JPS5883067A - Production of mar-resistant paint - Google Patents

Abstract

PURPOSE:To produce the titled paint which gives a coating film having excellent resistance to marring and wear, by adding specified acrylonitrile polymer particles to paint. CONSTITUTION:At least 80wt% acrylonitrile and no more than 20wt% ethylenically unsaturated compd. contg. a sulfonic (salt) group attached thereto are polymerized in water to obtain an aq. dispersion of acrylonitrile polymer (PAN), said dispersion containing PAN at a concn. of 10-30wt%. 1-10wt% (based on the amount of solid in the dispersion) org-solvent capable of dissolving PAN is added to the dispersion. The mixture is spray-dried at a temp. of 100 deg.C or higher, but not higher than the b.p. of said solvent to obtain PAN particles having an average particle size of 2-200mu. 5-100pts.wt. PAN particles is added to 100pts.wt. (on a nonvolatile matter basis) paint.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a scratch-resistant paint that can form an excellent coating film that is extremely scratch-resistant when applied to a metal plate or the like.

Conventionally, prevention of processing scratches and handling scratches that occur when processing or transporting painted metal plates, etc. has been an important issue in terms of practical performance, and various methods have been developed to impart scratch-resistant properties to the coating surface. Methods have been tried. For example, as a paint improvement, the crosslinking density of a thermosetting paint is increased to increase the hardness of the coating film, but this reduces the workability of the coated plate. A method of coating the outermost layer of the coating film with a silicone resin is also known, but there are problems with the adhesion of the outermost layer with the organic coating film and the increase in manufacturing steps. In addition, synthetic resin protective films are sometimes used to protect the paint film, but they are not often used for general building materials due to increased cost and difficulty cleaning up afterwards. be. Under these circumstances, the present inventors have previously discovered that adding acrylonitrile polymer particles to a paint has the effect of improving the scratch resistance of the paint film [Japanese Patent Application No. 12777/1983] Kaisho 55-10626
9)) disclosed that the scratch resistance of the coating film could be further improved by further heat-treating acrylonitrile polymer particles and then adding the particles to the paint (water-based paint) (Japanese Patent Application No. 11503/1983). However, the scratch resistance of the coating film thus obtained is not necessarily sufficient to withstand the severe shearing forces actually experienced, and further improvement in performance is desired.

The present inventors have conducted various studies with the aim of obtaining a paint that forms a coating film with improved scratch resistance based on the above-mentioned prior invention in which acrylonitrile polymer particles are added to the paint. An organic solvent capable of dissolving the acrylonitrile polymer is added before spray-drying the aqueous dispersion of polymer particles, and the granules obtained by spray-drying are added to the paint to create a paint with excellent scratch resistance. The present invention was achieved by discovering that it is possible to produce the following. That is, the present invention
An organic solvent capable of dissolving 1 -10% by weight of the acrylonitrile polymer based on the solid content in the aqueous solution is added to an aqueous dispersion of the acrylonitrile polymer, and the mixture is granulated using a spray drying method, with an average particle size of 2 to 2. A method for producing a scratch-resistant paint, which comprises obtaining 200 μm acrylonitrile polymer particles and adding 5 to 100 parts by weight of the acrylonitrile polymer particles to 100 parts by weight of non-volatile content of the paint. It is something.

The method for producing a scratch-resistant paint according to the present invention will be explained in detail below.

To obtain an aqueous dispersion of an acrylonitrile-based polymer (hereinafter sometimes abbreviated as PAN) used in the present invention, JP-A-52-8090 and JP-A-52-4056 are used.
No. 9, JP-A-52-107045, JP-A-54-18
The method disclosed in No. 858, JP-A-54-30281, etc. can be used. For example, as disclosed in JP-A-52-8090, acrylonitrile is the main component! :
1L Residue G2>E A monomer consisting of an ethylenically unsaturated compound containing a sulfonic acid or a salt thereof is polymerized in water to introduce a sulfonic acid group or a salt thereof into the resulting polymer. The microparticles form an aqueous dispersion of polymer droplets in a substantially molten state and are then cooled with stirring to prevent the polymer droplets from coalescing to harden the polymer droplets into a substantially spherical shape. An aqueous dispersion containing PAN is obtained.The concentration of PAN in the water-acid solution is not particularly limited, but is usually used at 10 to 30% by weight.

When the acrylonitrile (IJ) content of PAN is 80% by weight or more, it is possible to further improve the abrasion resistance.

Next, P was added to the aqueous dispersion of PAN obtained as described above.
An organic solvent capable of dissolving AN (hereinafter sometimes abbreviated as PAN solvent) is added. The PAN solvent may be one that has a high boiling point and can dissolve PAN, such as ethylene carbonate, γ-butyrolactone, dimethylformamide (DMF), and dimethylacetamide (D
MA), dimethyl sulfoxide (DMSO), etc., or a mixture of two or more of these PAN solvents may be used.

