JPH04103610A - Resin for crosslinking-curable coating and preparation thereof - Google Patents

Abstract

PURPOSE:To prepare the subject resin capable of forming a solution having a high solid content concentration and a low viscosity by radically copolymerizing a macro monomer having a radically polymerizable group at one end thereof with one or more radically polymerizable monomers in a specific ratio. CONSTITUTION:(A) A macro monomer having a radically polymerizable group at one end thereof and having a weight-average mol.wt. of 1000 to 10000 is copolymerized with (B) one or more radically polymerizable monomers in an A:B ratio of 40-99.5wt.%:60-0.5wt.% in the presence of a radically polymerization initiator in an amount of 1-10mol% based on the whole mol numbers of the polymerizable monomers to provide the objective resin, comprising a graft copolymer having crosslinkable functional groups and a weight-average mol.wt. of 5000 to 30000. The radically polymerizable group of the component A is preferably a (meth)acryloyl group.

Description

Detailed Description of the Invention (a) Purpose of the Invention [Field of Industrial Application] The present invention relates to a crosslinked curable coating resin suitable for coating automobiles, home appliances, etc., and a method for producing the resin. .

[Conventional technology and its problems]

BACKGROUND ART Conventionally, acrylic paints have been widely used as crosslinked curing paints used for painting automobiles, home appliances, etc. because of their excellent weather resistance and appearance.

The acrylic resin that forms the main component of the above acrylic paint includes alkyl (meth)acrylates such as butyl acrylate, methyl methacrylate, and butyl methacrylate, as well as 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate. Resins obtained by radical copolymerization of functional group-containing monomers are common, and paints obtained by adding a crosslinking agent such as melamine or polyvalent incyanate to an organic solvent solution of the resin cannot be baked after painting. This forms a strong coating film with a three-dimensional mesh structure.

As mentioned above, acrylic cross-linked curable paints are usually treated as organic solvent solutions, but recently there has been a growing desire to reduce the amount of ammonium chloride used due to pollution issues and resource conservation reasons. As a countermeasure to this problem, increasing the solid content concentration of the paint solution, that is, making the paint highly solid, is being considered.

It is easy to make paints high in solids, but in order to maintain good coating while increasing the solid content concentration, it is necessary to
It is necessary to maintain the viscosity of the paint solution below a certain level, and therefore various measures are required to make the paint solution highly solid, and currently studies are mainly aimed at lowering the molecular weight of paint resins.

However, when the molecular weight of acrylic resin is lowered, the proportion of polymer molecules that do not have functional groups in the molecule, that is, polymer molecules that cannot participate in the formation of a three-dimensional network structure during curing, increases, and as a result, the resulting coating film There was a problem in that the durability of the material decreased.

In order to solve the above problems, we increased the proportion of functional group-containing monomers in the monomer mixture that is the raw material for acrylic resin, and in line with this increase, we also increased the amount of crosslinking agents such as melamine or polyvalent isocyanates. A method of increasing the crosslinking density is being considered, but this method creates a new problem in that the overall crosslinking density becomes excessive and the flexibility of the coating film is impaired, and various solutions are being considered. At present, no satisfactory solution has been obtained.

On the other hand, high solids formation is also being investigated from a different direction than the method of lowering the molecular weight of the resin described above.

In other words, focusing on the fact that branched polymers have lower solution viscosity than linear polymers even if they have the same molecular weight, studies have been conducted to use branched polymers as coating resins. For example, the chemical formula (where R is A polyfunctional epoxy compound represented by a hydrocarbon residue such as aliphatic, alicyclic or aromatic, or n is an integer of 3 to 6), and a polyfunctional epoxy compound having a carboxyl group at one end and having a molecular weight of i, o o There is a proposal to use a polymer obtained by bonding an acrylic polymer of 0 to 100,000 by a reaction between an epoxy group and a carboxyl group as a paint resin (Japanese Patent Publication No. 11076/1983).
.

The viscosity of the organic solution of the branched acrylic polymer is:
The solution viscosity is about 30-50% lower than that of conventional linear acrylic polymers with comparable average molecular weights.

[Margin below]

However, the number of branches in one molecule of the branched acrylic polymer is limited by n in the chemical formula, and it is virtually impossible to introduce a large number of branches into the polymer. Therefore, it was difficult to apply to more advanced high solids production.

