JP2001049149A - Production of coating varnish - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a low-viscosity coating varnish excellent in coating film physical properties such as coating film mechanical strengths owing to its high solid content and high molecular weight. SOLUTION: This method for producing a coating varnish comprises solution polymerization of a monomer composition containing an acrylic vinyl monomer using a polymerization initiator; wherein the polymerization initiator to be used is a combination of dicinnamoyl peroxide with another polymerization initiator 65-130 deg.C in such a temperature as to be 10 h in its half-life in benzene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a coating varnish having high solids content, high molecular weight, excellent coating properties such as coating strength, and low viscosity.

[0002]

2. Description of the Related Art In recent years, in the field of paints, reduction of the emission of volatile organic compounds has become a major issue from the viewpoint of protection of the global environment. In response,
There are water-based paints, powder paints, and high-solid paints, each of which has been put to practical use. Among these, high solid paints (paints having a higher solid content or non-volatile content than conventional paints) have been most actively researched because of the advantage that existing equipment can be used. As a general method, JP-A-61-152772 discloses a method in which azobisisobutyronitrile or t-butylperoxy-2-ethylhexanoate is used as a polymerization initiator. However, in these methods, when the solid content is increased, the viscosity is increased and the coating becomes difficult. Therefore, as a method for achieving high solidification without increasing the viscosity of the coating by lowering the molecular weight of the resin, for example, JP
JP-168415 discloses t-amyl peroxy-2-
A method using ethylhexanoate as a polymerization initiator is disclosed.

On the other hand, by giving the resin a branched structure,
As a resin, there is a method of achieving a high solidification by lowering the viscosity of a paint while maintaining a sufficient molecular weight. That is, it is known that a branched polymer has a smaller radius of inertia in a solution and lowers a solution viscosity than a linear polymer.
Therefore, it is possible to suppress an increase in viscosity due to high solidification while maintaining a molecular weight that does not impair the physical properties of the coating film by imparting a branched structure to the resin. As a method for obtaining a branched resin, a macromonomer method, a living anion polymerization method using a polyfunctional initiator, and the like are known. For example, Polymer, Vol. 45, April, p. 262 (1996) discloses a method of synthesizing a branched high-solid coating resin by copolymerizing a macromonomer. Japanese Patent Application Laid-Open No. Hei 8-27202 discloses a method of synthesizing a star-shaped high-solid coating resin by reacting a prepolymer obtained by living anionic polymerization with a coupling agent.

[0004]

However, in general, varnishes for paints are required to have various performances such as water resistance, solvent resistance, weather resistance, etc. In particular, recently, the required levels have been increasingly sophisticated. . The coating varnish needs to react with a cross-linking agent to form a tough coating film having a three-dimensional network structure, and therefore it is necessary to have two or more functional groups in one molecule of the resin. . However, in the method of reducing the molecular weight of the resin disclosed in JP-A-63-168415, it is difficult to reliably introduce two or more functional groups in one molecule, and thus the physical properties of the coating film are deteriorated. And physical properties satisfying the required level could not be obtained.

The methods disclosed in Polymer, Vol. 45, April, pp. 262 (1996) and JP-A-8-27202 require complicated steps such as synthesis of macromonomers and prepolymers. However, industrialization had difficulties in terms of production efficiency and economy. The present invention has been made by paying attention to the problems existing in the prior art as described above. It is an object of the present invention to provide a method for producing a paint varnish having a high solid content, a high molecular weight, excellent coating properties such as coating strength, and a low viscosity.

[0006]

The present inventors have studied the problems of the above-mentioned conventional methods over a long period of time, and as a result, by using a specific polymerization initiator, have obtained a paint varnish which has solved those problems. And found that the present invention was completed. That is, the present invention relates to a method for producing a coating varnish for solution-polymerizing a monomer composition containing a (meth) acrylic vinyl monomer using a polymerization initiator, wherein the polymerization initiator comprises dicinnamoyl peroxide as a polymerization initiator. A method for producing a varnish for a coating, characterized by using together with another polymerization initiator having a half-life of 10 hours in benzene and a temperature of 65 to 130 ° C.

[0007]

Embodiments of the present invention will be described below in detail. In general, the most widely used commercial method for producing paint varnishes is the solution polymerization method.
In the production of a coating varnish by a solution polymerization method, a monomer composition containing a (meth) acrylic vinyl monomer (hereinafter, abbreviated as polymerization monomer), a solvent, and a polymerization initiator are blended. By heating and polymerizing, a varnish for paints that constitutes a coating film is manufactured. In the present invention, in producing a coating varnish by the solution polymerization method, the half-life of an earthquake cinnamoyl peroxide and in benzene as a polymerization initiator temperature of 10 hours (hereinafter, abbreviated as T _10.) 65 By using other initiators having a temperature of up to 130 ° C. in combination, it is possible to efficiently produce a coating resin containing a branched polymer. As a result, it is possible to obtain a coating varnish excellent in the balance between the properties of the coating film and the solution viscosity.

