DE1769666A1 - Coating compositions based on dimethylpolysiloxane - Google Patents

Description

Dimethylpolysiloxanes have gained great importance as release coatings for substrates such as paper, cardboard, textile fabrics and metal foils. Details of this are described in Canadian Patent 716,541. However, since now paper machines and other manufacturing devices have been developed with increasing throughput rates, the demand for dimethyl polysiloxane compositions that cure in seconds at temperatures below 7O ⁰ C and their quality as release coatings is as good at least, as the patent referred to in the charges compositions described.

From German Patent 1.104.176 it is also known to use silicic acid esters of the formula Si (OC ₂ ILOR ..) * as a crosslinking agent for organopolysiloxane molding compounds which can be hardened to elastomers at room temperature and thus to achieve faster curing than with silicic acid esters of the formula).

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However, the faster curing alone is not sufficient for a satisfactory release coating, since hardened release coatings still have the following absolutely necessary requirements must suffice:

1 · There must be no transfer of the siloxanes to the untreated side of the substrate or to the adhesive that comes into contact with the coated surface, a process that is often referred to as "migration ¹¹ " and 2. the release coating must be abrasion-resistant ·

This abrasion resistance is a combination of the following two effects:

a) Sufficient strength of the coating to withstand the abrasion that occurs during transport or storage the coated substrate surfaces and during the Manufacture of containers or articles of clothing from the same occurs and

b) Adequate adhesion of the coating to the substrate so that it does not peel off under abrasive conditions can·

However, the use of the above-mentioned silicic acid esters does not meet these requirements.

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The invention therefore binds, after the addition of catalysts, hardening Beechierungsmaasen based on dimethylpolysiloxanes and Kieselfläureeetern, which are characterized in that they are Genieehe

(1) Dimethyl polysiloxanes containing hydroxyl groups in the terminal units and having a viscosity of at least 2,000 cSt./25°C,

(2) Methylhydrogenpolysiloxanes with an average of at least three SiH groups per molecule, in amounts of 1 is called 10? t, based on the weight of (1),

(3) Silicic acid equivalents of the formulas

Si [(00 ₂ H ₄ ) ₂ 0R] ₄ or

where R is aliphatic hydrocarbon radicals having 1 to C atoms and R ^{1 is} aliphatic hydrocarbon radicals having 3 to 6 C atoms, in amounts from 0.05 to 25C, calculated as silicon, based on the weight of (1) and

(4) with isocyanates soluble in organic solvents an average of at least two isocyanate groups per molecule and a molecular weight of at least 173 in Amounts from 0.5 to. 5 #, based on the weight of (1)

contain.

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The type and amount of each component in the mixtures which can be used according to the invention is of crucial importance. For component (1) does not play a decisive role in the upper limit of the viscosity; these know either to be liquid or a no longer flowable Hasse with a viscosity of 10,000,000 cSt./25 ° C or above.

You component (2) know a methyl hydrogen polysiloxane from linear, cyclic or branched structure and either a homopolymer or a copolymer. You just have to specified amount must be available. Sa this component ale one of the crosslinkers is used »it is necessary that there are at least 3 SiH groups per molecule.

The second crosslinker in the mixtures that can be used according to the invention is a certain silicic acid ester which is derived from ethylene glycol. These include both silicic acid esters of the general formula Si [(OC ₂ H ₄ ) ₂ OR] ₄ , in which B denotes, for example, methyl, ethyl, isopropyl, butyl, vinyl or allyl, and those of the general formula UiLOC ₂ H ₄ OR ¹ J ₄ wherein R ^{1 is,} for example, propyl, allyl, butyl, pentyl, fentenyl or hezyl. It has been found that silicic acid esters of this type, the radicals of which do not correspond to the given definition, are either too active for satisfactory curing or else one

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the curing speed is too slow. The specified percentage amount relates to the Si content of the silicic acid ester, based on the weight of component (1).

