JPH0749559B2 - Primer or paint for painting plastics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has high crystallinity or small surface polarity, good adhesion of a coating film to the surface of plastics, and excellent inter-layer adhesion with various top-coat paints. The present invention relates to a primer or paint for plastics and a coated plastics molded product coated with the primer or paint.

[Conventional technology]

Plastics with high crystallinity or small surface polarity,
For example, polyacetal resins, polyester resins (polyethylene terephthalate, polybutylene terephthalate, wholly aromatic polyesters, etc.) have poor adhesion to paints, and therefore, it is customary to perform physical or chemical surface treatment prior to coating. For example, a physical method is a method of mechanically roughening the surface, a chemical method is a solvent treatment method, and a physicochemical method is a flame treatment, an ultraviolet treatment, a corona discharge treatment, a plasma treatment method, etc. There is. These all modify the plastic surface to improve the adhesion of the paint.

[Problems to be solved by the invention]

As described above, the method of coating the surface of the plastics physically or chemically does not only require a considerable amount of labor and a large amount of cost for the surface treatment, but also has a serious drawback that the surface-treated portion deteriorates. Was. From such a point, the development of a primer or paint that shows good adhesion just by directly painting without surface treatment is underway, and some materials are already in practical use. . The properties required of this primer or paint are (1) not invading the surface and inside of the plastics, (2) excellent inter-layer adhesion of the coating film (eg 1 mm
・ No peeling by 100 mass tape peeling), (3) Tough coating (small shrinkage during film formation and small internal strain), (4) Quick drying, wet-on-wet topcoat Can be painted (5) The coating is highly flexible and resistant to physical impact (impact resistance, chipping resistance), (6) The coating is solvent resistant, water resistant (adhesive) and heat resistant. And the like (including heat cycle resistance).

However, since the high crystallinity and small polarity plastics as described above have a low affinity for most materials, it is not easy to obtain high adhesion without surface treatment, and for example, for polyacetal or polyester molded products, No primer or paint is commercially available that exhibits satisfactory adhesion without surface treatment.

The present invention has been made in view of these circumstances, and it is a primer or paint capable of sufficiently exhibiting the above-mentioned required properties for plastics having high crystallinity or small surface polarity, and coating applied by the primer or paint. It is intended to provide plastic molded products.

[Means for solving problems]

The essential film-forming components of the primer or paint that can solve the above problems are (A) polyurethane resin, (B) ring-opening expandable spiro-ortho-ester resin, and (C) cellulose derivative. And (D) a hydroxyl group-containing surfactant, and the present invention relates to a primer or paint and a coated plastics molded product coated with the primer or paint.

[Action]

The coating film forming components of the primer or paint used in the present invention will be described. The component (A) is characterized by high tackiness and high elasticity, and has a function of enhancing the adhesion to the object to be coated and the impact resistance of the coating film, and a polyurethane resin is used in the present invention. Here, the polyurethane-based resin is a generic term for all modified polyurethane resins regardless of whether they are thermoplastic or thermosetting, and as long as the polyurethane-based resin is the main constituent material, high-adhesion coating
The most preferable one to give high elasticity is the average molecular weight (
n) It is a thermoplastic polyurethane-based resin of about 2000 to 10,000, more preferably about 4000 to 7,000. The component (B) mainly imparts non-shrinkage property to the coating film, and it undergoes intramolecular irreversible ring-opening in the presence of a cationic catalyst to exhibit a cross-linking structure and expands to form a coating film during film formation It is a component that plays a role in alleviating shrinkage, and in addition to the effect of alleviating external stress and reducing the residual strain (internal stress) of the film caused by shrinkage, it also exhibits an effective plasticizing effect even in the closed ring state. . This component is composed of a spiro-orthoester resin and, as a typical example, 2,2-bis [4- (2,3
-Epoxypropoxy) phenyl] propane-6-hexanolide polyadduct, 8,10,19,20-tetraoxatrispyro [5.2.2.5.2.2.] Heneicosane-2,14-diene and the like can be mentioned. Among them, the preferred degree of spiroorthoesterification is 250 to 500 g / eq, more preferably about 300 to 400 g / eq, and the epoxy value is 0 to 5.0 g / eq, and more preferably 4.6.
It is a spiro-orthoester resin of about 5 g / eq. The component (C) imparts film-forming property (heat fluidity) and film hardness, and is composed of a cellulose derivative. Among the cellulose derivatives, those suitable for the purpose of the present invention include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate,
Cellulose esters such as cellulose acetate butyrate and cellulose nitrate, especially those having a degree of butylation or propylation of 17 to 55% and a high degree of butylation or propylation Cellulose acetate butyrate, cellulose acetate propionate Is more preferable, the hydroxyl group concentration is 1.0 to 3.0, and more preferably about 1.0 (4
Anhydrous glucose unit), viscosity 0.01 ~ 20.0sec,
It is more preferably about 0.2 sec (standard falling ball viscosity). The component (D) is preferably a fluorine-containing or silicon-containing hydroxyl group-containing reactive surfactant having surface adjusting ability and reactivity of the film, and imparts surface adjusting of the film and adhesion between top coat layers. Specific examples thereof include hydroxyl group-introduced perfluoroalkyl as the fluorine type, and hydroxyl group-introduced organosiloxane as the silicon type, and those having a high hydroxyl value are effective. A part of the hydroxyl groups is exposed on the surface of the coating film in a non-bonded state and gives good adhesion to the overcoat layer.

