EP1625254B1 - Use of silane-functional polyvinyl alcohols in priming agents for separating papers and films - Google Patents

Abstract

Release films or papers with improved properties are prepared by employing a binder which is a partly or fully hydrolyzed silane-group-containing polyvinyl alcohol polymer derived from a vinyl ester polymer containing 1-alkylvinylester moieties.

Description

The invention relates to the use of silane-functional polyvinyl alcohols in primers for release papers and films.

For the production of release papers with adhesive properties against adhesives, the paper carriers are provided with a silicone layer. To improve the silicone layer, in particular to prevent the penetration into the substrate during the coating, the backing paper is provided with a primer before the application of the silicone layer.

From DE-A 3727078 it is known to use solutions of metal complexes and film formers such as polyvinyl alcohol as a primer. In DE-A 4425737, a water glass coating is formed as a primer on the paper. In the process of EP-A 396789, a suspension comprising film-forming substances, white pigment and noble metal catalyst is applied as primer. DE-A 19512663 recommends a pigment coating with aluminum hydroxide. In EP-A 399079, organosilanes or organosiloxanes are applied to the primer, alone or in admixture with binders, such as polyvinyl alcohol. US Pat. No. 5,358,977 describes the use of crosslinkable, aromatic or aliphatic substances as primers. JP-A 58/214596 describes silane-modified polyvinyl alcohol-coated paper which is suitable for the production of release paper.

A disadvantage of the primers previously used is their often unsatisfactory binding to the adhesive silicone layer and a consequent prolonged annealing time for the cross-linking silicone, as well as the unsatisfactory storage stability.

It is an object of the present invention to provide a primer which overcomes the abovementioned disadvantages and is particularly suitable for the production of release papers having a fast-curing, abhesive silicone coating.

• a) ein oder mehreren Vinylestern von unverzweigten oder verzweigten Alkylcarbonsäuren mit 1 bis 18 C-Atomen, wovon ein Anteil von 1 bis 30 Mol-%, bezogen auf Gesamtpolymer, ein oder mehrere 1-Alkylvinylester mit Alkylresten mit 1 bis 6 C-Atomen und von Carbonsäuren mit 1 bis 6 C-Atomen sind,
• b) 0.01 bis 10 Mol-% von einem oder mehreren Silan-haltigen, ethylenisch ungesättigten Monomeren, sowie gegebenenfalls
• c) weitere damit copolymerisierbare Comonomere,

und Verseifung der damit erhaltenen Polymerisate.The invention relates to the use of silane-functional polyvinyl alcohols in primer (primer) for release papers and films containing
at least one silane-containing polyvinyl alcohol based on fully hydrolyzed or partially hydrolyzed vinyl ester copolymers having a degree of hydrolysis of from 75 to 100 mol% obtainable by free-radical polymerization of

• a) one or more vinyl esters of unbranched or branched alkylcarboxylic acids having 1 to 18 carbon atoms, of which a proportion of 1 to 30 mol%, based on the total polymer, one or more 1-alkylvinyl esters having alkyl radicals having 1 to 6 carbon atoms and of carboxylic acids having 1 to 6 carbon atoms,
• b) 0.01 to 10 mol% of one or more silane-containing, ethylenically unsaturated monomers, and optionally
• c) further comonomers copolymerizable therewith,

and saponification of the resulting polymers.

Suitable silane-containing polyvinyl alcohols are fully hydrolyzed or partially hydrolyzed vinyl ester polymers having a degree of hydrolysis of from 75 to 100 mol. The fully saponified vinyl ester polymers have a degree of hydrolysis of preferably from 97.5 to 100 mol%, particularly preferably from 98 to 99.5 mol%. The partially hydrolyzed polyvinyl esters have a degree of hydrolysis of preferably 80 to 95 mol%, particularly preferably 86 to 90 mol%. The Höppler viscosity (according to DIN 53015 as 4% strength by weight aqueous solution) serves as a measure of the molecular weight and of the degree of polymerization of the partially or fully hydrolyzed, silanized Vinyl ester polymers, and is preferably from 2 to 50 mPas.

Suitable vinyl esters are vinyl esters of unbranched or branched carboxylic acids having 1 to 18 carbon atoms. Preferred vinyl esters are vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, vinyl pivalate and vinyl esters of α-branched monocarboxylic acids having 5 to 13 carbon atoms, for example VeoVa9 ^R or VeoVa10 ^R (trade name of the company Shell). Particularly preferred is vinyl acetate.