Component (4) is an organic isocyanate of the specified Type that, by definition, can be both monomeric and polymeric. This can, for example, be a partially hydrolyzed Toluene diisocyanate, i.e. a urea or polyurea derivative that still has isocyanate groups in the molecule or a polybiuret that still contains unreacted isocyanate groups. Further examples are reaction products of isocyanate with polyhydroxy compounds (i.e. polyuretanes or allophanates derived therefrom) or polyamines, which still

contain unreacted isocyanate groups; furthermore polymeric products in which the polymerization is carried out by a diisocyanate group non-touching process took place, e.g. connections of the formulas

or

H 0 I

OCN (CHg) ₆ I-CO

0 0

(CH _{2) 2} 0C (CH _{2) 6} NC0

Specific examples of effective isocyanates are the following:

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OH 0 H ^

CH ₅ CH ₂ CLCH ₂ OCH (CHg) ₆ NCOJ ₅ ; CH ₃ CH ₂ C [OHgOC-H - ^^ - HCOJ ₃ ·,

; Haphthalene diocyanate 1,5 »I ^ -Bitolylen

CH, ^ S ^^ S]; Oiphenylmethane-4,4'-

COH OH HCO diocyanate; CH ₃ - ^ VH-CH- ^ jN-CH ₃ ; 3.3 ^l -Bi »ethoxy-4.4 ^t

phenylene diisocyanate; 3 »3'-Dipheny1-4.4" -biphanylene-diieocy-

anat [OCN-

HCO]; 4.4 ^l -biphenylene diisocyanate;

3,3'-dichloro-4,4 ^f -biphenylene diocyanate j 2-nitrodiphenylene-

4,4'-diocyanate; Siphaiiyl8ulfoii-4,4 ^t -dil8ocyaziat; Pluor

diiaocyanate; Octamethylene diocyanate 1

0 H

H 0

CH ₃ C [CH ₂ OC-I-ZiVHCO] ₃ and OCH- ^ Ai-COCH ₂ CSCCH ₂ OC-I - ^^ - HC0

N f

The sugtgtbene manga of the Iaooyanatkoaponante must be in the specified range from 0.5 to 5 #, depending on the weight of component (1), since amounts outside this specified range have a disruptive effect on the Beschioirtungsmaaae ·

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The curing catalysts used can be any of those known for curing hydroxyl-containing siloxanes by means of SiH compounds and silicic acid esters. Examples of these are amines, amine salts of carboxylic acids, quaternary ammonium compounds and metal salts of carboxylic acids, such as lead oxygenate, cobalt octoate, iron naphthenate and tin oleate. Preferred catalysts are carboxylic acid salts of OrganoSinnverbindungen containing bonding carbon-tin at least one, such as Butylzinntriacetat, Äthyleinntrihexoat, Dibutylsinndilaurat, Dibutylzinnsuccinat, Octadecylzinndilaurat and Dihexyleinn-di-äthylhexoet 2 and salts of the formula Y ₂ Sn (OOCHgST ¹⁾ ₂ wherein T and T ^A denotes methyl, ethyl, octadecyl, butyl and isopropyl radicals.

The amount of catalyst required for good cure depends on the amount of catalyst on the type of catalyst, the particular crosslinker used and the curing temperature. For this reason no meaningful figures can be given for the amount of catalyst to be used, which is of course it goes without saying that sufficient amounts of each catalyst must be used in order to achieve curing in the desired period of time.

The coating compositions according to the invention can be applied to the Substrate can be applied in any way. If the Mixture is sufficiently liquid, it can be applied per se.However, it is generally advantageous to use the

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'Mix with an inert solvent such as hydrocarbons, halogenated hydrocarbons or ethers dilute. The amount of solvent used is not critical; however, it is beneficial when concentrating of organopolysiloxane chemistry in the range of 1 "to $ 10," based on the weight of the solution.

The coating gauges can be applied to the substrate by knife coating, dipping, or spraying. If the coating compound cures extremely quickly, it is advantageous to apply the mixture using a mixing head, which minimizes the time between the mixing of the components and application to the substrate. In the case of other coating compositions, however, it is often advantageous to pass the substrate through a bath containing the coating composition.

