JPH0273873A - Production of copolymer for electrodeposition - Google Patents

Abstract

PURPOSE:To obtain the subject copolymer, having a specific acid value and suitable for coating large-sized materials to be coated by copolymerizing a mixture of a carboxyl group-containing vinyl ether and amine salt thereof with fluoroolefin and other vinyl monomers. CONSTITUTION:The objective copolymer, obtained by copolymerizing (A) a mixture of a carboxyl group-containing vinyl ether and an amine salt thereof, preferably a monomer mixture of a monomer expressed by the formula (R1 and R2 are 2-10C bifunctional aliphatic or alicyclic group) and a tertiary amine salt thereof with (B) a fluoroolefin and (C) other vinyl monomers, consisting of a fluorine-containing copolymer having 30-150 acid value and suitable for coating large-sized materials of a large coating area to be coated.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a method for producing a fluorine-containing copolymer for electrodeposition coating, and a method for producing a fluorine-containing copolymer for electrodeposition coating, which is particularly suitable for coating objects with a large area to be coated. This invention relates to a method for producing a copolymer.

[Prior Art and Problems] A method for obtaining such a fluorine-containing copolymer for electrodeposition is disclosed in JP-A-58-138805, for example, by first copolymerizing a vinyl ether having a hydroxyl group and a fluoroolefin, and then copolymerizing a fluoroolefin. A method is described in which the resulting copolymer is treated with a tribasic acid anhydride to half-esterify the resulting copolymer, thereby converting hydroxyl groups into ester groups and imparting carboxyl groups (post-addition method). However, when the polymer obtained by this manufacturing method is electrodeposited on a small object, such as an alumite plate, it forms a somewhat good coating film, but when it is electrodeposited on a large alumite material such as an aluminum sash for building materials, it cannot be electrolyzed. If it does, paint film defects such as gas pins will occur. Furthermore, according to the research conducted by the present inventors, the higher the acid value of the polymer, the more likely this defect is to occur. As a result of further study on this point, the present inventors found that a fluorine-containing polymer for electrodeposition obtained by copolymerization using a mixed monomer of a carboxyl group-containing vinyl ether and its amine salt has a high acid value of 30 or more. figure,
Surprisingly, it was discovered that such problems do not occur, and the present invention was completed.

[Means for Solving the Problems] That is, the present invention provides an acid value of 30 by copolymerizing a mixture of a carboxyl group-containing vinyl ether and its amine salt, a fluoroolefin, and other vinyl monomers.
The present invention relates to a method for producing a copolymer for electrodeposition coating, which is characterized in that it produces a fluorine-containing copolymer having a molecular weight of 150 to 150 and suitable for coating objects having a large area to be coated.

[Function and Examples] The difference between the polymer obtained by the post-addition method and the polymer obtained by the present invention is that it is used in applications such as electrodeposition coating where minute differences in the composition of the polymer greatly affect the results. In,
This results in a clear difference in terms of effects such as paint film defects.

It is presumed that these differences are probably based on the following structural differences in the polymers. In other words, in the post-addition method, the acid anhydride is post-added to multiple hydroxyl groups in the polymer molecule, so within the practical production range, the addition has a statistical distribution spread (variation), and the acid anhydride does not react with the hydroxyl groups in the polymer,
It is presumed that it reacts with water in the system and remains as a free low molecular acid component. - The copolymerization method invented by Rikiki allows carboxyl groups to be introduced relatively uniformly into polymer molecules because the composition of the polymer is determined by the monomer reactivity ratio, and free low-molecular acid This is thought to be because there is no generation of . This difference in polymer composition and its effects cannot be predicted from post-addition methods.

The mixture of carboxyl group-containing vinyl ether and its amine salt used in the present invention has the formula: A monomer mixture of a monomer shown in
A ratio of 80/40 is preferred.

Tertiary amines have a PKa (acid dissociation index in water at 25°C) of 6 to 12, such as triethylamine,
trimethylamine, tri-n-propylamine, tri-n-
Butylamine, N,N-dimethylisopropylamine,
Examples include N,N-dimethylbenzylamine, triethanolamine, dimethylethanolamine, and methylgetanolamine, among which triethylamine, dimethylethanolamine, triethanolamine, and methylgetanolamine are preferably used. If the amount of the amine salt is small, the stability of the monomer will be impaired, and if the amount is too large, molecular weight reduction will likely occur due to chain transfer. The method and examples for producing the monomer are described in Japanese Patent Application No. 63-54437.