The proportion of 1-alkylvinyl ester is 1 to 30 mol%, based on the total polymer. Preference is given to 1-alkylvinyl esters having alkyl radicals having 1 to 6 C atoms and of carboxylic acids having 1 to 6 C atoms, such as 1-methylvinyl acetate, 1-ethylvinyl acetate, and 1-propylvinyl acetate. In a particularly preferred embodiment, 1-methylvinyl acetate is copolymerized.

Suitable ethylenically unsaturated, silane-containing monomers b) are ethylenically unsaturated silicon compounds of the general formula (I) R ¹ SiR ² _0-2 (OR ³⁾ _1-3, wherein R ^{1 has} the meaning CH ₂ = CR ⁴ - (CH _{2) 0- 3} or CH ₂ = CR ⁴ CO ₂ (CH ₂ ) _1-3 , R ^{2 is} C ₁ - to C ₃ -alkyl, preferably methyl or ethyl, C ₁ - to C ₃ -alkoxy, preferably methoxy or ethoxy, or halogen, preferably Cl or Br, R ^{3 is} an unbranched or branched, optionally substituted alkyl radical having 1 to 12 C-atoms, preferably 1 to 3 C-atoms such as methyl or ethyl, or an acyl radical having 2 to 12 C-atoms wherein R ^{3 may} optionally be interrupted by an ether group and R ^{4 is} H or CH ₃ .

Suitable ethylenically unsaturated, silane-containing monomers b) are also silane-group-containing meth (acrylamides) of the general formula (II) CH ₂ CRCR ⁵ -CO-NR ⁶ -R ⁷ -SiR ⁸ _m - (R ⁹ ) _3-m , where m = 0 to 2, R ^{5 is} either H or a methyl group, R ^{6 is} H or one Alkyl group having 1 to 5 C atoms; R ^{7 is} an alkylene group having 1 to 5 C atoms or a bivalent organic group in which the carbon chain is interrupted by an O or N atom, R ^{8 is} an alkyl group having 1 to 5 C atoms, R ^{9 is} an alkoxy group having 1 to 40 carbon atoms, which may be substituted with other heterocycles. In monomers in which 2 or more R ⁵ or R ⁹ groups are present, they may be identical or different.

Examples of such (meth) acrylamido-alkylsilanes are: 3- (meth) acrylamido-propyltrimethoxysilanes, 3- (meth) acrylamidopropyltriethoxysilanes, 3- (meth) acrylamido-propyltri (β-methoxyethoxy) silanes, 2- (meth) acrylamido-2 -methylpropyltrimethoxysilanes, 2- (meth) acrylamido-2-methylethyltrimethoxysilanes, N- (2- (meth) acrylamidoethyl) aminopropyltrimethoxysilanes, 3- (meth) acrylamido-propyltriacetoxysilanes, 2- (meth) acrylamido-ethyltrimethoxysilanes, 1- (meth ) acrylamido-methyltrimethoxysilanes, 3- (meth) acrylamido-propylmethyldimethoxysilanes, 3- (meth) acrylamido-propyldimethylmethoxysilanes, 3- (N-methyl- (meth) acrylamido) -propyltrimethoxysilanes, 3 - ((meth) acrylamido-methoxy) -3 -hydroxypropyltrimethoxysilanes, 3 - ((meth) acrylamido-methoxy) propyltrimethoxysilanes, N, N-dimethyl-N-trimethoxysilylpropyl-3- (meth) acrylamido-propylammonium chloride and N, N-dimethyl-N-trimethoxysilylpropyl-2- (meth) acrylamido -2-methylpropylammoniumchlorid.

