JPH06102768B2 - Two-component cross-linking topcoat - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Purpose of the invention [Industrial field of application] The present invention relates to a two-component cross-linking type topcoat comprising a (meth) acrylic acid alkyl ester-based copolymer and a polyfunctional isocyanate compound. The topcoat of the present invention relates to construction, automobiles, railway vehicles, aircraft, ships, tanks,
Since it can be used as a paint for bridges, electric appliances, plastics, wood, etc. and has high weather resistance, it is particularly suitable as a top coat for building exteriors.

[Prior art and its problems]

The outer wall surface of a building or the like is generally coated with an exterior paint or a decorative tile or the like for the purposes of aesthetics, water resistance and weather resistance.

In the coating of exterior coatings, an undercoat paint, a thick film paint and a topcoat paint are usually applied in order, and the topcoat paint is required to have particularly high weather resistance and antifouling property.

Urethane-based,
Although there are paints mainly composed of acrylic urethane-based or silicone-based resins, the durability of conventional top-coat paints is still a step away, and it is the current situation that the appearance of top-coat paints with even better weather resistance is desired. is there.

Japanese Patent Laid-Open No. 61-515272 discloses a highly weather-resistant coating composed of a radical-polymerizable silicone macromonomer, and the highly weather-resistant coating is a coating film in a long-term outdoor exposure or accelerated weathering test. The paint has excellent weather resistance such that the physical properties such as luster, flexibility, stretchability and tensile strength are hardly changed.

However, the above-mentioned paint is inferior in the adhesiveness of the coating films formed in each coating when the coating is repeated coating, that is, in the case where the same coating is divided into a plurality of coatings. There was a problem that it was difficult to obtain the thickness. Further, the silicone-based graft polymer used in the high weather resistance paint disclosed in the above publication has a problem that it takes a long time for the crosslinking reaction with the polyfunctional isocyanate compound at room temperature.

Further, JP-A-57-34107 discloses a room temperature-curable fluorine-containing copolymer, which has a very excellent gloss retention rate of a coating film in long-term outdoor exposure and accelerated weathering resistance test. In addition, it can be said that it is a highly weather resistant coating resin with little change in elongation of the coating film, but because of the inherently small flexibility and extensibility of the coating film, as a coating for building structures with large displacement, cracks due to displacement Since it has problems such as generation, a decrease in gloss accompanying it, a decrease in rust prevention property, etc., and its price is high, its use as a general-purpose paint is limited.

[Problems to be Solved by the Invention]

The present invention provides a topcoating agent having excellent weather resistance, capable of rapidly forming a crosslinked coating film at room temperature, and having good multicoating property.

(B) Structure of the Invention [Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, by isocyanate crosslinking, an alkyl acrylate for forming a crosslinked coating film at room temperature. As the system copolymer, a copolymer mainly composed of a (meth) acrylic acid alkyl ester monomer unit and a hydroxyl group-containing monomer unit is further added to the silicone unit, namely (Provided that R ₂ is a methyl group, an ethyl group or a phenyl group, and n is a positive number) and a monomer unit having a carboxyl group are present in specific amounts, respectively. It has been found that the use of the above-mentioned compound can provide a top coating composition which has excellent weather resistance and good overcoating property, and the crosslinking reaction with isocyanate is completed in a short time at room temperature, and has completed the present invention.

That is, the present invention is mainly composed of (meth) acrylic acid alkyl ester, 0.5 to 15% by weight of a silicone macromonomer represented by the following general formula, 1 to 30% by weight of a vinyl monomer having a hydroxyl group, and α, β- An organic solvent solution of a radical copolymer of a monomer mixture consisting of 0.1 to 3% by weight of an ethylenically unsaturated carboxylic acid and 0 to 20% by weight of another radically polymerizable monomer is used as a main agent, and a polyfunctional isocyanate compound or Two-component cross-linking type overcoating agent using the organic solvent solution as a curing agent General formula (In the formula, R is a hydrogen atom or a methyl group, R ₁ , R ₂ and R ₃ are a methyl group, an ethyl group or a phenyl group,
n is a positive number. And the two-component cross-linking type top coating agent according to the above-mentioned item 1, wherein a fluorine-based surfactant is added to the base material.