These A, B, C and D components are united to form a coating film having good coating film performance and good adhesion to the object to be coated and the topcoat paint.

In the present invention, these four-component (A) polyurethane resin,
It is necessary to determine the blending ratio so that the coating film forming components of the (B) spiro-ortho-ester resin, the (C) cellulose derivative, and the (D) hydroxyl group-containing surfactant fall within the following composition ranges.

(A) Polyurethane resin: 50 to 97 (wt%) (B) Spiro-ortho ester resin (Catalyst: 2.0
-40 (wt%) (C) Cellulose derivative: 1.0 to 9.0 (wt%) (D) Hydroxyl group-containing surfactant: 0.05 to 1.0 (wt%).

The reason for defining the above composition range is as follows.

(A) If the polyurethane-based resin is less than 50% by weight, the adhesive layer that gives high adhesiveness is insufficient and the adhesiveness is insufficient.
If it exceeds 5% by weight, atomization during spraying, surface flatness and surface hardness become extremely poor.

(B) If the spiro-orthoester resin is less than 2.0% by weight, neither expandability nor plasticizing effect is obtained, and the throwing power to the edge (corner / ridge) of the molded product is poor. Aggravates sex.

The ring opening of the spiro orthoester resin is caused by the cation component in the system. Usually, the ring-opening reaction is promoted by the coexistence of a catalyst such as methyl hexahydrophthalic anhydride or di-n-butyl tin dilaurate, but the -COOH, -SO ₃ H groups present in the system Or the like, or a filler having an acidic hydroxyl group (aluminum silicate type, magnesium silicate type, surface carboxyl type organic microgel, etc.) to open the ring.
An excellent plasticizing effect also appears in the ring closed state. Since this ring-opening reaction is unlikely to occur at room temperature, it is usually preferable to heat it at about 100 ° C. after applying the coating material or to accelerate the ring-opening reaction by utilizing the heat when baking the top coating material.

(C) If the amount of the cellulose derivative is less than 1.0% by weight, the effect on the heat fluidity and the surface hardness is insufficient, and if it exceeds 9.0% by weight, the adhesion is lowered.

(D) If the amount of the hydroxyl group-containing reactive surfactant is less than 0.05% by weight, the surface conditioning effect will not be exhibited, and the flatness of the coating film surface will be poor.
If it exceeds 1.0% by weight, a coating film defect (such as letter) occurs and the adhesion to the topcoat paint is deteriorated.

The coating composition containing the above-mentioned four components is subjected to a heat treatment after coating, in particular, the component (B) among the above components,
(C) and (D) are capable of reacting to form a coating film satisfying the above-mentioned required characteristics. In this sense, when used in combination with a thermosetting topcoat paint such as a baking paint, it is used during baking and curing. It is most advantageous to utilize the heat of to accelerate the crosslinking of the coating components. However, it is, of course, possible to apply a heat treatment after applying the coating material, and then apply a room temperature curing type top coating material.

Further, it is also possible to use it in a room temperature curing type in combination with the room temperature curing type top coating material within the blending range of the above four components.

By the way, in a usual coating composition, if necessary, a pigment, a filler, or other various additives are added to improve the physical properties of the coating film, the ultraviolet transmissivity, the conductivity, and the coloring property. Also in the present invention, it is possible to further enhance the coating film performance by adding these third components in combination. However, when determining the type and amount of pigments and fillers,
It is needless to say that care should be taken so that the primer or the paint-forming component of (A), (B), (C) or (D) can be stably mixed.

The coating film forming component and a pigment or other additive that is blended as necessary are diluted and mixed with a solvent to prepare a primer or a coating material. Of course, this solvent must not invade the surface of the plastics that is the object to be coated, and it is desirable that it be a quick-drying solvent, which may vary depending on the type of the object to be coated. Examples include those shown in the left column of Table 2 and mixtures thereof.