Examples of the fluoroolefins include tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, vinylidene fluoride, 2-trifluoromethyl-3,3,3-trifluoropropene, and vinyl fluoride. Among them, tetrafluoroethylene and chlorotrifluoroethylene are preferably used.

Other vinyl monomers include hydroxyl group-containing monomers, such as hydroxyalkyl vinyl ether or allyl alcohol. Among these, hydroxyalkyl vinyl ether is preferred in terms of polymerizability. Specific examples of hydroxyalkyl vinyl ethyl include 4-hydroxybutyl vinyl ether, 2-hydroquine ethyl vinyl ether, 3-hydroxy-〇-propyl vinyl ether, 2-hydroxy-1so-propyl vinyl ether, 2-hydroxy-
2-methylethyl vinyl ether, 2-hydroxy-1,
Examples include 1-dimethylethyl vinyl ether, 4-hydroxycyclohexyl vinyl ether, 3-hydroxycyclohexyl vinyl ether, and 2-hydroxycyclohexyl vinyl ether.

Other vinyl monomers include methyl vinyl ether, ethyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, n-hexyl vinyl ether, n-octadecyl vinyl ether, cyclohexyl vinyl ether,
2,2.24 Lifluoroethyl vinyl ether, 2,2
, 3. Vinyl ethers such as 3-tetrafluoropropyl vinyl ether; vinyl acetate, vinyl propionate,
Vinyl esters such as vinyl pivalate, vinyl butyrate, vinyl caproate, vinyl laurate, vinyl versatate, vinyl cyclohexanecarboxylate, vinyl stearate, etc.; α-olefins such as ethylene, propylene, 1-butene, isobutylene, styrene, etc. Examples include vinyl halides, acrylic esters, methacrylic esters, and among these, alkyl vinyl ethers and higher vinyl esters having 6 or more carbon atoms are preferably used in terms of polymerizability and stability.

The electrodeposition coating polymer produced according to the present invention has an acid value of 30 to 15o depending on the combination of the monomers mentioned above.

Preferably it is in the range of 40-120. Furthermore, those having a hydroxyl value of 30 to 150 are preferable, and the amount of fluoroolefins contained in this case is in the range of 20 to 80 mol%, preferably 40 to 60 mol%. When the acid value is low, the specific conductivity is low and the throwing power tends to be poor, and when the acid value is too high, the boiling water resistance and chemical resistance of the coating film are decreased. On the other hand, if the hydroxyl value is too small, curing tends to be insufficient, and if it is too large, the boiling water resistance and chemical resistance of the coating film decrease.

When used in electrodeposition paints, 30 to 120 mol%, preferably 40 to 100 mol% of the carboxyl groups in the polymer are used in the form of ammonia or primary to tertiary amine salts, but among these, coloring and other concerns are used. A tertiary amine is preferably used.

The molecular weight of the polymer obtained by copolymerization is 2.000.
~200,000, preferably 10,000~too,
It's ooo. If the molecular weight is too small, the resulting coating film will have reduced boiling water resistance and chemical resistance, and if it is too large, the smoothness of the coating film will be reduced. As for the electrodeposition paint, it is preferable to remove fluorine ions generated during the polymerization process and reduce the concentration to 15 ppm or less, preferably 10 ppHll or less in an electrodeposition bath.

Copolymerization is basically carried out using methods such as emulsion polymerization, suspension polymerization, and solution polymerization using a system containing the monomer composition, a solvent, and a polymerization initiator, among which solution polymerization is superior in terms of uniformity. .

The polymerization temperature can be changed as appropriate depending on the type of initiator and solvent, but is usually -20 to 150°C, preferably 5 to 150°C.
The temperature is 95°C. The reaction pressure can also be selected as appropriate, but is usually 0.
~50 kg/cJG. The method of charging the monomers is changed as appropriate depending on the reactivity of the monomers used, and the method is adjusted so that the resulting polymer has a uniform composition. More specifically, due to the difference in reaction rate, it is desirable to charge monomers other than fluoroolefins so that the concentration ratio in the reaction system remains constant from the initial stage to the end of the reaction.

