DE2131740C3 - Coating agents based on organopolysiloxanes that repel sticky substances - Google Patents

Description

CH, 0 - R.
I. O H - -si I.
Si ch, ch,

CH,

-Si-H

CH,

35

40

where R 'is hydrogen or the methyl radical, with the proviso that so many R' are hydrogen that the average ratio of the Si-bonded hydrogen atoms R 'to the Si atoms in the R'Si (CHi) O units is 0, 25 to 0.5, and m is an integer from 20 to 100. 4. Coating agent according to claim 1 to 3, characterized in that they contain as curing catalysts (3) reaction products of platinum (IV) chloro acid with cyclohexanone.

55

It is known that surfaces of paper or other solid materials can be coated with organopolysiloxane can to prevent sticky substances from sticking firmly to these surfaces (see for example W. Noil, "Chemistry and Technology of Silicones", Weinheirn 1968, pp. 520/521).

Compared to other previously known means for producing organopolysiloxane coatings that repel tacky substances the agents according to the invention have the particular advantages that they gel considerably less rapidly, d. H. a very long pot life have, and nevertheless at the hardening temperatures used in practice a very high one Have curing speed. The long pot life means that there are losses due to premature gelling the coating solution avoided; due to the very high curing speed, a better one Utilization of the coating machines achieved Furthermore, the coatings adhere to the documents particularly strong, and these coatings are very resistant to rubbing.

It is particularly surprising that compositions of the invention, the property of having a particularly long pot life, much to cure that combine rapidly with the property, at temperatures above 8O ⁰ C, even if they do not, the pot life extending agent as Tetramethylguanidincarboxylat, perchlorethylene or silazanes because platinum catalysts are used according to the invention and the previously known platinum catalysts are usually also effective at room temperature (see, for example, US Pat. No. 33 83 356).

The invention relates to coating compositions which repel sticky substances and consist of

(1) diorganopolysiloxanes containing Si-bonded vinyl groups in the terminal units,

(2) Organopolysiloxanes containing at least 3 Si-bonded hydrogen atoms per molecule and

(3) platinum complexes as curing catalysts, and optionally

(4) organic solvents

characterized in that they are organopolysiloxanes (2) containing Si-bonded hydrogen with at least one terminal Si-bonded hydrogen atom and as curing catalysts (3) Contains reaction products of platinum (IV) chloric acid with ketones.

The diorganopolysiloxanes (1) containing Si-bonded vinyl groups in the terminal units can through the general formula

(CH2 = CHMSiRyOi-

CH2),

be reproduced.

In this formula, R denotes a monovalent, optionally substituted hydrocarbon radical, χ is on average 0.9 to 1.1, preferably 0.99 to 1.01, y on average 1.9 to 2.1, preferably 1.99 to 2.01 , the sum of χ + y is 3 and π is an integer with a value of at least 100. As indicated, for example, by the average value of 1.9 to 2.1 for y , in addition to diorganosiloxane units, in the diorganopolysiloxanes (1) Siloxane units with a different degree of substitution, such as units of the formula RS1O3 / 2, may be present in small amounts.

Examples of hydrocarbon radicals in the diorganopolysiloxanes (1) and thus also for the hydrocarbon radicals R in the above formulas are alkyl radicals such as methyl, ethyl, isopropyl and octadecyl radicals; Alkenyl radicals, such as the vinyl radical and decenyl radicals; cycloaliphatic hydrocarbon radicals such as the Cyclohexyl radical, and aryl radicals, such as the phenyl radical. As an example of a substituted hydrocarbon radical the 3,3,3-trifluoropropyl radical should be mentioned. To as possible To obtain flexible coatings, however, are preferably not bonded to terminal Si atoms Hydrocarbon radicals in the diorganopolysiloxanes (1) free of aliphatic multiple bonds, in particular no vinyl groups. At least 50 percent is preferred because of easier accessibility the number of hydrocarbon residues in the

Diorganopoiysiloxanes (1) methyl groups. Besides the vinyl groups in the diorganopoiysiloxanes (1) Existing hydrocarbon radicals know to be the same or different, regardless of whether they are the same or different silicon atoms are bonded.