Preferred ethylenically unsaturated, silane-containing monomers b) are γ-acrylic or γ-methacryloxypropyltri (alkoxy) silanes, α-methacryloxymethyltri (alkoxy) silanes, γ-methacryloxypropylmethyldi (alkoxy) silanes; Vinylsilanes such as Vinylalkyldi (alkoxy) silanes and vinyltri (alkoxy) silanes, where as alkoxy groups, for example, methoxy, ethoxy, methoxyethylene, ethoxyethylene, Methoxypropylenglykolether- or Ethoxypropylenglykolether residues can be used. Examples of preferred silane-containing monomers are 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, Vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltris (1-methoxy) isopropoxysilane, vinyltributoxysilane, vinyltriacetoxysilane, methacryloxymethyltrimethoxysilane, 3-methacryloxypropyltris (2-methoxyethoxy) silane, vinyltrichlorosilane, vinylmethyldichlorosilane, vinyltris (2-methoxyethoxy ) silane, trisacetoxyvinylsilane, Allylvinyltrimethoxysilan, allyltriacetoxysilane, vinyldimethylmethoxysilane, vinyldimethylethoxysilane, vinylmethyldiacetoxysilane, vinyldimethylacetoxysilane, Vinylisobutyldimethoxysilan, Vinyltriisopropyloxysilan, vinyltributoxysilane, Vinyltrihexyloxysilan, Vinylmethoxydihexoxysilan, Vinyltrioctyloxysilan, Vinyldimethoxyoctyloxysilan, Vinylmethoxydioctyloxysilan, Vinylmethoxydilauryloxysilan, Vinyldimethoxylauryloxysilan as well as polyethylene glycol-modified vinyl silanes.

As silanes b), vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyltris (1-methoxy) isopropoxysilane, methacryloxypropyltris (2-methoxyethoxy) silane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane and methacryloxymethyltrimethoxysilane and mixtures thereof are most preferable.
The silanes b) are preferably copolymerized in an amount of 0.01 to 10.0 mol%, particularly preferably 0.01 to 1.5 mol% of ethylenically unsaturated, silane-containing monomers.

In addition to the silane-containing monomers, it is also possible for one or more further comonomers c) to be present in a proportion of preferably 0.1 to 25 mol%. For example, ethylene, propylene, isobutylene, butadiene, isoprene, chloroprene, styrene, α-methylstyrene, vinyl chloride, vinylidene chloride, vinyl fluoride, acrylonitrile, methacrylonitrile; Alkyl vinyl ethers such as ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, cyclohexyl vinyl ether, octadecyl vinyl ether, hydroxybutyl vinyl ether, cyclohexanedimethanol monovinyl ether; Vinyl methyl ketone, N-vinylformamide, N-vinyl-N-methylacetamide, N-vinylcaprolactam, N-vinylpyrrolidone, N-vinylimidazole. Also suitable are acrylic acid and methacrylic acid and their esters and amides such as methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, ethylhexyl (meth) acrylate, benzyl (meth) acrylate , 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, n-hexyl (meth) acrylate, isooctyl (meth) acrylate, iso-decyl (meth) acrylate, lauryl (meth) acrylate, methoxyethyl (meth) acrylate, Phenoxyethyl (meth) acrylate, isobornyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, α-chloroacrylic ester, α-cyanoacrylic ester. Further examples are vinylcarbazole, vinylidene cyanide, vinyl esters, acrylic anhydride, maleic anhydride, maleic and fumaric acid esters, sulfonic acid-modified monomers such as 2-acrylamido-2-methylpropanesulfonic acid and their alkali metal salts, cationic monomers such as trimethyl-3- (1- (meth) acrylamide 1,1-dimethylpropyl) ammonium chloride, trimethyl 3- (1- (meth) acrylamidopropyl) ammonium chloride, 1-vinyl-2-methylimidazole and their quaternized compounds.

The silane-containing vinyl ester polymers can be prepared in a known manner by means of polymerization; preferably by bulk polymerization, emulsion polymerization, suspension polymerization or by polymerization in organic solvents, more preferably in alcoholic solution. The adjustment of the molecular weight can be carried out in a manner known to the skilled worker by polymerization in the presence of molecular weight regulators. The saponification of the silane-containing vinyl ester polymers is carried out in a manner known per se, for example by the belt or kneader process or in a stirred tank, in the alkaline or acidic state with the addition of acid or base. After completion of the hydrolysis, the solvent is distilled off and the silane-containing polyvinyl alcohol is obtained as a powder. If appropriate, the aqueous solution of the silane-containing polyvinyl alcohols can also be atomized by means of spray drying be won, and the silane-containing polyvinyl alcohol as a powder. The preparation of powdery, silane-containing polyvinyl alcohols is described in detail, for example, in DE-A 10232666. Common drying processes are fluidized bed, thin film, freeze and spray drying.