Further, in adjusting the coating material, it is desirable to consider the particle size of the raw material so that the insoluble component among the film-forming components and pigments and other additives can be uniformly dispersed in the solvent in the form of fine particles of 10 or less. . The primer or coating material of the present invention can be provided as a dissolution type or dispersion type coating material by appropriately adjusting the type and amount of the solvent used.

As a coating method, spraying (air spray) coating, dip coating, electrostatic coating, airless coating, roller coating, curtain coating, shower coating and the like can be used by adjusting the viscosity and conductivity of the coating. After coating, it is cured by room temperature drying and hot air drying for an arbitrary time, and in the case of hot air drying, 40 minutes to 40 ° C. and 5 minutes to 20 minutes are suitable. The appropriate dry film thickness is 15 to 30, and it can be considered as 22 ± 2 as a standard.

〔Example〕

A primer or paint is prepared with the composition shown in Table 1 below, and diluted with a viscous / diluting solvent having the composition shown in Table 2
Polyacetal, polyethylene terephthalate, polybutylene terephthalate and the following completely aromatic polyester (constituent monomer units: After coating a dry film thickness of 22 ± 2 on the plate, the coating temperature is 80-140
The coating film-forming component was heat cured by drying with hot air at 20 ° C. for 20 to 30 minutes. Next, a melamine alkyd paint (“Amilak” manufactured by Kansai Paint Co., Ltd.), which is commercially available as a top coating material for automobile outer panels, is prepared with a thinner and applied by spraying to a dry film thickness of 30-40. so,
After setting for 10 minutes, it was dried with hot air at 140 ° C. for 30 minutes and heat cured.

The composition components in the left column of Table 1 are the following substances.

Burnock: (A) polyurethane resin [manufactured by Dainippon Ink and Chemicals, Inc.] exp-101: (B) spiroorthoester resin (catalyst:
Di-n-butyl tin dilaurate) [Toa Gosei Kagaku KK] CAB-551-0.2: (C) Cellulose acetate butyrate [Eastman Kodak KK] Defender MCF-312: (D) Hydroxyl group-containing fluorine -Based reactive surfactant [manufactured by Dainippon Ink and Chemicals, Inc.] BYK No-370: (D) Hydroxyl group-containing silicon-based reactive surfactant [manufactured by BYK Chemie] The coated plastics molded product with the primer or the paint compounded as described above does not invade the surface or the inside of the plastics with respect to any of the above-mentioned resins.

(2) Excellent inter-layer adhesion of the coating film after top-coating (1 mm, 100 mass, no peeling by tape peeling), (3) Tough coating (small shrinkage during film formation and internal strain) (4) It is fast-drying and can be applied on top by wet-on-wet. (5) The coating film is highly flexible and strong against physical impact (impact resistance, chipping resistance), (6) The coating film was excellent in water resistance (adhesiveness) and heat resistance (including heat cycle resistance).

[Comparative example]

For reference, for the polyacetal resin plate, the primer of the present invention was not used at all, only the top coat of the example was applied, and the same adhesion test (1 mm / 100 mass / tape peeling) as in the example was performed, All peeled off.

In addition, the same peeling test was carried out on the primer obtained by removing any one of the components A, B, C and D from the primer (Example 1) comprising the components A, B, C and D of the present invention. The average retention rate (average number of remaining pieces in 100 squares due to tape peeling) was as follows.

When A is not included 0/100 squares B 〃 20 squares / 100 squares C 〃 32 squares / 100 squares D 〃 7 squares / 100 squares [Effect of the invention] ) A primer or paint of the present invention comprising a polyurethane resin, (B) ring-opening expandable spiro-ortho-ester resin, (C) cellulose derivative and (D) hydroxyl group-containing reactive surfactant is highly crystalline, or Good adhesion of the coating film to the surface of plastics with a small surface polarity, eliminating the need for conventional chemical and physical surface treatment steps, and excellent inter-layer adhesion with various top-coat paints. Polyacetal resin, polyester resin Provide excellent coated plastics molded products that are extremely useful as primers or paints such as (polyethylene terephthalate, polybutylene terephthalate, wholly aromatic polyester). It is something.

Claims (1)

[Claims] 1. An essential film-forming component is (A) 50 to 97% by weight of a polyurethane resin (B) a ring-opening expandable spiro ortho ester resin 2.
0-40% by weight (C) Cellulose derivative 1.0-9.0% by weight and (D) Hydroxyl group-containing surfactant 0.05-1.0% by weight (however, the blending ratio of each component of (A)-(D) is (A),
(B), (C) and (D) in weight% based on the total).