JPH0524187B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new self-polishing paint. A typical self-polishing paint is a self-polishing ship bottom antifouling paint, which has a relatively uneven paint surface that gradually becomes roughened by seawater during ship operation, and becomes smooth. It becomes a surface,
Frictional resistance in the water is significantly reduced, which has the effect of reducing fuel consumption. Of course, there are applications for self-polishing paints in fields other than ship bottom paints, in which the paint film gradually dissolves when it comes into contact with water, constantly exposing a new paint film surface, but for convenience the following uses ship bottom antifouling paints. This will be explained using an example. In the self-polishing paints known so far, an acrylic resin (trialkyltin polymer compound) introduced into an organic tin is used as a hydrolyzable resin vehicle. Antifouling paints using this trialkyltin polymer compound as a vehicle not only reduce underwater frictional resistance during ship operation and help save on fuel consumption, but also maintain the desired antifouling performance over a long period of time. It is also attracting attention for its ability to demonstrate This is because the trialkyltin polymer compound resin gradually undergoes hydrolysis and elutes into seawater, and at the same time, the antifouling agent also elutes at a constant rate in proportion to the degree of elution of the resin. This is because the antifouling period can be extended proportionately. Also, unlike conventional rosin-based chlorinated rubber-based and vinyl-based antifouling paints, this antifouling paint dissolves the paint film and eliminates the old paint film, so it can be repainted with simple surface preparation. It also helps reduce painting work costs. However, recently, self-polishing paint vehicles that reduce or eliminate the use of organotin have attracted attention from environmental and public health considerations. For example, JP-A-55-36230 proposes the use of polymers or copolymers of maleic acid dialkyl esters or fumaric acid dialkyl esters as vehicles. However, maleic acid dialkyl esters and fumaric acid dialkyl esters are generally extremely poor in homopolymerizability and copolymerization with acrylic monomers, and only a small amount is incorporated into the resin, with the majority remaining as unreacted monomers. When these varnishes are used in paints, they tend to thicken and gel during storage, and due to their low copolymerizability, it is difficult to obtain resin compositions as designed, resulting in problems with lot-to-lot production. It was found that the dissolution rate of the coating film was difficult to control due to large variations in the dissolution rate. The object of the present invention is to provide a self-polishing paint that does not have such drawbacks and uses a slightly water-soluble resin that does not contain organic tin. According to the present invention, (a) General formula (In the formula, R ₁ and R ₂ represent alkyl having 1 to 8 carbon atoms) or an itaconic ester containing at least 20% by weight of the itaconic ester of formula (a) and an organic A self-polishing paint is provided which is characterized in that it contains a vehicle resin made of a copolymer with a tin-free unsaturated monomer, and (b) a known antifouling agent as essential components. According to the present invention, since the itaconate dialkyl ester of formula (a) has excellent copolymerizability with other monomers, only a trace amount of unreacted itaconate dialkyl ester monomer remains in the final resin solution. Therefore, for the same reason, a resin composition according to the designed value can be obtained. Therefore, there is no variation between lots in the same formulation, and it is possible to stably supply a coating material of the same quality. Furthermore, when used as an antifouling paint, the resin vehicle has slight water solubility, so the coating film gradually dissolves into seawater, and as a result, a certain concentration of antifouling agent is stably eluted, which is proportional to the film thickness. It has become impossible to maintain a constant antifouling effect over a long period of time. Additionally, since the resin does not contain organotins, it is safe from an environmental and public health perspective. The object of the present invention can be fully achieved by using a homopolymer of itaconic acid dialkyl ester of formula (a) as a vehicle, but it is possible to impart toughness to the coating film and to reduce the dissolution rate of the coating film. to control
It is also possible to use a copolymer of itaconic acid dialkyl ester of the formula (a) and other monomers,
In addition, in order to provide more slight water solubility, hydroxyl group-containing (meth)acrylic acid ester (Note: (meth)
Acrylic acid is a general term for acrylic acid and methacrylic acid. same as below. ) can also be used. The group R ₁ of the itaconic acid dialkyl ester of formula (a),
As R ₂ , an alkyl having 1 to 8 carbon atoms is suitable, and a polymer or copolymer using an itaconic acid dialkyl ester of formula (a) having an alkyl group of ₉ or more carbon atoms has poor water solubility and is coatable. No film elution was observed, making it unsuitable as a vehicle for antifouling paints with long-term antifouling properties. Preference is therefore given to methyl, ethyl, propyl and butyl esters. As the unsaturated monomer copolymerizable with the itaconic acid dialkyl ester represented by formula (a), (meth)
Methyl acrylate, ethyl (meth)acrylate,
(meth)acrylate n-butyl, (meth)acrylate isobutyl, (meth)acrylate t-butyl,
(meth)acrylic acid 2-ethylhexyl, (meth)
Isopropyl acrylate, (meth)acrylic acid n
- In addition to (meth)acrylic esters such as hexyl, acrylamide, acrylonitrile,
Vinyl acetate, vinyl ethyl ether, styrene,
Common unsaturated monomers such as α-methylstyrene and vinyltoluene can be used. In a copolymer with these monomers, it is generally preferable to contain at least 20% by weight of itaconic acid dialkyl ester of formula (a), and if it is less than 20% by weight, the water solubility is poor and the elution of the coating film may occur. is not recognized. Hydroxyl group-containing (meth)acrylic esters used for the purpose of imparting slight water solubility include:
Examples include 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate. If these hydroxyl group-containing (meth)acrylic acid esters are used in excess, the resin becomes hydrophilic and the coating film swells in seawater, making it impossible to obtain a tough coating film. weight%