The primer composition may optionally contain further binders and additives. Typical further additives and binders are: pigments, polyvinyl alcohols, carboxymethylcelluloses, starch, starch derivatives, alginates, proteins, aqueous polymer dispersions based on (meth) acrylic acid, (meth) acrylic esters, acrylonitrile, vinyl acetate, butadiene, styrene, and plasticizers, such as ethylene glycols , Glycerin, and catalysts

The application of the primer composition can be carried out in any suitable and widely known for the preparation of coatings of liquid substances, for example by dipping, brushing, pouring, spraying, rolling, printing, z. Example by means of an offset engraving coating device, knife or blade coating or by means of an air brush. The application is preferably carried out in an amount of 0.5 to 5.0 g / m ² , particularly preferably 1.5 to 3.5 g / m ² .

The methods and formulations for the release coating of release papers and films are known in the art. Suitable carriers are paper, especially base papers, and films such as polyethylene films, PET films, nonwovens, fabrics and Trennrohcrepp. After priming the carrier material, the silicone coating is applied by means of the aforementioned application method. Suitable silicone polymers having dehesive properties are known to the person skilled in the art, for example comprising chain-shaped hydroxy-terminated dimethylpolysiloxanes which are condensed under the action of elevated temperature and in the presence of organotin salts as a catalyst with silicic acid esters, or Obtained by addition crosslinking by reaction of chain-shaped polymers with vinyl end groups with hydrogen polysiloxanes under the action of temperature in the presence of platinum catalysts. The formulations for the silicone coating may optionally contain further additives, for example film-forming aids such as polyvinyl alcohol, carboxymethylcelluloses, or plasticizers such as ethylene glycol and glycerol.

Examples: Example 1:

612 g of water, 61.2 mg of copper (II) acetate and 61.2 g of a 5% strength by weight polyvinylpyrrolidone solution (PVP-K90) in water were placed under nitrogen in a thermostatted laboratory apparatus with a capacity of 2.5 liters.
While stirring, a solution of 620 mg of t-butyl per-2-ethylhexanoate (TBPEH 99% in water), 322 mg of t-butyl perneodecanoate (Pergan PND 95% in water) 4.9 g vinyltriethoxysilane, 48.9 g Isopropenylacetat and 42.8 g of isopropanol in 612 g of vinyl acetate. The reactor was heated to 51.5 ° C, after the reaction had stopped, it was gradually heated to 75 ° C. It was kept at this temperature for 2 hours, then cooled. The resulting polymer beads were filtered off with suction, washed well with water and dried.
In a 2.5 liter laboratory reactor, 90 g of polymer beads were dissolved in 810 g of methanol at 50 ° C. The solution was cooled to 30 ° C, covered with standing stirrer with 500 g of methanol and immediately mixed with methanolic NaOH (10 g of NaOH 46% strength in water dissolved in 90 g of methanol) and the stirrer turned on.
The solution became increasingly cloudier. During the gel phase, the stirrer was set to higher speed to crush the gel. After the gel phase was allowed to react for a further 2 hours, neutralized with acetic acid and the resulting solid was filtered off, washed and dried. It was a vollverseifter Polyvinyl alcohol having a Hoppler viscosity of 28 mPas (4% in water).

Comparative Example 1

Fully saponified polyvinyl alcohol containing vinylsilane units with a Hoppler viscosity of 25 mPas (4% in water).

Comparative Example 2:

Fully saponified, non-silane polyvinyl alcohol having a Hoppler viscosity of 25 mPas (4% in water).

Production of the paper:

The primers from the example and the comparative examples were each applied to a base paper by means of a laboratory size press and dried accordingly (coating 1.5 g / m ² to 3 g / m ² ). On the thus primed paper, a release layer of 100 parts by weight of a vinyl-terminated polysiloxane (Dehesive 920), 2.4 parts by weight of an H-containing siloxane (crosslinker V90) and 1 part by weight of Pt catalyst (catalyst OL) was applied and the coated paper annealed at 150 ° C for 7 seconds.

Description of the test methods: Migration:

A test adhesive tape was applied to the freshly siliconized side and then pulled off again. The tape was folded so that the adhesive surfaces touched. Then the ends were pulled apart (loop test). If the adhering layers have good adhesion, this indicates good adhesion of the silicone layer to the substrate. The grading of both tests takes place in school grades from 1 to 6: 1 = very good, 6 = very bad

Rub Off:

One rubs one's finger vigorously over the siliconized surface and looks at this spot in obliquely incident light. If brightness differences or stripes occur at this point, the silicone product does not adhere optimally. In addition, rub the silicone layer several times with a finger and observe the amount of abrasive particles. The grading of both tests takes place in grades 1 to 6.