As the solvent, a water-soluble solvent is preferably used, specifically an ether type, a ketone type, or an alcohol type, and these solvents may be used alone or in mixtures. The amount of solvent is 20 to 300% by weight, preferably 30 to 15% by weight based on the total monomer amount.
It is 0% by weight. If the amount of solvent is too small, the molecular weight tends to increase too much, and if the amount of solvent is too large, the molecular weight tends to decrease. Examples of initiators include persulfates (ammonium persulfate, potassium persulfate, etc.), redox initiators for persulfates and reducing agents, and organic peroxides (diisopropyl peroxydicarbonate, t-butyl peroxybutyrate, etc.). , isobutyryl peroxide, etc.), and azo compounds (azobisisobutyronitrile, azobisvaleronitrile, etc.).

The amount of initiator used is 0.001 to 0.001 to total monomers.
5% by weight, preferably 0.05-2.0% by weight.

The polymer or polymer solution obtained as an electrodeposition coating is made into a salt form in the above range, mixed with a curing agent, and mixed with deionized water in a solid content of 3 to 30% by weight, preferably 5 to 20% by weight.
is adjusted to The curing agent has the function of crosslinking by reacting with a functional group corresponding to a hydroxyl value or an acid value, such as blocked isocyanate in which an isocyanate such as hexamethylene diisocyanate trimer is blocked with phenol, melamine, methylolmethyl, etc. There are melamine-based curing agents such as melamine and butyrolmethylmelamine, and amino resins such as other benzoguanamine resins and urea resins, but alkoxymethylated melamine-based curing agents having 4 or less carbon atoms are preferably used. The amount of curing agent used is 0.2 to 4 times the total amount of hydroxyl value and acid value, preferably 0.5
~2.5 times. If the amount of curing agent used is too small, the hardness of the coating film will be reduced, and if it is too large, the weather resistance of the coating film will be reduced.

In addition to the above components, auxiliary solvents such as cellosolve solvents,
Alcohol-based solvents, ketone-based solvents, calpitol-based solvents, glyme-based solvents, pigments, fillers, and other additives can be used.

In electrodeposition coating, the coating composition temperature is usually 10 to 40℃.
°C, preferably 15-35 °C, voltage usually 50-500
■, preferably 100 to 300 ■, distance between electrodes usually 1 to
100 cm, preferably 5-50 cm s time is usually 0.5-10 minutes, preferably 1-5 minutes. After electrodeposition coating, the object to be coated is usually washed with water and then cured by heating at 150 to 200°C for 5 to 60 minutes. If the base material can withstand high temperatures, it may be heated to around 300°C. The coating film thickness is usually 2 to 50 m+, preferably 5 to 20 m+. The thicker the coating, the higher the cost and the less smooth it tends to be, making coating defects such as gas bubbles more likely to occur. Also, as the thickness becomes thinner, pinholes and blisters are more likely to occur.

The electrodeposition paint using the copolymer for electrodeposition coating obtained by the present invention is particularly suitable for aluminum substrates, although there are no limitations as long as the substrate is conductive, and has excellent weather resistance, corrosion resistance, stain resistance, etc. A uniform and smooth coating film can be formed.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited to these Examples.

Example 1 5258 g of acetone and 742 g of ethanol were charged into a 30 g glass-lined toclave equipped with a stirrer, and 4808 g was deoxidized with nitrogen gas.
of chlorotrifluoroethylene (hereinafter referred to as CTFE) was heated to 65°C, and 1871 g of hydroxybutyl vinyl ether (hereinafter referred to as HBVE) and a vinyl ester of a carboxylic acid having an alkyl group having 10 carbon atoms (manufactured by Shell Chemical Co., Ltd.) were added. Beoba 10 (hereinafter referred to as Va) 2
303 g and 10 mol % of triethylamine salt, 2731 g of a carboxyl group-containing alkyl vinyl ether (hereinafter referred to as CHHEM) represented by the formula: and 81 g of azobisisobutyronitrile (hereinafter referred to as AIBN)
．． After mixing 5 g and deoxidizing with nitrogen gas, continuous charging was carried out over 4 hours.

