Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/001—Release paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/10—Coatings without pigments
  • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
  • D21H19/24—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H19/32—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds obtained by reactions forming a linkage containing silicon in the main chain of the macromolecule
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
  • D21H19/62—Macromolecular organic compounds or oligomers thereof obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds

Definitions

• the invention relates to release paper, a process for the production of release paper and a process for the production of silicone release paper.
• silicone polymers have excellent release properties against sticky substances, e.g. Have pressure sensitive adhesives. These silicone polymers are e.g. in amounts of 0.3 g / m to 3 g / m (calculated), usually only in amounts of 0.5 g / m to 1.0 g / m, applied to the coating base paper as a backing material in order to give the paper adhesive properties .
• the base papers to be coated are approximately 50% highly satinised kraft paper, but also a large number of other papers ("Das Textil" (1985), No. 10 A, p. V 92 - V 96).
• thermal crosslinking systems are used today.
• release papers are now coated with a special surface glue mainly with addition-crosslinking silicone systems, chain-like polymers with vinyl end groups being crosslinked by reaction with hydrogen siloxanes under the influence of temperature and in the presence of predominantly platinum catalysts (special print from the magazine "Adhesion” (1973), No. 7 ).
• Usual processing temperatures for convection drying are therefore approx. 180 ° C for silicone systems containing solvents, approx. 120 ° C to 150 ° C for aqueous silicone systems (emulsions) and approx. 150 ° C for solvent-free silicone systems.
• the curing speed is between 2 and 25 seconds.
• the polyaddition can also be disrupted by small amounts of inhibiting constituents in the paper. These so-called “catalyst poisons” can delay or, in extreme cases, prevent the crosslinking reaction (see “Allgemeine Textilrundschau” (1986), No. 14, pp. 367-368).
• This reference gives an overview of the release paper that has been customary up to now.
• the length of time the silicone systems are stored before using them increases the crosslinking time.
• unfavorable interfacial tensions between paper and silicone systems can also lead to flow disturbances and adhesion problems (see “Paper and plastics processor” (3-1982), No. 17, p. 30).
• the release paper is coated with the various silicone polymers on separate systems. This is mainly due to the high demands on the surface quality of the carrier material before the silicone coating, in particular low micro-roughness, high solvent tightness and uniform thickness in the longitudinal and transverse directions of the paper web. Therefore the Most of all raw papers smoothed in a separate supercalender. This is the only way to later apply a uniform silicone film with a high abhesive effect to the backing paper with relatively small amounts of coating. So far it has not been possible to siliconize abhesive papers for the technical sector with a defined and reproducible release force level within the paper machine. On-line siliconization is only carried out if the requirements for the abhesive effect are low, for example for baking release papers and sack papers with hydrophobic properties.
• the dried paper web is coated with silicone resins within the paper machine by means of conventional application devices, such as a size press or blade.
• aqueous silicone systems emulsions
• various film formers and thickeners e.g. starch, alginates, carboxymethyl cellulose (CMC) or polyvinyl alcohol (PVA) can be added in small proportions according to the technical information sheets of the silicone manufacturers, see for example "Paper”, vol. 193, N o 11 June 1980 36-37.
• the silicone resin used always forms the main component because it affects the Abphasesiv Bonus the coated paper primary.
• aqueous emulsions with addition of a catalyst are still crosslinkers, for example based on methyl hydrogen siloxanes and often also adhesives (eg water-soluble reactive silane esters) and "controlled release" additives.
• the pretreated base paper Before any further (separate) silicone coating, the pretreated base paper is partially still satined. More or less strong adhesive properties of the (on-line) coated base papers should always be achieved.
• the object of the present invention is to produce release papers, preferably within the paper machine, with surface properties which have better adhesion and faster crosslinking at a lower temperature subsequent separate coatings with customary different silicone systems allowed. As a result, faster crosslinking at a lower temperature than before and an increase in the coating speed previously used can also be achieved. Another advantage is the easier use of stored silicone systems, the reactivity of which is already more or less impaired.
• Another object of the invention is to provide an improved process for the production of silicone release papers.
• the release paper can be made machine-smooth or subjected to subsequent smoothing, for example in a super calender, before it is siliconized in a separate coating system.
• the ideal possibility should thus be opened to economically advantageously coat even surfaces of low micro-roughness with minimal silicone applications without flow problems and adhesion difficulties.