Hereinafter, the present invention will be described in more detail.

Examples of the (meth) acrylic acid alkyl ester used in the present invention include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate. , 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, isononyl (meth) acrylate, stearyl (meth) acrylate and the like.

Considering availability and cost among these (meth) acrylic acid alkyl esters, methyl (meth) acrylate and n-butyl (meth) acrylate are preferable.

These (meth) acrylic acid alkyl esters can be used alone or in combination of two or more kinds.

The amount of the (meth) acrylic acid alkyl ester used is such that in the monomer mixture to be polymerized to obtain the copolymer,
It is preferably 50% by weight or more.

When the amount of the (meth) acrylic acid alkyl ester used is less than 50% by weight, the weather resistance is impaired and the film forming property is deteriorated.

Examples of vinyl monomers having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-hydroxybutyl. Examples thereof include (meth) acrylate and 2,3-dihydroxypropyl (meth) acrylate, and 2-hydroxyethyl (meth) acrylate is preferable.

The amount of the vinyl monomer having a hydroxyl group used in the copolymerization is 1 to 30% by weight, and more preferably 10 to 20% by weight in the monomer mixture. If it exceeds 30% by weight, the resulting polymer becomes insoluble in the non-polar organic solvent such as aromatic hydrocarbons and ketones used in the present invention.

Next, the silicone macromonomer will be described.

The silicone macromonomer used in the present invention has the general formula (Wherein R, R ₁ , R ₂ and R ₃ are as described above), which is a silicone macromonomer having either an acryloyl group or a methacryloyl group at one terminal of the molecule, and n in the above general formula is 1 A silicone macromonomer having a molecular weight of about 200 is preferable, and more preferably n is
10 to 100.

If n is not 1 or more, the effects due to silicone, that is, the effects such as high weather resistance and antifouling property, are not sufficiently exhibited, while if n exceeds 200, the radical polymerizability is poor and unpolymerized silicone macromomers are present. It is not preferable because it may be contained in the polymer.

R ₁ , R ₂ and R ₃ in the above general formula must be either a methyl group, an ethyl group or a phenyl group.

R ₁ is a group derived from an anionic polymerization terminator or the like represented by the chemical formula (C) described below, and is preferably a methyl group or a phenyl group, and R ₂ is preferably a methyl group, an ethyl group or a phenyl group. R ₂ bonded to one Si and R ₂ bonded to another Si when n is greater than ₂ may be the same or different, and
R ₃ is a group derived from the anionic polymerization initiator or the like represented by the chemical formula (a) described later, and is preferably a methyl group.

If even a part of R ₃ is a hydroxyl group or the like, the recoatability will be poor.

The silicone macromonomer can be produced by the method disclosed in JP-A-59-78236, which is outlined below.

That is, a living polymer obtained by anionically polymerizing a cyclic siloxane represented by the general formula (b) with a lithium trimethylsilanolate represented by the following chemical formula (a) as an initiator, and a radically polymerizable group represented by the chemical formula (C). It can be obtained by reacting with an organic silane compound having

Similar to the cyclic siloxane represented by the general formula (b), cyclic siloxanes that can be used when producing a silicone macromonomer include hexaethylcyclotrisiloxane, octaethylcyclotetrasiloxane, hexaphenylcyclotrisiloxane, Octaphenylcyclotetrasiloxane and the like are listed, and these are 2
You may use it in combination of 1 or more types.

Next, as the α, β-ethylenically unsaturated carboxylic acid,
Acrylic acid, methacrylic acid, maleic acid, maleic anhydride and the like can be used, and the amount used is required to be 0.1 to 3% by weight in the monomer mixture used for the polymerization.

The carboxyl group introduced into the copolymer by the α, β-ethylenically unsaturated carboxylic acid serves to accelerate the reaction when the hydroxyl group present in the copolymer reacts with the isocyanate group during coating curing. In addition to contributing, it also has the effect of improving the dispersibility of the pigment in the paint, and for these purposes, it is necessary to use at least 0.1% by weight. 3% by weight
If it is used in excess of this, the resulting polymer will have a high viscosity, making it difficult to add a desired amount of pigment or the like.

