JPS6330334B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a solvent solution of a low molecular weight acrylic copolymer (hereinafter abbreviated as low molecular weight acrylic copolymer) having a high solid content concentration.

Low-molecular-weight acrylic copolymers have recently attracted a lot of attention for the purpose of reducing the amount of solvent used in order to comply with solvent regulations.

By the way, acrylic copolymers having a number average molecular weight (hereinafter also simply referred to as molecular weight) of about 5,000 to about 30,000 have a small dilution effect with solvents.
Therefore, when the solid content concentration of the resin is in a high range of 70 to 95%, the viscosity becomes extremely high, making it difficult to use it for paints or adhesives.

Therefore, in order to obtain a practical acrylic copolymer in the high solids concentration range of 70 to 95%, it is necessary to use a low-molecular-weight copolymer that has an excellent diluting effect against solvents. Preferably, such low molecular weight acrylic copolymers have become widely sought after.

Therefore, a general method for obtaining an acrylic copolymer with a molecular weight of about 5,000 to about 10,000 is to carry out solution polymerization at 80 to 120°C under the reflux temperature of a solvent. As can be inferred from the kinetics of radical polymerization,
It can be said that the conditions are favorable for producing low-molecular copolymers because the monomer concentration can be reduced and the chain transfer effect of the solvent can be expected, but copolymers with even lower molecular weights of 500 to 3000 is extremely difficult to manufacture.

Moreover, in order to obtain a low molecular weight acrylic copolymer of 1,000 to 3,000 by such solution polymerization method, it is necessary to use a large amount of initiator and also a mercaptan-based chain transfer agent. Its use inevitably causes a bad odor in the obtained copolymer, which severely impairs workability, and also reduces the acid resistance and stain resistance of the film that is finally formed, so it is not practical. I can't say that there is.

However, the present inventors have conducted intensive studies to eliminate the above-mentioned deficiencies in conventional methods, and as a result, we have developed a method that is free of chain transfer agents and has low odor.
5,000, preferably 500 to 3,000, and have completed the present invention.

That is, in the present invention, in the presence of an initiator that generates a radical group, (a) 90 to 10 parts by weight of an acrylic ester or methacrylic ester or a mixture thereof (b) 0 to 90 parts by weight of an aromatic vinyl monomer (b) ) Diesters of ethylenically unsaturated dicarboxylic acids
0 to 40 parts by weight (d) Hydroxyl group-containing vinyl monomer, glycidyl group-containing vinyl monomer, or acid group-containing vinyl monomer, or a mixture thereof 1 to 40 parts by weight (e) Acrylic acid amide, methacrylic acid amide, acrylonitrile or methacrylonitrile, or Mixture thereof 0 to 20 parts by weight (f) Vinyl ester of monocarboxylic acid
0 to 60 parts by weight (t) Graftable alkyd resin or oil-free alkyd resin having unsaturated bonds, or a mixture thereof 0 to 30 parts by weight A mixture of monomers is solution-polymerized to produce a low-molecular-weight acrylic copolymer. The present invention provides a closed reaction method in which the internal temperature is maintained at 140 to 200°C in the presence of a solvent mainly consisting of an aromatic solvent, an ester solvent, a ketone solvent, or a cellosolve solvent. The above monomer mixture in a container and at least 70
Degradation half-life (at 100°C) of weight% greater than 10 minutes
polymerization by supplying an initiator having 70 to 95
% solid content and a molecular weight of 500 to 5000.

Here, as the reaction vessel used for producing the copolymer, for example, an autoclave type vessel having a pressure-resistant structure (gauge pressure: 10 to 12 kg/cm ² ) can be used. More specifically, this reaction vessel is an autoclave having a jacket and an internal coil, into which the monomer mixture is fed from the monomer mixture receiving tank and the initiator dissolving tank via a metering pump at a predetermined time. A mixture of these monomers and an initiator are supplied.

The temperature inside the reaction vessel is maintained at a set temperature by cascade control, and the polymerization heat generated as the polymerization progresses is removed by heat transfer from the jacket and internal coil.