• Silicon savings through thinner coatings while simultaneously securing the desired (usually low) release forces were previously only possible with the use of plastic films, but this in turn has the disadvantage of a lower one have thermal resilience.
• Another advantage of the desired surface of release paper should be the extensive suppression of the negative influence of inhibiting paper components (catalyst poisons) on silicone crosslinking.
• the invention also includes release papers which are obtainable by the process according to claim 1.
• the main group B organopolysiloxanes have at least 3 silicon-bonded hydrogen atoms per molecule and are preferably copolymers of: Dimethylhydrogensiloxane, methylhydrogensiloxane, dimethylsiloxane and trimethylsiloxane units, copolymers of trimethylsiloxane units, methylhydrogensiloxane units and hydrogensiloxan-, copolymers of trimethylsiloxane, dimethylsiloxane and Methyhydrogensiloxanäen, copolymers of Methyhydrogensiloxan- and trimethylsiloxane units, copolymers of methylhydrogensiloxane, diphenylsiloxane and trimethylsiloxane units, copolymers of methylhydrogensiloxane -, dimethylhydrogensiloxane and diphenylsiloxane units, copolymers of methylhydrogensiloxane, pheny
• organopolysiloxanes are preferably not saturated with hydrogen and siloxane oxygen atoms Silicon valences saturated by methyl residues. Methods for the production of organopolysiloxanes of this type are generally known.
• organopolysiloxanes used for the purposes of the invention are emulsified in water. All known procedures and dispersants for the emulsification of organopolysiloxanes in water can be used.
• organofunctional alkoxysilanes assigned to main group A also include alkylalkoxysilanes.
• organofunctional alkoxysilanes are: 3-glycidyloxypropyltrimethoxysilane, N-aminoethyl-3-aminopropyltrimethoxysilane, 3-aminopropyl-triethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyl-tris (2-methoxyethoxyethoxethoxysiloxysiloxysiloxysilane) 3 mercaptopropylmethyldimethoxysilane, 3-chloropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, ⁇ -chloromethyldi
• the following compounds are designated as typical representatives of the alkylalkoxysilanes: Methyltrimethoxysilane, methyltriethoxysilane, propyltrimethoxysilane, methyltriethoxysilane, propyltrimethoxysilane, propylmethyldimethoxysilane, propylmethyldiethoxysilane, isobutyltrimethoxysilane and butyltrimethoxysilane.
• organ silanes have the ability to react with both an inorganic substrate and with organic polymers to form solid bonds. This is due to the structure of the silane molecule, which has alkoxy groups that can react with the active sites of the inorganic material after hydrolysis.
• silanes have a functional group that is firmly attached to the silicon atom via a carbon chain. This group can undergo chemical reactions with suitable resins.
• organic silicon compounds mentioned are used alone or in combination with conventional impregnation or surface glue compositions for release base papers, which mostly consist of the film formers alginate, starch, CMC, PVA or other polymer solutions and polymer dispersions (latices) chemical structure exist, added proportionately.
• the organic silicon compounds are preferably added in proportions of 1 to 15% (calculated) of the usual surface preparation. Too large proportions lead to undesirable side effects such as the adhesive properties of the paper. In addition, these additions of organic silicon compounds represent an additional cost factor.
• the desired surface of release papers by means of silicone additives becomes a completely different chemical structure and properties than that of the aqueous silicone systems (emulsions) mentioned to the usual impregnation or surface solution, which in the paper machine on the almost dry paper web with a solid moisture content of 2 to 12% with usual Application devices are applied, achieved.
• Roller and doctor blade applicators or dip impregnation devices are known as customary application devices for surface finishing of release paper.
• a conventional solvent-free polysiloxane system with the following composition was used for the silicone coating.
• the coated paper was placed on a metal sieve in a circulating air oven operated at 150 ° C.
• the crosslinking time was set differently in order to follow the influence of the silanes on the crosslinking and anchoring process.
• Table 1 only the shortest crosslinking times are recorded, during which a complete hardening and anchoring of the silicone layer is still guaranteed.
• the paper samples hardened at different times were immediately subjected to a scratch test, with the finger being rubbed 8-10 times over the silicone film. The pressure is selected so that the fingertip heats up significantly when rubbed. A disruption in the silicone coating shows up in the form of rubbed off rubles and as a smeared area if you look at the paper sheet under the bevel.
• a paper As a reference paper (blank), i.e. a paper without silane additive, a paper was used which had also gone through the treatment stages described above, but contained no addition of the organosilanes mentioned in part a) in the PVA.
