DE2522241C3 - Coating agents - Google Patents

Description

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

(1) a hydrocarbon trialkoxysilane π of the formula R'Si (OR ") j, in which R 'is an alkyl group having 1 to 4 carbon atoms, is a phenyl or vinyl group and R "is an alkyl group having 1 to 4 carbon atoms mean, and / or

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

(3) Co-condensation products of 1 mol η of (1) and 0.05 to 1 mol 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-dialkoxy-so silane, 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 is an inert organic solvent in for components (a) and (b) or a mixture of such solvents.

2. Use of the coating agent according to claim I for coating moldings made of -n Polyacrylates.

The invention relates to a coating agent based on a partially hydrolysed siloxane compound which has been _b by hydrolysis of a silane or silane mixtures of water at 50-80 ° C for I to 10 hours o obtained 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 of the scratch b "> have persistence. These disadvantages are particularly serious when using the plastics to manufacture them used by 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 Abrasion resistant wedge worse. 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, "iss has on the surface of acrylic resin bodies or -gegenständen a protective layer having excellent surface hardness, scratch resistance and solvent resistance and resistance to crazing under stress.

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 hydrocarbon trialkoxysilane of the formula R ¹ Si (OR ")), in which 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) co-condensation products of (1) and I up 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 of 1 mole of (I) 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 mole of (I) and 0.05 to 1 mole of dialkyl-dialkoxysilane, in which the alkyl and alkoxy groups contain I 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 and / or zinc salts of naphtha, 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 of such solvents.

The new coating compositions according to the invention have a long pot life. The new coating agents can be applied to the surface of acrylic resin articles and cured to form a coating layer which, as previously mentioned, is essential has improved properties.

From GB-PS 12 41 236 coating agents are the known at the outset. These result, as from the following comparative tests (compare Table I) shows, but poorer coatings than

the coating agents 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 cause a condensation reaction.

The hydrocarbon trialkoxysilanes (I) are multifunctional Siloxane compounds of the formula R'Si (OR ") j, in which R 'is an alkyl group with 1 to 4 Denotes carbon atoms, a phenyl, vinyl group and other functional groups and R "denotes a Alkyl group having 1 to 4 carbon atoms means methyltriethoxysilane is preferred.

A partially hydrolyzed product of Kohlenwasserstofftrialkoxysilanen is, as described in US-PS 34 51 838, obtained by adding water is heated to Kohlenwasserstofftrialkoxysilanen and the resulting material at a temperature of 50 to 80 ⁰ C during 1 to 10 hours .

In the present invention, the hydrocarbon trialkoxysilane can be used mixed with 1 to 40% by weight of one or more organic silane compounds are like with phenyl- or vinyl-trialkoxy (Ci-Ct) -silanes, and either water or mineral acids such as hydrochloric acid can be added to this mixture add and heat, whereby the isil hydrolyzed wisely Co-condensation product is formed.

A partially hydrolyzed co-condensation product containing essentially 1 mole of the hydrocarbon trialkoxysilane as the main component and 0.05 to 1 mol of tetraalkoxy ^ Ci — Ct) silane as an additional component contains, forms a JJberzus: with improved Hardness.

A partially hydrolyzed Co-Kc -ndensalionic product of 1 mole of hydrocarbon trialkoxysilane and 0.05 to 1 mole of dialkyl (C, -C,) -dialkoxy (C, -C ₄ ) -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-combination product, coatings are obtained which have the desired properties.

The aforementioned partially hydrolyze products may contain less than about 5% by weight of water based on the total weight of the hydrolyzed Products included.

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

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

A higher solids concentration gives a higher coating weight of the layer, which is excellent Has 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 solids concentration results in a lighter coating weight of the layer,, and the layer is too poor in scratch resistance to be suitable for practical use Result in product.

The suitable coating weight of the agent according to the invention depends on the aeryl resin article to which the agent is applied. An amount of 2 to 6 g / m- ¹ in terms of solids applied to the ί acrylic resin article is most suitable for acrylic sunglass lenses in particular.

In order to obtain a layer present in the aforementioned amount (2 to 6 g / m ² ), it is preferred to put the acrylic article in the coating solution

immerse in and then remove the item from the coating solution at a rate of 10 to 40 cm / min to remove the coating layer on the article. The coating solution possesses has a viscosity of 10 to 3OcP and contains 10 to 40 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

be in.

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

> -i also found that such coating agents the applied layer give excellent properties in terms of scratch resistance and the resistance to crazing 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.die are present in crude mineral oils, with

r> the acids the formula

R "'(CH _,)" COOH

in which R '"denotes a cyclic nucleus consisting of one or more rings, for example a cyclohexane ring, a cyclopenian 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>-)" groups. The simplest and most typical acid, in which η means I, is cyclopentane acetic acid.

