JPS607549B2 - How to prepare a polymer latex bath - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preparing polymer latex materials in continuous coating of aluminum products.

Specifically, it is a method for preparing a polymer latex grade in which the polymer latex grade is treated with a cation exchange resin and aluminum ions present in the bath are removed from the system. The inventor is
First, an aluminum product that has been anodized and has a surface structure in an active state is immersed in a polymer latex containing negatively charged polymer particles and whose pH is adjusted to below 3.0. He discovered a method for forming a water-insoluble polymer coating layer on the surface and has already applied for a patent (see Tokuka Sho 54-109).

However, if anodized aluminum products are continuously coated using this method, the aluminum oxide will dissolve and the aluminum ions will elute and accumulate in the polymer latex, resulting in a loss of stability of the latex. become.

The present invention aims to solve the above problems and maintain a polymer latex bath in a stable state at all times.

According to experiments conducted by the present inventor, it has been found that aluminum ions accumulated in a polymer latex bath due to continuous coating can be easily removed by treating the latex with a cationic resin.

The present invention has been made based on the above findings. To summarize the present invention, an aluminum product which has been subjected to an anodizing treatment and has a surface structure in an active state, which has negatively charged polymer particles and has a pH of 3. In this method, the polymer latex is immersed in a polymer latex adjusted to 0 or less, and a water-insoluble polymer coating layer is formed on the surface. This is a method to remove aluminum ions.

Ion-exchange resin treatment is widely practiced in the art as a method of conditioning paints.

For example, the dew paint used for painting aluminum that has undergone anodizing treatment uses the carboxyl group of a synthetic polycarboxylic acid resin as a film-forming component, and neutralizes the resin with an organic base or ammonia, etc. However, it is an anionic substance dispersed in water and has a pH of 7 or more. In dew coating, the organic base or ammonia used as a neutralizing agent accumulates in the paint due to continuous operation, and the paint cannot be painted normally. In order to eliminate such defects, the electrodeposited paint is brought into contact with a cationic resin to remove excess neutralizing agent from the paint and control the unevenness. The present invention uses a polymer latex that has negatively charged polymer particles and has been adjusted to a pH of 3.0 or less, and by simply soaking the polymer latex in the polymer latex, water can be applied to the surface of anodized aluminum products. In this method of forming an insoluble polymer coating layer, which uses a different paint and coating method than haze coating, a cation cross-resin treatment is used to adjust the grade of the polymer latex, and this treatment allows the polymer latex to accumulate in the bath. This method removes aluminum ions from the system.

As a result, the polymer latex can be kept in a stable state at all times, resulting in coated products of consistent quality. To explain the present invention in more detail, a strongly acidic cationic sardine resin or a weakly acidic cationic exchange resin is used as the cation exchange resin.

The polymer latex is treated with a cation exchange resin at an appropriate time.

For example, you can set a control value for the concentration of aluminum ions in a polymer latex bath in advance, and then choose a method that will be applied when the aluminum ions in the bath reach its limit, or when the number of coated surfaces exceeds a certain value. For the cation exchange resin treatment, it is preferable to adopt the generally practiced method of filling an ion exchange column with a cation exchange resin and passing the polymer latex through the column.

In this case, it is appropriate that the flow rate of the polymer latex is SV = 10 or more, preferably SV = 30 or more.On the other hand, by continuous coating, the resin content in the polymer latex will gradually decrease. Therefore, it is also necessary to replenish the resin content.

In the present invention, a control value for the resin concentration of polymer latex is set in advance, and when the lower limit of the control value is reached, the polymer latex for replenishment is added to adjust the concentration, or the concentration is adjusted depending on the number of surface areas to be painted. Each time a coating is applied, polymer latex is added to adjust the amount of resin depending on the amount of resin used. The polymer latex to which the method used in the present invention can be effectively applied is one made by emulsifying one or more monomers having ethylenically unsaturated double bonds and, if necessary, adding and blending a crosslinking agent. It is obtained by polymerization, has negatively charged polymer particles, and has a pH adjusted to 3.0 or less. Monomers with ethylenically unsaturated double bonds include acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, alkyl acrylates, alkyl methacrylates, hydroxyalkyl acrylates, hydroxyalkyl methacrylates, acrylamide, methacrylamide, and the like. N-methylolated product or N
-Alkoxymethylol compounds: acrylic or methacrylic monomers such as acrylonitrile and methacrylonitrile, styrenic monomers such as styrene, P-chlorostyrene, and Q-methylstyrene, and vinyl monomers such as vinyl acetate and vinyl propionate. monomers, butadiene to isoprene, chloroprene, and other gen-based monomers.

