JP2010241944A - Primer composition for plastic coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a one-part primer composition for plastic coating that is excellent in adhesion to plastic materials (particularly nylon), moist heat resistance and storage stability. <P>SOLUTION: The primer composition for plastic coating includes a carboxyl group-containing polyurethane resin produced by reacting (A) a high-molecular-weight polyol having an Mn of 500-5,000 which contains (A1) a castor oil polyol containing an alkyl group in the side chain, (B) a low-molecular-weight polyol having a molecular weight of less than 500 which contains (B1) a carboxyl group-containing diol, and (C) an organic polyisocyanate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a one-pack type primer composition for plastic coating, which is excellent in adhesion to plastic (particularly nylon), moisture and heat resistance, and storage stability.

  In recent years, nylon and polycarbonate are widely used as plastic molded articles from the viewpoint of impact resistance, heat resistance, weather resistance, and the like. When coating such a molded product, it is necessary to apply the paint after first applying a primer to the surface of the molded product because sufficient adhesion cannot be exhibited only by the paint.

  As a primer used for nylon or polycarbonate, Patent Document 1 proposes a “primer composition comprising a urethane-urea resin solution”. Patent Document 2 includes “a urethane prepolymer and / or thermoplastic polyurethane, an epoxy resin, a ketimine compound having a ketimine (C═N) bond derived from a ketone or an aldehyde and an amine, and a solvent. Has been proposed.

  However, the primer of Patent Document 1 has insufficient moisture and heat resistance, and the primer of Patent Document 2 uses an epoxy resin, which may result in insufficient flexibility of the film.

  By the way, castor oil-based polyol has performances such as excellent stability, color retention, flexibility, pigment dispersibility, wettability, lubricity, low temperature characteristics, electrical characteristics, and the like, as shown in Patent Document 3. It has been proposed to be used as a two-component curable polyurethane-based heavy anticorrosion primer. However, since Patent Document 3 is a two-component curable type, the main agent and the curing agent must be blended during coating, and it is necessary to pay attention to blending errors. Moreover, it is necessary to use up after a mixing | blending from a viewpoint of pot life (pot life).

Japanese Patent Laid-Open No. 62-129361 JP 2006-249223 A JP 2001-347603 A

  The present invention has been made in view of the above circumstances. That is, an object of the present invention is to provide a one-component type primer composition for plastic coating that is excellent in adhesion to plastic (particularly nylon), heat and humidity resistance, and storage stability.

The present invention is shown in the following (1) to (3).
(1) A carboxyl group-containing polyurethane resin obtained by reacting a polymer polyol (A) having a number average molecular weight of 500 to 5,000, a low molecular polyol (B) having a molecular weight of less than 500, and an organic polyisocyanate (C). In the primer composition for plastic coating comprising
The polymer polyol (A) having a number average molecular weight of 500 to 5,000 contains a side chain alkyl group-containing castor oil-based polyol (A1),
The low molecular weight polyol (B) having a molecular weight of less than 500 contains a carboxyl group-containing diol (B1).
The primer composition for plastic coating characterized by the above-mentioned.

(2) The molar ratio of the side chain alkyl group-containing castor oil-based polyol (A1) and the carboxyl group-containing diol (B1) is (A1) / (B1) = 0.1-10, (1) Primer composition for plastic coating.

(3) The primer composition for plastic coating according to (1) or (2) above, wherein the carboxyl group content in the polyurethane resin is 0.1 to 1 mmol / g.

  Since the primer composition of the present invention is excellent in adhesion to plastic (particularly nylon) and the moisture and heat resistance of the primer itself, it is excellent in the adhesion and moisture and heat resistance of the entire coating film. Moreover, since it is a one-component type, it is excellent in workability during primer coating. Further, the storage stability of the primer is also excellent.

  The polyurethane resin which is a resin component of the primer composition of the present invention includes a high molecular polyol (A) having a number average molecular weight of 500 to 5,000, a low molecular polyol (B) having a molecular weight of less than 500, and an organic polyisocyanate (C). It is obtained by reacting.

