DE2522241B2 - Coating agents - Google Patents

Description

(a) 10 to 40% by weight based on the total weight of the coating agent of a hydrolysis product of

(1) a hydrocarbon trialkoxysilane r, of the formula R'Si (OR ") ₃ , where R 'is an alkyl group having 1 to 4 carbon atoms, a phenyl or vinyl group and R" is an alkyl group having 1 to 4 carbon atoms, and / or 2 »

(2) Co-condensation products of (1) and I up to 40% by weight of a phenyl- or vinyltrialkoxysilane, wherein the alkoxy group contains 1 to 4 carbon atoms, and / or

(3) Co-condensation products of 1 mole 2> of (1) and 0.05 to 1 mole of tetraalkoxysilane in which the alkoxy group has 1 to 4 carbon atoms contains, and / or

(4) Co-condensation products of 1 mol of (1) and 0.05 to 1 mol of dialkyl-dialkoxysiian, wherein the alkyl and alkoxy groups

Contain 1 to 4 carbon atoms,

(b) 0.05 to 5 parts by weight per 100 parts by weight of the Component (a) of one or more salts, namely alkali metal salts of naphthenic acid r, and / or zinc salts of naphthenic acid, or a mixture of these salts,

(c) 5 to 30% by weight, based on the total weight of the coating agent, acetic acid and

(d) the remainder e <n is an inert organic solvent for components (a) and (b) or a mixture of such solvents.

2. Use of the coating agent according to claim 1 for coating moldings made of 4ί polyacrylates.

50

The invention relates to a coating agent based on a partially hydrolysed siloxane compound which is obtained by hydrolysis of a silane or silane mixtures of water at 50-8O ⁰ C for 1 to 10 hours <, o, in an organic solvent.

In general, plastics are easily damaged and lose their luster because they are not high Surface hardness and no scratch resistance or scratch resistance. These disadvantages are particular serious when the plastics are used to manufacture optical products such as lenses.

In order to improve these poor properties, many methods have been proposed to make the surface to coat the plastic body with organic siloxane compounds and to harden the coating in order to to form a protective layer on the plastic body. However, these known methods do not yield any satisfactory protective layers.

For example, the protective layers or coatings are produced according to the known methods become so brittle that they tend to crack when attempts are made to improve their abrasion resistance. On the other hand, if one tries to improve their resistance to crazing, theirs becomes Inferior abrasion resistance. The known coating solutions also have too short a pot life and cannot be used for long periods of time.

The present invention has for its object to provide a coating agent that is based on the Surface of acrylic resin bodies or objects a protective layer with very good surface hardness, Scratch resistance and solvent resistance and resistance to crazing when exposed to stress owns.

The new object is achieved by a coating agent of the type mentioned at the beginning, which consists of

(a) 10 to 40% by weight, based on the total weight of the coating agent, a hydrolysis product of

(1) a hydrocarbyl trialkoxysilane of the formula R'Si (OR ") 3, where R 'is an alkyl group having 1 to 4 carbon atoms, a phenyl or vinyl group and R "is an alkyl group with 1 to 4 carbon atoms, and / or

(2) co-condensation products of (1) and 1 to 40% by weight of a phenyl- or vinyl-trialkoxysilane, wherein the alkoxy group contains 1 to 4 carbon atoms, and / or

(3) co-condensation products. 1 mole of (1) and 0.05 to 1 mole of tetraalkoxysilane, wherein the alkoxy group contains 1 to 4 carbon atoms, and / or

(4) Co-condensation products of 1 mol of (1) and 0.05 to 1 mol of dialkyl-dialkoxysilane, wherein the alkyl and alkoxy groups contain 1 to 4 carbon atoms,

(b) 0.05 to 5 parts by weight per 100 parts by weight of component (a) of one or more salts, namely alkali metal salts of naphthenic acid and / or zinc salts of naphthenic acid, or a mixture of these salts,

(c) 5 to 30% by weight, based on the total weight of the coating agent. Acetic acid and

(d) the remainder is an inert organic solvent for components (a) and (b) or a mixture such solvent.

The new coating compositions according to the invention have a long pot life. The new cover center can be applied to the surface of acrylic resin article and cured, leaving a coating layer is formed which, as mentioned above, has substantially improved properties.

From GB-PS 12 41 236 coating agents of the type mentioned above are known. These result as can be seen from the following comparative tests (see Table I), but poorer coatings al;

the coating compositions according to the invention.

The coating compositions can be applied directly to the surface of acrylic resin articles according to any conventionally used coating method, and cured at a temperature of about 80 °> to about 100 ⁰ C to the solvent !, contained therein to vaporize and to a condensation reaction to cause.