[0008] Disinnamoyl peroxide is produced by reacting a chloroform solution of cinnamoyl chloride (cinnamate chloride) with caustic soda and hydrogen peroxide at 0 ° C. This manufacturing method is described in, for example, Journal of Chemical Society (J. Chem. S.
oc. ), 1956, p. 427. In the present invention, as the polymerization initiator, by itself cinnamoyl peroxide and T ₁₀ are used in combination other polymerization initiator 65 to 130 ° C., it can be produced efficiently branched polymers. That is, low confidence cinnamoyl peroxide of T ₁₀ in the initial polymerization (T _10: 60 ℃) by to initiate the main polymerization, to produce a macromer having a vinyl group at the terminal. Then, the monomer and the macromer are copolymerized with another polymerization initiator used in combination, whereby a branched polymer can be obtained efficiently.

Accordingly, other polymerization initiator to be used in combination with seismic cinnamoyl peroxide, those T ₁₀ is moderately higher than the seismic cinnamoyl peroxide are preferred. T ₁₀ is 6
In the case of a polymerization initiator having a temperature of less than 5 ° C., polymerization by a polymerization initiator other than dicinnamoyl peroxide frequently occurs in the initial stage of polymerization, so that the efficiency of forming a branched polymer is reduced, and as a result, the solution viscosity when a high solid is formed is increased. . Further, the polymerization initiator T ₁₀ exceeds 130 ° C., the polymerization rate is lowered.

As other polymerization initiators to be used in combination, for example, diacyl peroxides such as dibenzoyl peroxide (T ₁₀ : 74 ° C.), ditoluyl peroxide (T ₁₀ : 73 ° C.), t-butyl peroxyacetate (T ₁₀ : 1
02 ° C.), t-hexyl peroxyacetate (T ₁₀ :
98 ° C.), di -t- butyl peroxy isophthalate (T _10: 107 ℃), di -t- butyl - cyclohexane-1,4-peroxy-carboxylate (T _10: 80
° C.), t-butyl peroxy laurate (T _10: 118
° C.), t-hexyl peroxy-2-ethylhexanoate _{(T 10: 70 ℃),} t- butyl peroxy-2-ethylhexanoate _{(T 10: 72 ℃),} t- butyl peroxy benzoate (T _10: 104 ° C.), t-hexylperoxybenzoate (T ₁₀ : 99 ° C.), t-octylperoxy-2-ethylhexanoate (T ₁₀ : 65)
° C.), 2,5-dimethyl-2,5-bis (benzoyl peroxy) hexane (T _10: 100 ° C.) peroxy esters such as, t- butyl peroxy isopropyl monocarbonate _{(T 10: 99 ℃),} t- hexyl peroxy isopropyl monocarbonate _{(T 10: 95 ℃),} t-
Butyl peroxy-2-ethylhexyl monocarbonate _{(T 10: 99 ℃),} 1,6- bis (t-butylperoxy carbonyloxy) hexane (T _10: 101 ℃),
1,1,1-tris (t-butylperoxy carbonyloxy) propane (T _10: 101 ℃) peroxymonosulfate carbonates such as 1,1-bis - t-butyl peroxy cyclohexane (T _10: 91 ℃), 2,2-
Bis - t-butylperoxy butane (T _10: 103
° C.), n-butyl-4,4-bis (t-butylperoxy) valerate _{(T 10: 105 ℃),} 1,1- bis -
t-butylperoxy-3,3,5-trimethylcyclohexane (T ₁₀ : 90 ° C.), 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane (T
₁₀ : 95 ° C.), di-t-butyl peroxide (T ₁₀ : 124 ° C.), t-butylcumyl peroxide (T ₁₀ : 120 ° C.), 2,5-di-t-butylperoxy- 2,5-dimethylhexane (T ₁₀ : 1
Alkyl peroxides such as 18 ° C.) and dicumyl peroxide (T ₁₀ : 116 ° C.).