The purpose of adding such a PAN solvent to the aqueous PAN dispersion is to strengthen the PAN particles obtained by directly granulating the aqueous PAN dispersion by spray drying.

In other words, granulation is achieved by a large number of PAN microparticles in an aqueous dispersion, which are secondary particles, coalescing to form secondary particles, but the bonding force between the secondary particles is not sufficient, and such The inventors' research has shown that when PAN secondary particles are added to a paint and are present on the surface layer of the paint film, when strong frictional force is applied, the bonds between the primary particles break down, causing scratches on the paint film surface. That's what I found out. Therefore, when granulating an aqueous PAN dispersion by spray drying, a solvent that has the ability to dissolve PAN particles is added in advance to strengthen the binding force between primary particles when secondary particles are formed. be.

This strengthening of the bonding force is due to the fact that the PAN solvent not only simply bonds the primary particles, but also makes the surfaces of the PAN particles compatible and slightly plasticizes them, resulting in a fused state between the primary particles. It is assumed that this is the case. The amount of the PAN solvent added is 1 to 10% by weight of the solid content in the aqueous PAN dispersion. If the amount added is less than 1% by weight, the effect of strengthening the bonding force of the primary particles will be insufficient, and if it exceeds 10% by weight, excess PAN bath agent will remain outside the secondary particles and the secondary particles once formed will be The PAN particles become more easily bonded, or the entire PAN particles become plasticized and become soft! L
<No.

The aqueous PAN dispersion to which the PAN solvent has been added as described above is then subjected to granulation by spray drying.

The heating temperature during spray drying is 100°C or higher, which is the boiling point of water, to evaporate the water in the aqueous PAN dispersion and prevent the PAN solvent from completely evaporating, and the boiling point of the PAN solvent used. Lower temperatures are preferred. Performing spray drying above the boiling point of the PAN solvent is a
This is undesirable because the PAN solvent evaporates before the plasticizing effect of the solvent is exerted. Thus obtained P
In the AN particles (secondary particles), the PAN solvent plasticizes and fuses between the primary particles of PAN, so that the entire secondary particles of PAN become tough particles.

The PAN particles thus obtained by granulation are then sieved into particles having an average particle size in the range of 2 to 200 μm (hereinafter sometimes referred to as appropriate particle size). Sieving can be performed by a conventional method such as a continuous method or a patch method.

After the PAN particles larger than the appropriate particle size are crushed, they can be added again to the aqueous dispersion of PAN particles together with those smaller than the appropriate particle size and subjected to granulation. In the present invention, the average particle size of the PAN particles added to the paint is 2 to 20 mm in order to fully exhibit the scratch resistance of the paint film, which is the main effect of the present invention.
It needs to be in the range of 0μ, especially lO~100
μ is preferred. The reason is that a normal coating film has a thickness of 5 to 200μ.
If the average particle size is less than 2μ, most of the PAN particles will be buried in the paint film when painted on a metal plate, making it impossible to prevent direct contact between the paint film and other objects, resulting in poor scratch resistance. If the average particle size exceeds 200μ, the dispersion state of PAN particles in the paint will deteriorate, reducing painting workability, and furthermore, when processing coated metal plates, the coating film on the processed area may deteriorate. This is because PAN particles may be missing.

The thus obtained PAN particles having an appropriate particle size are added and mixed into a paint. The mixing ratio is 5 to 100 parts by weight of P'AN particles to 100 parts by weight of non-volatile content of the paint, especially 1
0 to 30 parts by weight is preferred, preferably 4 cavities. The reason for this is that if it is less than 5 parts by weight, it will not be possible to sufficiently exhibit scratch resistance when coating a metal plate, and the hardness of the coating will not improve. Moreover, if the PAN particles exceed 100 parts by weight, it is difficult to obtain a uniform dispersion state in the paint, the viscosity of the paint increases, the painting workability decreases, and furthermore, the amount of PAN particles in the paint film when applied is difficult to obtain. This is because the ratio of the coating film-forming resin in the coating film is decreased, which is undesirable because the coating film becomes hard and extremely brittle, and the workability is significantly reduced. The paint to which PAN particles of appropriate particle size are added and mixed may be any paint that can uniformly disperse PAN particles, such as chilester-based, silicone resin-based, acrylic resin-based, fluororesin-based, vinyl chloride resin-based. It is possible to show paints such as

The method for producing a scratch-resistant paint according to the present invention is characterized in that the coating film of the scratch-resistant paint obtained by the method is very strong.
It has excellent scratch resistance because it is protected from direct contact with other objects by the particles, and it is not brittle due to the appropriate mixing ratio of PAN particles.
This is an extremely rational production method that can strengthen the PAN particles without consuming any special heat source by mixing the N solvent, and is industrially valuable.