In detail, the method for producing the copolymer using such a reactor is as follows: purging a well-equipped reactor with nitrogen gas, exhausting the air remaining in the reactor, and then purging the reactor with nitrogen gas using a vacuum pump. Drain and maintain vacuum at 50-100 Torr.

Next, a predetermined solvent or a mixture of the same and a monomer is supplied, and the temperature inside the vessel is maintained within a range of 140 to 200°C, preferably 150 to 185°C, and more preferably 165 to 180°C.

At that time, solvents whose temperature is above the boiling point exhibit a state in which an equilibrium relationship is established between the liquid phase and the gas phase within the reactor, and conversely, solvents whose temperature is below the boiling point generate some solvent vapor in the internal space of the reactor. ing.

Additionally, a pressure builds up inside this vessel that corresponds to the vapor pressure of the solvent at a given temperature, but the pressure increase is small because the gas components are removed at the beginning.
Therefore, the pressure created within the vessel is 1 to 7.
Kg/cm ² (gauge pressure), which is relatively low.

In a reactor exhibiting such a state, a mixture of a (meth)acrylate monomer and a functional group-containing monomer, or one or more monomers selected from the above-mentioned monomers A, H, H, H, and G are added. and the above-mentioned initiator, i.e. at least 70% by weight thereof is 100%
By co-supplying an initiator with a decomposition half-life of 10 minutes or more at °C for solution polymerization,
The desired low-molecular-weight acrylic copolymer can be easily and safely produced.

The acrylic copolymer thus obtained has an extremely low molecular weight of 500 to 5,000, preferably 500 to 3,000, so it has extremely good solubility in solvents, and is also extremely sensitive to changes in viscosity due to temperature. Even when the high solid content concentration of 70 to 95%, which is the objective of the present invention, is reached, the viscosity is relatively low at 30 to 300 cps at a reaction temperature of 140 to 200°C, and as a result, mixing and stirring in the reactor becomes difficult. This has the advantage that the heat transfer coefficient, which is important for removing polymerization heat, can be relatively large.

Furthermore, because the addition of the monomer mixture and initiator is done gradually, more preferably at a relatively slow rate of 2 to 8 hours, the heat of polymerization, which is governed by these feed rates, is very small and As a result, the cooling rate per unit time becomes sufficiently high, the reactor is easy to control and stable, and there is no risk of runaway reaction.

Low-molecular-weight acrylic copolymers produced by such a method have a wide range of uses, such as high-solids coating resins and adhesive resins. For example, a vinyl monomer containing a hydroxyl group, and a component selected from B, H, H, H, and D excluding the hydroxyl group-containing monomer.
Copolymerizing a species or two or more monomers,
Alternatively, a copolymer obtained by copolymerizing one or more monomers selected from components (a), (d), and (b) and (c), and further grafting a portion of the component (g) to this, is a melamine resin. It can be cured to form a tough film,
It is also possible to form a film having urethane crosslinks by using polyisocyanate as a curing agent.

In addition, it can be obtained from a vinyl monomer containing a glycidyl group in component (d), and one or more monomers selected from components (a), (b), (c), (g), and (d) excluding the glycidyl group-containing monomer. The copolymers can also be used as binders in combination with curing agents selected from amines, polycarboxylic acids and polyester resins with terminal acid groups.

Furthermore, it is obtained from a vinyl monomer containing an acid group of component (2), and one or more monomers selected from components (b), (c), (e), and (d) excluding the acid group-containing monomer. The copolymer can form a tough film through a curing reaction with polyepoxide, and one or more compounds selected from the group consisting of ammonia and organic amines can be used to cure part or all of the copolymer. It can be neutralized and dissolved in water and used as a binder for electrodeposition paints, or as a dispersant for soap-free emulsions.

