JPH06184225A - Production of multibranched polymer and coating composition composed of the same multibranched polymer - Google Patents

Abstract

PURPOSE:To provide a method for producing a multibranched polymer excellent in weather resistance and a coating composition using this multibranched polymer. CONSTITUTION:An ethylenically unsaturated monomer is made to react in the presence of a specific mercaptan compound to provide a polymer having a reactive group at one terminal. The resultant polymer is then allowed to react with a compound having a binding group reactive with the reactive group and an ethylenically unsaturated bond to afford a macromonomer. A predominant amount of the macromonomer is subsequently copolymerized with copolymerizable monomers to synthesize a multibranched polymer, which is then oxidized with a peroxide to provide a multibranched polymer excellent in weather resistance. A solution of the multibranched polymer obtained by this method in an organic solvent is used to afford a coating composition excellent in the weather resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a multi-branched polymer having excellent weather resistance and a coating composition comprising the multi-branched polymer. The coating composition obtained by the present invention is It is suitable as a coating material for metals, plastics, wood and the like, and is particularly suitable for coating automobiles and home electric appliances.

[0002]

2. Description of the Related Art Conventionally, for painting automobiles and home appliances,
Organic solvent-based acrylic paints are often used due to their excellent weather resistance and appearance, but recently it is possible to make such organic solvent-based paints into high solids due to environmental problems. Has become an industry challenge. Such high solidification requires a high concentration of solids and a low viscosity of the coating solution in order to maintain a good coating.Currently, the molecular weight of the coating resin should be minimized. High solidification is being studied to reduce the viscosity. However, if the coating resin is made to have a low molecular weight, for example, in a cross-linking type coating material, the proportion of a low-molecular weight polymer having no cross-linkable functional group increases, and thus the durability of the coating film generally decreases. There was a problem.

For this reason, recently, high solidification has been studied, in which a branched polymer having a large molecular weight and a low solution viscosity is used as a coating resin. For example, in JP-A-4-103610, when a macromonomer having a radical-polymerizable group and another radical-polymerizable monomer are copolymerized, a multi-branched polymer obtained by using the macromonomer in a high copolymerization ratio is disclosed. It has been proposed to use polymers in high solids solution paints. This multi-branched polymer has a structure in which a large number of polymer chains are branched from a trunk polymer having a short chain length, and even if the molecular weight is high, the solution viscosity is low, and it is effective as a resin for high solid coatings. Met.

[0004]

However, the above-mentioned multi-branched polymer has a problem that it is inferior in weather resistance as compared with the multi-branched polymer obtained by another method which does not use a macromonomer. As a result of various investigations, the inventors of the present invention have found that the weather resistance is improved by reacting the above-mentioned hyperbranched polymer with a peroxide, and previously filed as Japanese Patent Application No. 4-303825. .
As a result of subsequent studies, the inventors of the present invention have found that the solution viscosity in high solidification can be further reduced depending on the ratio of macromonomer units in the above-mentioned multi-branched polymer, and that the excellent weather resistance and coating property can be obtained. It was found that a coating composition having properties is obtained, and the present invention has completed the method for producing a multibranched polymer of the present invention and a coating composition comprising the multibranched polymer.

[0005]

That is, the method for producing a multibranched polymer of the present invention is characterized by the following steps [a] to [d]. [A] A step of radically polymerizing at least one ethylenically unsaturated monomer in the presence of a mercaptan compound having a reactive group and a thiol group in the molecule. [B] A step of reacting the polymer having a reactive group at one end obtained in the step [A] with a compound having a bonding group capable of reacting with the reactive group and an ethylenically unsaturated bond. [C] A macromonomer having an ethylenically unsaturated bond at one end of the molecule obtained in the step [B] and at least one monomer copolymerizable with the macromonomer are copolymerized to obtain a total amount. A step of synthesizing a multi-branched polymer in which the ratio of the macromonomer unit is more than 45% by weight and 99.5% by weight or less based on the total amount of the constituent units. [D] A step of reacting the hyperbranched polymer having a thioether bond in the molecule obtained in the above step [c] with a peroxide to oxidize a sulfur atom in the thioether bond to a sulfone.

The coating composition comprising the multi-branched polymer of the present invention is characterized by comprising a solution of the branched polymer obtained by the above method in an organic solvent.