The hydrocarbon trialkoxysilanes (1) are multifunctional siloxane compounds of the formula in R'Si (OR ") ₃ , where R 'is an alkyl group having 1 to 4 carbon atoms, a phenyl, vinyl group and other functional groups and R" is an alkyl group with ! means up to 4 carbon atoms. Methyltriethoxysilane is preferred. ι>

A partially hydrolyzed product of hydrocarbon trialkoxysilanes is, as described in US-PS 34 51 838, obtained by Water to hydrocarbon trialkoxysilanes and the resulting material at a temperature of 50 heated to 80 ° C for 1 to 10 hours.

In the present invention, the hydrocarbon trialkoxysilane can be used are mixed with 1 to 40% by weight of one or more organic silane compounds, such as with phenyl- or vinyl-trialkoxy (C, - d) -si- 2 '> lanen, and either water or mineral acids such as hydrochloric acid can be added to this mixture add and heat to form the partially hydrolyzed co-condensation product.

A partially hydrolyzed co-condensation product, which essentially contains 1 mole of the hydrocarbon trialkoxysilane as the main component and 0.05 to 1 mole of tetraalkoxy (C 1 -C ₄ ) silane as an additional component, forms a coating with improved hardness. «

A partially hydrolyzed co-condensation product of 1 mole of hydrocarbon trialkoxysilane and 0.05 to 1 mole of dialkyl (C, -C ₄ ) -dialkoxy (C, -C4) -silane forms a soft coating.

When a hydrocarbon trialkoxysilane, in which R 'is a vinyl group, as a component of the Co-condensation product is used, the silane increases the adhesion of the resulting layer to the Acrylic surfaces.

By appropriate selection of the components that are used in the co-condensation product, coatings are obtained which have the desired properties.

The aforementioned partially hydrolyzed products can contain less than about 5% by weight of water, based on the total weight of the hydrolyzed products.

The solids concentration of the partially hydrolyzed co-condensation products determines the coating weight of the protective layer that is formed on the surface v of the acrylic body.

The coating weight in turn determines the physical properties of the layer.

A higher solids concentration results in a higher coating weight of the layer, which has an excellent t> o has a good hardness and excellent scratch resistance, but is so brittle that it easily forms hairline cracks, when you bend it.

On the other hand, a lower solid concentration gives a lighter coating weight of the layer, and b5 the layer is too poor in scratch resistance to be suitable for practical use Result in product.

The suitable coating weight of the composition of the invention depends on the acrylic resin article to which the composition is applied. An amount of 2 to 6 g / m ² in terms of solids applied to the acrylic resin article is most suitable, particularly for acrylic sunglass lenses.

In order to obtain a layer which is present in the aforementioned amount (2 to 6 g / m ² ), it is preferred to immerse the acrylic article in the coating solution and then to remove the article from the coating solution at a speed of 10 to 40 cm / min to form the coating layer on the article. The coating solution has a viscosity of 10 to 30 cP and contains 10 to 40% by weight of the partially hydrolyzed product, calculated as solids.

The properties of the applied layer can vary widely, depending on the nature of the or the Catalysts used in the coating agent.

It has been found that a coating agent is obtained which has a longer pot life than known coating agents if metal salts of naphthenic acid are used as catalysts. It was has also found that such coating compositions of the applied layer have excellent properties give in terms of scratch resistance and crazing resistance under stress, Properties that somewhat compete with each other.

The term "naphthenic acid" as used in the present application and in the claims is used, means the general name for monocarboxylic acids of naphthenic hydrocarbons, which are present in crude mineral oils, the acids being the formula

R '"(CH ₂ ) _n COOH

in which R '"denotes a cyclic nucleus which consists of one or more rings, for example a cyclohexane ring, a cyclopentane ring and their alkylated cyclic nuclei in general, and in which η denotes an integer from 1 to 14.

The carboxylic acid group is connected to the ring nucleus (R '") via methylene (—CH ₂ -)" groups. The simplest and most typical acid, in which η means 1, is cyclopentane acetic acid.

Naphthenic acid is a mixture of non-separable organic acids with 7 to 20 carbon atoms and a cyclic core. The naphthenic acid that is used is accordingly a mixture from compounds of the formula given above.

Acceptable metal salts of naphthenic acid are alkali metal and zinc salts, and in those of the invention Coating agents can be one of these salts or a mixture thereof. Other metal salts do not give a satisfactory catalytic effect with respect to the coating agent. Is preferred Sodium naphthenate is used.

