JPS6014630B2 - 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 baths in the continuous coating of aluminum products.

Specifically, it is a method for adjusting the grade of a polymer latex in which the polymer latex is subjected to an ultrafiltration treatment to remove aluminum ions present in the filtrate from the system. The inventor has previously developed an aluminum product having a surface structure that is anodized and in an active state, which has negatively charged polymer particles.
In addition, he discovered a method for forming a water-insoluble polymer coating layer on the surface of polymer latex by soaking it in a polymer latex adjusted to pH 30 or less, and has already applied for a patent (Hakama Akisho 54-109).
(see number). However, if aluminum products that have been anodized using this method are painted continuously, the aluminum oxide will dissolve and aluminum ions will elute and accumulate in the polymer latex, impairing the stability of the latex. It turns out.

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

According to the inventor's experiments, ultra-moat filtration treatment can separate substances with a certain molecular weight or less, so aluminum ions that accumulate in the polymer latex can be easily removed from the system by continuous coating. It turns out it can be done.

The present invention has been made based on the above findings. To summarize the present invention, an aluminum product having a surface structure which has been anodized and is in an active state, which has negatively charged polymer particles and has a pH of 3.0 In the method of soaking in a polymer latex prepared as follows and forming a water-insoluble polymer coating layer on its surface, the polymer latex is subjected to ultra-supertreatment, and the polymer latex is immersed in the liquid by continuous coating. This method removes aluminum ions that elute and accumulate from the system.

Ultra-transient treatment is used in the art as a method for removing neutralizing agents such as amines and ammonium that accumulate in electrodeposition coatings, and also as a method for eliminating wastewater during the coating process.

In this method, a paint liquid is passed under pressure through one side of a pore-filled membrane with a pore size of approximately 0.1 to several micrometers. It separates substances. In the present invention, a commonly used ultrafiltration system is used to process the polymer latex matrix.

By this treatment, aluminum ions that accumulate in the polymer latex can be removed from the system after each coating. Therefore, the polymer latex can be kept in a stable state at all times, and coated products of constant quality can be obtained.
By the way, when the ultraviolet filtration treatment is performed as described above, the low-molecular substances permeate through the pore-forming membrane, so that water and acid in the polymer latex are reduced.

Therefore, when ultra-ditching, the polymer latex bath is supplemented with water and acid to reduce the resin concentration and grade to 3.0.
Must be kept below. As make-up water, it is possible to reuse water obtained by subjecting the polymer latex to an ultra-horizontal filtration treatment and treating the permeate that has passed through the pore-forming membrane with a cation exchange resin. On the other hand, since continuous coating causes the resin content in the polymer latex to gradually decrease, it is also necessary to replenish the resin content.

In the present invention, a control value for the resin concentration of the polymer latex grade 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 level to correspond to the amount of resin used. The polymer latex used in the present invention is obtained by emulsion polymerization of one or more monomers having ethylenically unsaturated double bonds, with the addition of chopped wood if necessary. be. Monomers with ethylenically unsaturated double bonds include acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, alkyl acrylates, furkyl methacrylates, hydroxyalkyl acrylates, hydroxyalkyl methacrylates, acrylamide, methacrylamide and 4N-methylolated products or N-alkoxymethylolated products thereof,
Acrylic or methacrylic monomers such as acrylonitrile and methacrylonitrile; styrenic monomers such as styrene, P-chlorostyrene, and Q-methylstyrene;
Contains vinyl monomers such as vinyl acetate and vinyl propionate, and diene monomers such as butadiene, isoprene, and chloroprene.

In addition, 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, mono(2-hydroxyethyl acrylate) acid phosphate, mono(2-hydroxyethyl acrylate) acid phosphate,
-hydroxypropyl acrylate) acid phosphate, ZO mono(2-hydroxypropyl methacrylate) acid phosphate, mono(3-hydroxypropyl acrylate) acid phosphate, mono(3-hydroxypropyl methacrylate) acid phosphate, etc. primary phosphates of taacrylates or methacrylates, including allyl alcohol acid phosphates, vinylphosphonic acid, paravinylbenzenephosphonic acid, monomers with sulfonic acid groups and ethylenically unsaturated double bonds, e.g. Sulfomethyl a○
Acrylate, 2-sulfoethyl acrylate, 2-sulfopropyl acrylate, 3-sulfopropyl acrylate, sulfomethyl methacrylate, 2-sulfoethyl methacrylate, 2-sulfopropyl methacrylate,
3-sulfopropyl tamethacrylate, styrene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, etc. can also be used. Examples of compounds to be added and blended as crosslinking agents include thermosetting epoxy compounds, amino compounds, block polyisocyanate compounds, and phenol compounds. In order to prepare a polymer latex, one or more of the above-mentioned monomers may be blended with a crosslinking agent if necessary, and then polymerized by an emulsion polymerization method.