  The polymer polyol (A) is a compound having a number average molecular weight of 500 to 5,000, preferably 1,000 to 3,000, containing a hydroxyl group as a reactive group of an isocyanate group, and comprising a side chain alkyl group-containing castor. The oil-based polyol (A1) is contained. Castor oil-based polyols that do not have side chain alkyl groups are (i) poorly compatible with polyols described below, and the resin solution becomes cloudy over time. It is easy for problems to occur.

  The polymer polyol (A) has a number average molecular weight of 500 to 5,000, preferably 1,000 to 3,000, and is a compound containing a hydroxyl group as a reactive group of an isocyanate group, other than the above (A1). These polyols, for example, polyester polyols, polyether polyols, polycarbonate polyols, polyolefin polyols, etc. are preferably used in combination, and polyester polyols are particularly preferred in view of adhesion to the substrate. These can be used as one kind or a mixture of two or more kinds.

  Polyester polyols include phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, succinic acid, tartaric acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, kurtaconic acid, azelaic acid, sebacic acid, Succinic acid, adipic acid, sebacic acid, azelaic acid, 1,4-cyclohexyldicarboxylic acid, α-hydromuconic acid, β-hydromuconic acid, α-butyl-α-ethylglutaric acid, α, β-diethylsuccinic acid, One or more kinds of dicarboxylic acid / anhydride / dialkyl ester such as maleic acid and fumaric acid, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6- Xanthdiol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, diethylene glycol, dipropylene Glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, dimer acid diol, bisphenol A ethylene oxide and propylene oxide adducts, bis (β-hydroxyethyl) benzene, xylylene glycol, glycerin, tri Examples thereof include those obtained from a polycondensation reaction with one or more low molecular polyols having a molecular weight of 500 or less, such as methylolpropane and pentaerythritol. Furthermore, there are lactone polyester polyols obtained by ring-opening polymerization of cyclic ester (so-called lactone) monomers such as ε-caprolactone, alkyl-substituted ε-caprolactone, δ-valerolactone, and alkyl-substituted δ-valerolactone. Further, a low molecular polyol such as hexamethylene diamine, isophorone diamine, monoethanol amine or the like may be used as a part of the low molecular polyol. In this case, a polyester-amide polyol is obtained.

  Examples of the polyether polyol include those obtained by ring-opening addition of epoxides or cyclic ethers such as ethylene oxide, propylene oxide, and tetrahydrofuran using the low molecular polyol used in the polyester polyol as an initiator. Or the thing which added another kind of epoxide and cyclic ether after adding the single item of epoxide and cyclic ether to an initiator is mentioned.

  The polycarbonate polyol is obtained from a dealcoholization reaction or a dephenol reaction between one or more low molecular polyols from the above-mentioned polyester polyol source and a dialkylene carbonate such as ethylene carbonate or diethyl carbonate, or a diaryl carbonate such as diphenyl carbonate. Is mentioned.

  Examples of the polyolefin polyol include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene.

  Moreover, if it has a number average molecular weight of 500 to 5,000 and an average of one or more active hydrogen groups in one molecule, in addition to dimer acid polyol, hydrogenated dimer acid polyol, epoxy resin, Active hydrogen group-containing resins such as polyamide resin, polyester resin, acrylic resin, rosin resin, urea resin, melamine resin, phenol resin, coumarone resin, and polyvinyl alcohol can be used in combination.

  In the present invention, in view of adhesion to nylon and various durability, a polyester polyol using two or more kinds of raw material glycols is preferable.

  The low molecular polyol (A) is a compound having a molecular weight of less than 500, preferably 62 to 300, containing a hydroxyl group as a reactive group of an isocyanate group, and containing a carboxyl group-containing diol (B1). When the carboxyl group-containing diol (B1) is not used, the adhesion to nylon tends to decrease.

  Examples of the carboxyl group-containing diol (B1) include 2,2-dimethylolpropionic acid (DMPA) and 2,2-dimethylolbutanoic acid (DMBA).