Also, "monomers having a phosphoric acid group and an ethylenically unsaturated double bond, such as mono(2-hydroxyethyl acrylate) acid phosphate, mono(2-hydroxyethyl methacrylate) acid phosphate"
Hydroxypropyl acrylate) acid phosphate, mono(2-hydroxypropyl methacrylate) acid phosphate, mono(3-hydroxypropyl acrylate) acid phosphate, mono(3-hydroxypropyl methacrylate) acid phosphate, etc. Primary phosphate esters of acrylates or methacrylates containing hydroxyl groups such as allyl alcohol acid phosphate, vinylphosphonic acid, paravinylbenzenephosphonic acid, monomers with sulfonic acid groups and ethylenically unsaturated double bonds, e.g. Sulfomethyl acrylate, 2-sulfoethyl acrylate, 2-sulfopropyl acrylate, 3-sulfopropyl acrylate, sulfomethyl methacrylate "2-sulfoethyl methacrylate, 2-sulfopropyl methacrylate, 3
-Sulfopropyl methacrylate, styrene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, etc. can also be used. Examples of the compound to be added as a crosslinking agent include thermosetting epoxy compounds, amino compounds, block polyisocyanate compounds, and phenol compounds.

The polymer latex is obtained by polymerizing one or more of the above monomers, blended with a crosslinking agent if necessary, by an emulsion polymerization method.

In the present invention, anodized aluminum products with an active surface structure are to be painted.

This active state surface structure means that the anodic oxide film is
Aluminum blue is a type of dye used in the dyeing test of S (Japanese Industrial Standards) Day 8683.
mBlue) 4W is used, it is immersed in this IW/V% aqueous solution at 20qo for 15 minutes, and as a result of washing with water, it refers to a surface structure that is dyed even slightly blue. The method of the present invention includes
Since this is a surface treatment method in which an aluminum product having the above-described specific surface structure is immersed in a polymer latex to form a water-insoluble resin film on the surface of the aluminum product, the pH of the polymer latex must be adjusted to 3.0 or less. , and it is necessary to use polymer particles whose surfaces are negatively charged.

This is true for any type of polymer latex.
When H is 3.0 or higher, even if anodized aluminum products with a surface structure that is dyed in a dyeing test are immersed, no hydrophobic resin layer will be formed. Based on the knowledge that even with polymer latex whose pH has been adjusted to 3.0 or less, formation of a water-resistant resin layer is not observed in latex without negatively charged polymer latex particles. This is the reason why In order to obtain an anionic polymer latex with negatively charged polymer particles, anionic polymerization initiators and/or emulsifiers are used.

Alternatively, a monomer having a functional group that causes the polymer latex to be negatively charged may be used. In the present invention, the types and amounts of these particles are not particularly limited, as long as negatively charged polymer latex particles can be obtained as a whole.

For example, even if an initiator such as 414-azobisisobutyramidinium hydrochloride is used, the entire particle can be negatively charged using an anionic emulsifier such as sodium lauryl sulfate. Can be used for invention methods. Therefore, the polymerization method for the polymer latex used in the present invention includes radical emulsion polymerization using a nonionic surfactant or anionic surfactant as an emulsifier and potassium persulfate, ammonium persulfate, etc. as an initiator, hydrogen peroxide, etc. Emulsion polymerization using a redox initiator such as Fe20 and Fe20 can be used.

Further, emulsion polymerization without using an emulsifier, emulsion suspension polymerization using azobisisobutyronitrile, penzoyl peroxide, etc. can also be used. Examples of nonionic surfactants include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene nonylphenol ether, sorbitan monolauryl ester, sorbitan dioleyl ester, polyoxyethylene sorbitan monostearyl ester, etc.
Examples of anionic surfactants include oleic acid sodium salt, lauryl alcohol sulfate sodium salt, stearyl alcohol sulfate trietanoamine salt, dodecylbenzenesulfonic acid sodium salt,
Examples include octylnaphthalene sulfonic acid potassium salt, dioctyl sulfosuccinic acid sodium salt, polyoxylauryl sulfate sodium salt, and polyoxyethylene nonylphenol sulfate ester potassium salt. The pH of polymer latex can be adjusted using mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid.
This may be carried out by adding an organic acid such as acetic acid or oxalic acid.