In the present invention, in addition to the above-mentioned essential monomers, radical-polymerizable monomers copolymerizable with those listed above can be used in the range of 0 to 20% by weight.

Copolymerizable monomers include low molecular weight unsaturated hydrocarbons such as ethylene and propylene, vinyl halides such as vinyl chloride and vinyl fluoride, vinyl esters of organic acids such as vinyl acetate, styrene and styrene derivatives, vinyl. Such as vinyl aromatic compounds such as pyridine and vinylnaphthalene, N-vinyl compounds such as acrolein, acrylonitrile, N-vinylpyrrolidone and N-vinylcaprolactam, (meth) acrylic acid amides, N-butoxymethyl (meth) acrylic acid amides Amide compound, γ-
Examples thereof include vinyl silanes such as (meth) acryloyloxypropyltrimethoxysilane and γ- (meth) acryloyloxypropylmethyldimethoxysilane.

By radical-polymerizing a monomer mixture containing the above-mentioned monomer as a component, it is possible to obtain a copolymer which is a main component of the overcoating agent of the present invention. As the radical polymerization method, a conventionally known method can be used, for example, a radiation irradiation method, a method using a radical polymerization initiator or the like can be used. However, considering the ease of the polymerization operation, a method using a radical polymerization initiator is used. Good to use. Thereby, the molecular weight can be easily adjusted and various polymerization methods can be used. Specifically, any of a solution polymerization method using a solvent, a bulk polymerization method, an emulsion polymerization method and the like can be used, but the solution polymerization method is preferable.

As the organic solvent used in the solution polymerization, toluene, xylene, methyl ethyl ketone, ethyl acetate, butyl acetate and methyl isobutyl ketone are preferable.

The organic solvent solution of the copolymer obtained by solution polymerization,
It can be used as a main ingredient as it is, or may be used after appropriately diluted with the above-mentioned organic solvent.

The copolymer obtained by a polymerization method other than solution polymerization can be used by dissolving it in an organic solvent after isolation from the polymerization system and drying.

In the present invention, a fluorine-based surfactant may be added to the main component composed of the above copolymer in an amount of 0 to 1.5 parts by weight per 100 parts by weight of the copolymer. The preferred addition amount of the fluorine-based surfactant depends on the amount of the silicone macromonomer in the copolymer used, and when the amount of the silicone macromonomer is 0.5 to 5% by weight, 0.5 part by weight per 100 parts by weight of the copolymer is used. If the amount of the silicone macromonomer is 5 to 15% by weight, it is 0.5 to 1.5 parts by weight.
If it is used in excess of the above upper limit, the water repellency of the copolymer tends to be impaired.

Typical examples of the fluorinated surfactant include fluorinated alkyl esters, and specific examples thereof include Fluorard FC-431 (manufactured by Sumitomo 3M Limited).

The timing of addition of the fluorine-based surfactant to the main agent is not particularly limited, and may be within the period from the polymerization of the copolymer to the mixing of the main agent and the curing agent.

The addition of the above-mentioned fluorine-based surfactant makes the overcoating property of the topcoating agent of the present invention more excellent.

Next, the curing agent will be described.

The curing agent in the present invention is a solution in which a polyfunctional isocyanate compound is dissolved in an organic solvent such as toluene, and the polyfunctional isocyanate compound is hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, 1-methylcyclohexane- Non-yellowing diisocyanates such as 2,4-diisocyanate and dimethylcyclohexane diisocyanate are preferred.

The use of a polyfunctional isocyanate compound is determined according to the amount of hydroxyl groups (OH equivalent) in the copolymer to be used, and the ratio of isocyanate amount (NCO equivalent) to OH equivalent is usually NCO / OH = 1 / 1-
It is recommended to use it at a ratio of 1.2 / 1.

When the above main agent and curing agent are mixed to form a paint, an organotin compound such as dibutyltin dilaurate or dibutyltin maleate, phosphoric acid, or p-toluenesulfonic acid is used for the purpose of accelerating the curing of the coating film after coating. Known compounds such as acidic compounds such as ethylenediamine and amines such as ethylenediamine and triethylenetetramine may be added, and the amount thereof is 0.001 to 10% by weight, preferably 0.01 to 5% by weight, based on the resin for coating.
Is.

