JPH06172451A - Coating resin - Google Patents

Abstract

PURPOSE:To provide a coating resin composed of a specified carboxyl group- containing monomer structural unit, etc., excellent in shelf life, film hardness and weather resistance and suitable for electrodeposition, etc. CONSTITUTION:The objective coating resin is a solvent-soluble fluororesin containing hydroxyl groups and carboxy groups and synthesized by suspension polymerization of raw material monomers, e.g. a fluoroolefin such as tetrafluoroethylene and a carboxylic acid vinyl ester such as vinyl acetate. The carboxyl group-containing monomer structural unit of this resin is composed of a >=6C monomer structural unit and a <6C monomer structural unit. In addition, the ratio of the above >= 6C monomer structural unit to the <6C monomer structural unit is preferably 10/90 to 90/10. The acid value of this resin is preferably 5 to 100mg KOH/g and the hydroxyl number is preferably 10 to 150mg KOH/g.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating resin, and more specifically, by combining a specific carboxyl group-containing monomer, the content of unreacted monomer in the resin can be reduced and the storage stability can be improved. And a fluororesin for electrodeposition coating having improved coating film hardness.

[0002]

2. Description of the Related Art Electrodeposition coating is a coating method that uses electric energy. This coating method has good throwing power, is less prone to film defects, is easy to mechanize, and can be used as a medium in the surrounding environment. In recent years, it has been applied to a wide range of fields because of the fact that it uses water, which has little influence. That is, it has been widely used in undercoat coating for automobiles and interior applications.

Initially an epoxy resin as a resin for electrodeposition coating,
Alkyd resin and acrylic resin have been mainly used, but when they are used outdoors, their service life is relatively short and their performance is not sufficient.

[0004] Further, with the expansion of applications, not only as a base coating material but also used as being exposed to the outdoors, an electrodeposition coating material having higher performance is being demanded.

In recent years, therefore, attempts have been made to utilize solvent-soluble fluororesins for paints as resins for electrodeposition paints. For example, JP-A-62-59676
JP-A-62-127362, JP-A-2-55776, JP-A-2-
Various resins have been proposed in the specification such as 166173.
All the resins for electrodeposition coatings described in these are produced by solution polymerization to once produce a resin having no carboxyl group, and then a method of converting a part of hydroxy groups in the resin into a carboxyl group is taken. There is. Generally, when a polymer is produced by solution polymerization, not all of the charged monomers are incorporated into the polymer, but more or less unreacted monomers always remain. In particular, when a large amount of a monomer having a functional group such as a hydroxy group or a carboxyl group remains, a reaction with a curing agent occurs and the physical properties of a cured coating film are affected. Generally, a monomer having a functional group such as a hydroxy group or a carboxyl group has a high boiling point, and therefore, most of it remains by simple drying. As a result, when it is used as a paint for electrodeposition, it lacks the stability of the bath, which is one of the most important requirements. Therefore, in order to use the resin produced by the solution polymerization method as a coating material for electrodeposition, it was necessary to take a step of distilling off the solvent used at the time of polymerization, drying, and re-dissolving in a water-soluble solvent again. .

[0006]

[Problems to be Solved by the Invention] Japanese Patent Application No. 3-91838 proposed by the present applicant to solve the above-mentioned problems results in suspension by using a specific carboxyl group-containing monomer as an acid site. It is described that the resin can be produced by polymerization, and as a result, the remaining amount of the unreacted monomer can be reduced to significantly improve the storage stability. However, the resin for electrodeposition requires a resin having a relatively high acid value in terms of the required performance, and therefore, the proportion of the carboxyl group-containing monomer incorporated in the resin also increases accordingly. However, in this case, the carboxyl group-containing monomer
Has 6 or more carbon atoms in its molecule,
A large number of molecules having a relatively long side chain are present in the resin, and there is a drawback that the hardness of the cured coating film is hard to increase due to the plasticizing effect of the side chain alkyl group.

[0007]

Means for Solving the Problems The inventors of the present invention have made further intensive studies in view of the above points, and as a result, in producing a polymer by a suspension polymerization method in which particles are obtained as washable particles, It has been found that a fluororesin for electrodeposition coating having excellent bath stability and high coating hardness can be obtained by combining a relatively long-chain carboxyl group-containing monomer and a short-chain carboxyl group-containing monomer. The invention was completed.

That is, the present invention is a fluoroolefin,
When a fluororesin containing a carboxylic acid vinyl ester, a hydroxyl group-containing monomer and a carboxyl group-containing monomer as essential components is produced by a suspension polymerization method, the total number of carbon atoms constituting the molecule as the carboxyl group-containing monomer is 6 or more. It is a resin for electrodeposition paint, which is characterized by using a monomer and a monomer having a number of less than 6 in combination.