Here, the solvent used in carrying out the method of the present invention includes an aromatic solvent represented by xylene or toluene; an ester represented by ethyl acetate, i-propyl acetate, n-butyl acetate, etc. Typical solvents are ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, or cyclohexanone; or cellosolve solvents such as methyl cellosolve, ethyl cellosolve, or butyl cellosolve; however, the use of alcohol solvents is prohibited. ,
Among the above-mentioned (meth)acrylate monomers and functional group-containing monomers, hydroxyl group-containing monomers and glycudyl group-containing monomers, diesters of ethylenically unsaturated dicarboxylic acids, and vinyl esters of monocarboxylic acids When monomers such as F are used, a transesterification reaction occurs between each of these monomers and the alcoholic solvent, and as a result, a copolymer with the desired coating performance cannot be obtained, and on the other hand, When using an acid group-containing monomer among the functional group-containing monomers, an esterification reaction is caused between the monomer and the alcohol solvent, and in the same way, a desired coating performance can be obtained. Since the copolymer cannot be obtained, the use of only the alcoholic solvent should be avoided by all means.

However, with respect to the various solvents listed above, there is no problem in using the alcoholic solvent in an amount within a range that does not cause any transesterification reaction or esterification reaction.

Of course, the various solvents listed above can be used alone or in combination of two or more.
Furthermore, the solvent and the monomer may be used in combination by partially mixing the monomers listed below.

Next, typical examples of the above-mentioned acrylic ester or methacrylic ester component A are methyl (meth)acrylate, ethyl (meth)acrylate, (meth)butyl acrylate,
Isobutyl acrylate (meth)acrylic acid-2-
Ethylhexyl or lauryl (meth)acrylate, etc. Typical examples of the aromatic vinyl monomer component (2) include styrene or vinyltoluene, and representative examples of the diester component (3) of the ethylenically unsaturated dicarboxylic acid. Examples include diptyl fumarate, dimethyl fumarate, diisofumarate, and dibutyl itaconate.

Among the above two components, the typical hydroxyl group-containing vinyl monomers are β-
Examples include hydroxyethyl (meth)acrylate, β-hydroxypropyl methacrylate, and β-hydroxyisopropyl methacrylate.Next, typical glycidyl group-containing vinyl monomers include (methyl)glycidyl methacrylate and glycidyl acrylate. Typical acid group-containing vinyl monomers include (meth)acrylic acid, fumaric acid, maleic acid, and itaconic acid.

Furthermore, typical vinyl esters of the monocarboxylic acids include vinyl acetate, vinyl propionate, vinyl laurate, and vinyl benzoate.

Furthermore, among the above-mentioned components, representative examples of diols and polyols useful in preparing oil-free alkyd resins having unsaturated bonds include glycerin,
ethylene glycol, 1,4-butanediol,
1,6-hexanediol, trimethylolethane, trimethylolpropane or pentaerythritol or mixtures thereof;
Useful acid components include succinic acid, adipic acid, azelaic acid, sebacic acid, decane-1,10-dicarboxylic acid, terephthalic acid, isophthalic acid or phthalic anhydride or mixtures thereof; Itaconic acid, fumaric acid or maleic acid may be used as the acid component containing a bond.

Next, typical examples of oil components useful for producing graftable alkyd resins include soybean oil, castor oil, dehydrated castor oil, tall oil, linseed oil, or safflower oil; fatty acids, etc., which can be used singly or as a mixture of two or more,
As useful acid components and polyol components, those used for the preparation of the oil-free alkyd resin described above can be used as they are.

The above-mentioned initiator used in the present invention refers to one containing at least 70% by weight of an initiator whose decomposition half-life at 100°C is 10 minutes or more. The degradation half-life of
Typical examples of "initiators for 10 minutes or longer" include di-tertiary butyl hydroperoxide, tertiary-butyl hydroperoxide, cumyl peroxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, or Examples of initiators with a decomposition half-life of 10 minutes or less at 100°C that may be partially used in combination with these include benzoyl peroxide, lauryl peroxide, and tert-butyl peroxide. Peroxides such as -2-ethylhexanate or acetyl peroxide may be mentioned.

Next, the present invention will be specifically explained using examples.

In the following, all parts and percentages are based on weight unless otherwise specified.

