JPS6216148B2 - - Google Patents

Description

Detailed Description of the Invention The present invention improves surface properties such as surface hardness and chemical resistance of plastic molded products, wood products, metal products, etc., and has very good heat resistance, heat cycle resistance, and weather resistance. The present invention relates to a surface coating method that provides a coating film. Plastic molded products such as polycarbonate, polymethyl methacrylate, polystyrene,
Thermoplastic resins such as polyvinyl chloride are used in large quantities due to their advantages such as light weight, easy processability, and impact resistance. However, their soft surfaces easily damage them, and they also swell when they come in contact with solvents. , it has disadvantages such as being prone to dissolution. As a method to improve these drawbacks, a method has been proposed in which a paint mainly containing a hydrolyzate of tetraalkoxysilane and organotrialkoxysilane is applied to plastic molded products to impart surface hardness and solvent resistance. (Refer to JP-A-48-55884 and JP-A-48-56230). This method has the disadvantages of easy cracking in the coating layer, poor water resistance, and poor adhesion to plastic molded products other than polymethyl methacrylate resin, but is not satisfactory in practice. It's not a thing. The present inventor places more emphasis on the hot water resistance, heat cycle resistance, and weather resistance of the coating film, and improves these.
Furthermore, as a result of intensive study on improving the surface characteristics of various objects to be coated, including plastic molded products, to achieve practical satisfaction, we have found that a two-step coating method using the specific paints, including processing conditions, etc. The present invention was completed based on the finding that the surface properties were significantly improved and were practically satisfactory. That is, the present invention applies a paint containing an acrylic chelate resin containing less than 50% by weight of methyl methacrylate in the resin solid content as an undercoat to an object to be coated, and then applies a topcoat containing mainly a hydrolyzate of organosiloxane. This is a surface coating method characterized by applying a coating liquid. More specifically, as an undercoat, an acrylic chelate resin mainly consisting of (1) an acrylic linear copolymer having a carboxyl group in the molecule, (2) an aluminum alcoholate complex, and (3) a keto-enol type tautomeric compound is used. (1) General formula RnSi
(OR') _4-o (wherein, n is an integer of 1 to 3, R is a hydrocarbon group having 1 to 6 carbon atoms, and R' is an alkyl group having 1 to 4 carbon atoms); Consisting of a copartial hydrolyzate with tetraalkoxy silicon or/and a mixture of each partial hydrolyzate, RnSiO
The above general formula RnSi(OR') calculated as (where n and R are as defined above) _4-o
Tetraalkoxysilicon partial hydrolyzate calculated as _SiO2 for 100 parts by weight of partial hydrolyzate of 5~
a silicon compound partial hydrolyzate containing 100 parts by weight;
(B) General formula calculated as RnSiO〓〓 in (A)
RnSi(OR') _4-o alkyl acrylate or/and alkyl methacrylate (hereinafter abbreviated as alkyl (meth)acrylate)) and hydroxyalkyl acrylate to 100 parts by weight of the partial hydrolyzate of the compound represented by 4-o. or/and a copolymer with hydroxyalkyl methacrylate (hereinafter referred to as hydroxyalkyl (meth)acrylate) (hereinafter referred to as acrylic copolymer) and 5 to 200 parts by weight of etherified methylolmelamine. 0~150
This is a surface coating method characterized by using a coating composition obtained by dissolving parts by weight in a solvent. In other words, the present invention provides excellent adhesion to any material to be coated, including plastic molded products other than resins mainly made of methyl methacrylate, wood products, metals such as iron and aluminum, and inorganic materials such as glass and ceramics. A paint containing acrylic chelate resin is used as the undercoat paint, which has excellent properties such as surface hardness, water resistance, heat cycle resistance, and weather resistance. While increasing the ratio of the partial hydrolyzate of an organosilicon compound to the partial hydrolyzate of alkoxy silicon to improve the hot water resistance, heat cycle resistance, and weather resistance of the coating film, the ratio is This is a surface coating method characterized by using a material that has abrasion resistance within a certain range, and which has improved flexibility by adding an acrylic copolymer or etherified methylolmelamine to improve flexibility, which is insufficient with a silicon component alone. The objects to be coated in the present invention include plastic molded products such as polymethyl methacrylate resin, polycarbonate resin, polyvinyl chloride resin, polystyrene resin, acrylonitrile-butadiene-styrene resin, methyl methacrylate-styrene resin, acrylonitrile-styrene resin, iron,
Metals such as aluminum, vacuum-deposited or sputtered products such as chromium, aluminum, and stainless steel, inorganic materials such as glass and ceramics,
Although any material, such as wood products, can be successfully targeted, it is generally particularly effective for plastic products and products with vacuum-deposited or sputtered metal films. The acrylic chelate resin paint used in the present invention is easily crosslinked and cured at room temperature or below the deformation temperature of the plastic material, forming a strong coating film. Since this curing reaction starts with the volatilization of the solvent in the paint, the stability of the paint during storage and use is extremely good, and conventional coating equipment can be used without any modification. In addition to the acrylic chelate resin, the paint used in the present invention may contain acrylic chelate resin solids if desired.