Since the resin for electrodeposition coating composition of the present invention is produced by suspension polymerization, unreacted monomers can be easily removed from the produced resin, so that the amount of unreacted monomer remaining in the varnish is reduced. As a result, the stability of the electrolytic bath using this resin is significantly improved. Further, since the carboxyl group-containing monomer having a small number of carbon atoms is also used, the hardness of the electrodeposition coating film is significantly improved.

Fluoroolefins used in the present invention include trifluoroethylene, tetrafluoroethylene,
Chlorotrifluoroethylene, hexafluoropropylene, vinyl fluoride, vinylidene fluoride and the like can be mentioned, but from the viewpoint of polymerization reactivity, chlorotrifluoroethylene,
Tetrafluoroethylene is preferred.

Examples of the vinyl carboxylate include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl isocaproate, vinyl pivalate, vinyl caprylate, vinyl capric acid, vinyl stearate, and veova. Examples thereof include fatty acid vinyl esters such as 9 (manufactured by Showa Shell Sekiyu) and Veova-10 (manufactured by Showa Shell Sekiyu) and aromatic carboxylic acid vinyl esters such as vinyl benzoate and vinyl p-t-butylbenzoate. It is also possible to use two or more of these vinyl esters in combination.

The hydroxyl group-containing monomer has the general formula CH ₂ ═CHCH ₂ —O— (CH ₂ CH ₂ O) mH (m is 1
To an integer of 5), a general formula Normaler, general formula CH ₂ ═CH—O— (CH ₂ ) nOH (n is an integer of 1 to 5), a general formula Monomer, and And monomers obtained by modifying the OH groups of these monomers with ε-caprolactone.

As the carboxyl group-containing monomer having a total number of carbon atoms of 6 or more, 2-hexenoic acid, 3-hexenoic acid, 5-hexenoic acid, 2-heptenoic acid, 3-heptenoic acid, 3-octenoic acid, 2-nonenoic acid, 3-
Nonenoic acid, 9-decenoic acid, 10-undecenoic acid, 2-dodecenoic acid, 2-tridecenoic acid and the like can be mentioned, but in consideration of polymerizability, 5-hexenoic acid and 9-decenoic acid having a double bond at the terminal. Acid, 10-undecenoic acid and the like are preferable.

Examples of the unsaturated carboxylic acid having less than 6 carbon atoms constituting the molecule include acrylic acid, methacrylic acid, crotonic acid, allyloxyacetic acid and vinylacetic acid.

Alkyl vinyl ethers added as necessary include methyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, 2-ethylhexyl vinyl ether, isooctyl vinyl ether. -Ethylene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, etc. are mentioned, but in consideration of economical efficiency, ease of handling, etc., ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, Hydroxyethyl vinyl ether and hydroxybutyl vinyl ether are preferred.

Next, as a typical composition of the solvent-soluble fluororesin in the present invention, fluoroolefin, carboxylic acid vinyl ester, hydroxyl group-containing monomer, and the total number of carbon constituting the molecule is 6 or more and less than 6. The total amount of the carboxyl group-containing monomer and the content of the alkyl vinyl ether are 25 to 75 mol%, 10 to 70 mol%,
3 to 40 mol%, 0.1 to 20 mol% and 0 to 50 mol%, preferably 40 to 60 mol% and 2 respectively.
0-50 mol%, 5-30 mol%, 0.3-10 mol%
And 0 to 40 mol%.

The solvent-soluble fluororesin of the present invention has a polystyrene reduced number average molecular weight of 1,000 to 100,000. If it is less than 1000, the weather resistance of the resulting coating film is not sufficient, and if it exceeds 100,000, the viscosity of the solution when it is dissolved in a solvent becomes high. Therefore, the solid content concentration must be lowered, and in addition, electrodeposition was performed. It is not preferable because unevenness is likely to occur in the coated film when it is post-baked and cured.

The content of the fluoroolefin can be arbitrarily changed depending on the amount of each monomer at the time of charging, but if it is too high, the resin for the fluorine-containing coating material has a low solubility in an organic solvent and the content in the production side is low. There is a problem in the yield of the resin for a fluororesin, and conversely, when the amount is small, the excellent characteristics inherent to the fluororesin such as weather resistance and chemical resistance do not appear, which is not preferable.

Further, a resin for fluorine-containing coating material having an excessively high content of vinyl carboxylate is inferior in weather resistance and chemical resistance and is not preferable in terms of physical properties. If it is too low, the molecular weight is lowered and the yield is lowered. It is not preferable in terms of manufacturing.