In the present invention, anodized aluminum products having an active surface structure are to be painted. The surface structure in the active state refers to the surface structure that is dyed in the sealing test based on dyeability, and the anodic oxide film is treated with aluminum blue (AIuminimmOBblue), which is used in the JIS (Japanese Industrial Standards) day 8683 dyeing test. na W's lw/
It refers to a surface structure that is dyed even slightly blue as a result of being immersed in an aqueous solution of v% at 20oo for 15 minutes and washed with water. The coating method to which the method of the present invention is applied is a coating method in which an aluminum product having the above-described specific surface structure is immersed in polymer latex to form a water-insoluble resin film on the surface of the aluminum product. Combined latex boat 3.0
It is necessary to adjust the amount as follows and use polymer particles whose surfaces are negatively charged.

This means that no matter what kind of polymer latex you use, if the pH is above 3.0, anodized aluminum products with a surface area that will be dyed in a sealing test based on dyeability will be used as the coating object. Even if the polymer latex is soaked, no formation of a water-insoluble resin layer is observed, and even if the pH is adjusted to 3.0 or less, the latex does not have negatively charged polymer latex particles. This is because of the knowledge that formation of a water-insoluble resin layer was not observed. 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 4,4-azobisisobutyroamidinium hydrochloride is used, the entire particle can be negatively charged using an anionic emulsifier such as sodium lauryl sulfate. , can be used in the method of the present invention. Therefore, the polymerization method for the polymer latex used in the present invention includes radical emulsifier polymerization using a nonionic surfactant or anionic surfactant as an emulsifier and potassium persulfate, ammonium persulfate, etc. as an initiator, hydrogen peroxide, etc. and Fe2
Emulsion polymerization using a redox-based initiator such as those described in 10, etc. 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, solpitan monolauryl ester, sorbitan dioleyl ester, and polyoxyethylene sorbitan monostearyl ester. ,
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 potassium octylnaphthalene sulfonate, sodium dioctyl sulfosuccinate, sodium polyoxylauryl sulfate, and potassium polyoxyethylene nonylphenol sulfate. Spots in the polymer latex can be controlled by adding mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid, and organic acids such as acetic acid and noctic 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 dipping time for forming a water-insoluble resin layer by immersing an anodized aluminum product with a surface structure in an active state in polymer latex varies depending on the desired resin film thickness, but it depends on the thickness of the resin layer. Formation is already observed in sand with a soaking time of 1, and usually 5 to 30 resin films can be obtained with 3 to 1 minute of soaking time. If necessary, the aluminum product pulled from the polymer latex is further washed in water to remove excess polymer latex particles, and then dried. Drying is usually at room temperature to 20 pi○5
Done in ~60 minutes. The aluminum products targeted by the present invention include plates, rods, wires, and other molded products having 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 used. Next, Examples will be shown in order to explain the present invention more specifically.

Note that all parts in the following examples are parts by weight.
Preparation of Latex 1 1/2 cup of deionized water in a four-round flask equipped with a sieve, a thermometer, a reflux condenser, a dropping funnel and a nitrogen gas inlet tube.
5 parts, 1.5 parts of sodium polyoxyethylene nonylphenol sulfate, and 0.5 parts of potassium persulfate were added thereto, and the mixture was heated to 80°C under lighting.

Add to this 6 parts of ethyl acrylate, 4 parts of methyl methacrylate.
The mixed solution 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 to prepare a latex with a conversion rate of 95% or more. This latex was diluted to a solids content of 2% by weight and the cape was measured to be 2.5. Preparation of test materials Using a JISA5052 aluminum plate (200 side x 6.5 side x 0.5 sail) pretreated by a conventional method as an anode and carbon as a cathode, the material was heated at 20°C in a 15 wt% sulfuric acid aqueous solution, IA'd〆, 3 ■ After turning on the power and washing with tap water for each line, 80q.
The sample was soaked in warm water of 0 for 5 minutes.

Painting 30% of the test material was sequentially added to 50% of the latex prepared above.
00" Soaked repeatedly for 5 minutes.

Comparative Example 1 Table 1 shows the coating thickness and the aluminum ion concentration in the latex when the above coating was repeated.

Table 1 Example 1 The above painting was repeated and the coating was applied at a rate of 20 coats/min.
(permeate: 1.5 so/hr).

Table 2 shows the coating film thickness and the aluminum ion concentration in the latex as the coating area changes in that case. However, an aqueous sulfuric acid solution with a concentration of 2.5 points corresponding to the amount of permeated liquid was added every hour. Table 2 - Example 2 Painting due to changes in the coating area when the ultrafiltrated liquid in Example 1 was brought into contact with the cation exchange resin without being discharged from the system and then returned to the coating chamber. Table 3 shows the film thickness and the aluminum ion concentration in the latex.

Table 3

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 that has negatively charged polymer particles and whose pH is adjusted to below 3.0. In the method of forming a water-insoluble polymer coating layer on the surface, the polymer latex is subjected to ultrafiltration treatment, and aluminum ions that elute and accumulate in the polymer latex bath are removed by continuous coating. A method for preparing a polymer latex bath, characterized by: 2. The method according to claim 1, wherein the ultrafiltration permeate is brought into contact with a cation exchange resin. 3. The method according to claim 1 or 2, wherein an acid is added to the polymer latex bath to maintain the pH of the bath at 3.0 or less.