Used below. Acrylic acid or methacrylic acid may also be used in some cases. The resin containing itaconic acid dialkyl ester used as a vehicle in the present invention does not itself have antifouling properties, so when used as a resin for a vehicle for antifouling paint, copper compounds such as cuprous oxide and copper rhodanide, Low molecular organotin compounds such as bis(tributyltin) oxide, tributyltin chlorand, tributyltin fluoride, tributyltin acetate, zinc ethylene-bis(dithiocarbamate), manganese ethylene-bis(dithiocarbamate), tetramethylthiuram monolerphide, Thiocarbamates such as zinc bis(dimethyldithiocarbamate) and other commonly used antifouling agents and disinfectants must be used alone or in combination. Resin (meta)
When a monomer having a free carboxyl group such as acrylic acid is contained as a constituent component, it is not preferable because it may react with cuprous oxide or thiocarbamates, causing thickening or gelation of the paint during storage. Since the resin used as a vehicle in the present invention is itself slightly water-soluble, it is not necessary to use an elution aid such as rosin, although it may be used. In order to adjust polishing, it is also possible to use a low molecular compound and a high molecular compound in combination.
Further, the strength of the coating film can be adjusted using a known plasticizer. Although the present invention has been mainly described with respect to self-polishing antifouling paints, the present invention is also applicable to paints for fishing nets, encapsulants for agricultural chemicals, architectural paints, etc. that are slightly soluble in seawater or water. It is clear that it can be applied to all required fields. Examples are shown below. In the examples, "part" means "part by weight", the viscosity is a value measured at 25°C, and the number average molecular weight of the resin was calculated in terms of polystyrene using the GPC method. Example 1 40 parts of xylene and 30 parts of dimethyl itaconate were placed in a four-necked flask equipped with a dropping funnel, a condenser, and a stirrer.
of water and heat to 90℃. Next, in this solution, 30 parts of methyl methacrylate, 20 parts of ethyl acrylate,
5 parts acrylonitrile, 15 n-butyl acrylate
A mixed solution of 1.2 parts of azobisisobutyronitrile and 1.2 parts of azobisisobutyronitrile was added dropwise over 4 hours, and then kept warm for 4 hours. During this time, the reaction temperature was maintained at 85-90°C. Next, 60 parts of xylene was added. Solid concentration 50.2%, viscosity
Varnish A with 18 poise and resin number average molecular weight of 18,000
I got it. Example 2 Using the same equipment as in Example 1, xylol 50
1 part, and 50 parts of dibutyl itaconate, and keep at 85°C. Next, in this solution, 30 parts of methyl methacrylate,
A mixed solution of 20 parts of ethyl acrylate and 1.2 parts of azobisisobutyronitrile was added dropwise over 4 hours.
Thereafter, it was kept warm for 4 hours. During this time, the reaction temperature is 80-85
It was kept at ℃. Next, 50 parts of xylol was added, and the solid concentration was 49.8.
%, a viscosity of 16 poise, and a resin number average molecular weight of 17,000. Example 3 Using the same equipment as in Example 1, xylol 50
1 part, and 70 parts of dimethyl itaconate, and keep at 85°C. Next, in this solution, 10 parts of methyl methacrylate,
A mixed solution of 20 parts of ethyl acrylate and 1.2 parts of azobisisobutyronitrile was added dropwise over 4 hours.
Thereafter, it was kept warm for 4 hours. During this time, the reaction temperature is 80-85
It was kept at ℃. Next, 50 parts of xylene was added, and the solid content concentration was 50.3.
%, a viscosity of 16 poise, and a resin number average molecular weight of 17,000. Example 4 Using the same equipment as in Example 1, xylol 50
1 part, and 50 parts of dimethyl itaconate, and keep at 85°C. A mixed solution of 30 parts of methyl methacrylate, 10 parts of ethyl acrylate, 5 parts of methyl acrylate, 5 parts of 2-hydroxyethyl acrylate, and 1.2 parts of azobisisobutyronitrile was added dropwise to this solution over 4 hours, and then It was kept warm for 4 hours. During this time, the reaction temperature is maintained at 80-85°C. Next, 50 parts of xylol was added to obtain Varnish D having a solid content concentration of 48.9%, a viscosity of 21 poise, and a resin number average molecular weight of 18,000. Example 5 Using the same equipment as in Example 1, xylol 50
1 part, 25 parts of dimethyl itaconate, 20 parts of 2-ethylhexyl itaconate, and 5 parts of vinyl acetate, and heated to 80°C.
Keep it. In this solution, 30 parts of methyl methacrylate,
5 parts of ethyl acrylate, 10 parts of methyl acrylate,
A mixed solution of 5 parts of 2-hydroxyethyl acrylate and 1.5 parts of benzoyl peroxide was added dropwise over 5 hours, and then kept warm for 4 hours. During this time, the reaction temperature was 75
Keep at ~80°C. Next, 50 parts of xylol was added, solid concentration 49.6%, viscosity 20 poise, number average molecular weight of resin.
Obtained 18000 Varnish E. Comparative Example 1 Using the same equipment as in Example 1, xylol 40
1 part, and 50 parts of dimethyl itaconate, and keep at 85°C. Next, a mixed solution of 20 parts of methyl methacrylate, 30 parts of ethyl acrylate, and 1.5 parts of benzoyl peroxide was added dropwise over 4 hours, and the mixture was then kept warm for 4 hours.
During this time, the reaction temperature was maintained at 80-85°C. Next, 60 parts of xylol was added to obtain comparative varnish A having a solid content concentration of 43.2%, a viscosity of 3.1 poise, and a resin number average molecular weight of 17,000. Comparative Example 2 Using the same equipment as in Example 1, xylol 50
1 part, and 50 parts of dimethyl acrylate, and keep at 80°C. Tributyltin methacrylate 60% in this solution
A mixed solution of 30 parts of methyl methacrylate, 10 parts of isobutyl methacrylate, and 1.5 parts of benzoyl peroxide was added dropwise over 4 hours, and then kept warm for 3 hours. During this time, the reaction temperature was maintained at 80-85°C. Next, 50 parts of xylol was added, and the solid content concentration was 50.2%, and the viscosity was
Comparative varnish B having a resin number average molecular weight of 5.6 poise and a resin number average molecular weight of 15,000 was obtained. Note that a resin varnish similar to this comparative varnish B is a system that has been put into practical use as a hydrolyzable polymer organic trialkyl tin compound. Comparative Example 3 Comparison of 50% methyl isobutyl ketone solution of vinyl chloride resin VAGH manufactured by UCC Company in the United States Varnish C
shall be. The resin varnishes in Examples and Comparative Examples either do not have antifouling properties or have poor antifouling properties, so in order to clarify the characteristics of the resins, the resin varnishes were dispersed in a ball miller using the paint formulations shown in Table 1. Manufactures antifouling paint,
Tested. The test results are shown in Table 1.