The metal salts of naphthenic acid used according to the invention are used in an amount of 0.05 to 5 Parts by weight per 100 parts by weight of the partially hydrolyzed Hydrocarbon trialkoxysilane product or co-condensation product used. Will If the salts are used in an amount below 0.05 part by weight, they are ineffective and have an effect no satisfactory curing reaction in that

Coating agents.

On the other hand, if the salts are used in an amount exceeding 5 parts, they will escape from the Inside on the surface of the applied layer.

The effect of the catalysts is that the coating agent hardens slowly or gently, a property that the excellent hardness and scratch resistance and also good adhesion and resistance to Hairline cracking of the applied layer results. The catalysts also cause the solution the coating agent is very stable.

The catalysts dissolve very well in the solvents for the partially hydrolyzed products from hydrocarbon alkoxysilanes and their co-condensation products.

According to the invention it is also important that the coating agents contain acetic acid. The acetic acid must be added in an amount of 5 to 30% by weight, based on the total weight of the coating agent. The acetic acid acts as a solvent and also effected that the coating layer adheres firmly to the surface of the acrylic resin article.

The acetic acid is also effective in preserving the pot life of the coating solution for long periods of time and also prevents the applied solution from any tarnish marks shows.

The acetic acid prevents the acrylic resin bodies from forming hairline cracks due to the influence of solvents, which is otherwise easily the case when the acrylic objects come into contact with alcohol.

If the acetic acid is added in an amount above 30%, some of it will remain after the agent was cured under normal conditions; this creates an unpleasant odor. If the On the other hand, acetic acid is used in an amount less than 5%, the resulting layer has one insufficient adhesion.

Glacial acetic acid is preferred, but technical grade acetic acid can also be used.

The other organic solvents used in addition to acetic acid are not critical, and they can be used among known solvents for partially hydrolyzed siloxane compounds and naphthenic acid salts such as alcohols, ketones, ethers and / or aromatic hydrocarbons can be selected. Ethanol is one of these solvents used to produce the coating agent for acrylic bodies and isopropyl alcohol are particularly preferred because of their boiling points and solvency. the The amount of the other organic solvent must be sufficient to remove the partially hydrolyzed compound and to completely dissolve the naphthenic acid salt together with the acetic acid and to reduce the concentration of the partially hydrolyzed compound to 10 to 40% by weight, calculated as solids and based on the Total weight of the coating agent.

In order to coat acrylic resin bodies with the agent in the present invention, any method can be used such as immersion, spray and flow or fluidized bed coating and similar processes use. The acrylic resin bodies coated in this way are then heated to remove the siloxane resin (the partially hydrolyzed compound) to harden. This hardening can be carried out at a temperature which is much lower than the temperature normally used.

Since the curing temperature is higher, the shorter the curing time, it is preferable to cure the coated layer at a temperature which is as high as possible but lower than the heat distortion temperature of the acrylic resin. Generally, it is> preferable at 80 to 100 ⁰ C for 2 to 40 hours to ^r th eh.

The following examples and comparative examples illustrate the invention.

^{1 (1} example 1 to 4

Water becomes a solution of methyltriethoxysilane given in ethanol. The mixture is heated at 75 ° C for 3 hours and then further heated at 145 ° C,

r to distill off the azeotropic mixture of alcohol and water, one being partially hydrolyzed Obtains condensate solution containing about 50 wt .-% partially hydrolyzed siloxane compound and those in the following Table I as component (a)

2 (i is designated. The solution is then made with n-butanol diluted.

Sodium naphthenate, identified as component (b) in Table I, is in a portion of the glacial acetic acid solved, which is referred to as component (c), the total pre-calculated amount in Table I is specified. The solution of components (b) and (c) then partially becomes that previously described given hydrolyzed condensate / n-butanol solution.

The resulting solution is adjusted by adding n-butanol, as required, so that it contains the three components (a), (b) and (c) in the amounts given in Table I. Coating solutions are obtained.

Injection molded optical lenses made from

j-, methyl methacrylate resin will work well with a degreaser and then rinsed with cleaning fluids and then immersed in the above-described coating solutions and at one speed taken from 30 cm / min. The coated lenses are then placed and placed in an oven at 95 ° C left for 16 hours to allow the coating to harden,

The coated lenses obtained in this way are examined, and the adhesion, the pencil hardness

A ^r , te, the scratch resistance (the abrasion with steel wool) and the resistance to hairline cracking under stress. In addition, the pot life of the coating solutions is determined using an accelerated pot life test. The receive-

The results are shown in the table.