Conceptually, it is a type of branched polymer, but its basic idea is completely different from the branched polymer described in the above-mentioned publication.It is a branched polymer that radically co-constitutes a macromonomer having a radically polymerizable group with an acrylic acid ester. Graft polymers obtained by polymerization and generally produced by the macromonomer method are known, but no studies have been conducted to date on the application of such graft polymers to high solids crosslinking and curing paints. Ta.

That is, JP-A-1-245067 discloses an invention relating to a two-component acrylic urethane paint made of an acrylic graft polymer and a polyisocyanate compound produced by the macromonomer method, and JP-A-1-245,062
In each of the publications, inventions related to room temperature drying paints made of graft polymers made by the same method are proposed, but in these inventions, characteristics based on the trunk polymer and branch polymers formed by different structural units are proposed. The sole purpose of this study is to improve the physical properties of the resulting coating film.

In fact, the cross-linked curable paint made of the graft polymer described in the above-mentioned publication had an extremely high solution viscosity at a high solids concentration, making it impossible to achieve high solids.

[Problem to be solved by the invention]

The present invention aims to provide a coating resin made of a crosslinked curable graft polymer capable of forming a solution with a high solid content concentration and low viscosity, and a method for producing the same. It is a branched polymer with crosslinkable functional groups in which an extremely large number of branch polymers are bonded to a long chain trunk polymer.

(C) Structure of the Invention [Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors found that the weight average molecular weight is 1. A graft polymer obtained using a radically polymerizable macromonomer of OOO to 10°000, which contains 40% by weight or more of the macromonomer unit based on the total amount of all structural units, and has a weight average molecular weight of 5.000. It was discovered that the organic solvent solution of a graft polymer having a molecular weight of ~30,000 has a low viscosity even at a high solid content concentration, and the present invention was completed.

That is, the present invention has a radically polymerizable group at one end of the molecule and a weight average molecular weight of 1.000 to 10.00.
0 macromonomer copolymerized with other radically polymerizable monomers, the proportion of macromonomer units is 40 to 99.5% by weight based on the total amount of all constituent units. Another aspect of the present invention is a crosslinked curable coating resin comprising a graphite polymer which further contains a crosslinkable functional group and has a weight average molecular weight of 5.000 to 30.000. has a radically polymerizable group at one end, and has a weight average molecular weight of 1
．． 000 to io, o o o, and (b) other radically polymerizable monomers, and the ratio of component (a) to component (b) is 40 to 99.5% by weight to 60 to 60. In a molecule, 0.5% by weight of a polymerizable component is radically copolymerized using a radical polymerization initiator of 1 to 10 mol% based on the total number of moles of the polymerizable component. This is a method for producing a cross-linked and curable coating resin containing a cross-linkable functional group and a weight average molecular weight of s, o o o to 30,000.

The present invention will be explained in more detail below.

[Macromonomer]

As mentioned above, the macromonomer used in the present invention is a macromonomer having a radically polymerizable group at one end of the molecule and having a weight average molecular weight of i, o o o to 10.000, and the radically polymerizable group is , (meta)
Examples include an acryloyl group, a styryl group, an allyl group, a vinylbenzyl group, a vinyl ether group, and a vinyl ketone group, with a (meth)acryloyl group being preferred.

The weight average molecular weight of the macromonomer can be determined by a method normally used to measure the weight average molecular weight of polymers, such as gel permini-silane chromatography (hereinafter referred to as GPC),
Or it is a value measured by low angle light scattering method etc.
If it exceeds 10.000, the resulting graft polymer will have an excessive molecular weight, and the solution viscosity of the graft polymer will become too high, making it unsuitable for use as a crosslinked and curable coating resin in terms of coating properties.

On the other hand, the weight average molecular weight is 1. When it is less than OO, the solution viscosity does not decrease due to the branching effect of the graft polymer, and the more preferable weight average molecular weight is 1,000 to 5.
．． It's OOO.

As the monomer forming the polymer part of the macromonomer, that is, the part that supports the radically polymerizable group, (meth)
Methyl acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, perfluoroalkyl acrylate, (meth)acrylic #2-hydroxyethyl, (meth)acrylic acid 2
Examples include -hydroxypropyl, styrene, α-methylstyrene, (meth)acrylonitrile, and polyethylene glycol mono (meth)acrylate, which can be used alone or in combination of two or more.

The polymer portion of the macromonomer preferably has a crosslinkable functional group described below, such as a hydroxyl group or a carboxyl group.