The working time of the coating compositions according to the invention after mixing is of course dependent on the temperature. For longer storage they should be kept at low temperatures, for example at -20 ° to -25 ⁰ C; but when they are used immediately after the mixing, the temperature does not Bolle, it has been found that the processing time of Besohichtungsmassen after mixing by using Methyläthyl-

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ketone extended as a solvent or solvent additive can be. The methyl ethyl ketone is advantageously used in 2 to 4 times the amount by weight of component (1). If necessary, the methyl ethyl ketone can also be used as the only solvent. In this pail should the coating compounds can be processed within a few hours after mixing.

The best type of packaging for the coating compositions according to the invention consists of mixtures of components (1) and the methylhydrogensiloxane (2) and mixtures of to pack components (3) and (4) separately. The consumer can then mix the coating bath the mixtures of (1) and (2) with the mixture of (3) and (4) and the curing catalyst itself. Here it is advantageous if the second pack contains the mixture of (3) and (4) in a weight ratio of 4: 1 to 1: 4. By varying the ratio, the processing time of the coating composition can be regulated.

The coating compositions according to the invention are for any Substrates can be used e.g. metal, ceramics, wood, paper, Textiles such as cotton, wool, nylon, Royon, polyesters, fabrics containing vinyl, polyacrylonitrile fabrics and vinyl chloride vinylidene chloride polymeric polymers. In addition, the coating compositions according to the invention can also be used for inorganic

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Textiles such as glass, glass fabric or asbestos can be used.

In addition to the desired release properties, the invention Coating also makes the substrates water-repellent and give them excellent hand and other advantageous properties.

The weight of the coating applied to the substrate can vary widely depending on the purpose of use can be varied. PUr release coatings made of paper can vary the amount of hardened mass applied 0.1 to 5 # based on the weight of the paper. Pure Other types of application such as water-repellent finishing of the substrates or surface protection can reduce the amount of hardened coating up to 50jt based on weight of the substrate.

Although the mixtures which can be used according to the invention are particularly suitable for rapid curing at low temperatures, they can also be cured below the decomposition point of the substrate and / or the coating according to any temperature schedule. For example, the coating featuring be cured at an oven temperature of 200 ⁰ C in less than 1 second. PUr any given mixture extends the cure more rapidly, depending hfher the temperature.

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Example 1:

This example shows the effect of the elimination of components (2), (3) and (4) on the coating compositions according to the invention.

Effect of the elimination of methylhydrogenpolysiloxane (A) To 100 parts by weight of a solution containing 7% by weight of a highly viscous diraethylpolysiloxane with hydroxyl groups in the terminal units and a viscosity of about 10,000,000 cSt./25 ° C in xylene 5.4 ^ of the silicic acid _{ester of the formula O) 2} ]. Si, 2 # of the isocyanate of the formula

OO

^H 2 "" ^ n ^where & has an average value of 6

had and 656 di-butyl-tin-di-2-ethylhexoate, respectively based on the weight of the dimethylpolysiloxane added,

(B) This dope had the same composition like (A) with the exception that they also 1 based on the weight of the dimethylpolysiloxane of a methylhydrogenpolysiloxane of the formula (CH ₅ KSi (OSl) Si (CH ₅ ) ₅ with a viscosity of 35 cSt./25 ° C ^CH 3 contained.

Each of these coating masses was applied to supercalendered Kraft paper and heated for 60 seconds at 53 ^° C.

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dries. Each sample was immediately tested for abrasion resistance

Abrasion of the coating tested in the same way. Sample A

However, Sample B did not show excessive abrasion.

Sample B also gave excellent release values when it was like

detailed below, has been checked.

Effect of eliminating the isocyanate

(0) feu 100% by weight of a solution which contained 7% by weight of the high-risk diethylpolyeiloxane containing hydroxyl groups in the terminal units in xylene, 4.5% of the silicic acid ester was represented by the formula [OR-O (CH ₂ OH ₂ O) ₂ ] ^ »3J * of methyl hydrogen polyeiloxane

H of the formula (CH ₃ J ₃ Si (0Ai) ₂₅ Si (OH ₃ J ₃ and 6 * _f , based in each case on the weight of the dimethyl polysiloxane, dibutyl bin di-2-ethylhexoate) were added.