The present invention will be described in more detail below. In the method for producing a multibranched polymer of the present invention, the mercaptan compound used in the step [a] is a mercaptan compound having a reactive group and a thiol group in the molecule, and the reactive group includes a carboxyl group and a hydroxyl group. Etc. can be mentioned. Specific examples of such mercaptan compounds include mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid and 2-mercaptoethanol. The mercaptan compound in the polymerization in the above step [a] acts as a chain transfer agent, and the average molecular weight of the obtained polymer is adjusted by the amount of the mercaptan compound used. The preferred amount of mercaptan compound added to the polymerization system is 10
It is 1 to 30 parts by weight, and more preferably 5 to 20 parts by weight, per 0 parts by weight. By this step [a], a polymer in which the reactive group in the mercaptan compound is bonded to one end of the molecule (hereinafter referred to as a reactive group-containing polymer) is obtained.

The weight average molecular weight of the reactive group-containing polymer is preferably 1,000 to 10,000, more preferably 1,000 to 4,000. Weight average molecular weight is 1
If it exceeds 20,000, the molecular weight of the obtained multi-branched polymer becomes excessive, and the solution viscosity tends to be high and the coatability tends to be poor. On the other hand, when the weight average molecular weight is less than 1,000, it is difficult for the solution viscosity to decrease due to the branching effect.

The ethylenically unsaturated monomer used in the above step [a] to obtain the above-mentioned reactive group-containing polymer includes methyl (meth) acrylate, ethyl (meth) acrylate and butyl (meth). Acrylate,
Isobutyl (meth) acrylate, t-butyl (meth)
Alkyl esters of (meth) acrylic acid such as acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, isobornyl (meth) acrylate and cyclohexyl (meth) acrylate. Hydroxyalkyl esters of (meth) acrylic acid, such as 2-hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate,
Acrylamides such as (meth) acrylamide and N-methylolacrylamide, polyfluoroacrylates, perfluoroalkylacrylates and the like, and organosilicon monomers such as (meth) acryloyloxypropyltrimethoxysilane, styrene, α-methylstyrene, (meth) ) Vinyl esters such as acrylonitrile, vinyl acetate and vinyl propionate can be mentioned. Among these, in terms of weather resistance, alkyl (meth) acrylate and (meth) acrylate
(Meth) acrylic acid esters such as hydroxyalkyl acrylate are more preferably used.

As a polymerization method for obtaining a polymer containing a reactive group, solution polymerization is preferable, and for example, a polymerization solvent such as toluene, xylene or methyl isobutyl ketone is preferably used, and an azo-based polymerization initiator is used as a polymerization initiator. Alternatively, a peroxide-based radical generating compound can be used.

In the step [b], the compound to be reacted with the above reactive group-containing polymer (hereinafter referred to as a polymerizable group-introducing compound) is a group which reacts with a reactive group such as a carboxyl group or a hydroxyl group and an ethylenic group. A compound having an unsaturated bond, and examples of such a compound include glycidyl methacrylate, glycidyl acrylate, and N- [4- (2,3-
Epoxypropoxy) -3,5-dimethylbenzyl] acrylamide, methacrylic acid chloride, P-vinylbenzyl chloride, P-vinylaniline and the like,
More preferred are glycidyl methacrylate and glycidyl acrylate.

A macromonomer having a polymerizable group such as an acryloyl group, a methacryloyl group or a vinylbenzyl group at one end of the molecule by reacting the above-mentioned polymerizable group-introducing compound with the reactive group-containing polymer in an approximately equimolar amount. Is obtained. This reaction is carried out in an organic solvent at a temperature of 60 to 120 ° C.
If necessary, the catalyst can be used in an appropriate amount.

The step [c] is a step of synthesizing a multi-branched polymer comprising copolymerizing the macromonomer obtained by the above method and another monomer copolymerizable therewith, which is the multi-branched polymer in the present invention. The polymer has a composition in which the ratio of the macromonomer units is more than 45% by weight and 99.5% by weight or less based on the total amount of all the structural units, and preferably has a weight average molecular weight of 5,000 to 30,000. belongs to. When the proportion of macromonomer units in the multi-branched polymer is 45% by weight or less, the degree of branching becomes insufficient, and the solution viscosity becomes high in high solids. on the other hand,
A multi-branched polymer having a macromonomer unit ratio of more than 99.5% by weight is difficult to synthesize with high purity, and a large amount of unpolymerized macromonomer is likely to be contained. If the weight average molecular weight of the multi-branched polymer is less than 5,000, the durability of the coating film is poor, and if it exceeds 30,000, the solution viscosity is high and the coating property on the substrate is poor.