Macromonomers are described, for example, in Chapter 2, Synthesis of Macromonomers, 39-77, "Chemistry and Industry of Macromonomers," edited by Yuya Yamashita, published by IBC Publishing, September 20, 1989.

Schematics can be synthesized by various methods such as those shown below.

That is, using an anionic polymerization initiator such as butyl lithium, an anionic polymerizable monomer such as styrene is made into a monofunctional ping polymer by solution polymerization, and when the desired molecular weight is reached, end-camping is performed using ethylene oxide or the like. A method of obtaining a macromonomer having a radically polymerizable group such as a methacryloyl group at one end by reacting it with methacrylic acid chloride or the like (Japanese Unexamined Patent Publication No. 125186/1986): Methyl methacrylate is reacted with p-vinylbenzyl A method for obtaining a polymethyl methacrylate macromonomer having a p-vinylbenzyl group at the terminal by anionic polymerization at low temperature using magnesium chloride as an initiator (Polym, J, 18.581.
(1986); and a radically polymerizable monomer such as (meth)acrylic acid ester, styrene or acrylonitrile in an organic solvent in the presence of a mercaptan chain transfer agent having a carboxyl group such as thioglycolic acid or mercaptopropionic acid. , a method of reacting a polymer having a carboxyl group at one end of the molecule obtained by radical polymerization with glycidyl (meth)acrylate to obtain a macromonomer having a methacryloyl group at one end (Japanese Patent Publication No. 6)
2-62801, etc.).

In addition, macromonomers having carboxyl groups in the polymer skeleton can be obtained by synthesizing macromonomers having tertiary alkyl ester groups such as t-butyl (meth)acrylate monomer units, and then synthesizing them in the presence of an acid catalyst. It is synthesized by hydrolysis to decompose t-butyl groups and the like into carboxyl groups and isobutylene, and form carboxyl groups on the macromonomer side.

[Graft polymer]

The graft polymer in the present invention is composed of the above macromonomer unit and other radically polymerizable monomer units described below, and the proportion of the macromonomer unit is 40 to 99.5% by weight based on the total amount of all structural units. contains a crosslinkable functional group in the molecule, and has a weight average molecular weight of s, o
It is a graft polymer with o~30.000.

If the proportion of macromonomer units in the graft polymer is less than 40% by weight, the degree of branching in the molecular structure will be insufficient, and at high solids concentration, the solution viscosity will increase, making it impossible to obtain a high solids coating, which is preferable. The proportion of macromonomer units is 45-99.5% by weight.

On the other hand, graft polymers containing 99.5% by weight of macromonomer units are difficult to synthesize with high purity and contain a large amount of unpolymerized macromonomers as impurities, resulting in poor coating film durability. is inferior.

The weight average molecular weight of the graft polymer in the present invention is
This is a value measured by a low-angle light scattering method. If the weight average molecular weight is less than 5.000, the durability of the resulting coating film will be poor, and if it exceeds 30,000, the viscosity of the paint solution will increase. Poor coating properties.

The crosslinkable functional group must be present in the trunk polymer and/or branch polymer of the graft polymer, and preferred crosslinkable functional groups include hydroxyl group, carboxyl group, amino group, glycidyl group, and 100NH ( C
H,0R) (in the formula, R is a hydrogen atom or an alkyl group), and more preferably a hydroxyl group or a carboxyl group.

The number of the above-mentioned functional groups in the graft polymer may be one type or two or more types.

The preferred amount of crosslinkable functional groups in the graft polymer varies somewhat depending on the type of functional group, but when expressed in terms of the amount of monomer units containing the functional group, the total amount of all monomer units constituting the graft polymer is It is about 0.5 to 30% by weight based on the standard.

Other radically polymerizable monomers to be copolymerized with the macromonomer include (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 18 carbon atoms, vinyl acetate, styrene, α-methylstyrene, and (meth)acrylonitrile. ,
Perfluoroalkyl (meth)acrylate, (meth)acrylic acid, maleic anhydride, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate, (meth)acrylamide , N-methylolacrylamide, N-butoxymethylacrylamide, N.

Examples include N-dimethylaminoethyl (meth)acrylate and (meth)acryloyloxypropyltrimethoxysilane.

As mentioned above, the graft polymer in the present invention needs to have a crosslinkable functional group in the molecule, so when using a macromonomer that does not contain the functional group, the monomer to be copolymerized Among the monomers mentioned above, for example, monomers having a crosslinkable functional group such as (meth)acrylic acid, maleic anhydride, 2-hydroxyethyl (meth)acrylate, and glycidyl (meth)acrylate are used. There is a need.