【table】

[Table] Storage stability test of paint and its results In the storage stability test of paint, the paint capacity was 250 c.c. and the capacity was 300 c.c.
The condition of the paint (change in viscosity) was investigated after it was sealed in a glass container and stored at 50°C for two months.
The results are shown in Table 2.

[Table] From the above results, the antifouling paint using the resin composition according to the present invention has very good storage stability. Paint film wear test and its results A test plate coated with a test paint to a constant film thickness was attached to a day rotor plate, and exposed to sea water (water temperature 17 to 22°C).
℃) at a constant speed (peripheral speed of about 35 knots) day and night for 60 days, and the degree of wear was measured by observing the cross section of the coating under a microscope, and comparing it with that before the test, the degree of wear was measured according to the following formula. . Degree of wear = initial film thickness - film thickness after test/initial film thickness The results are shown in Table 3.

[Table] From the above results, the cleaning action of the antifouling paint using the resin composition according to the present invention is clear. Immersion test and results A test sandblasted steel plate with a size of 100 x 300 mm that had been pre-coated with anti-corrosion paint was brushed twice so that the dry film thickness was approximately 100μ at each time.
An antifouling performance test board was created. The antifouling performance test was conducted by immersing a test raft in Aioi Bay in Hyogo Prefecture to a depth of approximately 1 meter underwater, and observing with the naked eye the amount of animals such as barnacles and serpura, and plants such as sea lettuce and blue seaweed as percentage of the adhering area. evaluated. The test results are shown in Table 4.

【table】

[Table] As is clear from the above results, the paint of the present invention has extremely excellent antifouling performance, and even after 36 months, 0% of organisms were attached to it. From the above, the paint storage stability test results, paint film wear rate test results, and antifouling performance test results show that the paint of the present invention has excellent storage stability, maintains antifouling performance over a long period of time, and has an abrasive action. It can be said that it is an extremely excellent paint.

Claims (1)

[Claims] 1 (a) General formula (In the formula, R ₁ and R ₂ represent alkyl having 1 to 8 carbon atoms) or an itaconic ester containing at least 20% by weight of the itaconic ester of formula (a) and an organic A self-polishing paint characterized by containing a vehicle resin made of a copolymer with a tin-free unsaturated monomer, and (b) a known antifouling agent as essential components.