Naphthenic acid is a mixture of inseparable

"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

"η alkali metal and zinc salts, and in those according to 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

Used with sodium naphthenate.

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

he, 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 in an amount of over 5 parts are used, they escape from the inside onto the surface of the applied layer.

The effect of the catalysts is that the coating agent hardens slowly or mildly, 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 to come out the coating material 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 will. The acetic acid acts as a solvent and also causes the coating layer to adhere to the The surface of the acrylic resin article is adhered.

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 otherwise easily happens 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 To manufacture de-; Of these solvents, coating agents for acrylic bodies are ethanol 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 Naphlhensäuresalz 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 use acrylic resin bodies according to the invention To coat agents, you can use any method such as immersion, spray and flow or Use fluidized bed coating and similar processes. The acrylic resin bodies coated in this way are then heated to remove the siloxane resin (the partially hydrolyzed compound) to harden. This lliirtcn can be done at a temperature that is much lower than the temperature at which it is used commonly used.

Since the air temperature is higher. the shorter the curing time, it is preferable to cure the coated layer at a temperature as high as possible but lower than the thermal deformation temperature of the acrylic resin. In general, it is preferred ^{to cure at 80 to 100 °} C. for 2 to 40 hours.

The following examples and comparative examples illustrate the invention.

B e i s ρ i e I e 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, to distill off the azeotropic mixture of alcohol and water, one of which is partially hydrolyzed Obtains condensate solution which contains about 50 wt .-% partially hydrolyzed siloxane compound and which is referred to in the following Table I as component (a). The solution is then made with n-Buianol diluted.

Sodium naphthenate, which is in 1 ar? T! Le! as a component (b) is dissolved in a part of the glacial acetic acid, which is called component (c), whose total pre-calculated amount is given in Table I. The solution of components (b) and (c) is then added to the previously described partially 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 methyl methacrylate resin optical lenses are rinsed well with a degreaser and then with cleaning fluids, and then immersed in the above-described coating solutions and removed at a rate of 30 cm / min. The coated lenses are then placed in an oven at 95 ^° C. and left therein for 16 hours so that the coating layer can cure.

The coated lenses obtained in this way are examined, and the adhesion, the pencil hardness, the scratch resistance (the abrasion with steel wool) and the resistance to hairline cracking Determined stress. In addition, the pot life of the coating solutions is determined, for which purpose one used accelerated Topfzcit test. The crhaltcncn 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 made with a sharp blade cross-hatched with ten horizontal and ten vertical lines with Spaces of I mn <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 repeated three times

, repeated. The adhesion obtained in this way is in five Classes coiled from A (no delamination) to E (complete iintlaminicrung), depending on the Extent to which the layer has been peeled off.

2. Lead lift aria

A pencil hardness device, a so-called pencil hardness tester, which is used to determine the hardness of carbs, varnishes and similar materials, is used, to determine the hardness of the applied layer. A pencil core that rests on the applied surface of a lens sample held at a 45 ° angle to the surface became approximately 3 mm pulled forward at a load of 1.0 ± 0.05 kg and a speed of 0.5 mm / sec. The test results are given as the minimum hardness of the pencil core, which the applied layer at damaged these conditions.

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 was rubbed hard with the steel wool pad;

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

C = slightly scratched if the surface is moderately using the steel wool has been rubbed.

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 ι '> Deformation is less than 5%.

5. Pot life

A coating agent is placed in a test tube, which is then sealed, and in a hot one

2i) water bath at 50 ⁰ C left to stand. 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 as that

2Ί number of hours indicated during which the mean shows no gel formation.

Comparative Examples 1 to 6

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

Table I.

Example and upper pulling means

Comparative example! Component (a)

[Solids conc.

N]

Comp. (B) [parts by weight per 100 parts Comp. (A)]

Comp. (C) sodium acetate

[Conc. (%). [Parts by weight, rel.

related to d. whole to 100 parts
Mass] of comp. (A)]

example 1

2 3 4th

15th 30th 35 35

2.5 0.2 1.4 5.0

15th 21 21 21

Comparative example

1*) 2

3 *) 4th 5 6th

Remarks:

component
component
component

30th 30th 30th 30th 30th 30th

1.7 1.7

18th

35

18th

1.7

= partially hydrolyzed methyltriethoxysilane condensate solution. = NatriuranaphthenaL
= Acetic acid.

*) Mixtures according to GB-PS 12 41 236.

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) Comparative A. 6H age Hairline cracking for example A. 7 H. verdict Λ 7H - A. A. A. 72 example A. A. 72 I. 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. Λ 5 6th

*) Mixtures according to GBPS I24I 236.

Claims (1)

Patent claims: I. Coating agent based on a partially hydrolyzed siloxane compound, which has been obtained by hydrolysis of a silane or of silane mixtures in water at 50 to 80 ⁰ C for 1 to 10 hours, in an organic solvent, characterized in that that it exists III