The graft polymer in the present invention has (
It is preferable that the main unit is a monomer (hereinafter simply referred to as an acrylic monomer) having a (meth)acryloyl group represented by a meth)acrylic acid ester monomer, and specifically, all structural units are Based on the total amount of Particularly preferred acrylic monomers are methyl methacrylate, butyl (meth)acrylate and #2-ethylhexyl (meth)acrylate.

The graft polymer constituting the cross-linked curable coating resin of the present invention can be obtained by radical copolymerizing the macromonomer and other radically polymerizable monomers (hereinafter collectively referred to as polymerizable components) in an organic solvent. It is obtained by

As the organic melting material, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, etc. are preferable, and the concentration of the above polymerizable component in solution polymerization is 10 to 8.
It is preferably 0% by weight, and the polymerization temperature is suitably about 60 to 100°C.

As the polymerization initiator, an azo compound such as 2,2-azobisisobutyronitrile (hereinafter referred to as AIBN) or an organic peroxide such as benzoyl peroxide can be used.
The amount used is 1 to 10 moles, more preferably 5 to 1 mole, per 100 moles of the total number of moles of the polymerizable component.
It is 0 mole.

Furthermore, the molecular weight of the graft polymer can be effectively adjusted by using a chain transfer agent. As the chain transfer agent, dodecyl mercaptan, lauryl mercaptan, thioglycolic acid, etc. can be used, and the preferred amount used is 1 to 40 mol per 100 mol of the total number of moles of the polymerizable component.

The graft polymer, which is the crosslinked curable coating resin of the present invention, is crosslinked and cured, for example, by the method shown below.

That is, the graft polymer having a carboxyl group as a crosslinkable functional group is preferably cured by heating at 120 to 160°C using an amino resin such as hexamethylolated melamine, hexabutoxylated melamine, or a condensate thereof as a crosslinking agent.

Graft polymers having hydroxyl groups include hexamethylene diisocyanate, tolylene diisocyanate,
Polyvalent isocyanates such as isophorone diisocyanate,
and their adducts are used together as a crosslinking agent, and cured at room temperature or under heating.

The graft polymer having a glycidyl group can be cured in the presence of a curing accelerator such as a tertiary amine or a quaternary ammonium salt.
Using polyhydric carboxylic acid as a crosslinking agent, the temperature is 80-20
It can be cured by heating at 0°C, and can also be cured at room temperature or under heating using a polyvalent amine such as triethylenetetramine as a crosslinking agent.

The usage ratio of the crosslinking agent in each of the above-mentioned graft polymers may be determined according to the usage ratio of the crosslinking agent in polymers having similar crosslinkable functional groups.For example, in the case of a graft polymer having hydroxyl groups, the usage amount of polyvalent isocyanate is suitably 0.5 to 1.5 equivalents of hydroxyl group.

Furthermore, a graft polymer having an N-methylolamide group self-crosslinks when heated.

[Examples and comparative examples]

Hereinafter, the present invention will be explained in more detail by showing Examples and Comparative Examples. In addition, the macromonomer used in each example was the macromonomer synthesized in the following reference example.

Reference Example Toluene 106 was placed in a glass flask equipped with a stirrer, reflux condenser, dropping funnel, thermometer and nitrogen gas inlet.
．． 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) as a chain transfer agent at a temperature of 80 to 85°C while blowing nitrogen gas. A mixed solution consisting of 10.6 parts by weight of mercaptoacetic acid and 2 parts by weight of AlBN as a polymerization initiator was continuously added dropwise over 3 hours to carry out polymerization, and then heating was continued for an additional 2 hours to complete the polymerization. A polymer having a carboxyl group at the end was obtained.

A portion of the toluene solution of the above polymer was collected 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, hydroquinone monomethyl ether as a polymerization inhibitor was added to the toluene solution of the double polymer, and using a quaternary ammonium salt as a catalyst, glycidyl methacrylate in an amount equivalent to 1.1 times the measured acid value was added to the terminal carboxyl of the polymer. In order to react with the group, a temperature of 9
It was maintained at 0°C for 6 hours. The reaction rate determined from the decrease in acid value was 98.5%.

