JPS5933144B2 - Vehicle composition for paints - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to paint vehicle compositions containing high solids capable amino resins and alkyd resins.

A mixture of an amino resin made by etherifying a methylolated product such as melamine, urea, or benzoguanamine with methanol or butanol, etc., and an alkyd resin whose main components are a polyhydric alcohol, a polybasic acid, and an oil or fat is widely used in paints as a vehicle for baking paints. It is used.

In recent years, research and development of mono-isolide paints has been intensively carried out with the aim of preventing air pollution caused by volatile solvents and saving resources.

Regarding amino alkyd resin paints, research has been carried out to improve both amino resins and alkyd resins, but in general, in order to lower the solution viscosity, a method is used to reduce the molecular weight of the resin. However, coating films using alkyd resins with low molecular weights have the disadvantage of being prone to defects such as repellency and craters. The object of the present invention is to provide a method for modifying an alkyd resin in which the solid content and viscosity of the paint are the same and the appearance of the paint film is improved, particularly defects such as cracks, craters, etc. Many studies have been reported regarding paint film...

For example, if the viscosity of the vehicle is low, cissing and cratering are likely to occur, which can be improved to some extent by incorporating high molecular weight substances such as cellulose acetate butyrate, nitrocellulose, etc. to increase the viscosity. It can also be improved by using animal and vegetable oils or synthetic fatty acids in the resin composition. However, these methods have problems with compatibility, and in the case of oil-modified alkyds, it may be difficult to obtain the desired coating performance due to staining and insufficient hardness of the coating. Therefore, we have conducted extensive research into short oil length or oil-free alkyd resins in order to improve repellency, cratering, etc., resulting in the present invention. That is, in the present invention, a dibasic acid and a divalent resin are added to 100 parts by weight of an alkyd resin having an oil length of 0 to 20% and a viscosity of Z6 or less on a Gardna viscometer when diluted with xylene to a solid content of 75% by weight. Consisting of alcohol, molecular weight 1000-20000
For the hydroxyl group of polyester with an acid value of 5 or less,
Urethane prepolymer having at least one isocyanate group in the molecule obtained by reacting 1 to 2 equivalents of diisocyanate and having a molecular weight of 5000 or more (B) 3 to 2
Modified alkyd resin (1) virtually free of isocyanate groups and amino resin (1) obtained by reacting 0 parts by weight
A paint vehicle composition comprising:

This vehicle composition for paint has significantly improved paint film defects such as scratches and craters (compared to paints made of alkyd resin and amino resin of the same solid content which are not modified by component B).

In the present invention, the alkyd resin having an oil length of 0 to 20% refers to common polyhydric alcohols such as glycols such as ethylene glycol, propylene glycol, 1,3-butylene glycol, neopentyl glycol, and 1-6 hexanediol, and glycerin. , trimethylolpropane,
Trimethylolethane, pentaerythritol, etc.
Polybasic acids and their products such as phthalic anhydride, isophthalic acid, adipic acid, sepacic acid, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, hexahydrophthalic anhydride, hexahydroterephthalic acid , trimellitic acid and/or fatty acids, or an alkyd resin with an acid value of 20 or less and a hydroxyl value of 50 to 300, obtained by the reaction of oils and fats, optionally containing an oxirane compound such as Cardiura 8E (trade name of Ciel Chemical Co., Ltd.), There is no problem with denaturation with basic acids such as benzoic acid.

As the oil used as necessary, known animal and vegetable oils or their fatty acids are used, such as soybean oil, linseed oil, cottonseed oil, safflower oil, tung oil, bean oil, castor oil, etc., and these fatty acids. .

These are used so that the oil length is 20% or less. If the oil length exceeds 20%, the coating properties, especially the adhesion, will deteriorate.
The viscosity of the alkyd resin (4) can be varied depending on the materials and formulation used. For example, when using the same materials, the greater the ratio of alcohol component to acid, or the greater the glycol content in the polyhydric alcohol, the smaller the molecular weight and the lower the viscosity. Although the viscosity of the alkyd resin (A) is specified as a xylene solution, when used as a paint vehicle, there is no problem in using it dissolved in a solvent other than xylene. Alkyd resin viscosity is xylene 7
When Z6 is exceeded in a 5% solution, it becomes difficult to achieve high solidity differentiation.

The urethane prepolymer (B) in the present invention has a molecular weight of about 5,000 obtained by reacting 1 to 2 equivalents of diisocyanate with the hydroxyl group of a linear polyester with an acid value of less than 5 and a molecular weight of 1,000 to 20,000.
It has 1 to 2 isocyanate groups in one molecule, which is about 20,000 to about 20,000.

The molecular weight of the polyester is a value calculated from the hydroxyl value and acid value, and corresponds to a hydroxyl value of about 100 to 5. This polyester can be obtained by subjecting an alkyd resin to polycondensation of a dihydric alcohol and a dibasic acid or anhydride thereof. In addition, a trifunctional or higher functional acid or alcohol may be added in a small amount, preferably 10
It may be used in amounts of up to mol%. This polyester also includes terephthalic acid-based polyesters such as polyesters obtained from oligomers obtained by decomposing polyethylene terephthalate with glycols and dibasic acids other than terephthalic acid. Examples of the diisocyanate include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and the like. The reaction between polyester and diisocyanate is preferably carried out in a solvent such as toluene or xylene.