Moreover, it is preferable to add a pigment, a filler and the like to the overcoating agent of the present invention, and specific examples thereof include:
Examples thereof include titanium oxide, silica, calcium carbonate, magnesium carbonate, iron oxide and glass fiber. Further, a dispersion stabilizer and an ultraviolet absorber may be added.

[Examples and Comparative Examples]

Hereinafter, the present invention will be described more specifically by showing Examples and Comparative Examples. In addition, all "parts" in each example mean "parts by weight".

Reference Example 1. In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet, R ₁ , R ₂ and R ₃ in the above general formula are all methyl groups, and n is 50 on average. Yes, 0.5 part of a silicone macromonomer having a methacryloyl group at one end of the molecule (hereinafter abbreviated as Si-MM), 40 parts of methyl methacrylate (hereinafter abbreviated as MMA), butyl acrylate (hereinafter B
Abbreviated as A) 33.5 parts, styrene (hereinafter abbreviated as St) 1
0 part, 2-hydroxyethyl methacrylate (hereinafter abbreviated as HEMA) 15 parts, acrylic (hereinafter abbreviated as AA) 1 part,
Azobisisobutyronitrile (abbreviated as AIBN below) 1.
Add 2 parts to 81.8 parts of toluene to make a homogeneous solution,
Polymerization was carried out for an hour, 0.5 part of AIBN was further added, and polymerization was carried out for 3 hours to obtain a copolymer.

Reference Examples 2 to 5 Using the monomer mixture having the monomer composition shown in Table-1,
Polymerization was performed in the same manner as in Reference Example to obtain a copolymer.

Examples 1 to 3. 55% by weight of the copolymers obtained in Reference Examples 1 to 3 (hereinafter simply referred to as%) in 100 parts of toluene solution, 19.8 parts of hexamethylene diisocyanate and 137.8 parts of toluene were added, and 45% by adding 74.8 parts of titanium oxide and mixing evenly
A solution is obtained and the dry film thickness is applied to a tin plate using a bar coater.
It was coated so as to have a thickness of 20 μm and cured at room temperature for 1 week to obtain a paint test piece.

The copolymer of Reference Example 1 was used in Example 1, the copolymer of Reference Example 2 was used in Example 2, and the copolymer of Reference Example 3 was used in Example 3.

The coating film physical properties of the coating test pieces thus obtained were evaluated by the following methods, and the results are shown in Table-2.

Pencil scratch test The test was performed according to the JIS K5400 pencil scratch test.

Adhesion test (government cellophane tape peeling test) After drawing 100 goggles at 1 mm intervals on the coating film with a cutter knife, a cellophane tape peeling test was performed and the number of remaining coating films was shown.

Impact resistance test According to JIS K5400 impact resistance method B (impact deformation test), 50c
From the height of m, a 500-g columnar weight having a diameter of 1/2 in. was dropped onto the coating film, and the state of the coating film was visually determined.

○: No abnormalities were found in the coating film.

Δ: The coating film is slightly cracked and peels off.

X: The coating film cracks and peels off.

Bending Resistance Test According to JIS K5400 bending resistance, the bending resistance tester was tested by changing the diameter of the mandrel in various ways, and expressed by the diameter of the smallest diameter mandrel when cracks or peeling were not observed in the coating film.

Solvent resistance test Gauze is thoroughly impregnated with methyl ethyl ketone, and this is wrapped around the index finger and the coated surface is rubbed. Indicates the number of round trips until the background appears.

Stain resistance test Draw a line on the coated surface using red and black magic ink. twenty four
After standing for a period of time, this wire was rubbed back and forth 20 times with gauze impregnated with xylene, and it was visually judged whether or not traces of the magic ink remained on the coating film.

○: Nothing remains.

△: A little remains.

×… A lot remains.

Chemical resistance test 5% NaOH, 5 according to JIS K5400 alkali resistance and acid resistance
The test piece is dipped in a% H ₂ SO ₄ aqueous solution for 5 days. After taking out, it was thoroughly washed with water and immediately evaluated by visual judgment.