Further, if the content of the hydroxyl group-containing monomers is too high, the molecular weight is lowered and the weather resistance of the coating film is lowered, which is not preferable. On the contrary, if the content of these is too low, the curing reaction with the curing agent is less likely to occur, resulting in deterioration of physical properties such as chemical resistance and weather resistance,
In addition, overcoating becomes difficult. In the obtained solvent-soluble fluororesin, the hydroxyl value, which is an index of the degree of curing, is preferably in the range of 10 to 150 mgKOH / g, and further 2
The range of 0 to 100 mg KOH / g is more preferable.

When the total amount of the carboxyl group-containing monomers having the total number of carbon atoms constituting the molecule of 6 or more and less than 6 is too large, the water resistance of the resin is deteriorated, and the weather resistance is deteriorated, which is preferable. Absent. . On the contrary, when the amount is small, the dispersibility of the pigment is deteriorated, and it is difficult to make the aqueous solution. Therefore, in order to apply the solvent-soluble fluororesin to electrodeposition, the acid value is usually 5 to 5
The range of 100 mgKOH / g is preferable, and further 10-70 mgK
More preferred is the OH / g range. Further, the mixing ratio of the carboxyl group-containing monomers whose total number of carbon atoms constituting the molecule is 6 or more and less than 6 is 6 when the total amount of the carboxyl group-containing monomers is 100.
If the proportion of the above-mentioned monomers is too large, the hardness of the coating film is lowered, and if it is too small, it hinders the synthesis of the resin by suspension polymerization, so that the range of 10/90 to 90/10 is preferable. The range of 20/80 to 80/20 is more preferable.

In order to use the resin for fluorine-containing coating material of the present invention for electrodeposition, it is necessary to dissolve it in a water-soluble solvent. Examples of such a solvent include methanol and ethanol.
, I-propanol, t-butanol, n-butanol-
Examples thereof include alcohols such as alcohols, and glycol ethers such as dimethyl carbitol, methyl cellosolve, ethyl cellosolve, and butyl cellosolve.

Further, the electrodeposition liquid using the resin for fluorine-containing coating material of the present invention neutralizes at least a part of the carboxyl groups in the resin dissolved in the above water-soluble solvent with a basic compound, and then a suitable amount of It can be adjusted by adding a curing agent and, if necessary, a pigment, an ultraviolet absorber, a light stabilizer, an antioxidant, a leveling agent, a matting agent and the like, and then gradually adding water with stirring. Usually, the concentration of the electrodeposition liquid is adjusted to 3 to 25% by weight, preferably 5 to 20% by weight before use.

The basic compound used for the neutralization of the carboxyl group is ammonia, monoethylamine, diethylamine, triethylamine, trimethylamine or the like.
-, Secondary-, and tertiary-alkylamines, alkanolamines such as diethanolamine, triethanolamine, and diisopropanolamine; alkylenepolyamines such as ethylenediamine and propylenediamine; pyridine;
Examples thereof include nitrogen-containing cyclic compounds such as piperidine.

Any curing agent may be used as long as it has a function of reacting with the fluorine-containing resin and crosslinking. For example, hexamethylene diisocyanate trimer block isocyanate, methyl etherification, Examples include alkoxymethylated melamine resins such as methylbutyl mixed etherified and methylisobutyl mixed etherified resins, benzoguanamine resins, and urea resins. The amount of curing agent is 10
It is preferable to use 5 to 100 parts by weight with respect to 0 parts by weight.

Examples of the ultraviolet absorber include benzophenone type, benzotriazole type and acrylic type. The amount of the ultraviolet absorber added is preferably 0.2 to 15 parts with respect to 100 parts by weight of the fluororesin.

As the light stabilizer, a hindered amine light stabilizer is preferably used. Fluorine-containing resin 1
It is preferably used in a ratio of 0.1 to 5 parts with respect to 00 parts by weight.

The electrodeposition coating using the resin for fluorine-containing coating of the present invention is carried out in the above-mentioned electrodeposition coating liquid by a simple metal such as iron, copper, aluminum, titanium or alloys thereof, and further by metal plating on the surface. , Plastics, etc. as the anode, and a suitable cathode as the counter electrode, voltage 50-280V, 1
It is achieved by applying for 0 to 250 seconds.

After completion of the electrodeposition coating, the coated article is washed with water and further heated at a temperature of 140 to 250 ° C. for 5 to 30 minutes to complete the curing reaction, whereby a desired electrodeposition coated article is obtained. Next, examples will be shown to more specifically describe the present invention, but the present invention is not limited thereto.