The diorganopolysiloxanes (1) can be identical copolymers or mixtures of different ones Copolymers each with the same degree of polymerization or mixtures of the same or act different copolymers with different degrees of polymerization. With the copolymers it can be those with a statistical distribution of the various units or around Act block copolymers.

If a particularly high degree of repellency of sticky substances, combined with high economic efficiency, for example in the production of packaging for foodstuffs, everyone should Hydrocarbon radicals that are present in the diorganopoiysiloxanes (1) apart from the terminal vinyl groups, Be methyl groups. However, if a lesser degree of sticky repellency, e.g. B. for the production of documents for self-adhesive labels, if desired, this is best done thereby achieved that 3 to 30 mole percent, preferably 5 to 20 mole percent, of the non-terminal units in the Diorganopoiysiloxanes (1) are diphenylsiloxane while at least 50 percent of the number of units Hydrocarbon radicals in the other non-terminal units of the diorganopolysiloxanes (1) methyl groups are. The higher the proportion of diphenylsiloxane units, the lower the extent of the Rejection of sticky substances.

If a particularly high curing speed, combined with good properties of the coating, if desired, it is expedient to have Si-bonded vinyl groups in the terminal units Diorganopolysiloxanes (1) mixtures of

(A) diorganopolysiloxanes containing Si-bonded vinyl groups in the terminal units with a viscosity of 3000 to 50,000 cSt, preferably 5000 to 10,000 cSt, each measured at 25 ° C, and

(b) diorganopolysiloxanes containing Si-bonded vinyl groups in the terminal units with a viscosity of 50,000 to 1,000,000 cSt, preferably 100,000 to 200,000 cSt, each measured at 25 ° C,

with the proviso that, at the same temperature, the viscosity of the polysiloxane (b) is at least 50,000 oCSt higher than the viscosity of the polysiloxane (a) selected in each case. The low viscosity of the polysiloxane (a) contributes to the high curing rate, while the high viscosity of the polysiloxane (b) contributes to the good physical properties of the tacky-repellent coating. The polysiloxanes (a) mostly correspond to organopolysiloxanes of the formula given above, in which π is 100 to 500, while the polysiloxanes (b) mostly correspond to organopolysiloxanes of the formula given above, η is 1500 to 3000. The polysiloxanes (a) are preferably used in amounts of 25 to 75 percent by weight, in particular 50 or about 50 percent by weight, based in each case on the total weight of the organopolysiloxanes (a) and (b).

In particular because of the easier accessibility there are at least 3 Si-bonded hydrogen atoms in the The organopolysiloxanes containing the molecule

(2) the terminal Si-bonded hydrogen atoms in units of the formula

HSi (CH3) 2O) / 2

before. For example, copolymers of trimethylsiloxane, dimethylhydrogensiloxane and methylhydrogensiloxane units, Mixed polymers of dimethylhydrogensiloxane, trimethylsiloxane and phenylhydrogensiloxane, Dimethylsiloxane and / or phenylmethylsiloxane units be used. Because of the easier accessibility and high effectiveness are as organopolysiloxanes (2) those of the general formula

CH ₃

H-Si-O-Si-O

CH ₁

R '

CH.,

CH ₃
Si-H

CH,

preferably where R 'is hydrogen or the methyl radical with the proviso that so many R' are hydrogen that the average ratio of the Si-bonded hydrogen atoms R 'to the Si atoms in the R'Si (CH3) O units is 0, 25 to 0.5 and m is one

is an integer from 10 to 500, preferably from 20 to 100

The proportion of Si-bonded hydrogen in the organopolysiloxanes (2) is preferably from 0.4 to 1.4 percent by weight, in particular 0.4 to 0.5 percent by weight

The organopolysiloxanes (2) preferably have a viscosity of 30 to 70 cP at 25 ° C. Production of organopolysiloxanes (2), including those of the preferred type, is known. For example, you can by mixed hydrolysis of dimethylchlorosilane, methyldichlo ^ silane and dimethyldichlorosilane or by Equilibration of hydrolysates of the silanes mentioned take place by means of an acidic catalyst.