Example 1 The main reaction vessel was an autoclave with a pressure-resistant structure consisting of a stirrer, a thermometer, a nitrogen gas inlet tube, a heating and cooling jacket, and a cooling coil, and the autoclave had the following:
A device equipped with a metering pump that quantitatively supplies a monomer mixture, a metering pump that quantitatively supplies a dissolved initiator, and a vacuum pump for removing gas remaining in the autoclave. First, 25 parts of xylene was charged into an autoclave as an initial charge for the reaction, and the temperature inside the reactor was set to 165°C by heating through a jacket, and the temperature was maintained at this temperature.

Next, styrene was placed inside the container held in this way.
A monomer mixture consisting of 35 parts of ethyl acrylate, 21 parts of ethyl acrylate and 14 parts of β-hydroxyethyl methacrylate, and an initiator mixture of 5 parts of xylene, 2 parts of di-tert-butyl peroxide and 0.2 parts of cumene hydroperoxide were prepared. After continuous supply using a metering pump for 3 hours, the reaction was continued for an additional 2 hours.

After that, the contents of the reactor were cooled, the resulting polymer solution was taken out, and its resin properties were examined, and it was found that the solid content was 70% and the Gardner viscosity (25°C; the same applies hereinafter) was V to W. . In addition, the number average molecular weight was as low as 1740, and it was obtained as an acrylic copolymer with a considerably low molecular weight.

Example 2 A solution of a low-molecular acrylic copolymer having the following resin properties was obtained by repeating the same operation as in Example 1, except for changing the conditions below.

Reaction temperature 170°C Initial reaction charge Butyl acetate 18 parts Monomer mixture Styrene 32 parts n-butyl methacrylate 16 parts β-hydroxyethyl acrylate 12 parts Dibutyl fumarate 20 parts Initiator mixture solution Butyl acetate 2 parts Ditertiary butyl per Oxide 2.5 parts Cumene hydroperoxide 0.8 parts Solid content concentration 80% Number average molecular weight 1400 Gardner viscosity Z ₂ - _{Z 3} Example 3 Repeat the same operation as Example 1 except for changing the conditions below. A solution of a low-molecular acrylic copolymer with such characteristic values was obtained.

Reaction temperature 180°C Initial reaction charge Cellosolve acetate 9 parts Dibutyl fumarate 13.5 parts Monomer mixture Styrene 45 parts Butyl acrylate 9 parts β-hydroxyethyl methacrylate 21 parts Acrylic acid 1.5 parts Initiator mixture solution Cellosolve acetate 1 part Diterciary Butyl peroxide 3 parts Tertiary butyl perbenzoate 1 part Solid concentration 90% Number average molecular weight 950 Gardner viscosity Z ₆ Example 4 Repeat the same operation as Example 1 except for changing the conditions below. A solution of a low-molecular acrylic copolymer with such characteristic values was obtained.

Reaction temperature 170℃ Monomer mixture Styrene 28 parts Methyl methacrylate 21 parts Dibutyl fumarate 7 parts Glycidyl methacrylate 14 parts Initiator mixture solution Xylene 5 parts Ditertiary butyl peroxide 2.5 parts Cumene hydroperoxide 0.5 parts Solid content concentration 70% Number average molecular weight 1800 Gardner viscosity T~U Example 5 The same operation as in Example 1 was repeated except that the following conditions were used to prepare a solution of a low molecular weight acrylic copolymer having the following characteristic values. Obtained.

Reaction temperature 170℃ Monomer mixture Styrene 35 parts n-butyl methacrylate 22 parts Acrylic acid 8 parts Acrylonitrile 5 parts Initiator mixture solution Xylene 5 parts Ditertiary butyl peroxide 4 parts Cumene hydroperoxide 0.5 parts Solid concentration 70% Number average molecular weight 1400 Gardner viscosity Y~Z Example 6 The reaction temperature was 180°C, the amount of xylene used as the initial reaction filler was 18 parts, and the composition of the monomer mixture and the composition of the initiator mixture were as follows. The procedure was carried out in the same manner as in Example 1 except for the following changes. Methyl methacrylate Vinyl acetate β-hydroxymethyl methacrylate 56 parts 14 10 80%, number average molecular weight is 2000,
A solution of a low molecular acrylic copolymer having a Gardner viscosity of Z ₃ to _{Z 4} was obtained.