The resin concentration of the polymer latex used in the present invention is 0.5
~60% by weight (resin solid content) is suitable; if it is less than 0.5% by weight, the formed water-insoluble resin layer will be thin and the adhesion to the object to be coated will be poor; on the other hand, if it is more than 6% by weight, This is undesirable because the viscosity becomes high and it becomes difficult to obtain a stable polymer latex.

Considering economic efficiency from the resin film thickness and precipitation rate, 1 to 4% by weight is preferable. The soaking time for forming a water-insoluble resin layer by soaking an aluminum product that has been anodized and has a surface structure in an activated state in the polymer latex varies depending on the desired resin film thickness. The formation of this can already be observed with sand soaking for 1 minute, and usually a resin-free film of 5 to 30 μm can be obtained after sand soaking for 3 nights to 1 minute. If necessary, the aluminum product pulled from the polymer latex is further soaked in water to remove excess polymer latex, and then dried.

Drying is usually done at room temperature to 200°C for 5 to 30 minutes. The aluminum products targeted by the present invention include plates, rods, wires, and other molded products with complex shapes, and are not limited in shape or size.

Furthermore, when processing long shapes such as aluminum sashes, either horizontal or vertical hanging methods can be adopted. According to the method of the present invention, an anodized aluminum product having an active surface structure is continuously heated in a polymer latex bath in which polymer particles are negatively charged and whose pH is adjusted to below 3.0. The latex bath can be prepared very advantageously when coating.

Next, the method of the present invention will be explained in more detail with reference to Examples.

Preparation of latex, thermometer, 1 cup of deionized water in a four-round flask equipped with a reflux condenser, dropping funnel and nitrogen gas inlet tube.
5 Boto, polyoxyethylene ~ Add 1.5 parts of sodium nonylphenol sulfate and 0.5 parts of potassium persulfate,
It was heated to 80℃ while worshiping in the sea.

A mixture of 6 acrylic acid esters and 4 methyl methacrylates was added dropwise from the dropping funnel over a period of 2 hours. After the dropwise addition was completed, the reaction was continued for another 4 hours, and the conversion rate was 95.
% latex was prepared. This latex was diluted to a solid content of 2% by weight, and the pH was measured to be 2.5.

Preparation of test materials A JISA5052 aluminum plate (200 skins x 6.5 sides x 0.5 fences) pretreated by a conventional method was used as an anode and carbon was used as a cathode 3, and 2 pi○ and IA nod were used in a 15 wt% sulfuric acid aqueous solution.
After turning on the electricity for 30 minutes and washing with tap water for 18 minutes,
The sample was soaked in 0oo warm water for 5 minutes.

Painting 50% of the test material was added to the latex prepared above.
It was soaked repeatedly for 5 minutes at 30 qo. Comparative Example 1 Table 1 shows the coating film thickness and aluminum ion concentration in the latex when the above coating was repeated.

．． Table 1 Example 1 The above coating was repeated and the latex coated in step 10 was treated with cation exchange resin lmacZ-5 (lma
Liquid passing rate SV = 50 in a column packed with
The solution was passed for 1 hour.

After that, the paint film thickness when painting again is 15〆,
Measuring the aluminum ion concentration in latex shows 6
It was the 9' sleeve. Example 2 While repeating the above coating, the latex was brought into continuous contact with a cation exchange resin lmac Z-5 (manufactured by lmac) 500 at SV=300, and the aluminum ion concentration in the latex was 0 to 10. Although the coating thickness varied within this range, a uniform coating thickness was always obtained within the range of 14±1 mm.

Claims (1)

[Claims] 1 An aluminum product that has been anodized and has a surface structure in an active state is immersed in a polymer latex containing negatively charged polymer particles and whose pH is adjusted to below 3.0, and water is applied to the surface of the product. Preparation of a polymer latex bath in a method for forming an insoluble polymer coating layer, characterized in that the polymer latex is subjected to an on-exchange treatment to remove aluminum ions eluted and accumulated in the bath by continuous coating. Method.