Examples 1-20. Comparative Examples 1 to 6 450 parts by weight of acrylonitrile (hereinafter abbreviated as "parts"), 40 parts of methyl methacrylate, 10 parts of sodium p-styrene sulfonate and 1181 parts of water were charged into an autoclave with a capacity of 21 Fr, and further added as a polymerization initiator. After adding ammonium persulfate in an amount of 0.5% based on the total amount of monomers, the mixture was sealed and polymerized for 23 minutes at a temperature of 150°C with stirring.
After cooling to ℃, the polymerization product was taken out from the autoclave and unreacted monomers were removed, resulting in a solid content concentration of 25%.
An aqueous dispersion of PAN was obtained. To this aqueous dispersion, each PAN bath agent of each weight % shown in Table 1 based on the solid content was added, and the mixture was fed to a spray dryer at a rate of 1//hour to produce products at each drying temperature shown in Table 1. It was granulated and sieved to obtain PAN particles with an average particle size of 20 μm.

Next, the PAN particles obtained in the above manner were added to and mixed with the solvent-based polyester-based blue enamel paint having a non-volatile content of 50% by volume as shown in Table 1, based on the unresolved part of the paint. A scratch-resistant paint was obtained.

On the other hand, about 50% of epoxy resin paint was applied as a primer to a galvanized iron plate with a thickness of 0.35 m that had been subjected to ordinary phosphate treatment.
Each coated plate was coated with a roll to a thickness of μ and baked, and then the scratch-resistant paint was coated with a roll to a thickness of 20 μ to obtain each coated plate. The scratch resistance of each coated plate was tested by the following method.

Scratch resistance test method: Two coated plates with a size of 8Q m x 15Q m were placed on top of each other horizontally so that their coated surfaces were in contact with each other, and a cylinder with a cross-sectional area of 32.8 d was placed on top of them. Furthermore, on top of that
After placing a weight on the O'i4 and rotating the upper painted plate 90 times while keeping the lower painted plate fixed, the state of damage to the paint film surface was observed and the damage was found to be severe (1). ) to almost no scratches (5) were evaluated in 5 grades and expressed numerically.

Evaluation Degree of scratches l...Severe 2...Slightly severe 3...Moderate 4...Slightly 5...Almost none For comparison, when no PAN solvent was used (Comparative Example 2)
In addition to ~6), a case (Comparative Example 1) was also conducted in which the paint was used as it was without adding or mixing any PAN particle numbers. The results are also shown in Table 1.

Based on the comparison between Comparative Example 1 and Comparative Examples 2 to 6 in Table 1 below, PAN particles granulated without using PAN solvent were added to the paint and cases were not added. Although the scratch resistance of the coating film is considerably improved compared to the above, it is still not sufficient. However, the scratch resistance of the coating films mixed with PAN particles (each example) in which the bond between primary particles was strengthened using a PAN solvent was further improved, especially when the temperature during granulation by spray drying was It turns out that the higher the value, the better.

Claims (1)

[Claims] l -10% by weight of acrylonitrile based on the solid content in the aqueous solution in an aqueous dispersion of an acrylonitrile polymer) IJ
Acrylonitrile polymer particles with an average particle size of 2 to 200μ are obtained by adding an organic solvent capable of dissolving the acrylonitrile polymer and granulating it by spray drying. A method for producing a scratch-resistant paint, which includes adding 5 to 100 parts by weight of polymer particles. 2. The method for producing a scratch-resistant paint according to claim 1, wherein ethylene carbinate is used as the organic solvent capable of dissolving the acrylonitrile polymer. 3. Using r-butyrolactone as an organic solvent capable of dissolving an acrylonitrile polymer: A method for producing a scratch-resistant paint according to claim 1. 4. The method for producing a scratch-resistant paint according to claim 1, wherein trimethylformamide is used as the organic solvent capable of dissolving the acrylonitrile polymer. 5. The method for producing a scratch-resistant paint according to claim 1, wherein trimethylacetamide is used as the organic solvent capable of dissolving the acrylonitrile polymer. 6. The method for producing a scratch-resistant paint according to claim 1, wherein trimethyl sulfoxide is used as the organic solvent capable of dissolving the acrylonitrile polymer. 7. Any one of claims 1 to 6 in which the spray drying temperature is 100 C or higher and lower than the boiling point of the organic solvent that can dissolve the acrylonitrile polymer. A method for producing a scratch-resistant paint as described in .