Based on 100 parts by weight, 25 parts by weight or less of a plasticizer, 25 parts by weight or less of a cellulose derivative, 70 parts by weight or less of an acrylic resin that dries at room temperature, and extender pigments, coloring pigments, etc. can be blended. If the amount of plasticizer exceeds 25 parts by weight, it is possible to form a coating, but the hardness of the coating decreases more than necessary, making it susceptible to the effects of the solvent in the top coat. Furthermore, when the amount of cellulose derivative is increased to more than 25 parts by weight, the adhesion to the material gradually decreases and eventually disappears. Furthermore, when the room temperature drying acrylic resin exceeds 70 parts by weight, the crosslinking density decreases and the resin becomes susceptible to the effects of the solvent of the top coat. The paint containing the acrylic chelate resin used in the present invention contains an acrylic linear copolymer having a carboxyl group in the molecule, an aluminum alcoholate complex compound, a keto-enol type tautomer compound as a stabilizer, and a solvent. After coating, when the keto-ethanol type tautomeric compound and the solvent evaporate, it becomes three-dimensional at room temperature and forms a coating film with excellent solvent resistance. Specifically, butanol is an acrylic monomer selected from the group consisting of methacrylic esters such as methyl methacrylate, butyl methacrylate, and ethyl methacrylate; acrylic esters such as butyl acrylate, and monomers such as methacrylic acid and acrylic acid.・Polymerize in a xylene mixed solvent under a catalyst such as benzoyl peroxide or kyumene hydroperoxide to obtain an acrylic linear copolymer having a carboxyl group in the molecule, and then add keto enol as a stabilizer. After adding one or more type tautomeric compounds such as acethiacetone, ethyl acetoacetate, benzoylacetone, diester of aronic acid, etc. and mixing well, further add an ethyl acetoacetate complex of aluminum isopropoxide, ethyl salicylate. Formed by adding a solution of an aluminum alcoholate complex compound such as a complex compound. Plasticizers that can be used in the present invention include plasticizers that can be used in solvent-based paints, such as phthalate esters such as dibutyl phthalate and dioctyl phthalate, ricinoleate adipates such as methyl acetylsinolate and dioctyl adipate, and azelate sebacates. , polyester/epoxy fatty acid esters, maleic acid esters, fumaric acid esters, phosphoric acid esters, chlorinated fatty acid esters, chlorinated normal paraffins, and the like. As the cellulose derivative, for example, acetic acid or butyric acid ester of nitrocellulose such as cellulose acetate butyrate can be used. The room temperature drying acrylic resin is, for example, a copolymer or homopolymer of methacrylic acid ester or acrylic acid ester such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl, and acrylic acid. Preferably, it contains ethyl methacrylate and butyl methacrylate. Furthermore, the proportion of methyl methacrylate in the resin solid content in the acrylic chelate resin paint used in the present invention is preferably less than 50% by weight, and if it contains 50% by weight or more, the flexibility of the coating film will decrease. It deteriorates significantly and is prone to cracking. As extender pigments, all extender pigments commonly used for paints can be used, such as calcium carbonate silicate, magnesium silicate, aluminum silicate, barium sulfate, and the like. Examples of coloring pigments include titanium white, red iron,
All coloring pigments commonly used for paints, such as carbon black, cyanine green, cyanine blue, organic red pigments, and organic yellow pigments, can be used. The obtained undercoat paint is coated after adjusting the viscosity to an appropriate level with thinner or the like depending on the coating method. For painting, commonly used methods such as brushing, spray painting, and dipping can be used without any problems. After applying the above-mentioned undercoat to the object to be painted, the painted object is dried in an oven at a predetermined temperature or left at room temperature, and after the surface is in a state where it will not stain your fingers even if you touch it, the surface characteristics are improved. Apply a top coat of paint. The tetraalkoxy silicon used in the present invention is one in which the alkoxy group is methoxy, ethoxy, propoxy, butoxy, or the like. Also, the general formula RnSi
(OR′) In the organosilicon compound represented by _4-o ,
Specifically, the hydrocarbon group R having 1 to 6 carbon atoms is an organic group such as methyl, ethyl, propyl, butyl, pentyl, hexyl, vinyl, allyl, phenyl, etc., and the alkyl group R′ having 1 to 4 carbon atoms. means methyl group, ethyl group, propyl group, butyl group, etc. These partial hydrolysates of silicon compounds are prepared by combining tetraalkoxy silicon and the organosilicon compound of the general formula RnSi(OR') _4-o, separately or in a mixture, in the presence of an acid in a mixed solvent such as water and alcohol. It is obtained by hydrolysis below. In some cases, these partial hydrolysates of silicon compounds can also be obtained by directly hydrolyzing silicon chlorides such as SiCl ₄ and RnSiCl _4-o .
In general, it is often better to mix these silicon compounds and co-hydrolyze them at the same time than to hydrolyze them separately, especially for compounds with the general formula RnSi.
In the case of a compound in which n=2 or n=3 in (OR') _4-o , it is preferable to perform cohydrolysis after mixing with tetraalkoxy silicon. The ratio of the tetraalkoxysilicon partial hydrolyzate obtained in this way to the partial hydrolyzate of the organosilicon compound of RnSi(OR′) _4-o is calculated as _{RnSiO〓〓〓} It is preferable that at least one partial hydrolyzate of the organosilicon compound of _o is 5 to 100 parts by weight of a tetraalkoxy silicon partial hydrolyzate calculated as SiO ₂ per 100 parts by weight. If the content of the tetraalkoxy silicon partial hydrolyzate is less than 5 parts by weight, the hardness of the coating film will decrease and practical abrasion resistance will be lost; if it is more than 100 parts by weight, the coating film will have poor hot water resistance and heat cycle resistance. , weather resistance tends to deteriorate. The acrylic copolymer used with the silicon component combines alkyl (meth)acrylate and hydroxyalkyl (meth)acrylate with azobisisobutyronitrile, benzoyl peroxide, di-
It can be obtained by bulk polymerization, emulsion polymerization, suspension polymerization or solution polymerization in the presence of a radical polymerization initiator such as tert-butyl peroxide. As the alkyl (meth)acrylate, (meth)acrylic acid esters of alcohols having 1 to 18 carbon atoms can be selected. Particularly useful are ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and the like. Examples of hydroxyalkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate,
Glycerol mono(meth)acrylate and the like can be used. Alkyl (meth) in acrylic copolymers
There is no particular limit to the composition ratio of acrylate and hydroxyalkyl (meth)acrylate, but the weight ratio is 1/10 or more, considering the adhesion between the final coating film and the base material, the flexibility of the coating film, etc. It is preferably within the range of 10/1. The amount ratio of the acrylic copolymer in the composition of the present invention is calculated as RnSiO〓〓
(OR′) Partial hydrolyzate of compound represented by _4-o 100
It is desirable that the amount of the acrylic copolymer be in the range of 5 to 200 parts by weight. If the amount of the acrylic copolymer is less than 5 parts by weight, the final coating film will have poor heat cycle resistance and will have a strong tendency to crack. If the amount of the acrylic copolymer exceeds 200 parts by weight, the hardness of the coating film will be impaired and the coating film will tend to whiten when immersed in hot water. The production method of the etherified methylolmelamine used in the composition of the present invention has already been described in many documents, and there are also many commercially available products. Preferred are hexa(alkoxymethyl)melamines, such as hexa(methoxymethyl)melamine, hexa(ethoxymethyl)
Melamine, hexa(propoxymethyl) melamine, hexa(isopropoxymethyl) melamine,
Examples include hexa(butoxymethyl)melamine and hexa(cyclohexyloxymethyl)melamine. The amount ratio of etherified methylolmelamine in the composition of the present invention is calculated as _{RnSiO〓〓〓〓〓〓〓〓〓〓〓〓〓} It is preferable that the amount is in the range of 150 parts by weight; if it exceeds this amount, the adhesion of the coating film, especially the adhesion in hot water, will be adversely affected. Solvents used in the production of coating compositions include alcohols, ketones, esters, ethers, cellosolves, halides,
Carboxylic acids, aromatic compounds, etc. can be used, but their selection will depend on factors such as the polymer material base used and evaporation rate, and may be mixed in a wide range of proportions with the components of the coating composition. used. In particular, lower alkyl carboxylic acids such as formic acid and acetic acid are effective in increasing the adhesion between the substrate and the coating film. Lower alcohols (e.g. methanol, ethanol, propanol, butanol),
lower alkyl carboxylic acids (e.g. formic acid, acetic acid,
propionic acid), aromatic compounds (e.g. benzene, toluene, xylene) and cellosolves (e.g. methyl cellosolve, butyl cellosolve)
It is particularly useful to use them in combination. The amount of solvent used can be appropriately selected depending on the required thickness of the coating film, coating method, etc. The above composition of the present invention is heated at 70°C after coating on the base material.
A cured coating film can be obtained by baking at a temperature above, but in order to further lower the curing temperature and shorten the curing time, it is necessary to use acids such as hydrochloric acid, toluenesulfonic acid, organic amines, organic carbon It is useful to use curing accelerating catalysts such as acid metal salts, thiocyanate metal salts, nitrite metal salts, organotin compounds, and the like. In addition, when a particularly thick coating is required, yuzu skin,
In order to prevent surface defects such as shrinkage and to prevent paint film from repelling, it is also possible to add a surfactant to the composition of the present invention. Adding a small amount of coalescent produces a good coating. A small amount of these curing accelerating catalysts and surfactants is sufficient, and the purpose of addition can be achieved at 5% by weight or less based on the solid content of the composition. Coating with these compositions of the present invention can be done by any of the commonly used methods such as spraying, dipping, and brushing, and can be applied for 70 minutes after being applied to the substrate.
By baking and curing at a temperature of .degree. C. or higher, a transparent coating film with good hardness, water resistance, hot water resistance, chemical resistance, heat cycle resistance, weather resistance, and antistatic effect can be formed. It depends on the heat resistance of the object to be coated, but in general
1 to 2 hours at 80 to 100°C is appropriate. The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited by these Examples. It should be noted that all "parts" and "%" in the examples indicate parts by weight and % by weight unless otherwise specified. Production example 1 [Preparation of acrylic chelate resin paint] 1 Component A (1) Acrylic chelate resin (MGC Acrylic 1051
Mitsubishi Gas Chemical product, MMA content in resin 47wt
% 55.0 parts (2) Butyl acrylate/ethyl acrylate copolymer resin (Acryloid B-48N Rohm Co., Ltd. product)
23.5 parts (3) Phthalate ester 3.0 parts (4) Ethyl cellosolve 3.0 parts (5) Isopropyl alcohol 5.0 parts (6) Ethyl acetate 3.0 parts (7) Methyl isobutyl ketone (MIBK) 4.0 parts (8) Cellulose acetate butyrate 3.5 Part First, (1) to (7) were uniformly dissolved, and then (8) was added and dissolved while stirring. 2 Component B (1) Acrylic chelate resin (MGC acrylic
1051, Mitsubishi Gas Chemical Company product, MMA content in resin 47wt% 80.0 parts (2) Polyester plasticizer (Adekasizer PN
-250 manufactured by Adeka Argus) 4.0 parts (3) Ethyl cellosolve 3.0 parts (4) Butyl cellosolve 1.0 parts (5) IPA 5.0 parts (6) Ethyl acetate 3.0 parts (7) MIBK 4.0 parts Stir (1) to (7). However, it was dissolved uniformly. 3 Component C (1) Acrylic chelate resin (MGC Acrylic 1051
Mitsubishi Gas Chemical product, MMA content in resin 47wt
%) 64.5 parts (2) 1/4 second nitrified cotton 6.5 parts (3) Chlorinated paraffin 2.5 parts (4) Ethyl cellosolve 4.0 parts (5) Butyl cellosolve 1.5 parts (6) IPA 6.5 parts (7) MEK 5.0 parts (8) ) MIBK 4.5 parts (2) was dissolved in (4) to (8), then (1) and (3) were added and stirred until uniform. 4 Preparation of paint To 100 parts each of Component A, Component B, and Component C, add 20 parts of ethyl cellosolve, 20 parts of MIBK, 20 parts of ethyl acetate, and 20 parts of isopropyl alcohol, and stir evenly to prepare acrylic chelate resin paint-A, respectively. -B and -C were prepared. Production Example 2 [Preparation of coating liquid] (1) Preparation of co-partial hydrolyzate solution of tetraethoxy silicon and methyltriethoxy silicon (components) In a hydrolysis reactor equipped with a reflux condenser, add 68 g of isopropyl alcohol and tetraethoxy silicon. 38 g of methyltriethoxy silicon and 72 g of methyltriethoxy silicon were charged, mixed and dissolved, and 36 g of a 0.05N aqueous hydrochloric acid solution was further added, and the solution was heated under reflux for 5 hours with stirring to perform cohydrolysis.
After the reaction, the mixture was cooled to room temperature to obtain a copartial hydrolyzate solution. The resulting solution contained 5.1% tetraethoxy _silicon partial hydrolyzate calculated _{as SiO2} , _CH3SiO1.5
It contained 12.6% of methyltriethoxy silicon partial hydrolyzate, calculated as (2) Synthesis of acrylic copolymer (components) 40 g of butyl acrylate, 10 g of 2-hydroxyethyl methacrylate, and 0.5 g of azobisisobutyronitrile were dissolved in 300 g of ethyl alcohol, and the mixture was heated at 70°C under a nitrogen atmosphere for 50 minutes. The mixture was heated and stirred for a period of time to polymerize. After the reaction was completed, the contents were poured into petroleum ether to remove unreacted monomers to obtain a copolymer. (3) Preparation of coating agent Mix the components or hexa(butoxymethyl)melamine as shown in Table 1, and apply n-
Dissolved in 60 parts of butanol, 40 parts of acetic acid, 20 parts of xylene, 0.4 parts of sodium acetate, NUC manufactured by Nippon Unicar Co., Ltd.
A coating agent was prepared by adding 0.2 part of silicone Y-7006. Examples 1 to 9 and Comparative Examples 1 to 7 The objects to be coated were polymethyl methacrylate resin plate molded products (manufactured by Sumitomo Chemical Co., Ltd., Sumipex B MHO, hereinafter abbreviated as PMMA), polycarbonate resin plates (manufactured by Tsutsunaka Plastics Co., Ltd., Polycarbonate Ace, hereinafter referred to as PMMA). (abbreviated as PC), acrylonitrile-butadiene-styrene copolymer resin flat plate molded product (manufactured by Sumitomo Naugatatsu Co., Ltd., Clarastic MH, hereinafter abbreviated as ABS),
A urethane resin paint (SM1700D manufactured by Fujikura Kasei Co., Ltd.) is applied as an undercoat layer to the ABS resin flat plate molded product (as described above), and after heating and drying, a vapor deposition device (manufactured by Shinko Seiki Co., Ltd., EG-6 type) is applied. Samples in which chromium and aluminum were deposited for 1 minute at a vacuum level of 1×10 ^-5 Torr (abbreviated as Cr and Al, respectively).
As shown in Table 1, the acrylic chelate resin paint obtained in Production Example 1 was spray-painted using the following method, and the coating was dried by heating at 70° C. for 1 hour. Furthermore, as shown in Table 1, the coating liquid obtained in Production Example 2 was applied by dip coating, and the coating was dried by heating at 80° C. for 2 hours. The performance of the obtained painted products and coated products was examined as follows, and the results are shown in Table 1. a. Appearance: The painted and coated surfaces were observed with the naked eye for abnormalities such as cracks, whitening, blisters, and peeling, and for changes in gloss. b Adhesion...Make 100 cuts reaching 1 mm square on the coating film using a steel knife, stick cellophane tape (manufactured by Sekisui Chemical) on top of the cuts, and then pull the cellophane tape strongly in an upward direction of 90 degrees. Evaluation was made based on the number of squares remaining when peeled off. c Abrasion resistance...Toyo Paper No. 1 under a load of 10Kg/ ^cm2.
50 and rubbed it 20 times to check its resistance to scratches. A: No scratches B: Some scratches C: Many scratches The polymethyl methacrylate board that was not painted at all was grade C. d Hot water resistance test: The condition of the coating film was examined after immersing it in hot water at 90°C and leaving it for 2 hours. e. Heat cycle test: The sample was placed in a hot air dryer at 80°C for 2 hours and then placed in ice brine at -20°C for 2 hours. After repeating this process 10 times, the state of the coating film was examined. f Weather resistance... Measure the sample with a sunshine weather meter (WE-SUN-HCA- manufactured by Suga Test Instruments Co., Ltd.)
The state of the coating film was observed after 500 hours of irradiation with Type 1). 【table】

Claims (1)

[Scope of Claims] 1. A coating material containing an acrylic chelate resin containing less than 50% by weight of methyl methacrylate in the resin solid content is used as an undercoat layer on the object to be coated, and a coating liquid mainly composed of an organosiloxane hydrolyzate is applied as an overcoat layer. A surface coating method that coats as a layer. 2. As a paint containing an acrylic chelate resin, (1) an acrylic linear copolymer having a carboxyl group in the molecule, (2) an aluminum alcoholate complex, and (3)
2. A surface coating method according to claim 1, characterized in that a coating material mainly composed of a keto-enol type tautomeric compound is used. 3 As a coating liquid mainly composed of organosiloxane hydrolyzate (A) General formula RnSi (OR') _4-o
(In the formula, n is an integer of 1 to 3, R is a hydrocarbon group having 1 to 6 carbon atoms, and R' is an alkyl group having 1 to 4 carbon atoms.) Co-partial hydration of a compound represented by the formula and tetraalkoxy silicon The above general formula RnSi(OR′) _{4-o is composed of a decomposition product or/and a mixture of each partial hydrolyzate, and is calculated as RnSiO〓〓〓, where n and R are as defined above.} A silicon compound partial hydrolyzate containing 5 to 100 parts by weight of a tetraalkoxy silicon partial hydrolyzate calculated as sio ₂ based on 100 parts by weight of the partial hydrolyzate of (B) and (A).
General formula RnSi(OR′) calculated as _RnSiO〓〓4
-0 to 200 parts by weight of a copolymer of alkyl acrylate or/and alkyl methacrylate and hydroxyalkyl acrylate or/and hydroxyalkyl methacrylate and etherified methylol melamine to 100 parts by weight of the partial hydrolyzate of the compound represented by _-o . The surface coating method according to claim 1, characterized in that a coating composition obtained by dissolving ~150 parts by weight in a solvent is used.