The organopolysiloxanes (2) are preferably used in amounts of 1 to 20 percent by weight, in particular 10 up to 15 percent by weight, each based on the weight of the Si-bonded units in the terminal units Vinyl group-containing diorganopolysiloxanes are used.

For the preparation of the reaction products of platinum (IV) chloroic acid used according to the invention

(H2PtClb 6 H2O)

with ketones (3) are preferably monoketones, since they are more easily accessible, than ketones, and indeed expedient those which are free from aliphatic multiple bonds are used. Examples of in manufacturing the curing catalysts (3) used in the coating composition according to the invention are preferred usable ketones are thus

Cyclohexanone, methyl ethyl ketone, acetone,
Methyl n-propyl ketone, methyl iso-butyl ketone,
Methyl-n-amyl ketone, diethyl ketone,
Ethyl n-butyl ketone, ethyl iso-amyl ketone,
Diisobutyl ketone and acetophenone.

If desired, however, ketones with more than one ketone group, such as acetylacetone, and / or aliphatic Multiple bonds, such as mesityl oxide, can be used. Appropriately, the ketones do not contain more than 15 carbon atoms so that they are liquid at room temperature and when the coatings cure evaporate sufficiently quickly from the agents according to the invention. Particularly good results are achieved with

Cyclohexanone obtained a The reaction products are appropriate because this involves the least effort requires, used in the form of solutions in which the solvent to at least 20 times the amount of the amount of platinum chloro acid used in each case consists of the same ketone that was used to prepare the reaction products, "ind e.g. with a content of 0.05 to 0.5 weight percent Pt and stored hot

The reaction products are conveniently prepared in that P! Atin (IV) -chlorosäure is dissolved in the respective selected ketone and the resulting solution for 5 minutes to 15 hours, preferably 0.5 hours to 5 hours at 60 to 12O ⁰ C at the pressure the surrounding atmosphere, i.e. at 760 mm Hg (abs.) or about 760 mm Hg (abs.), before this solution is brought into contact with the diorganopolysiloxanes (1) and / or the organopolysiloxanes (2). If desired, subatmospheric or superatmospheric pressure can be used during the heating for the catalyst preparation, but this is not preferred because of the greater effort 25 ° C) for at least 3 hours, expediently at least 21 days, preferably with exclusion of light, if the standing time is more than 24 hours. There is no upper limit to the duration of this standing. This limit is only determined by economic considerations.

The proof that sufficient reaction products have formed can be most easily carried out by adding about 0.2 mg of Pt in the form of z. B. a solution containing 0.05 to 0.5 percent by weight Pt, prepared by dissolving platinum (IV) chloroic acid in the ketone, mixed after heating and cooling to room temperature or standing at room temperature with a mixture of 0.05 mol of trichlorosilane and 0.05 mol of alkyl chloride and it is determined whether there is a noticeable rise in temperature, e.g. of at least 2 ° C, within about a minute. he follows. Such a proof can also be done by other methods, ι. B. Observation of the change in the infrared spectrum or determination of released water.

It is advisable to use the solutions of the reaction products of platinum (IV) chloroic acid with ketones to remove the water released during the implementation or by the heating, e.g. B. by means of desiccants, such as anhydrous sodium sulfate, or already during the heating z. B. by means of one under the Reflux condenser attached water trap before these solutions with the diorganopolysiloxanes (1) and / or the organopolysiloxanes (2) are brought into contact.