Through the above operations, the number average molecular weight in terms of polystyrene by GPC method was 1.340, the weight average molecular weight was 2.600, and MMA/HEMA-80/20 (
% by weight) of a single-end methacryloyl type macromonomer was obtained.

EXAMPLE The above macromonomer, styrene and MMA were used in a weight ratio of 45:25:30, and the polymerization initiator AIBN was added to 8% based on the total number of moles of these polymerizable components.
．． 4 mol% was added, and the polymerizable component was polymerized as a 20% by weight toluene solution at a temperature of 60° C. for 8 hours.

As a result of measuring the amount of unpolymerized macromonomer in the obtained polymer solution by GPC, it was found that 10% by weight of the macromonomer remained based on the charged macromonomer. From this, the composition of the generated graft polymer is macromonomer units, styrene units, and M
MA units are 42%, 26% and 32% by weight, respectively.
It turned out to be 1i1%.

Weight average molecular weight (MY) and solution viscosity (η) of the above graft polymer measured by low-angle light scattering method (viscosity measured by Ubbelohde viscosity needle of a 40% by weight acetone solution of the graft polymer at a temperature of 25° C.).

same as below. ) were as follows.

Mw: 14.000 η: 1 1. 6 (cps) Example 2 A graft polymer was produced in the same manner as in Example 1 except that 70% by weight of the macromonomer, 12% by weight of MMA and 18% by weight of styrene were charged.

As a result of CPC analysis of the polymerization product, it was found that 10% by weight of unpolymerized macromonomer was present based on the charged macromonomer, and the composition of each unit in the graft polymer produced from this was: macromonomer units, M
MA units and styrene units are 68% by weight and 1% by weight, respectively.
3% and 19% by weight.

M of the graft polymer measured in the same manner as in Example 1
w and η were as follows.

Mw: 23,100 η: 13.2 (cps) Example 3 Macromonomer 93% by weight and styrene 7% by weight were used, and AIBN was 8.4 mol% based on the total number of moles of these polymerizable components. Then, 7.5 mol% of lauryl mercaptan was added as a chain transfer agent, and polymerization was carried out at a temperature of 60° C. for 8 hours as a 20% by weight toluene solution.

As a result of analysis by GPC, the amount of unpolymerized macromonomer based on the charged macromonomer was 15% by weight, and from this, the amount of macromonomer units in the produced graft polymer was 92% by weight, and the amount of styrene units was 15% by weight. It was found to be 8% by weight.

MY and η of the graft polymer were as follows.

Mw: 19.000 η: 11.4 (cps) Comparative Examples 1 to 2 30% by weight of MMA and 20% by weight of HEMA were dissolved in a mixed solvent of toluene-isobutanol, the monomer concentration in the solution was set to 20% by weight, and polymerization was carried out. Based on the total number of moles of the sexual components, 8.4 mol% of A I B N and 4 mol% of lauryl mercaptan (Comparative Example 1) or 1 mol% of lauryl mercaptan (Comparative Example 2) were added, and for other conditions. Polymerization was carried out in the same manner as in each case described above.

MY and η of the obtained linear polymer were as follows.

(c) Effects of the Invention According to the present invention, a crosslinked curable coating resin having a low solution viscosity even at high concentrations can be easily obtained, and the resin is suitably used for making high solid coatings.

Patent applicant Toagosei Kagaku Kogyo Co., Ltd. Patent applicant Toyota Motor Corporation Representative Patent attorney Sachi 1) Hiroshi Zen

Claims (1)

[Claims] 1. A macromonomer having a radically polymerizable group at one end of the molecule and having a weight average molecular weight of 1,000 to 10,000 is copolymerized with other radically polymerizable monomers. A graft polymer in which the ratio of macromonomer units is 40 to 99.5 based on the total amount of all structural units.
% by weight, further contains a crosslinkable functional group, and has a weight average molecular weight of 5,000 to 30,000. 2. Consisting of (a) a macromonomer having a radically polymerizable group at one end of the molecule and having a weight average molecular weight of 1,000 to 10,000, and (b) other radically polymerizable monomers, the above-mentioned The ratio of component (a) to component (b) is 40
~99.5% by weight of the polymerizable component to 60 to 0.5% by weight of the polymerizable component, based on the total number of moles of the polymerizable component.
Containing a crosslinkable functional group in the molecule, characterized by radical copolymerization using a mol% radical polymerization initiator,
A method for producing a crosslinked and curable coating resin having a weight average molecular weight of 5,000 to 30,000.