[0030]

【Example】

[Synthesis of Fluorine-Containing Resin] Synthesis Example 1 Vinyl pivalate (VPv) 46.1 g, veova was added to a stainless steel autoclave with an internal capacity of 1.0 L equipped with a magnetic stirrer.
9 (V-9) 33.2 g, ethylene glycol monoallyl ether (EGMAE) 25.7 g, methacrylic acid (MA
A) 2.7 g, undecylenic acid (UdA) 14.9 g, sodium carbonate 0.46 g, and Parloyl L (manufactured by NOF Corporation) as an initiator
2.30 g, methylcellulose as a suspending agent 0.46 g, water 180
g was charged, and the inside of the autoclave was replaced and deaerated with nitrogen gas three times.

Thereafter, the autoclave was cooled with ice water,
After introducing 4.8 g of chlorotrifluoroethylene (CTFE), the temperature was gradually raised. After polymerizing at 60 ° C. for 24 hours, unreacted CTFE was removed and the autoclave was opened. Fine particles of polymer were formed in the autoclave, and almost no scale was observed. Then, the fine particles thus obtained were repeatedly washed with water three times to obtain 40
It was dried under reduced pressure at 24 ° C. for 24 hours. Yield 163g (yield 72
%)Met.

The obtained resin was dissolved in butyl acetate so as to have a concentration of 50%, filtered, and then subjected to measurement of physical properties of varnish and measurement of residual amount of unreacted monomer. The residual amount of the unreacted monomer was measured by using a gas chromatograph mainly on the hydroxyl group-containing monomer and the carboxyl group-containing monomer, which would pose a problem if they remained.

The molecular weight (Mn) of the resulting resin is
21,500 (polystyrene equivalent number average molecular weight), OH number 55m
gKOH / g (acetylation method with acetic anhydride), acid value 35mgKOH
It was / g (JIS K 5400). The remaining EGMA
The amount of E is 0.020 wt% when converted per gram of polymer, and the residual amounts of MAA and UdA are 0.003 and 0.0, respectively.
It was 10 wt%.

[0034]

[Table 1]

Synthetic Examples 2-3 By the same method as in Synthetic Example 1, the copolymerization composition shown in Table 1 (however, the amount of parloyl L charged was 0.5 wt% / monomer).
Polymerization was carried out and the yield, molecular weight, OH value, acid value and unreacted monomer content were measured. The results are shown in Table 1.

Synthesis Comparative Example 1 Polymerization was carried out with the copolymerization composition shown in Table 1 in the same manner as in Synthesis Example 1, but as a carboxyl group-containing monomer, the total number of carbon atoms constituting the molecule was 6 or more. Only undecylenic acid was used.

Synthetic Comparative Example 2 VPv 46.1 g, V-9 33.2 g, EGMAE 1 in a stainless steel autoclave with an internal capacity of 1.0 L equipped with an electromagnetic stirrer.
8.4 g, MAA 5.4 g, UdA 19.9 g, butyl acetate 138 g as solvent, sodium carbonate 0.69 g as acid acceptor,
1.64 g of perbutyl PV (manufactured by NOF CORPORATION) was charged as an initiator, the system was replaced with nitrogen gas three times, and then degassed.

Then, 106.9 g of CTFE was introduced, and the temperature was 55 ° C.
Polymerization was carried out for / 24 hours. Unreacted CTFE after polymerization
Was removed and the autoclave was opened. Then, the polymerization liquid was once concentrated to 70%, and the unreacted monomer dissolved was removed.
The concentration was adjusted so that the concentration became%, and finally the mixture was filtered using a filter. The clear varnish obtained was synthesized as in Example 1.
Physical properties and unreacted monomers were measured in the same manner as in.

As a result, it was found that a large amount of unreacted monomer remained as compared with the suspension polymerization, even though the unreacted monomer was removed after the polymerization. Examples 1 to 3 and Comparative Examples 1 and 2 [Preparation of electrodeposition liquid] The fluororesins produced in the synthetic examples and synthetic comparative examples were dissolved in isopropanol (IPA),
A 50% paint solution was prepared. However, in Synthetic Comparative Example 2, the polymerization liquid was once concentrated to 70%, dried in a drier until the solvent was scattered, and the obtained polymer was pulverized to obtain a fine powder resin, which was then dissolved in IPA. Then, a 50% coating liquid was prepared. Then, add this coating liquid 10 to a reaction vessel equipped with a stirrer.
Add 0 parts and mix with methylbutyl etherified methylol melamine (Nikalac MX-40, Sanwa Chemical) 21
Part of the mixture was mixed, and triethylamine was added to this mixture while stirring so that the degree of neutralization was 60% to prepare a stock solution of the electrodeposition coating composition.