The platinum catalysts are expediently used in amounts of from 0.001 to 0.1 percent by weight, preferably 0.01 to 0.05 percent by weight, each calculated as elemental platinum and based on the weight of the Organopolysiloxanes containing vinyl groups are used.

In addition to the ketone, that with the catalyst used in the agents according to the invention is introduced into the mixture of diorganopolysiloxane (1) and organopolysiloxane (2), further organic solvents can also be used.

These further solvents should as far as possible be anhydrous and inert to those contained therein to be loosened connections. Furthermore, these organic solvents should be kept at 70 to 180 ° C and

Rapidly evaporate 760 mm Hg (abs.). Examples of suitable solvents are or can be hydrocarbons, such as gasoline, e.g. alkane mixtures with a boiling range of 80 to 110 ° C 760 mm Hg (abs.). Benzene, toluene and xylenes; Ether,

ίο e.g. di-n-butyl ether; Esters, e.g., ethyl acetate, and further amounts of ketone and / or other ketones than used for the preparation of the catalyst solution became. Solvents are the predominant constituents because of their easier accessibility Hydrocarbons, especially gasolines, preferably those in addition to the ketone that is in with the catalyst the mixture of diorganopolysiloxane (1) and organopolysiloxane (2) is also used Solvents are expediently in amounts of 200

up to 5000 percent by weight based on the weight of the Si-bonded vinyl groups in the terminal units having diorganopolysiloxanes (1) are used. For the preparation of the coating compositions according to the invention the diorganopolysiloxanes having Si-bonded vinyl groups in the terminal units (1), the at least 3 Si-bonded hydrogen atoms organopolysiloxanes having at least one terminal Si-bonded hydrogen atom per molecule (2), reaction products of platinum (IV) chloroic acid with ketone (3) and the, if applicable used solvents mixed with one another in any order. Advantageously can the resulting ready-to-use solutions for the production of the sticky-repellent coatings stored at room temperature for at least 7 days or in the storage containers of the devices for the Production of the coatings are stored without gelation of the solutions or the The curing speed of the coatings at higher temperatures is impaired.

If the surfaces to be made repellent are not or only slightly absorbent, the diorganopolysiloxanes (1) and the organopolysiloxanes (2) are expediently used in amounts of 0.1 to 0.5 g per m ^{2 of} surface to be made repellent . If the anti-adhesive absorbent to be made surfaces, the vinyl groups and Si-bonded hydrogen are organopolysiloxanes containing zweckmäß'g in amounts of 1 g to 3 m ^J tacky substances used for solubilizing repellent surface. The additional expenditure on organosilicon compounds and thus also on platinum catalyst for absorbent surfaces can be avoided if these surfaces are coated with pore-closing substances, e.g. B.

a solution of polyvinyl alcohol in water or of polyvinyl acetate in an organic solvent, be pretreated.

The application of the coating compositions according to the invention on the sticky substances to be made repellent surfaces can be used in any for the manufacture of Coatings made of liquid substances in a known manner, for. B. by dipping, painting, pouring, Spraying, rolling, printing, knife or squeegee coating, including those with a Meyer rod (Meyer-Rod).

In order to remove the solvents quickly and to accelerate the hardening of the coatings, it is necessary to apply

at least 8O ⁰ C are heated. To avoid damaging the sticky materials to avoid repellent documents to be made, such as paper, and / or the top features in this heating, the temperature should not exceed 200 ⁰ C. Heating to 140 to 160 ° C is particularly advantageous.

With the coating compositions according to the invention, sticky substances can repellant coatings on any solid surface, eg. B. on paper, cardboard, wood, cork, plastic films, cotton fabrics, metals, glass and ceramic objects. The agents according to the invention are therefore suitable, for example, for the production of separating, cover and follower papers, cardboards, foils and cloths, for finishing the backs of self-adhesive tapes and self-adhesive foils or the inscribed sides of self-adhesive labels, and for finishing of packaging material such as paper, cardboard boxes, metal foils and barrels, e.g. B. made of cardboard, plastic, wood, iron and other solid materials that are used for the storage and / or transport of sticky foods such as honey, cakes and other confectionery, e.g. B. candies, also meat or adhesives, including the so-called "transfer process", or other sticky substances, such as self-adhesive labels. Raw rubber, asphalt or bitumen.