  The low molecular polyol (A) has a number average molecular weight of less than 500 and is a compound containing a hydroxyl group as a reactive group for an isocyanate group, such as a polyol other than the above (B1), for example, a low molecular weight used in the above polyester polyol. Examples include molecular polyols.

  In the present invention, the molar ratio of the side chain alkyl group-containing castor oil-based polyol (A1) to the carboxyl group-containing diol (B1) is preferably (A1) / (B1) = 0.1-10, A1) / (B1) = 0.5-5 is preferable. When (A1) / (B1) is less than the lower limit, the carboxyl group of the side chain alkyl group is insufficiently shielded, and moisture from the outside is directly attacked by the carboxyl group, so that the heat and humidity resistance of the polyurethane resin is likely to be lowered. . When (A1) / (B1) exceeds the upper limit, the shielding of the carboxyl group of the side chain alkyl group becomes excessive, the contact of the carboxyl group with nylon is insufficient, and the adhesion tends to be lowered.

  The carboxyl group content in the polyurethane resin is preferably from 0.1 to 1 mmol / g, and preferably from 0.3 to 0.8 mmol / g. When the carboxyl group content is less than the lower limit, the contact of the carboxyl group with the nylon becomes insufficient, and the adhesion tends to be lowered. When the carboxyl group content exceeds the upper limit, the heat and humidity resistance of the polyurethane resin tends to decrease.

  Examples of the organic polyisocyanate (C) include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, , 5-naphthylene diisocyanate, 1,4-naphthylene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, o-xylylene diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, tetramethylxylylene diisocyanate, 4 , 4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3, Aromatic diisocyanates such as 3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, Aliphatic diisocyanates such as 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, And alicyclic diisocyanates such as hydrogenated tetramethylxylylene diisocyanate and cyclohexyl diisocyanate. Moreover, modified polyisocyanates such as these adduct-modified products, allophanate-modified products, biuret-modified products, carbodiimide-modified products, uretonimine-modified products, uretdione-modified products, and isocyanurate-modified products can also be used. These can be used as one kind or a mixture of two or more kinds.

  In the production procedure of the polyurethane resin used in the present invention, the high-molecular polyol (A) and the low-molecular polyol (C) are appropriately diluted with a solvent such as ketone, ester or aromatic hydrocarbon which does not have active hydrogen. An organic polyisocyanate is added to this mixed solution, a urethanization catalyst is added as necessary, and the reaction is carried out for several hours at a temperature in the range of 30 to 100 ° C. to obtain the desired polyurethane resin. In this case, the molar ratio of isocyanate group / hydroxyl group is preferably 0.8 or more and less than 1, and particularly preferably 0.85 to 0.99. When the molar ratio of isocyanate group / hydroxyl group is less than 0.8, the durability of the resulting polyurethane resin becomes poor. In the case of 1 or more, solubility in a solvent and adhesion are poor.

  The number average molecular weight of the polyurethane resin thus obtained is 10,000 to 30,000, particularly 12,000 to 28,000. When the number average molecular weight of the polyurethane resin is less than 10,000, the strength is insufficient, and when it exceeds 30,000, spray coating becomes difficult.

  Examples of the solvent include aromatic solvents such as toluene and xylene, ester solvents such as ethyl acetate and butyl acetate, and ketone solvents such as acetone and methyl ethyl ketone. Further, during the amine extension reaction, an alcohol solvent such as methanol, ethanol or isopropanol may be present. In the present invention, a mixed solvent of toluene, methyl ethyl ketone, and isopropanol is preferable.

  In addition, the primer composition of the present invention includes a pigment, a dye, an antiblocking agent, a dispersion stabilizer, a thixotropic agent, an antioxidant, an ultraviolet absorber, an antifoaming agent, a thickener, a dispersant, an interface as necessary. Various additives such as an activator, a catalyst, a filler, a lubricant, an antistatic agent, and a plasticizer can be blended.