Deionized water was added to this undiluted solution for electrodeposition coating so that the total solid content concentration became 8% to prepare an electrodeposition coating. [Electrodeposition coating] Put the electrodeposition paint prepared above into the electrodeposition tank,
Anodized aluminum plate (thickness 0.8 mm)
Was used as the anode, and a bath temperature of 20 ° C. and a voltage of 180 V were applied for 3 minutes to apply electricity to the aluminum plate.

[0041]

[Table 2]

The obtained aluminum plate was thoroughly washed with water,
A curing reaction was carried out at 180 ° C. for 20 minutes, and the physical properties of the coating film were measured as follows. The results are shown in Table 2. -Film thickness: Measured using a film thickness measuring device manufactured by Kett Science Laboratories-Gloss: 60 degree specular gloss measurement based on JIS K 5400-Adhesion: JIS K 5400-based cross-cut test followed by serote -Peeling off-Smoothness: Visual observation of the surface condition of the cured coating film ○: Good Δ: Partially unevenness is observed ×; Poorness-Hardness: Pencil hardness (damage hardness) based on JIS K 5400-Weather resistance Property: Sunshine weather meter Gloss retention rate after 4000 hours (%) Further, changes in physical properties of the bath when the above electrodeposition paint was stored for a long time were traced. The results are shown in Table 3.

[0043]

[Table 3]

[0044]

When the resin composition for electrodeposition coating of the present invention is used for electrodeposition coating, as shown in the results of Table 3, there is no change in the state of the bath even after a long time has passed since the adjustment. on the other hand,
As shown in Table 2, the obtained coating film has an effect of maintaining a high hardness without deteriorating the excellent weather resistance originally possessed by the fluororesin.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] December 14, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

Alkyl vinyl ethers added as necessary include methyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, 2-ethylhexyl vinyl ether, isooctyl vinyl ether. Examples thereof include ethyl ether, hydroxyethyl vinyl ether, cyclohexyl vinyl ether and hydroxybutyl vinyl ether. Considering economical efficiency and easiness of handling, ethyl vinyl ether, n
-Butyl vinyl ether, isobutyl vinyl ether,
Hydroxyethyl vinyl ether and hydroxybutyl vinyl ether are preferred.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C08F 220/04 MLU 7242-4J 220/26 MMN 7242-4J C09D 127/12 PFG 9166-4J 129 / 10 PFP 6904-4J 131/02 PFR 6904-4J 133/02 PFW 7921-4J 133/14 PFY 7921-4J

Claims (8)

[Claims] 1. A solvent-soluble fluororesin having a hydroxyl group and a carboxyl group, which is produced by a suspension polymerization method,
A coating resin, wherein the carboxyl group-containing monomer structural unit comprises a monomer structural unit whose total number of carbon atoms is 6 or more and a monomer structural unit whose carbon number is less than 6. 2. The ratio of the monomer structural unit having a total number of carbon atoms of the carboxyl group-containing monomer structural unit of 6 or more and the proportion of the monomer structural unit of less than 6 is from 10/90 to 90/10.
The paint resin according to claim 1. 3. The coating resin according to claim 1, wherein the fluoroolefin structural unit is a chlorotrifluoroethylene structural unit or tetrafluoroethylene. 4. The coating resin according to claim 1, wherein the solvent-soluble fluororesin containing a hydroxyl group and a carboxyl group contains at least fluoroolefin and vinyl carboxylate as raw material monomers. 5. The coating resin according to claim 1, wherein the solvent-soluble fluororesin containing a hydroxyl group and a carboxyl group contains at least a vinyl ester structural unit. 6. A solvent-soluble fluororesin containing a hydroxyl group and a carboxyl group has at least the general formula CH ₂ ═CHCH ₂ —O— (CH ₂ CH ₂ O) mH (m is an integer from 1 to 5), (N is an integer of from 1 to 5), the general formula _{CH 2 = CH-O- (CH} 2) nOH (n is an integer of from 1 to 5) Formula (N is an integer of 1 to 5) The coating composition according to claim 1, which has a structural unit having a basic skeleton of one or more kinds of monomers selected from monomers represented by the following formula and monomers obtained by modifying the OH groups of these monomers with ε-caprolactone. Resin. 7. The solvent-soluble fluororesin has an acid value of 5 to 10.
The coating resin according to claim 1, wherein the resin has a hydroxyl value of 0 mgKOH / g and a hydroxyl value of 10 to 150 mgKOH / g. 8. A paint resin according to claim 1,
A resin composition for an electrodeposition coating material, which comprises a curing agent and a solvent.