The monomer to be copolymerized with the macromonomer is a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 18 carbon atoms, vinyl acetate, styrene, α-methylstyrene, (meth) acrylonitrile,
Perfluoroalkyl (meth) acrylate, (meth) acrylic acid, maleic anhydride, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, glycidyl (meth) acrylate, ( (Meth) acrylamide,
Examples thereof include N-methylol acrylamide, N-butoxymethyl acrylamide, N-dimethylaminoethyl (meth) acrylate and (meth) acryloyloxypropyltrimethoxysilane. These can be used alone or in combination of two or more. .

Among these, from the viewpoint of weather resistance of the resulting multi-branched polymer, (meth) acrylic acid ester is preferably used, and more preferably, methyl (meth) acrylate, butyl (meth) acrylate and ( A (meth) acrylic acid alkyl ester such as 2-ethylhexyl (meth) acrylic acid is used. Further, the preferred constitution of the hyperbranched polymer composed of the macromonomer and the above-mentioned monomer is such that the amount of the (meth) acrylic acid alkyl ester monomer unit is 60 to 80% by weight, based on all the constitutional units. .

Copolymerization of the macromonomer and the other copolymerizable monomer (hereinafter, these may be collectively referred to as a polymerizable component) in the step [c] is preferably carried out by solution polymerization. Are preferably toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone and the like. The concentration of the polymerizable component in the polymerization system is preferably 10 to 80% by weight, and the polymerization temperature is 60 to 1
00 ° C is suitable. The polymerization initiator is preferably an azo compound such as 2,2-azobisisobutyronitrile or an organic peroxide such as benzoyl peroxide, and the preferable amount thereof is 100 mol per 100 mol of the total number of the polymerizable components. It is 1 to 10 mol, and when the chain transfer agent described below is used in combination, 1 to 3 mol is more preferable.

In the polymerization in the step [c], it is preferable to use a chain transfer agent such as dodecyl mercaptan, mercaptoethanol and thioglycolic acid together, and the preferable amount thereof is 2 to 100 moles of the total of the polymerizable components.
It is 15 mol.

As the peroxide used in the next step [d], organic peracids such as perbenzoic acid, m-chloroperbenzoic acid, peracetic acid and perhexanoic acid, t-butyl hydroperoxide, cumene Examples thereof include hydroperoxides such as hydroperoxide, and inorganic peroxides such as hydrogen peroxide, potassium persulfate, oxone, magnesium monoperoxyphthalate, and ozone, and more preferably organic peracids and inorganic peroxides. Oxides, particularly preferably m-chloroperbenzoic acid, hydrogen peroxide and ozone. A catalyst may be used in combination with the above-mentioned peroxide, and a preferable catalyst is, for example, phosphotungstic acid.

In the step [d], the thioether bond in the hyperbranched polymer obtained in the step [b], that is,
The sulfur atom in the thioether bond, which is inevitably introduced into the hyperbranched polymer by the use of the macromonomer, is converted into a sulfoxide by the first-stage oxidation and is converted into a sulfone by the subsequent second-stage oxidation. By oxidizing the sulfur atoms to sulfones, excellent weather resistance is exhibited. Therefore, the amount of the peroxide used is required to be at least twice the equivalent of the thioether bond contained in the hyperbranched polymer. When the amount of the peroxide is less than 2 equivalents, part of the sulfur atoms forming the thiol bond remains in the sulfoxide, and the weather resistance is still insufficient.

When a powdered organic peracid such as m-chloroperbenzoic acid is used as the peroxide, it may be added to the hyperbranched polymer solution in the form of powder or an organic solvent solution of the organic peracid may be added. You may add. When using a water-soluble inorganic peroxide such as hydrogen peroxide, add the inorganic peroxide aqueous solution to the multi-branched polymer solution, contact both solutions efficiently by stirring, and then centrifuge. A method of separating the aqueous layer and the organic layer by using, for example, is preferable. When ozone is used, a method of bubbling ozone into the hyperbranched polymer solution is suitable.