  The primer composition of the present invention can be suitably used for plastic molded articles typified by (exterior) parts of automobiles, and has good adhesion to adherends made of nylon that is considered to be difficult to adhere. Expresses sex.

  Next, although the Example and comparative example of this invention are demonstrated in detail, this invention is not limited to these Examples. Unless otherwise specified, “parts” and “%” in the examples mean “parts by mass” and “% by mass”, respectively.

Production of polyurethane resin solution <Synthesis Example 1>
In a 2 liter four-necked flask equipped with a stirrer, thermometer, Arene condenser tube, and nitrogen gas inlet tube, 179.7 g of polyol-1, 185.5 g of polyol-2, 7.2 g of DMPA, and cyclohexanone were added. 360 g was charged and stirred uniformly. To this polyol solution, 167.6 g of MDI and 0.05 g of DOTDL as a urethanization catalyst were added, and the reaction was started at 80 ° C. As the viscosity increased, it was appropriately diluted with cyclohexanone. The total amount of cyclohexane charged is 630 g. After confirming disappearance of the isocyanate group by FT-IR analysis, 630 g of MEK was charged and cooled to 40 ° C. with uniform stirring to obtain a polyurethane resin solution PU-1. The solid content of PU-1 is 30%, the viscosity is 80 mPa · s (25 ° C.), the number average molecular weight of the polyurethane resin is 23,000, the storage stability is good, the COOH content from the preparation and the side chain alkyl group-containing castor The molar ratio of oil-based polyol / carboxyl group-containing diol was 0.1 mmol / g and 5, respectively. These are summarized in Table 1.

<Synthesis Examples 2-9>
PU-2 to 9 were obtained in the same procedure as in Synthesis Example 1 with the raw materials and preparation amounts shown in Table 1.

Synthesis Examples 1-9, in Table 1, Polyol-1:
Side chain alkyl group-containing castor oil-based polyol Product name URIC Y-403 (manufactured by Ito Oil Co., Ltd.)
Hydroxyl value = 162.8 mgKOH / g
Polyol-2:
Polyester polyol obtained from mixed glycol and mixed dicarboxylic acid Mixed glycol = ethylene glycol / neopentyl glycol = 1/1 (molar ratio)
Mixed dicarboxylic acid = terephthalic acid / isophthalic acid = = 1/1 (molar ratio)
Hydroxyl value = 56.1 mgKOH / g
Polyol-3:
Castor oil-based polyol (no side chain alkyl group)
Product name URIC AC-006 (Ito Oil Co., Ltd.)
Hydroxyl value = 181.2 mgKOH / g
Polyol-4:
Acrylic polyol Product name UT-1001 (manufactured by Soken Chemical Co., Ltd.)
Hydroxyl value = 56.4 mgKOH / g
MDI:
4,4-diphenylmethane diisocyanate HDI:
Hexamethylene diisocyanate C-2770:
Coronate 2770; allophanate-modified polyisocyanate of hexamethylene diisocyanate, NCO content = 21.1%
* "Coronate" is a registered trademark of Japan Polyurethane Industry Co., Ltd. DOTDL:
Dioctyltin dilaurate DMPA:
2,2-dimethylolpropionic acid MEK:
Methyl ethyl ketone polyurethane resin molecular weight measurement conditions Measurement conditions and measuring instrument: "HLC-8120" (manufactured by Tosoh Corporation)
Column: “Styragel HR2 DMF” (manufactured by Nippon Waters Co., Ltd.)
Particle size = 5 μm, size = 7.8 mm ID × 30 cm × 4, carrier: N, N-dimethylformamide (DMF) containing LiBr 0.1%
-Detector: Parallax refraction-Sample: 0.1% LiBr / DMF solution-Calibration curve: Polyethylene glycol

Storage stability evaluation After production, the product was allowed to stand in a cool and dark place for 24 hours to confirm the appearance. The results are shown in Table 2.
○: No turbidity, transparent ×: Turbidity is generated XX: Resin is deposited and separated.