Further, as a reaction catalyst, a catalyst such as dibutyltin dilaurate can also be used. When the molecular weight of the urethane prepolymer is less than 1000, the repellency which is the object of the present invention,
Improvements to Crater 1 have little effect and are difficult to put into practical use. Modified alkyd resin (1) is alkyd resin (A) 100
Urethane prepolymer (B) in a solution containing 3 parts by weight
It is obtained by reacting with 20 parts by weight.

If the urethane prepolymer (B) is less than 3 parts by weight, the effect of the present invention is not sufficient, and if it exceeds 20 parts by weight,
The effect of high solid differentiation, which is the object of the present invention, is virtually eliminated. The paint vehicle composition of the present invention can be obtained by blending 50 to 90 parts by weight of the modified alkyd resin (1) with 50 to 10 parts by weight of an amino resin generally used in the paint industry.

The amino resin may be blended at any stage before or after forming the coating. Furthermore, in order to improve the adhesion and corrosion resistance of the paint, there is nothing wrong with blending an epoxy resin or adding a paint stabilizer. The above amino resin is one obtained by addition condensation of an amino compound such as melamine, urea, benzoguanamine, etc. and an aldehyde such as formaldehyde, and is obtained by etherifying this with a monohydric alcohol having 1 to 4 carbon atoms such as methanol or butanol. There are things etc. The present invention will be explained below with reference to Examples.

Production Example 1 [Production of alkyd resins (A1 to A4)] Resins were synthesized at 170 to 220°C in a nitrogen gas atmosphere according to the formulations shown in Table 1 in a flask equipped with a demultiplexer and a stirrer.

Table 1 shows the properties of the resin obtained in each case. Production Example 2 [Production of urethane prepolymer (B1)] 166 gr of isophthalic acid, 146 gr of adipic acid, 120 gr of neopentyl glycol at 170 to 220°C.
A polyester with an acid value of 4 and a hydroxyl value of 48 (number average weight: 2150) was synthesized by a time reaction, and then 215g of the polyester was dissolved in 2157g of xylene, and 20.5g of tolylene diisocyanate was added and reacted at 100°C for 3 hours. Urethane prepolymer B-1 having a cardner viscosity of X was obtained.

Production Example 3 [Production of urethane prepolymer (B2)] Vylon 300200gr, manufactured by Toyobo Co., Ltd., which is a terephthalic acid polyester resin, was mixed with xylene Σkei (200g).
r, was dissolved in 300 gr of cyclohexanone, 4.4 t of hexamethylene diisocyanate was added, and the mixture was reacted at 100° C. for 3 hours to obtain prepolymer B-2 having a Gardner viscosity of S.

Production Example 4 [Production of modified alkyd resin] Alkyd resins A1 to A4 and urethane prepolymer B1
Or B2 in &. of Table 2. Modified alkyds were prepared with formulations 2-6, 8 and 10.

The reaction was carried out using a predetermined amount of an 80% xylene solution of algide resin and a urethane prepolymer at 100° C. for 3 hours.

This resin liquid showed no change in viscosity even after being left at 25°C for one week, indicating that it contained virtually no free isocyanate groups. Examples and Comparative Examples Paints were produced using the modified alkyd resin obtained in Production Example 4 or the alkyd resin obtained in Production Example 1 and Melan 8243 (methyl etherified methylol melamine manufactured by Hitachi Chemical Co., Ltd.) as a vehicle. did.

This paint was adjusted with a thinner containing xylene ethyl cellosolve acetate and xylene ethyl cellosolve acetate in a ratio of 1:1 (weight ratio) so that the viscosity of a food cup #4 at 25°C would be 20 seconds, and the paint was spray coated on a tin plate.

The coating film was dried after being left at room temperature for 10 minutes after spray coating, and then at 160° C. for 20 minutes. Table 2 shows the solid content during coating and the appearance of the coating film. Reference Example 750 parts of the above alkyd resin Al were dissolved in 250 parts of xylene, 50 parts of tolylene diisocyanate was added, and the mixture was heated to 100°C.
After reacting for 3 hours, the mixture was diluted with xylene so that the solid content was 75%.

The resin viscosity at this time was Z3. This resin was made into a paint in the same manner as in the example. The solid content at the time of coating was 61%, and the coating film had a score of 2 on a 5-point scale. As shown in Table 2, it can be seen that the Examples (Black 2, 3, 4, 8, and 9) have no repellency in the coating film and have a superior coating appearance compared to the Comparative Examples (Black 1 and 7).

In particular, in Examples ▲2, 5 and 6, the appearance of the coating film was significantly improved, even though the solid content of the coating material was higher than that of Comparative Example Haruka 7. The reference example was obtained by reacting alkyd A1 with a diisocyanate to increase the molecular weight, and compared to Examples 2, 3 and 4, the coating film appearance was inferior despite the lower coating solid content. As is clear from the above, the present invention can provide a paint vehicle composition that can be highly solidified and exhibits an excellent coating film appearance compared to conventional compositions.

Claims (1)

[Claims] 1 Add a dibasic acid and a divalent resin to 100 parts by weight of an alkyd resin (A) having an oil length of 0 to 20% and a viscosity of Z^6 or less when diluted with xylene at a solid content of 75% by weight using a Gardna viscometer. For the hydroxyl group of polyester consisting of alcohol with a molecular weight of 1000 to 20000 and an acid value of 5 or less,
Urethane prepolymer (B) 3-2 having a molecular weight of 5000 or more and having at least one isocyanate group in the molecule obtained by reacting 1 to 2 equivalents of diisocyanate
Modified alkyd resin (I) which has virtually no isocyanate groups and amino resin (II) obtained by reacting 0 parts by weight of
) A paint vehicle composition consisting of: