JPS583494B2 - Film-forming composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a composition for forming a vine film that imparts excellent surface hardness, scratch resistance, gloss and solvent resistance to the surface of a plastic molded article, and a method for using the composition.

Plastic molded products are used in large quantities due to their advantages such as light weight, easy processability, and impact resistance. However, they are easily damaged due to their low hardness, and they are also susceptible to swelling and dissolution when they come into contact with solvents. There are some cases where this is lacking, which may pose a practical obstacle.

Many proposals have been made to improve these shortcomings, and although some methods have been put into practical use, there are still many problems that remain.

For example, a method for coating an alkyltrialkoxysilane hydrolyzate (USP No. 3,451,858) and a method for coating an ethyl silicate hydrolyzate (USP
No. 3, 4, 7, 6, 8, 2, 7) requires a high temperature for crosslinking and curing after coating, and cannot be applied to plastics whose heat distortion temperature is relatively low.

In addition, in order to improve this drawback, a method using a curing catalyst that enables low-temperature curing; for example, a method using lead naphthenate or an alkali metal thiocyanate (Japanese Patent Application No. 46-60288 [Japanese Unexamined Patent Publication No. 48-26822]) In this case, cracks appear due to changes in the cured coating film over time, or a whitening phenomenon appears to be caused by precipitation of metal salts onto the cured coating film.

Also, a method of applying a hydrolyzate of aminoalkoxysilane and eboxyalkoxysilane (Japanese Patent Laid-Open No. 48-8487
The method shown in No. 8) has drawbacks such as the coating film being brittle and lacking in durability.

Various other curing catalysts have been proposed to enable curing at low temperatures, but as mentioned above, many of these catalysts cause whitening of the coating film, deterioration of coating performance, or problems with plastics. However, it has problems such as being difficult to apply as a coating.

The inventors of the present invention have conducted intensive studies on a method of forming a good organic silicon compound coating film on a plastic object by processing at a relatively low temperature and in a short time without impairing the original characteristics of the plastic. , 1,8 diazabicyclo(5,4,0) undecene-7 and/or its salts have been found to have a remarkable effect, and have thus arrived at the present invention.

That is, the present invention provides a hydrolyzate of tetraalkoxy silicon of (A general formula 81 (OR) 4 (wherein R is an alkyl group having 1 to 4 carbon atoms)) and (B) general formula R 1Ss (OR2)
3 (wherein, R1 is a hydrocarbon group having 1 to 3 carbon atoms, R2 is an alkyl group or acyl group having 1 to 3 carbon atoms), and is a hydrolyzate of a silicon compound of (A) and (B). Weight ratio is 0~
40:100 to 60, and further comprising (C) 1,8 diazabicyclo(5,4.0) undecene-7 or/and a salt thereof, and a method for using the same.

(A) Tetraalkoxy silicon represented by the general formula Si(OR)4 (where R is an alkyl group having 1 to 4 carbon atoms), specifically, the alkoxy group is a methoxy, ethoxy, propoxy, or butoxy group. However, ethoxy, propoxy, and butoxy groups are preferred.

As a hydrolyzate of tetraalkoxy silicon, 0.01 to 0.0. A suitable compound is one obtained by adding 20 to 50 parts of 1N hydrochloric acid aqueous solution to the silicon compound, hydrolyzing it, and aging it.

(B) General formula R1Si(OR2)a (however, R1
is a hydrocarbon group having 1 to 3 carbon atoms, and R2 is an alkyl group or acyl group having 1 to 3 carbon atoms. Unsaturated hydrocarbon groups such as vinyl and allyl are preferred. These are methyl group, ethyl group, and vinyl group.

Specific examples of R2 include alkyl groups such as methyl and ethyl, and acyl groups such as acetyl.

Next, the hydrolyzate of the above silicon compound can be obtained by the same method as the above-mentioned hydrolysis of tetraalkoxy silicon.

Further, it is a solution obtained by removing the solvent from this hydrolyzate solution by evaporation or the like (for example, Japanese Patent Publication No. 49-45320).

Hydrolyzate of the above-mentioned tetraalkoxy silicon and general formula R'S
The blending ratio of the silicon compound hydrolyzate represented by i (OR")3 or 0 to 40/100 to 60 (polymerization ratio)
is preferable; if the amount of the tetraalkoxy silicon hydrolyzate is larger than that, it will be difficult to form a continuous film when cured.

Next, the solvent present during or after the production of the hydrolyzate of the silicon compound mentioned above is one that homogeneously dissolves the system before and after the reaction, including by-products from the hydrolysis reaction. For example, taking a silicon compound represented by the general formula R1Si(OR2)3 as an example, the complete hydrolysis and condensation reaction in this case can be expressed by the following formula.

Putting these two equations together gives the following equation. Therefore, theoretically, the minimum required amount of water for the silicon compound represented by R1S i(OR")3 is 1.5 mol per 1 mol of the silicon compound, and the hydrolysis reaction Therefore, R2 of the above formula
3 moles of alkanol and alkanoic acid represented by 0H are produced as by-products.

The by-products act as solvents for other products and reactants, thereby homogenizing the initially heterogeneous reaction mixture, thereby serving to keep the reaction constant throughout the reactor.

Therefore, it is also meaningful to blend a solvent having such effects in advance before the hydrolysis reaction.

Next, (C) 1,8 diazabicyclo (5,40) of the present invention
Undecene-7 is soluble in a variety of solvents, dissolves uniformly in the solution of the silicon compound mentioned above, is extremely effective as a curing catalyst, and has excellent compatibility with coatings, so it can be used in coatings. It does not damage the appearance of the membrane.

In addition, this salt is obtained by reacting an equivalent amount of this 1,8 diazabicyclo(54,0) undecene-7 with a relatively highly volatile acid such as carbonic acid, hydrochloric acid, formic acid, or acetic acid.
, 8 diazabicyclo(5,4.0) undecene-7 to neutralize its strong alkalinity and facilitate its handling, and is useful as a latent curing catalyst for the hydrolyzate of the silicon compound.

The amount of the curing catalyst added to the silicon hydrolyzate varies depending on the desired heating temperature and time for curing, but is suitably about 0.1 to 10 parts.

If the amount is less than this, the effect will be insufficient, and if it is more than this, there will be a tendency for the adhesion of the coating film to the substrate to decrease.

Since the present invention is primarily aimed at improving the surface hardness of the plastic surface, heating is usually performed below the heat distortion temperature of the plastic.

A suitable temperature at this time is 50 to 125°C.

In the method of the present invention, in addition to the above-mentioned components, it is convenient to apply the components as a solution dissolved in a solvent.
Examples of this solvent include alcohols such as ethyl alcohol, propyl alcohol, and butyl alcohol, ketones and esters such as methyl ethyl ketone, ethyl acetate, and butyl acetate, cellosolves such as ethyl cellosolve and butyl cellosolve, acetic acid, dioxane, toluene, xylene,
and chlorinated hydrocarbons such as tricrene and ethylene dichloride, or a mixture thereof.

Among them, 20 to 70 parts of lower alcohol and 3 to 70 parts of acetic acid.
A mixed solvent containing 30 parts is preferable because it has a high solution stabilizing effect.

The amount of these solvents to be blended is preferably such that the concentration of the hydrolyzate of the silicon compound is 5 to 30% (wt%).

In addition, small amounts of methylolated melamine, etherified methylolmelamine, polyvinyl butyral, acrylic ester resin, etc. may be added for the purpose of improving the coating suitability of the solution, flexibility of the cured film, or adhesion to the substrate. It is possible.

It is also possible to add dyes, pigments, fillers, etc. for decorative effects.

Further, as a coating method, brush coating, dipping method, spray method, roll coating method, etc. can be applied.

The base material to be coated is mainly plastic molded products such as methacrylic resin, polycarbonate resin,
Molded products of thermoplastic and thermosetting resins such as diethylene glycol bisallyl carbonate resin, diacetate resin, AS resin, ABS resin, vinyl chloride resin, melamine resin, and diallyl phthalate resin, as well as aluminum, glass, and wooden products. It can also be applied to

The present invention will be further explained below with reference to Examples.

Note that parts in the text represent parts by weight.

Example 1 Methyltrimethoxysilane hydrolyzed precondensate (trade name: Glass Resin 650, product of Owens-Illinois)
20 parts of 99.5% ethanol/glacial acetic acid - 80/2
1,8 diazabicyclo (5,
4,0) Undecene-7 and its carbonate, hydrochloride, and for comparison, 2 parts each of lead octenoate, dibutyltin dilaurate, zinc acetate, and sodium thiocyanate, which are known curing catalysts, were added and mixed. This was used as a coating liquid.

Immerse a methacrylic resin plate (product name Delaglass A, Asahi Kasei Corporation product) in this coating solution for about 30 seconds (liquid temperature 20
℃), and then heated at 80°C for 4 hours.

The degree of hardening of the obtained board was examined, and then 3
It is shown in Table 1 in stages.

Rank A: Fully cured, Rank B; Cured to a non-sticky level, Rank C;
Example 2 with stickiness (1) Preparation of n-tetrabutoxysilicate hydrolyzate solution K] 100 parts of 1-tetrabutoxysilicate was dissolved in 70 parts of ethyl alcohol, and the mixture was heated under stirring at O. IN hydrochloric acid aqueous solution 3
0 part was added, and the mixture was further stirred for 1 hour, and then left at 15°C overnight.

This solution contains 18 gr of hydrolyzate of n-tetrabutoxysilicate.

(2) Preparation of methyltrimethoxysilane hydrolyzate 60 parts of ethyl alcohol to 100 parts of methyltrimethoxysilane
After adding 40 parts of 0.01N hydrochloric acid aqueous solution with stirring and continuing stirring for 1 hour, the mixture was left at about 15°C overnight.

This solution is a hydrolyzate of methyltrialkoxysilane 3
Contains 2 gr.

The silicon hydrolyzate in each solution of (11 and (2)) was blended so that it would be as shown in Table 2, 20 parts of glacial acetic acid was further added, and 1,8 diazabicyclo was added as a curing catalyst. 5 parts of (5,4,0) undecene-7 was added and mixed to the silicon hydrolyzate to prepare a coating liquid.

This coating solution was applied to a Delaglass A3mm plate by dipping, pulled up at 60 cm/min, and then heated to 80°C.
It was heated and cured in a hot air dryer for 2 hours.

The surface characteristics of the obtained coated board were evaluated using the following test method.

(b) Appearance: Examine transparency and other defects by visual observation.

(B) Adhesion...Make 100 cuts in the white surface of the substrate that reach from the coating surface to the base material surface, apply cellophane tape, peel it off rapidly, and count the number of cuts that remain (C) Scratch resistance... Rub it with ≠1000 Steel Whirl to see how easily it gets scratched.

Judgments were given in the following ranks.

A: No scratches even with strong friction B: Slight damage with strong friction C; Quite light with strong friction, but no damage with light rubbing D: No damage even with light friction (d) Pencil hardness...JIS - According to D.0202.

Example 3 30 parts of tetraethoxysilane and 70 parts of vinyltriethoxysilane were mixed with 60 parts of ethanol, 25 parts of chloroform, 5 parts of butyl acetate, and 10 parts of glacial acetic acid and mixed with 0.05 parts of glacial acetic acid while stirring.
30 parts of N-hydrochloric acid aqueous solution was added for hydrolysis.

After the reaction was completed, the solution was allowed to stand at 15° C. for 2 days to age.

This solution contains 16% of the hydrolyzate of the silicon compound.

Next, 1,8 diazabicyclo(5,4,0)undecene-7 was added to and mixed with the hydrolyzate of the silicon compound in the proportions shown in Table 3 to prepare a coating liquid, and a methacrylic resin cast plate ( Asahi Kasei Kikuyuki product, Delaglas K) was immersed for about 30 seconds at 40 cm/min.
The coating film was then cured by heating at 100° C. for 1 hour.

The surface characteristics of the obtained plate were evaluated in the same manner as in Example 2, and the results are also shown in Table 3.

Example 4 The coating liquid obtained in Experiment A24 of Example 3 was applied to a methacrylic resin cast plate (Delaglas K), polycarbonate molding method (Teijin Kasei ■ product, Panlite 1225),
ABS resin molded plate (Toray product, Toyorakku), unsaturated polyester cast plate (Takeda Pharmaceutical product, Polymer 82)
35A was reaction-cured in our laboratory) by dipping, and the polycarbonate plates were cured at 120°C for 4 days.
The methacrylic resin cast plate was heated at 100°C for 60 minutes, and the others were heated at 80°C for 2 hours to cure the coating film.

Table 4 shows the evaluation results of the surface characteristics of this product.

Note that the transmittance indicates the total light transmittance at λmax 570 mμ.

Also, the falling sand test is ASTM-D-673.
- 4 80 mesh carbon random was dropped according to 4.

The specular glossiness was shown by the specular reflectance of 45° x 45° before and after the sand drop test.

Table 4 also shows the evaluation results of the base material for comparison.

Claims (1)

[Claims] 1(A) General formula Si(OR)4 (wherein R has 1 to 4 carbon atoms)
hydrolyzate of tetraalkoxy silicon (B) is an alkyl group of A hydrolyzate of a silicon compound (which is an alkyl group or an acyl group) in which the weight ratio of (5) and (B) is 0 to 40 to 100 to 6.
0, and (C) 1,8 diazabicyclo (5,4.
0) A film-forming composition comprising undecene-7 or/and a salt thereof. 2. The film-forming composition according to claim 1, wherein a solvent is present during or after the production of the hydrolyzate.