Example 7 The reaction temperature was 170°C, and the initial reaction charge was
A mixture of 19.7 parts of xylene and 13.3 parts of alkyd resin, and the composition of the monomer mixture and initiator mixture, respectively, were added to 35 parts of styrene ethyl acrylate β-hydroxyethyl methacrylate 13 14 xylene ditertiary butyl peroxide cumene hydroper A low molecular weight acrylic copolymer with a solid content concentration, number average molecular weight and Gardner viscosity of 70%, 2000 and Y, respectively, was prepared in the same manner as in Example 1, except that oxide was changed to 5 parts 1〃 0.8〃. A solution of was obtained.

The alkyd resin mentioned above includes 28.7 parts of soybean oil fatty acid, 17.4 parts of pentaerythritol,
13.1 parts of ethylene glycol and phthalic anhydride
Gardner viscosity is
~Y, acid value 6, hydroxyl value 100, oil length 30%
I used something that is.

Example 8 The reaction temperature was set to 170°C, the initial reaction charge was a mixture of 12 parts of xylene and 15 parts of oil-free alkyd, and the composition of the monomer mixture was 40.5 parts of styrene.
Example 1, except that 28.5 parts of ethyl acrylate and 12 parts of β-hydroxyethyl methacrylate were used, and the composition of the initiator mixture solution was changed to 2 parts of xylene, 3 parts of ditertiary butyl peroxide, and 1 part of cumene hydroperoxide. In exactly the same manner as above, a solution of a low-molecular-weight acrylic copolymer having resin characteristic values of solid content concentration, number average molecular weight, and Gardner viscosity of 90%, 1050, and Z ₅ to Z ₆ was obtained, respectively.

The oil-free alkyd resin has a hydroxyl value of 100 obtained by an esterification reaction from 50 parts of isophthalic acid, 2 parts of maleic anhydride, 11.6 parts of adipic acid, 25.4 parts of trimethylolpropane, and 47.8 parts of neopentyl glycol. Gardner viscosity W at solid content 60% (solvent: xylene)
~X and an acid value of 5 were used.

Claims (1)

[Claims] 1. In the presence of an initiator that generates a radical group, (a) 90 to 10 parts by weight of an acrylic ester or methacrylic ester or a mixture thereof (b) 0 to 90 parts by weight of an aromatic vinyl monomer (c) Diester of ethylenically unsaturated dicarboxylic acid
0 to 40 parts by weight (d) Hydroxyl group-containing vinyl monomer, glycidyl group-containing vinyl monomer, or acid group-containing vinyl monomer, or a mixture thereof 1 to 40 parts by weight (e) Acrylic acid amide, methacrylic acid amide, acrylonitrile or methacrylonitrile, or Mixture thereof 0 to 20 parts by weight (f) Vinyl ester of monocarboxylic acid
0 to 60 parts by weight (t) Graftable alkyd resin or oil-free alkyd resin having unsaturated bonds, or a mixture thereof 0 to 30 parts by weight A mixture of monomers is solution-polymerized to produce a low molecular weight acrylic copolymer. In the method for producing , the above monomer is placed in a closed reactor with an internal temperature maintained at 140 to 200°C in the presence of a solvent mainly consisting of an aromatic solvent, an ester solvent, a ketone solvent, or a cellosolve solvent. and at least 70% by weight of
Polymerization is carried out by supplying an initiator having a half-life of decomposition at 100°C for 10 minutes or more, and having a solid content concentration of 70 to 95% by weight and a number average molecular weight of 500.
A method for producing a low molecular weight acrylic copolymer, the method comprising obtaining a solvent solution of an acrylic copolymer having a molecular weight of ~5000.