The total amount of the polymerization initiator used in the present invention is usually 1 to 15% by weight, preferably 5 to 15% by weight, based on the total amount of the monomers for polymerization. If the amount is less than 1% by weight, the polymerization is not completed. The amount of disinnamoyl peroxide, which is an essential component of the polymerization initiator, depends on the total amount of the polymerization initiator.
Usually, 5 to 50% by weight, preferably 10 to 30% by weight is used. When the content is less than 5% by weight, the amount of the branched polymer produced is reduced, and when it exceeds 50% by weight, a gel component tends to be easily produced.

The polymerization monomer used in the present invention is usually at least one selected from the group consisting of hydroxyalkyl acrylates and hydroxyalkyl methacrylates (hereinafter simply referred to as component A) and the acrylic acid. It may contain at least one selected from the group consisting of acrylates and methacrylates other than hydroxyalkyl esters and hydroxyalkyl methacrylates (hereinafter simply referred to as component B).

Examples of the hydroxyalkyl acrylate include 2-hydroxyethyl acrylate,
Examples of hydroxypropyl acrylate include hydroxyalkyl methacrylate. Examples of hydroxyalkyl methacrylate include 2-hydroxyethyl methacrylate and hydroxypropyl methacrylate. Examples of the acrylate include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, isobutyl acrylate, and 2-ethylhexyl acrylate. Examples of the methacrylate include methacrylic acid. Methyl, ethyl methacrylate, methacrylic acid n
-Propyl, isobutyl methacrylate, n-methacrylate
-Butyl, n-octyl methacrylate, lauryl methacrylate and the like.

The proportion of the component A in the total amount of the monomers for polymerization is usually 10 to 40% by weight, preferably 20 to 30% by weight. If it is less than 10% by weight, the strength of the coating film becomes insufficient, and if it exceeds 40% by weight, the viscosity of the varnish increases and the curing tends to proceed too much. The proportion of the component B in the total amount of the monomers for polymerization is usually 0 to 90% by weight, preferably 30 to 80% by weight.

In the polymerization monomer of the present invention, in addition to the acrylic vinyl monomer, a vinyl monomer copolymerizable therewith may be further added. That is, a case where the monomer composition containing the component A and the component B further contains a copolymerizable vinyl monomer, a case where the monomer composition containing the component A further contains a copolymerizable vinyl monomer, and the like. is there. Examples of the copolymerizable vinyl monomer include styrene, acrylonitrile, acrylic acid, methacrylic acid, maleic acid, itaconic acid, glycidyl methacrylate, and acrylamide. These are usually 40
Used at weight percents or less. Selection of the type of these monomers for polymerization is used in an appropriate combination according to the required physical properties as a varnish, the type of a curing agent used for curing, and the required physical properties of a coating film when a coating film is formed.

The ratio of the total amount of the polymerization monomer to the entire raw material of the coating varnish is usually 40 to 80% by weight, preferably 50 to 70% by weight. If the amount is less than 40% by weight, the amount of the solvent in the coating varnish increases, which is economically disadvantageous, and the amount of volatile organic solvent increases, which is not preferable on environmental issues. If it exceeds 80% by weight, the viscosity of the polymer becomes too high. There is a tendency. As the solvent in the present invention, for example, toluene, aromatic hydrocarbons such as xylene, methyl ethyl ketone, ketones such as methyl isobutyl ketone,
Acetates such as butyl acetate, alcohols such as n-butyl alcohol, and mixtures thereof are used.

The polymerization method of the present invention comprises mixing a polymerization monomer, a polymerization initiator and a solvent, and
0 to 150 ° C, preferably 2 to 10 at 100 to 140 ° C
The polymerization is carried out for a time, preferably for 3 to 6 hours. Polymerization temperature is 8
If the temperature is lower than 0 ° C., the polymerization rate is low, and the average molecular weight of the obtained polymer becomes large.
If the polymerization time is less than 2 hours, it is difficult to control the heat of polymerization. Conversely, if it exceeds 10 hours, there is no particular advantage and it is economically disadvantageous. Further, in order to prevent unreacted monomers from remaining in the polymer at a later stage of the polymerization reaction, a generally used polymerization initiator may be added.

A specific method of mixing the monomer for polymerization, the polymerization initiator and the solvent may be any of the following methods. (1) A method of stirring and mixing while continuously or intermittently adding a mixture of a polymerization monomer, a polymerization initiator, and a solvent to an empty polymerization tank. (2) A method of stirring and mixing while continuously or intermittently adding a mixture of a polymerization monomer and a polymerization initiator to a polymerization tank containing a solvent. (3) A method in which a polymerization monomer, a polymerization initiator, and a solvent are independently and simultaneously added in parallel to a polymerization tank while stirring and mixing. In these methods, there is no problem even if a part of the polymerization monomer is previously mixed in the solvent to be used and a part of the solvent is mixed in the polymerization monomer in advance. The mixing ratio in each of these cases is appropriately determined according to the polymerization apparatus, polymerization conditions, and the like.