Primer composition preparation examples 1-5, comparative examples 1-4
PU-1 to 9 were each diluted with a mixed solvent of toluene / MEK / IPA = 3/4/3 (mass ratio) so as to have a solid content of 9%.

Preparation of Base Layer Forming Resin Composition The base layer forming resin composition to be overcoated on the primer composition coating is oxidized to 100 parts of acrylic resin “Acridic A-801-P” (manufactured by DIC Corporation). It was prepared by adding 20 parts of titanium and 230 parts of toluene and kneading for 10 minutes in a disperser.

Preparation of Resin Composition for Forming Top Layer The top layer-forming resin composition to be overcoated on the base layer-forming resin composition is an acrylic resin “Acridic A-801-P” (manufactured by DIC Corporation) 100. Add 18 parts (NCO / OH = 1/1: molar ratio) of polyisocyanate curing agent “Coronate HX” (manufactured by Nippon Polyurethane Industry Co., Ltd.) and 110 parts of toluene, and knead in a disperser for 10 minutes. It was prepared by.
* "Coronate" is a registered trademark of Nippon Polyurethane Industry Co., Ltd.

Storage stability measurement method After dilution, leave in a cool and dark place for 24 hours to confirm the appearance.
○: No turbidity, transparent ×: Turbidity is generated XX: Resin is deposited and separated.

Normal adhesion evaluation method For each of the obtained test specimens (primer / base / top laminated coating sample), a 1 mm square grid (10 × 10) cut was formed on the coating surface and adhered. A peel test using a tape was performed to measure the number of remaining sheets. Three test pieces were prepared for each of Examples 1 to 5 and Comparative Examples 1 to 4, and the average value of the remaining number of the three test pieces was obtained. The results are shown in Table 2.

Moisture and heat resistance evaluation method Each of the obtained test pieces (primer / base / top laminated coating sample) was allowed to pass in an atmosphere of 50 ° C. × 90% RH for 240 hours and immediately became a 1 mm square grid. A (10 × 10) cut was formed on the coating surface and a peel test with an adhesive tape was performed to measure the number of remaining sheets. Three test pieces were prepared for each of Examples 1 to 5 and Comparative Examples 1 to 4, and the average value of the remaining number of the three test pieces was obtained. The results are shown in Table 2.

As shown in Table 2, in the examples, good results were obtained in each test. On the other hand, since Comparative Example 1 did not use the side chain alkyl group-containing castor oil-based polyol itself, the heat and moisture resistance became insufficient. Since Comparative Example 2 did not use a carboxyl group-containing diol, adhesion was insufficient. Since Comparative Example 3 uses a castor oil-based polyol, the compatibility with the raw material polyester is good and the storage stability is good, but this castor oil-based polyol is not a side chain alkyl group-containing type. Although not as much as in Example 1, the heat and humidity resistance was insufficient. In Comparative Example 4, acrylic polyol (no side chain) was used instead of castor oil-based polyol, so compatibility with the raw material polyester was poor and storage stability was not good. In addition, since it isolate | separated after primer preparation, subsequent evaluation was stopped.

Claims (3)

A plastic comprising a carboxyl group-containing polyurethane resin obtained by reacting a high molecular polyol (A) having a number average molecular weight of 500 to 5,000, a low molecular polyol (B) having a molecular weight of less than 500, and an organic polyisocyanate (C). In the primer composition for coating,
The polymer polyol (A) having a number average molecular weight of 500 to 5,000 contains a side chain alkyl group-containing castor oil-based polyol (A1),
The low molecular weight polyol (B) having a molecular weight of less than 500 contains a carboxyl group-containing diol (B1).
The primer composition for plastic coating characterized by the above-mentioned.   The molar ratio of the side chain alkyl group-containing castor oil-based polyol (A1) and the carboxyl group-containing diol (B1) is (A1) / (B1) = 0.1-10, Primer composition for plastic coating. The primer composition for plastic coating according to claim 1 or 2, wherein the content of carboxyl groups in the polyurethane resin is 0.1 to 1 mmol / g.