• Example 1 The procedure of Example 1 was repeated with one exception, only the pH of the PVA mixture was adjusted to 9.5 with ammonia. The minimum crosslinking time for this paper is shown in Table 1.
• Example 1 The procedure of Example 1 was repeated, but instead of 5 g of 3-aminopropyltriethoxysilane in the PVA solution, 5 g of N-aminoethyl-3-aminopropyltrimethoxysilane were added.
• the shortest crosslinking time for a paper coated in this way is shown in Table 1 below.
• Example 3 The procedure of Example 3 was repeated, only the pH of the PVA mixture was raised to 9.5 this time with ammonia.
• the result of the cross-linking test is shown in Table 1.
• Example 1 The procedure of Example 1 was repeated. Instead of 5 g of 3-aminopropyltriethoxysilane to the PVA solution, 5 g of a mixture of vinyltriacetoxysilane and triemethoxyepoxy-functional silane were added. The shortest crosslinking time for paper provided with such a line can be seen from Table 1.
• Example 5 The procedure of Example 5 was repeated, but the pH of the PVA mixture was raised to 9.5 with ammonia. The result of the cross-linking test is recorded in the table below.
• the crosslinking time for the subsequent silicone coating was reduced by 10 to 80% compared to the blank samples (without the addition of silicone).
• This paper finished in this way was additionally satinized in a 16-roll supercalender at a pressure of 330 kN / m and a speed of 300 m / min.
• the test was repeated according to the production process described in Example 7, but with a different surface formulation.
• organosilane was used.
• the line recipe used here had the following composition: 100 parts of PVA 10 parts CMC 11 parts of silane mixture according to Ex. 5 The pH of this mixture was adjusted to 4.0 with sulfuric acid.
• the papers produced according to Examples 7 and 8 were siliconized with a width of 1 m on a Revo 303 A coating system from the Kroenert / Hamburg machine factory. This pilot plant is designed for a maximum speed of 200 m / min.
• the two surface-refined test papers were made together with a paper product which also corresponds to that in Examples 7 and 8 described method had been prepared, but contained no organosilane in the line (zero sample), coated with a solvent-based silicone system of the following composition: 80 parts white spirit 15 parts Si-adhesive 930 0.5 part of crosslinker V 93 0.05 parts of catalyst OL
• the solids content of this coating composition was 5% and the viscosity according to Ford-Becher was 12 s.
• the silicone was applied to the paper web by means of an anilox roller (40 screen per cm). The air temperature in the floating dryer was set to 190 ° C.
• the degree of curing was determined immediately after the siliconization directly on the coated rolls using the finger abrasion test described in Example 1 and using Tesa 104 adhesive tape. In this series of tests, the web speed was varied, while the drying temperature remained constant at 190 ° C.
• Table 2 Paper type Silicone application g / m Max. Speed m / min Separation force, mN / cm after 20 h after 4 weeks K-7476 A-8475 K-7476 A-7475 Blank test 0.4 150 303 74 210 103 Paper from example 7 0.4 163 308 69 244 72 Paper from example 8 0.4 165 281 63 197 60
• the coating speed could be increased by about 10% compared to the blank sample with approximately the same level of release forces after siliconization.
• the separation forces were measured according to FINAT test method No.10 (FTM 10).
• FTM 10 FINAT test method No.10
• a rubber adhesive tape K-7476 and an acrylic adhesive tape A-7475 were used as adhesive tapes.
• the measurements were carried out in a tensile tester by peeling the adhesive tape off the silicone-coated test paper at an angle of 180 ° and a clamp speed of 300 mm / min.
• the amounts of silicone applied were determined by means of X-ray fluorescence measurements.
• test papers produced according to Examples 7 and 8 were also coated on the coating system mentioned above with silicone systems on a solvent-free basis. A four-roll application unit was used for this. Since the maximum speed of the system of 200 m / min was already reached with the reference paper (blank sample), the minimum temperature for complete hardening of the silicone coating at a constant maximum speed of 200 m / min was sought in this test series instead.
• the minimum temperature for curing the silicone coatings could be reduced by approx. 5 to 10%.
• Example 10 The procedure of Example 10 was repeated. Another system, also on a solvent-free basis, was used for the silicone coating.
• the coating composition had the following composition: 100 parts of Silcolease 8000 (ICI) base polymer silicone from ICI 2 parts Silicone Crosslinker 95 A 2 parts Silicone Crosslinker 96 A 4 parts Catalyst 95 B.