(D) Sample D was identical to Sample C except that they additionally 0.3 parts by weight, based on the weight of the dimethylpolysiloxane of the isocyanate of the formula

HCO (~ 4> / CH ₂ - ) _n where η had an average value of 6, contained. Samples G and D were each applied to supercalendered Kraft paper and 10 minutes air dried at room temperature. Sample C showed one excessive «/ briob pro> > e D, however, none. Sample D gave excellent separation values when it was used as below.

0088 * 9/1810.

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has been checked.

Effect of the elimination of the silicic acid ester B (E) To 100 parts by weight of a solution which contained 7% by weight of the highly viscous dimethyl polysiloxane in the terminal units containing hydroxyl groups in xylene, 3% of the methyl hydrogen polysiloxane were added

H
Formula (CHj ^ iOCSiO ^ SiCCH ^ with a viscosity

CH ₅

from 35 cSt./25 ° C and 6 $ », each based on the weight of diinethylpolysiloxane, dibutyltin di-2-ethylhexoate added.

(F) This sample was identical to Sample E except that they add 0.3? * »based on the weight of the Diine thylpolysiloxane, the silicic acid ester of the formula

O) _{contained 2} LSi. Every sample was on

supercalendered kraft paper applied and 60 seconds bet 7O ⁰ C cured. Sample E showed excessive "migration" of SL loxane when tested as detailed below, while Sample F showed no "migration" of SL loxane and recorded separations as tested below.

In samples (B) and (P), no loocyanot was used, since it had no effect on the hardening rate of compliance. For aLLan samples this BqI-

0 0 9 3 4.9 i φ a 1 0 bad

The separation value of the coating was tested as follows »

A polyvinyl ethyl ether adhesive was applied to the cured silosan film and an uncoated paper was glued to it. This laminate was then stretched on an Inetron machine using clamping devices at a speed of 127 cm / min. pulled apart · The force required for this, measured in g / 2.54- cm paper width, is the separation value. she Samples B, Ώ and F each had release values of 50 g / 2.45 cm paper width.

The "migration" of the siloxane from the coating was tested by applying a cellophane tape to the coated paper. The adhesive strip was then peeled off the coated surface and folded so that the adhesive surfaces of the strip came into contact with one another. The adhesive surfaces were then separated by hand and the force required for this was observed an excess of "migrated" BLloxane, i / uo indicated that the film had been insufficiently cured, while in sample f the adhesive itself did not adhere to itself and thus had no "migrated" 8iloxane.

BAD ORIGfNAL

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Example 2t

The same hardening and the same release values were obtained when the following Kieaelaäuasater in an amount of 0.3% Si ₉ based on the weight of the diethylpolysiloxane in sample B in Example 1 were used 1 C ₄ HgOGH ₂ OH ₂ O] ₄ Bi, [O ₂ H ₅ O (OH ₂ OH ₂ O) ₂ ] ₄ Bi, [O ₄ H ₉ O (CH ₂ OH ₂ O) ₂ ] ₄ βi, and [O ₆ H ₁₃ OOH ₂ OH ₂ O] ₄ Bi.

Baisplal 3t

(A) 100 parts by weight of a solution containing Ii dea Diaethylpolyailoxene from sample A la Example 1 in xylene »were old 35t of the methylhydrogenpolysiloxane of Forael

H (OH ₅ ) ₃ Bi (oSi) ₂₅ O8i (OH ₃ ) ₃ , of the silicic acid tray

Forael [OH ₃ O (OH ₂ OH ₂ O) ₂ I ₄ Si in amounts of 0.3 * 81, di-butyl-one-di-2-ethylhexoet and 2 *, each based on the weight of the dimethylpolysiloxane, a commercially available raw mixture aua partially hydrolysed toluene-aiiBocyentt, which showed urea blinding, Yernish. They solution was applied to superlcalandrierteo kraft paper and 60 seconds at 60 ⁰ C erhltit · The resulting coating showed no wear and had excellent release values ·

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(B) The above-described composition of the sample was made repeated except that the isocyanate used corresponded to the formula O «C« = N- ^ ^- ) VcH ₂ - / ^ VN «G« O ·.