[0019]

The present invention will be specifically described below with reference to examples and comparative examples. In these examples, the abbreviations of the polymerization initiator are as follows. CIPO: disinnamoyl peroxide (T ₁₀ : 60
° C.) BUZ: t-butyl peroxybenzoate (T _10: 1
04 ℃) HexZ: t- hexyl peroxybenzoate _{(T 10: 99 ℃) BuO} : t- butyl peroxy-2-ethylhexanoate _{(T 10: 72 ℃) HexO} : t- hexyl peroxy-2-ethylhexanoate _{(T 10: 70 ℃) OctO} : t- octyl peroxy-2-ethylhexanoate _{(T 10: 65 ℃) BuA} : t- butyl peroxy acetate (T _10: 10
2 ℃) BuE: t- butyl peroxy-2-ethylhexyl monocarbonate _{(T 10: 99 ℃) AmO} : t- amyl peroxy-2-ethylhexanoate (T _10: 73 ℃)

Example 1 200 g of xylene was placed in a 1-liter four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen gas inlet tube and dropping funnel, and heated to 130 ° C. while introducing nitrogen gas.
, And a mixture of butyl methacrylate, 2-hydroxyethyl methacrylate and acrylic acid as monomers for polymerization (in a weight ratio of 72: 2, respectively) from the dropping funnel.
6: 2) 300 g and CIPO 2.0 as a polymerization initiator
g and 9.0 g of BuZ were added dropwise at a constant rate over 3 hours. After the completion of the dropwise addition, the polymerization was continued at 130 ° C. for another hour. The viscosity of the obtained solution was measured with a Gardner viscometer. The solution was further dried at 110 ° C. for 3 hours to determine the solid content. Further, the number average molecular weight (abbreviated as Mn in the table) and the weight average molecular weight (abbreviated as Mw in the table) of the obtained polymer were measured by a gel permeation method (GPC method). The molecular weight was expressed as a linear polymethyl methacrylate conversion value. The results are shown in Tables 1 and 2.

Examples 2 to 7 Polymerization was carried out in the same manner as in Example 1 except that the polymerization initiators shown in Table 1 were used as polymerization initiators, and the results are shown in Tables 1 and 2.

[0022]

[Table 1]

[0023]

[Table 2]

Comparative Examples 1 to 3 Polymerization was carried out in accordance with Example 1 except that the conventional polymerization initiators (BuA, BuO, AmO) shown in Table 1 were used as polymerization initiators, respectively. 2 is shown.

In Examples 1 and 2, the resin of the coating varnish obtained had a weight-average molecular weight higher than that of Comparative Example 1 by 20% or more, but the viscosity was almost the same. Alternatively, it was observed in Example 4 and Comparative Example 3. Further, in Examples 4 and 6, the weight average molecular weight of the resin of the coating varnish was comparable to that of Comparative Example 1, but the viscosity was 40.
% Or more, and the same tendency was observed in Examples 5 and 7 and Comparative Example 2. As described above, according to the method for producing a coating varnish of the present invention, a coating varnish excellent in the balance between the molecular weight and viscosity of the resin of the coating varnish as compared with the conventional method, that is, the coating film properties after crosslinking are good. It has been found that a coating varnish having a relatively high viscosity can be produced although the molecular weight is so high as to be as follows. Therefore, according to the present invention, it has become possible to make a varnish for coating a high solid while maintaining both the coating film properties such as the coating film strength and the solution viscosity.

[0026]

According to the method for producing a varnish for a coating material of the present invention, the use of a specific polymerization initiator makes it possible to obtain a high solid content and a high molecular weight, thereby providing excellent coating properties such as coating strength and low coating properties. This enables a method for efficiently producing a paint varnish having a viscosity.

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 4J011 HA03 HA04 HB02 HB14 HB22 4J015 BA03 BA06 4J038 CG141 NA11 4J100 AB02R AJ02R AJ09R AL03Q AL04Q AL05Q AL09P AL10R AM02R AM15R CA01 CA03 CA04 CA05 FA03 FA19 JA01

Claims (1)

[Claims] 1. A method for producing a varnish for a paint, in which a monomer composition containing a (meth) acrylic vinyl monomer is solution-polymerized using a polymerization initiator, wherein dicinnamoyl peroxide and benzene are used as polymerization initiators. Has a half-life of 10
A method for producing a varnish for a paint, characterized by using together with another polymerization initiator having a temperature of 65 to 130 ° C as a time.