Test results:

Example 1 Vbsp. 1 Vbsp. 2 Example 1 Vbsp. 1 Vbsp. 2 storage time 0 0 0 7 d 7 d 7 d migration 1 1 4 1 5 5 Rub Off 1 1 4 1 5 6

The test shows the superiority of the silane-containing polyvinyl alcohols used according to the invention after storage.

Determination of storage stability of 11% aqueous solutions of the modified polyvinyl alcohols at pH = 8.5: storage time Höppler viscosity [mPas] Example 1 Höppler viscosity [mPas] Comparative Example 1 immediately 28.1 25.1 1 day 28.1 27.8 2 days 28.1 31.4 3 days 28.2 35.8 5 days 28.2 42.9 7 days 28.2 61.7 14 days 28.3 90.5

The test shows that the silane-containing polyvinyl alcohols used according to the invention show no increase in viscosity on storage.

Claims (7)

1. Use of silane-functional polyvinyl alcohols in primers for release papers and release films, comprising
   at least one silane-containing polyvinyl alcohol based on fully or partly hydrolysed vinyl ester copolymers having a degree of hydrolysis of 75 to 100 mol%, obtainable by free-radical polymerization of

   a) one or more vinyl esters of unbranched or branched alkylcarboxylic acids having 1 to 18 carbon atoms, of which a fraction of 1 to 30 mol%, based on total polymer, are one or more 1-alkylvinyl esters having alkyl radicals having 1 to 6 carbon atoms, and of carboxylic acids having 1 to 6 carbon atoms,

   b) 0.01 to 10 mol% of one or more silane-containing, ethylenically unsaturated monomers, and, if desired,

   c) further comonomers, copolymerizable therewith,

   and hydrolysis of the resultant polymers.
2. Use according to Claim 1, characterized in that the silane-containing polyvinyl alcohol is obtained by copolymerization with vinyl acetate.
3. Use according to Claim 1 or 2, characterized in that one or more 1-alkylvinyl esters from the group consisting of 1-methylvinyl acetate, 1-ethylvinyl acetate, and 1-propylvinyl acetate are copolymerized.
4. Use according to Claim 1 to 3, characterized in that the silane-containing polyvinyl alcohol is obtained by copolymerizing one or more ethylenically unsaturated, silane-containing monomers from the group consisting of
   ethylenically unsaturated silicon compounds of the general formula (I) R¹SiR² _0-2(OR³)_1-3, where the definition of R¹ is CH₂=CR⁴-(CH₂)_0-3 or CH₂=CR⁴CO₂(CH₂)_1-3, R² has the definition C₁ to C₃ alkyl radical, C₁ to C₃ alkoxy radical, or halogen, R³ is an unbranched or branched, unsubstituted or substituted alkyl radical having 1 to 12 carbon atoms, or is an acyl radical having 2 to 12 carbon atoms, it being possible if desired for R³ to be interrupted by an ether group, and R⁴ stands for H or CH₃, and meth(acrylamides) containing silane groups, of the general formula (II) CH₂=CR⁵-CO-NR^6-R⁷-SiR⁸ _m-(R⁹)_3-m, where m = 0 to 2, R⁵ is either H or a methyl group, R⁶ is H or an alkyl group having 1 to 5 carbon atoms, R⁷ is an alkylene group having 1 to 5 carbon atoms or a divalent organic group in which the carbon chain is interrupted by an O or N atom, R⁸ is an alkyl group having 1 to 5 carbon atoms, and R⁹ is an alkoxy group having 1 to 40 carbon atoms, which may be substituted by further heterocycles.
5. Use according to Claim 4, characterized in that the silane-containing polyvinyl alcohol is obtained by copolymerizing one or more ethylenically unsaturated, silane-containing monomers from the group consisting of γ-acryloyl- and γ-methacryloyl-oxypropyltri(alkoxy)silanes, α-methacryloyloxymethyltri(alkoxy)silanes, γ-methacryloyloxypropylmethyldi(alkoxy)silanes, vinylalkyldi(alkoxy)silanes and vinyltri(alkoxy)silanes, examples of alkoxy groups which can be present including methoxy, ethoxy, methoxyethylene ethoxyethylene, methoxypropylene glycol ether and/or ethoxypropylene glycol ether radicals.
6. Use according to Claim 1 to 5, characterized in that 0.01 to 1.5 mol% of ethylenically unsaturated, silane-containing monomers are copolymerized.
7. Use according to Claim 1 to 6 in methods of release-coating release papers and release films, application of the primer to a backing being followed by application of a silicone coat.