O: No damage is observed on the coating film.

△: A little prister occurred.

×: A prister was generated on the entire surface of the coating film.

Salt spray test It was conducted according to JIS K5400 salt spray test. The test piece was kept in a 5% salt water mist for 500 hours, and judged from the degree of damage of the cut part.

O: No damage is observed on the coating film.

△: Damage of cut part is 1mm or less.

×: Damage to the cut part is 1 mm or more.

Boiling water resistance According to JIS K5400 boiling water resistance test, put the test piece in boiling water 1
It was maintained for 0 hour and then judged from the state of the coating film.

○: No abnormalities are observed.

Δ: A slight amount of prister is generated or slight glossiness is observed.

×: 10% or more of the total area of pristers is generated on the surface of the coating film.

Accelerated weather resistance test Using a WEL-SUN-DC type sunshine weather meter manufactured by Suga Test Instruments Co., Ltd., a black panel temperature of 63 ± 3 ° C,
A weather resistance test was conducted under the conditions of relative humidity 60% and splat 18 minutes / 2 hours. The coated test piece was washed with water after a predetermined time test by an accelerated weather resistance tester, and the gloss value at that time was measured. The retention rate (%) was defined assuming that the glossiness before the accelerated weather resistance test was 100.

Overcoat compatibility was performed in accordance with JIS K5400 Overcoat compatibility. That is, the paint prepared in Example or Comparative Example is applied and cured on one surface of the glass plate, and then the same paint is applied again on the test piece.

The presence or absence of abnormality was checked by visual judgment on this test piece, and further an adhesion test (governed cellophane tape peeling test) was performed.

◯: Number of remaining coating films 95 or more Δ: 85 to 95 × × less than 85 Comparative Example 1 Using the copolymer obtained in Reference Example 4, a coating material was obtained in the same manner as in Examples 1 to 3. The above paint was applied to a tin plate to obtain a coating test piece.

The physical properties of the obtained test pieces were measured, and the results are also shown in Table 2.

Example 4 To 100 parts of a 55% toluene solution of the copolymer obtained in Reference Example 5, 0.6 parts of Florade FC-431, 19.8 parts of hexamethylene diisocyanate, 137.8 parts of toluene and 7 parts of titanium oxide were added.
4.8 parts were added and mixed.

The result of evaluating the heavy coating property of the obtained coating material was good.

(C) Effect of the Invention The overcoating agent of the present invention has excellent weather resistance derived from the silicone unit and has good multi-coating property, so that the overcoating layer having a desired film thickness can be easily formed. In addition, since the reaction between the hydroxyl group and the isocyanate group proceeds rapidly, a cured coating film can be formed within a short time at room temperature.

Therefore, it is useful as a top coat for materials exposed outdoors such as building materials.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A 1-275674 (JP, A) JP-A 2-64120 (JP, A) JP-A 63-46271 (JP, A) JP-A 64-- 74275 (JP, A) JP 64-33169 (JP, A) JP 64-31870 (JP, A) JP 62-252473 (JP, A) JP 62-253670 (JP, A) Japanese Unexamined Patent Publication No. 62-253661 (JP, A)

Claims (2)

[Claims] 1. A vinyl monomer 1 having 0.5 to 15% by weight of a silicone macromonomer represented by the following general formula and having a hydroxyl group, which contains an alkyl (meth) acrylate as a main component.
~ 30% by weight, α, β-ethylenically unsaturated carboxylic acid 0.1
~ 3 wt% and other radically polymerizable monomers 0-20
A two-component cross-linking type overcoating agent containing, as a main component, an organic solvent solution of a radical copolymer of a monomer mixture of 1% by weight and a polyfunctional isocyanate compound or an organic solvent solution thereof as a curing agent. General formula (In the formula, R is a hydrogen atom or a methyl group, R ₁ , R ₂ and R ₃ are a methyl group, an ethyl group or a phenyl group,
n is a positive number. ) 2. The two-part crosslinkable topcoat agent according to claim 1, wherein a fluorine-based surfactant is added to the main agent.