effect was remarkably improved.
Next, the flexural modulus and strength of the cured product obtained by allowing the composition to stand for 3 days at room temperature were measured and found to be 1.90 GPa and 17.6 MPa, respectively.

Comparative Example Instead of the chitosan aqueous solution neutralized with glycolic acid in Example 4, an aqueous dispersion of chitosan not subjected to glycolic acid treatment was used to prepare a room temperature curable lacquer clay composition.
This composition was subjected to differential scanning calorimetry (DSC) in the same manner as in Example 4. As a result, the total calorific value at 30 ° C. for 72 hours was 17.87 mJ / mg. Further, the elastic modulus and strength of the cured product obtained by leaving the cured product in the atmosphere at room temperature for 3 days were 1.62 GPa and 17.2 MPa, respectively.

Like conventional lacquer clay, it can be used as a production material for various shaped objects.

Claims (9)

  A room temperature curing accelerator for lacquer composed of water-soluble chitosan in which some of the amino groups present therein are neutralized with oxycarboxylic acid.   The room temperature curing accelerator for lacquers according to claim 1, comprising 30 to 60% of amino groups present therein in water-soluble chitosan neutralized with oxycarboxylic acid.   The room temperature curing for lacquer according to claim 1 or 2, wherein the oxycarboxylic acid is at least one selected from glycolic acid, lactic acid, α-oxybutyric acid, malic acid, α-oxyglutaric acid, citric acid and glyceric acid. Accelerator.   (A) A lacquer base, (B) a filler, and (C) water-soluble chitosan in which a part of an amino group present therein is neutralized with an oxycarboxylic acid, Composition.   (C) Content of a component is 0.1-20 mass parts based on 100 mass parts of (A) component, The normal temperature curable lacquer clay composition of Claim 4.   6. The room temperature curable lacquer according to claim 4, wherein the oxycarboxylic acid is at least one selected from glycolic acid, lactic acid, α-oxybutyric acid, malic acid, α-oxyglutaric acid, citric acid and glyceric acid. Clay composition.   The room temperature curable lacquer clay composition according to any one of claims 4 to 6, wherein the filler is at least one selected from fibrous substances and inorganic fillers.   The room temperature curable lacquer clay composition according to claim 7, wherein the fibrous substance is pulp.   The room temperature curable lacquer clay composition according to claim 7, wherein the inorganic filler is porcelain clay.