The temperature inside the system was maintained at 65℃, and after the preparation was completed, the temperature was increased to 65℃.
The reaction was continued for 6 hours to obtain a carboxyl group-containing fluorine-containing copolymer solution. The yield was 17 kg and the copolymer concentration was 64.
It was 5% by weight.

Acid value of polymer: 49 (KOHo+g/g) Hydroxyl value of polymer: 81 (KOHmg/g) Molecular weight (Mn) of polymer (GPC analysis): 72,000 Examples 2 to 3 Preparation shown in Table 1 A carboxyl group-containing fluorine-containing copolymer was obtained in the same manner as in Example 1 except for the composition.

Comparative Example 1 (Post-addition method) The solvent was Monogram eooo g, CTPE4808
g.

) 18,123,000 g, Va: 2,303 g, triethylamine: 100 g, and IBN: 61.5 g, but polymerization was carried out in the same manner and operation as in Example 1. After completion of polymerization, 1,2-cyclohexanedicarboxylic anhydride was added to
500g was charged, and the reaction system was heated to 80°C and reacted for 10 hours. The properties of the obtained fluorine-containing copolymer are shown in Table 1.

The abbreviations in Table 1 indicate the following.

EVE: Ethyl vinyl ether amber HEM: [Left below] Electrodeposition coating examples 1 to 3 and comparative coating example 1 The carboxyl group-containing fluorine-containing copolymer obtained in Examples 1 to 3 and comparative example 1 was mixed with isopropyl alcohol (IPA).
The copolymer was diluted to a polymer concentration of 25% by weight, MgO was added in an amount of 40% of the copolymer, stirred at 60°C for 24 hours, and filtered through a glass filter to remove fluorine ions and chloride ions. . The 25% by weight varnish from which halogen had been removed was concentrated under reduced pressure to obtain a 65% concentration varnish.

The obtained varnish was neutralized with dimethylethanolamine so that the total neutralization amount was 0.85 equivalent, and an electrodeposition paint was prepared according to the following recipe.

Part by weight varnish Butyl cellosolve 80% methyl methylrolled melamine resin (Hitachi Chemical Melan 620゜Solid content 70% by weight) Ion-exchanged water (test conditions) Electrodeposition bath: 50g Bath temperature: 22℃ Distance between electrodes: 15cm Pole Ratio (+/-): 2/1 Current application: 180vX 3 minutes Test plate: Alumite-treated 6063S aluminum alloy plate (alumite film thickness 9 pti) 300 m+s x 1000 mm Electrodeposition coating was performed under the above test conditions. Afterwards, wash it with water and dry it at 18
It was baked and cured at 0°C for 30 minutes to obtain an electrodeposited coating.

The appearance of the resulting coating film as shown in Table 2 was examined.

[Blank below] Gas bottle Bubble marks generated during electrodeposition repelling Repelling marks and water drop marks during washing Water splashes after washing [Effects of the invention] As described above, the present invention can be applied especially to exterior products such as large-area aluminum sashes. The obtained copolymer provides a coated product with excellent appearance and no coating defects, and can provide a product with high commercial value and excellent weather resistance.

Special permission Out wish Man Kansai Paint Co., Ltd. 1 other person

Claims (1)

[Scope of Claims] 1. By copolymerizing a mixture of a carboxyl group-containing vinyl ether and its amine salt, a fluoroolefin, and other vinyl monomers, the product has an acid value in the range of 30 to 150 and has a large coating area. A method for producing a copolymer for electrodeposition coating, characterized by producing a fluorine-containing copolymer suitable for coating objects to be coated. 2 A mixture of a carboxyl group-containing vinyl ether and its amine salt has the formula: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R_1 and R_2 are the same or different, and are divalent aliphatic groups having 2 to 10 carbon atoms. or an alicyclic group) and its tertiary amine salt in a molar ratio of 99/1 to 50/50. 3. The production method according to claim 1, wherein the other vinyl monomer is a hydroxyl group-containing monomer, a higher vinyl ester, and/or an alkyl vinyl ether.