This coating composition was applied to paper and

60 seconds cured at 5O ⁰ C. Ea were excellent

Results related to abrasion resistance and release values

obtain.

example Ai

Excellent release values were obtained when the following catalysts were used in the coating (B) from Example 1 were used: dibutyl tin dilaurate, lead octoate and Lead neodecanoate.

Example 5: The solvent used in this example was xylene

or a mixture of xylene and methyl ethyl ketone in the ratio given below. The task of this example consisted in the retarding effect of methyl ethyl ketone on gel formation in solution (processing time) after

Mixing all ingredients to show. For each approach a solution, the 7 #, based on the Weight of the total solvent, the highly viscous, in the

terminal units containing hydroxyl groups, dimethyl polysiloxane contained, 2j6, based on the weight of the di-

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methylpolysiloxane, the isocyanate's formula NCO

j, 3 / ^ i based on the weight of the dimethyl

polysiloxane, the methyl hydrogen polysiloxane of the formula

H
(OH ₃ ), Si0 (Si0) ₂ ^ Si (OH,) ₅ , silicic acid ester of the lormel

₅₂₂ O) ₂ J ₄ Si in amounts of 0.3 $ Si, "based on the weight of the dimethylpolysiloxane and 6 $, based on the weight of the dimethylpolysiloxane, dibutyltin-di-2-ethylhexoate. The table below shows the processing time at room temperature of the solution in relation to the percentage of methyl ethyl ketone, based on the total weight of the solution:

Methyl ethyl ketone
in # Processing time at
Room temperature 0 12 minutes VJl 30 minutes 10 60 minutes 25th 4 hours 50 4 hours

Each solution was applied to paper and ^{cured at 55 °} C. for 60 seconds. In both cases, excellent abrasion resistance and release properties were obtained.

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Example 6: The same results were obtained when liquid di-

methylpolysiloxanes of the formula *, ^ '2

HO (SiO) _n H with the following

Viscosities used according to the procedure in Example 1 (B) has been

5,000 c3t./25°C

10,000 cSt./25 ° C

100,000 cSt./25 ° C

1,000,000 cSt./25°C

Example 7: The following ingredients in percent by weight became one Solution made!

4.75O ^£ ^ of a dimethylpolysiloxane having hydroxyl groups in the terminal units 0.150 # Hethylhydrogenpolysiloxan 0.1655 ^ of the isocyanate of the formula (~ Vk (6 is an average value) 0.085 $ of the silicic acid ester of the formula 3.000 $ methyl isobutyl ketone 0.250 $ acetic acid

0.300Ji dibutyl bin di-2-ethylhexoate 91.3005s lylene.

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This solution was applied to glassine paper and semi-bleached Kraft paper (40 pound 525 semibleached Kraft). In both cases the paper was cured at 82 ^° C. for 30 seconds. Excellent abrasion resistance and release properties were achieved.

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Claims (1)

Coating compounds that harden after the addition of catalysts based on dimethylpolyeiloxanes and silicic acid meters, characterized in that they mixes out (1) Dimethylpolyeiloxanes containing hydroxyl groups in the terminal units and having a viscosity of at least 2,000 cSt./25°C, (2) Methylhydrogenpolysiloxanes with an average of at least three SiH groups per molecule, in amounts of 1 up to 10 #, based on the weight of (1), (3) Silicic acid esters of the formulas Sit (OC ₂ H ₄ ) ₂ 0H] ₄ or where R is aliphatic hydrocarbon radicals with 1 to 4 C atoms and R * aliphatic hydrocarbon radicals with 3 to 6 carbon atoms mean, in amounts of 0.05 to 2? T, calculated as silicon based on the weight of (1) and (A) Isocyanates soluble in organic solvents with an average of at least two isocyanate groups per molecule and a molecular weight of at least 1731 in amounts of 0.5 to 55% based on the weight of (1) contain. 009849/1810