The physical properties of the coated lenses as shown in Table I became as will definitely follow.

"1. Adhesion

The layer applied to each of the lenses is cross-hatched with a sharp blade with ten horizontal and ten vertical lines with wi spaces of 1 mm between the lines.

A cellophane tape is then stuck firmly over the cross-hatched lines of the lens and peeled off sharply at a 90 ° angle to the applied layer. This procedure is three times <, 5 repeated. The adhesion thus obtained is in five Classes from A (no delamination) to E (complete delamination), depending on the Extent to which the layer has been peeled off.

2. Pencil hardness

A pencil hardness device, a so-called pencil hardness tester, with which the hardness of paints, varnishes and similar materials is determined, is used to determine the hardness of the applied layer. A pencil core that rests on the applied surface of a lens sample at an angle of 45 ° to the Surface was held forward approximately 3 mm at a load of 1.0 ± 0.05 kg and one meter Pulled speed of 0.5 mm / sec. The test results are as the minimum hardness of the pencil core indicated that damaged the applied layer under these conditions.

ι ι

3. Scratch resistance (steel wool abrasion test)

The coated surface of the lenses was rubbed with a steel wool pad. The results were rated according to the following three categories, depending on the extent to which the Surface was scratched:

A = no scratches even if the surface is strong

rubbed with the steel wool pad; 2 ">

B = slightly scratched when the surface was rubbed with the steel wool;

C = slightly scratched if the surface was rubbed moderately with the steel wool.

4. Resistance to crazing
when used

Lens samples with a diameter of 80 mm were placed between the clamp and the compression cell under the load of an INSTRON testing device given. The samples were continuously compressed at a rate of 20 mm / min until their surface showed crazing; at this point the voltage applied was and Recorded stress. The resistance to crazing under stress was rated as follows:

excellent (A) = no crazing even if the permanent set exceeds 12.5%;

good (B) = no hairline cracking when the permanent set is 5 to 12.5%;
bad (C) = hairline cracking if the permanent deformation is below 5%.

5. Pot life

A coating agent is added in a test tube which is then sealed and left standing in a hot water bath at 5O ⁰ C. The coating agent in the test tube is observed at intervals, and the turbidity, whitening, consistency, gel formation and the like are evaluated. In Table I, the pot life is reported as the number of hours during which the composition does not gel.

Comparative Examples 1 to 6

Coating agents are prepared as described above, but the amounts of components (b) and (c] are adjusted as described in Table I. Be: Comparative Example 6, sodium acetate is used instead of the Component (b) used. These comparative coating agents are applied to the surface of lenses as in FIG Examples 1 to 4 applied above, cured in the same manner, and the same properties become certainly. The test results are shown in Table I.

Tabel

Example and Coating agents Comparative example Component (a) [oil conc. example 1 15th 2 30th 3 35 4th 35 Comparative example 1*) 30th 2 30th 3 ·) 30th 4th 30th 5 30th 6th 30th Remarks:

Comp. (B) Comp. (C) sodium acetate

[Part by weight per ΓΚοηζ. (%) [Parts by weight, ^b ez.

Parts related to d. whole to 100 parts

Comp. (A)] mass] of comp. (A)]

2.5
0.2
1.4
5.0

1.7
2.5

15th
21
21
21

18th

35

18th

Component la) = partially hydrolysed Mcthyltriiilhoxysilankondcnsatlüsuni ;. Component (b) = sodium naphthalenes. Component (c) = acetic acid c.

"1 (icnwhc nc muH (ilil'S 1241 2Jb.

Test results pencil 25th 22 241 10 adhesion hardness 9 Pot life remarks Table I (continued) Scratch resistance (accelerated Example and 5H persist opposite to Attempt) Comparison A. 6H age Hairline cracking
ί \ Λ ι IJ η ο η example A. 7H Del DCdIl "
verdict A. 7H - A. A. A. 72 example A. A. 12th 1 2 B A. A. 2 E. 2 B A. A. 3 D. H 4th B. 4H-5H - Comparison C. 5H-6H C. C. - example A. 7H B. B. 1*) A. C. C. - a little vinegar- 2 B. B. - like smell 3 ·) A. A. 48 4th A. A. 5 *) Mixtures according to GB-PS 12 41 236. 6th

Claims (1)

Patent claims: 1. Coating compositions based on a partially hydrolysed siloxane compound represented by hydro - silane obtained from silane mixtures and in water at 50 to 80 ⁰ C for 1 to 10 hours, analysis of a, in an organic solvent, characterized in that it consists of in