In the following examples, all parts and percentages relate to the Weight, unless otherwise stated.

The catalyst solution used in the following examples was prepared as follows: To 200 g of cyclohexanone which are heated to 8O ⁰ C, within 30 minutes, 1 g of platinum (IV) -chlorosäure is given. The solution obtained in this way is then heated to 80 ° C for 45 minutes and finally dried using anhydrous sodium sulfate,

example 1

a) 2.5 parts of a vinyldimethylsiloxy having as terminal units dimethylpolysiloxane with a viscosity of 700OcSt at 25 ⁰ C are first with 2.5 parts of a vinyldimethylsiloxy groups as terminal units and having a dimethylpolysiloxane having a viscosity of 150 00OcSt at 25 ° C and then with 0 , 4 parts of the catalyst solution, the preparation of which was described above, mixed

The mixture thus obtained is first dissolved in 10 parts of toluene and diluted with 84 parts of an alkane mixture having a boiling range of 80 to 110 ⁰ C at 760 mm Hg (abs.) The diluted solution is mixed with 0.7 parts of a copolymer of Dimethyihydrogensiloxan-, Methylhydrogensiloxane and dimethylsiloxane units with a Si-bonded hydrogen content of 0.45% and a viscosity of 40 cSt at 25 ° C mixed.

b) In a continuously operated system, a glassine paper web is coated with this solution shortly after its production by means of rollers. The paper takes up about 0.5 g of organosulfur compounds per m ² . After coating, the paper is passed through a drying tunnel. The air in the drying tunnel has a temperature of 150 ° C. Part of the paper web is transported at a speed of 6s 120 m / minute, another part of the paper web at a speed of 150 m / minute and a third part of the paper web is guided through the drying tunnel at a speed of 180 m / minute, corresponding to dwell times of 8.6 or 5.4 seconds. At all these speeds, the coating is completely cured when it leaves the drying tunnel, adheres firmly to the base and is very resistant to rubbing.

When using the coated glassine paper as described above to cover self-adhesive films, it has excellent release properties, without even after prolonged storage to impair the adhesive strength of the self-adhesive films.

Example 2

To illustrate the long pot life of the agents according to the invention, those in Example 1 measures described repeated with the modification that the finished solution 8 days at room temperature was stored before the glassine paper web was coated with it. It turned out to be the same good ones Get results.

Example 3

In a continuously operated system, a Glassine paper web with the solution, the preparation of which was described in Example 1 under a), with a Coated squeegee, with a rod wrapped with 0.2 mm thick stainless steel wire as the squeegee stainless steel is used, and passed through the drying tunnel with a dwell time of 5 seconds. The air in the drying tunnel has a temperature of 150 ° C.

Samples of the paper web coated in this way are tested for the degree of repellency of sticky substances, i.e. the so-called "release force level": 2 strips of self-adhesive tape 3 cm wide are placed on the cover and pressed on with a rubber roller with a force of 15 kg / cm. Then one tape is peeled off immediately at a speed of 30 cm / minute, the other tape only after aging by 20 hours of heating at 70 ° C under a load of 20 g / cm ² at the same speed and the force measured is required to peel off the adhesive tape. Before and after aging, the release force level is 0 to 6 g / cm. The adhesive strength of the adhesive tape is unchanged after it has been peeled off.