[0021] The reaction temperature is preferably 0 ° C to room temperature when m-chloroperbenzoic acid or ozone having a strong oxidizing power is used, and 50 to 50 when hydrogen peroxide having a moderate oxidizing power is used. About 80 ° C is preferable. The reaction time is 1 hour to 20 hours. The degree of progress of the oxidation reaction is ¹
It can be determined by 1 H-NMR by measuring the chemical shift of the hydrogen atom in CH ₂ adjacent to the sulfur atom in the hyperbranched polymer.

The multi-branched polymer obtained by the above method can provide a resin solution having high solidity and low viscosity, and has excellent weather resistance. Therefore, the organic solvent solution of the polymer is coated on various substrates. Most suitable as a composition for use.

[0023]

The method for producing a multi-branched polymer of the present invention comprises a step (d) in which the multi-branched polymer containing macromonomer units obtained through the steps [a] to [c] is contained in a predetermined ratio. By being oxidized by the method, it is possible to easily produce a multi-branched polymer which is excellent in weather resistance and which is composed of a resin solution of high solid and low viscosity. Also,
The coating composition of the present invention comprising the multi-branched polymer can easily form a coating film having excellent weather resistance by using the multi-branched polymer in an organic solvent solution. .

[0024]

EXAMPLES The present invention will be described more specifically below with reference to examples and comparative examples. Example 1 A glass flask equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer and a nitrogen gas blowing port was charged with 10 parts of toluene.
Charge 6.2 parts by weight, while blowing nitrogen gas, at a temperature of 80 to 85 ° C., 80 parts by weight of methyl methacrylate (hereinafter referred to as MMA) and 20 parts by weight of 2-hydroxyethyl methacrylate (hereinafter referred to as HEMA), and chain transfer. A mixed solution consisting of 10.6 parts by weight of mercaptoacetic acid as an agent and 2 parts by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator was continuously added dropwise over 3 hours to carry out polymerization, followed by addition for 2 hours. Polymerization was completed by maintaining the temperature to obtain a polymer having a carboxyl group at one end. A part of the toluene solution of the above polymer was sampled, and hexane was added thereto to precipitate and separate the polymer. The acid value of the obtained polymer was measured and found to be 0.82 mg equivalent / g.

Next, in a toluene solution of the polymer, 200 ppm of hydroquinone monomethyl ether as a polymerization inhibitor was added.
Was added, and 1.1 times equivalent of glycidyl methacrylate of the acid value measured was added using a quaternary ammonium salt as a catalyst, and the temperature was maintained at 90 ° C. for 6 hours to react with the terminal carboxyl group of the polymer. The reaction rate calculated from the acid value of this reaction solution was 98.5%. By the above operation, the polystyrene reduced number average molecular weight by the GPC method was 1.340 and the weight average molecular weight was 2,600.
MA / HEMA = 80/20 (% by weight) was obtained to obtain a methacryloyl-type macromonomer at one end.

With respect to 70% by weight of this one-terminal methacryloyl type macromonomer, 12% by weight of MMA and 18% by weight of styrene were charged, and based on the total number of moles thereof, the polymerization initiator AIBN was 8%. 0.4 mol% was added, and a 20% toluene solution of the polymerizable component was added at a temperature of 6
Polymerization was carried out at 0 ° C. for 8 hours.

50 wt% toluene solution of this polymer
15 parts by weight of m-chloroperbenzoic acid (purity 80%) (10% by weight as a polymer, mole number of sulfur atoms contained in the polymer: 8.05 mmol) Number of moles: 69.5 mmol) was added and the temperature was 2
While reacting at 0 ° C., the amount of peroxide was quantitatively analyzed by the iodine method, and the reaction was stopped when the amount of residual peroxide was almost constant. The reaction time required 3 hours. afterwards,
The treated solution was washed with 200 parts by weight of a 10% aqueous sodium hydrogen carbonate solution to remove the residual peroxide and remove the solvent, and then vacuum dried at room temperature for 4 hours to obtain a polymer. Weight average molecular weight (Mw) and solution viscosity (η) of this polymer by a low angle light scattering method (viscosity of a 40% acetone solution of the polymer at a temperature of 25 ° C. by an Ubbelohde viscometer; the same applies hereinafter)
Was: Mw: 23,100 η: 13.2 (cps)

This polymer was dissolved in toluene to give a 50% solution, which was coated on a glass plate with a bar coder. Then, this coating film was dried and cured, and the obtained film-shaped coating film was subjected to an accelerated weathering test [SWOM (Sunshine Weather O-meter), temperature 83 ° C., no water spraying]. No yellowing was observed in the coating film.