• Silcolease 8000 ICI
• the minimum temperature for curing the silicone coatings could again be reduced by approximately 5 to 10%.
• the following coating system was used for the solvent-free siliconization: 100 parts of Rhodorsil 11347 silicone polymer from Rhone-Poulanc 3 parts catalyst 11091 for the base polymer.
• test papers were coated at a speed of 200 m / min. The lowest curing temperatures were again determined, as can be seen from Table 5.
• release force values and the silicone application quantities were determined in accordance with Example 9.
• Table 5 Paper type Silicone application g / m Minimum temp. ° C for curing Separation force, mN / cm after 20 h after 4 weeks K-7476 A-7475 K-7476 A-7475 Zero sample 2.0 150 152 225 140 246
• the application weight was around 1.5 g / m (calculated).
• the uncoated base paper had an air permeability according to Schopper of 62 cm / min and a degree of sizing according to Cobb-Unger of 50 g / m.
• the paper treated with it was satinized in a laboratory calender.
• the line pressure was 4000 dN.
• the surface temperature of the steel roller was 100 ° C.
• Example 6 The further processing of the test paper was carried out as described in part b) of Example 1. The results of the crosslinking test are summarized in Table 6.
• Example 13 The procedure of Example 13 was repeated. After adding the organopolysiloxane emulsion, the pH was 5.5. The results of the crosslinking test are shown in Table 6 below.
• Example 13 The procedure of Example 13 was repeated, but instead of coating the test paper with the solvent-free silicone system described in part b) of Example 1, a solvent-containing system with the following composition was chosen: 74 parts white spirit 20 parts Silcolease 7420 (ICI) base siloxane 0.2 parts Crosslinking Agent 91 A crosslinker 0.8 parts Catalist 90 B
• the siliconization was carried out analogously to Example 1, part b) a laboratory doctor device, the silicone application again being about 1 g / m (calculated). The shortest networking times determined are shown in Table 5.
• Example 14 The procedure of Example 14 was repeated. However, the laboratory siliconization was carried out using the solvent-containing silicone system described in Example 15. The minimum required networking times are shown in Table 6.
• Example 13 The procedure of Example 13 was repeated. However, instead of 3.5 this time, 7 g of the organopolysiloxane emulsion were added to the solution of 22 g of polyvinyl alcohol and 3 g of carboxymethyl cellulose in 475 g of water, with stirring. The pH of this mixture was again adjusted to 4.0 with sulfuric acid. The further processing corresponded to the procedure described in Example 13. The results of the crosslinking test are summarized in Table 6.
• Example 17 The procedure of Example 17 was repeated, the pH the stroke mix, however, is set to 5.5.
• the results of the crosslinking test are shown in Table 6.
• Example 17 The procedure of Example 17 was repeated. However, the test paper was coated with a solvent-containing silicone system from ICI. The composition of this coating composition has already been described in Example 15. The results of the crosslinking test are shown in Table 6.
• Example 18 The procedure of Example 18 was repeated. However, the laboratory siliconization was carried out using the solvent-containing silicone system described in Example 15. The required shortest networking times are shown in Table 6.
• Paper samples were used as a comparison (zero sample), which had been surface-finished with a mixture consisting of 22 g of polyvinyl alcohol and 3 g of carboxymethyl cellulose in 475 g of water, but without any addition of organopolysiloxane emulsion.
• the pH values of these surface preparations were adjusted to 4.0 as well as 5.5.
• the laboratory siliconization was carried out using the silicone systems described in part b) of Example 1 and in Example 15.
• the required minimum crosslinking time can be found in Table 6.
• Table 6 Test paper pH value of the surface preparation minimum required crosslinking time, s (150 ° C) 4.0 5.5 LF * LH * 1.Example 13 X 8th 2.
• Example 14 X 12th 3.Example 15 X 15 4.Example 16 X 18th 5.Example 17 X 5 6.Example 18 X 8th 7.Example 19 X 15 8.Example 20 X 18th 9.
• Sample 1 as a comparison (Ex. 21-22)
• X 10th 20th 10.Null sample 2 as a comparison (Ex. 23-24)
• X 15 20th * LF solvent-free silicone system) approx.
• LH solvent-containing silicone system) 1 g / m (solid) silicone application.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Paper (AREA)
• Adhesive Tapes (AREA)
• Silicon Polymers (AREA)
• Separation Using Semi-Permeable Membranes (AREA)

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