Comparative tests 1

1. a) 2.5 parts of a vinyldimethylsiloxy groups as terminal units and having a dimethylpolysiloxane having a viscosity of 700 cSt at 25 ⁰ C are first mixed with 25 parts of a vinyldimethylsiloxy groups as terminal units and having dimethylpolysiloxane with a viscosity of 15000OcSt at 25 ° C and the resulting , a mixture having an average viscosity of 45,000 cP at 25 ° C as a significant change compared to Example 1 with 1 part of a 05% Pt-containing solution of a reaction product of chloroplatinic acid and alcohol according to German Auslegeschrift 12 57 752 mixed. This catalyst solution was prepared as follows: 5,4 platinum (IV) -CH orosäure in 100 g of n-octanol was heated to 6O ⁰ C Ii hours at 20 mm Hg (abs.). The excess n-octanol is then distilled off at 20 mm Hg (absolute). The residue is taken up in 393 g of benzo.

The mixture of organopolysiloxanes and catalyst solution is first dissolved in 10 parts of toluene

609 653166

then diluted with 72 parts of an alkane mixture with a boiling range from 80 ⁰ C to HO ⁰ C at 760 mm Hg (abs.). The dilute solution is mixed with 0.7 parts of the copolymer described in Example 1, which contains Si-bonded hydrogen.

b) Glassine paper is coated with the solution obtained in this way by means of a doctor blade, a with a doctor blade 0.2mm thick stainless steel wire wrapped stainless steel rod is used. Adheres after hardening The coating, like the coatings according to Example 1, is firmly attached to the substrate and is very resistant to rubbing; Furthermore, in the test of the release force level described in Example 3, as in Example 3, the Value 0 to 6 g / cm obtained before and after aging. However, curing in the drying cabinet requires im In contrast to the 5 seconds of Example 3, 15 seconds.

II. The procedures described under I. are repeated with the modification that the finished coating solution prepared according to a) is left to stand for 8 hours before application to the paper. The coating is then not completely cured even after 120 seconds at 15O ⁰ C, and the adhesive force applied thereto by the self-adhesive tape is impaired.

Comparative tests 2

I. The working methods described in comparative experiment 1 under I. are repeated with the modification, that instead of the catalyst solution used there, 3 parts of a 0.4% Pt-containing solution of one Reaction product of platinum tetrachloride and cyclohexene (cf. US Pat. No. 3,178,464 or M. S. Kharasch et.al., "Journal of the American Chemical Society", Volume 58, 1936, pp. 1733 ff.) Is used in benzene will. After curing, the coating, like the coatings according to Example 1, adheres firmly to the Underlay and is very resistant to rubbing; furthermore, when testing the separation force level, as in example 3, the value obtained from 0 to 6 g / cm before and after aging. Curing in the drying cabinet is required however, in contrast to the 5 seconds of Example 3, 30 seconds.

II. The procedures described under I. are repeated with the modification that the finished coating solution prepared according to a) is left to stand for 8 hours before application to the paper. Even after 120 seconds at 150 ^° C., the coating is not yet fully cured, and the adhesive strength of the self-adhesive tape applied to it is impaired.

Claims (3)

Patent claims: 1. Covering agents that repel sticky substances, consisting of (1) have Si-bonded vinyl groups in the terminal units - P diorganopolysiloxanes, (2) at least 3 Si-bonded hydrogen atoms organopolysiloxanes containing per molecule and (3) platinum complexes as curing catalysts, and optionally (4) organic solvents, characterized in that they are organopo-jysiloxanes containing Si-bonded hydrogen (2) those with at least one terminal Si-bonded hydrogen atom and as Curing catalysts (3) contain reaction products of platinum (IV) chloric acid with ketones. 2. Coating agent according to claim 1, characterized in that they are used as diorganopolysiloxanes (1) Mixtures of (A) diorganopolysiloxanes containing Si-bonded vinyl groups in the terminal units with a viscosity of 5000 to 10,000 cSt at 25 ° C and (b) having in the terminal units and Si-bonded vinyl groups having a viscosity Diorganopolysil oxanen 100000-200 00OcSt at 25 ⁰ C contain. 3. Coating agent according to claim 1 and 2, characterized in that they are used as organopolysiloxanes (2) those of the general formula