Example 2 7% by weight of styrene was used with respect to 93% by weight of the macromonomer synthesized in Example 1, and 8.4 mol of the polymerization initiator AIBN was used based on the total number of moles of these polymerizable components. % And 7.5 mol% of lauryl mercaptan as a chain transfer agent
To prepare a 20 wt% toluene solution at a temperature of 60 ° C.
It was polymerized for 8 hours.

Toluene solution 50 containing 20% by weight of the above polymer
20 parts by weight of m-chloroperbenzoic acid (80% purity) to 10 parts by weight (10% by weight of the polymer, the number of moles of sulfur atoms contained in the polymer: 10.7 mmol) (m-chloroperbenzoic acid) Was carried out in the same manner as in Example 1 except that the accelerated weather resistance test was carried out. As a result, only a slight yellow discoloration of the coating film was observed. Then, the Mw of the polymer measured by the same method as in Example 1
And η were as follows. Mw: 19,000 η: 11.4 (cps)

Comparative Example 1 80% by weight of MMA and 20% by weight of HEMA were mixed with toluene-
Dissolved in a mixed solvent of isobutanol, the monomer concentration in the solution to 20% by weight, based on the total number of moles of the polymerizable component, AIBN 8.4 mol% and lauryl mercaptan 1 mol%, Polymerization was performed in the same manner as in Examples 1 and 2 under other conditions. M of the obtained polymer
w and η are as follows, and the solution viscosity was extremely high. Mw: 22,000 η: 70.3 (cps)

Comparative Examples 2 and 3 The multibranched polymers obtained in the polymerization steps of Examples 1 and 2 and not subjected to the oxidation treatment with peroxide were placed on glass plates in the same manner as in Examples 1 and 2. It was applied with a bar coder and dried and cured to form a film-shaped coating film. When an accelerated weathering test was carried out on this coating film, all the coating films were discolored to dark brown after 220 hours had elapsed.

[0033]

EFFECTS OF THE INVENTION According to the method for producing a multi-branched polymer of the present invention, the multi-branched polymer obtained during the production process is added with an oxidation step using a peroxide, so that it is excellent in weather resistance and high. A multibranched polymer capable of providing a solid and low-viscosity resin solution can be easily produced.

Further, the coating composition of the present invention can form a coating film having excellent weather resistance by using the multi-branched polymer obtained by the production method of the present invention as an organic solvent solution, It has excellent utility in coating various coating materials such as metals, plastics and woods, especially automobiles and home appliances.

Front page continued (72) Inventor Hiroshi Hibino 1 at 1 Funami-cho, Minato-ku, Nagoya Toagosei Chemical Industry Co., Ltd. Nagoya Research Institute (72) Inventor Shiro Kojima 1 Toagosei, Funami-cho, Minato-ku, Nagoya Chemical Industry Co., Ltd., Nagoya Research Institute (72) Inventor, Kishiro Higashi 1-14-1 Nishi-Shimbashi, Minato-ku, Tokyo Toagoi Seigaku Chemical Co., Ltd. (72) Inventor, Kazuyuki Kuwano Toyota-cho, Toyota City, Aichi Prefecture Address: Toyota Motor Co., Ltd. (72) Inventor Takeshi Kawakami 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor: Mamoru Sugiura 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd.

Claims (2)

[Claims] 1. A method for producing a multi-branched polymer, characterized by being produced by the following steps [a] to [d]. [A] A step of radically polymerizing at least one ethylenically unsaturated monomer in the presence of a mercaptan compound having a reactive group and a thiol group in the molecule. [B] A step of reacting the polymer having a reactive group at one end obtained in the step [A] with a compound having a bonding group capable of reacting with the reactive group and an ethylenically unsaturated bond. [C] A macromonomer having an ethylenically unsaturated bond at one end of the molecule obtained in the step [B] and at least one monomer copolymerizable with the macromonomer are copolymerized to obtain a total amount. A step of synthesizing a multi-branched polymer in which the ratio of the macromonomer unit is more than 45% by weight and 99.5% by weight or less based on the total amount of the constituent units. [D] A step of reacting the hyperbranched polymer having a thioether bond in the molecule obtained in the above step [c] with a peroxide to oxidize a sulfur atom in the thioether bond to a sulfone. 2. A coating composition comprising an organic solvent solution of a multi-branched polymer obtained by the production method according to claim 1.